WO2025203344A1 - Optical connector and method for manufacturing optical connector plug - Google Patents

Abstract

To provide an optical connector capable of connecting an optical fiber with low loss, and a method for manufacturing the optical connector plug.　An optical connector includes an optical connector plug (100). The optical connector plug (100) has a waveguide (20) formed using a photocurable resin (13). The waveguide (20) is connected to a core end surface of an optical fiber (10) whose one end is fixedly inserted in the optical connector plug (100), and can transmit an optical signal of a core of the optical fiber (10) to the other end. The waveguide has a tapered form in which an end surface of the other end is larger than an end surface of the one end.

Description

Optical connector and method of manufacturing optical connector plug

This disclosure relates to a method for manufacturing an optical connector and an optical connector plug.

With the spread of the Internet, the transmission capacity of information networks is expanding year by year. Methods for increasing transmission capacity in optical fiber include time division multiplexing, wavelength division multiplexing, and space division multiplexing. In particular, space division multiplexing is a technology that achieves high capacity by placing multiple cores or multiple modes in a single optical fiber. With single-mode uncoupled multicore fiber, by using an interface such as fine-in-fan-out, it is possible to increase transmission capacity without changing the configuration of conventional transceiver equipment.

Furthermore, one method of increasing transmission capacity is mode multiplexing transmission technology, which places multiple propagation modes in a single core and transmits different signals in each mode, thereby increasing capacity. With this technology, an interface such as fine-in-fan-out is used to use each mode in each core as a different signal transmission path, thereby increasing transmission capacity.

In order to use space division multiplexing transmission technology in data centers, access networks, etc., it is necessary to lay multicore fiber optical cables that serve as transmission paths for space division multiplexing transmission. To maintain the scalability of laying multicore fiber cables, optical connectors that can connect multicore fibers are required. With multicore fiber connector technology, the fiber cores are positioned off-center relative to the outer diameter of the fiber, so they must be mounted with rotational alignment to achieve low connection loss. Non-patent documents 1 and 2 have proposed technologies for achieving low connection loss.

Morishima, T., Saito, Y., Shimakawa, Osamu, Manabe, K., Nakanishi, T., Sano, T., Hayashi, T., "Multicore fiber connection technology," IEICE General University, BCI-1-5, 2021. Hidetaka Terazawa, Takeshi Yukikawa, Keisuke Kondo, and Okihiro Sugihara, "Fabrication of near-infrared self-written optical waveguides and their application to multi-channel optical waveguides," IEICE General University, C-13-2, 2013.

(1) Regarding single-mode connectors with one core propagation mode Non-Patent Document 1 describes a method for suppressing rotational misalignment when fabricating a single-core or multi-core connector plug for connecting multicore fibers. However, this technology requires precise alignment, including rotational alignment, and has the problem of requiring the use of parts and rotational alignment methods with higher precision than conventional connectors.

Non-Patent Document 2 describes a technique for connecting specific combinations of multi-core fibers using self-forming waveguides. However, because optical connectors are required to be able to connect any combination, cores must be positioned in standardized design target positions, but the document does not describe a method for positioning cores in the design target positions.

(2) Mode multiplexing transmission with multiple core propagation modes When connecting cores with multiple propagation modes, mode conversion may occur at the optical connection point even if no optical loss occurs. In mode multiplexing transmission, different signals are transmitted in each mode, so if mode conversion occurs, the signals will interfere with each other, leading to signal degradation.

The technology in Non-Patent Document 1 discloses an average connection performance of 0.07 dB when connecting single-mode cores. For example, if this is a two-mode core, and the connection loss between the fundamental modes is 0.07 dB, and this loss is due to mode conversion from the fundamental mode to a higher-order mode, then the extinction ratio, i.e., the ratio of the fundamental mode propagating light before the connection point to the light converted to the higher-order mode, is -18 dB. For example, in wavelength multiplexing transmission, an extinction ratio of -30 dB or less is required in wavelength multiplexing/demultiplexing devices, and an extinction ratio of -18 dB can be said to be high for multiplexed transmission. As described above, the technology in Non-Patent Document 1 has issues with mode conversion.

Furthermore, the technology in Non-Patent Document 2 does not describe a method for placing cores at the design target positions of optical connectors.

This disclosure has been made in consideration of the above circumstances, and its purpose is to provide an optical connector that can connect optical fibers with low loss, and a method for manufacturing an optical connector plug.

One aspect of the present disclosure is an optical connector including an optical connector plug, the optical connector plug having a waveguide formed using a photocurable resin, one end of the waveguide being connected to the core end face of an optical fiber inserted and fixed into the optical connector plug, and capable of transmitting an optical signal from the core of the optical fiber to the other end, the end face of the other end being tapered larger than the end face of the one end.

One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber, and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out, and by irradiating the photocurable resin with light from the core of the optical fiber at a wavelength that increases the refractive index of the photocurable resin and hardens it, the irradiated portion of the photocurable resin increases the refractive index and hardens, thereby forming a tapered waveguide.

One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug comprising: a ferrule capable of holding a connection end of an optical fiber and photocurable resin; the connection end of the optical fiber inserted and fixed within the ferrule; photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber; and a sealant that forms a removable end face of the ferrule and prevents the photocurable resin from leaking out; the removable end face of the ferrule is opposed to the core end face of another optical fiber inserted and fixed in another optical connector plug for fabricating a waveguide; the core of the optical fiber is irradiated with light of a wavelength that increases the refractive index of the photocurable resin and hardens it, and light of the same wavelength is irradiated from the core of the other optical fiber to the photocurable resin, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

One aspect of the present disclosure is a method for manufacturing an optical connector plug for use in an optical connector, the optical connector plug comprising: a ferrule capable of holding a connection end of an optical fiber and photocurable resin; the connection end of the optical fiber inserted and fixed within the ferrule; photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber; and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out. Light of a wavelength that increases the refractive index of the photocurable resin and hardens it is irradiated from the core of the optical fiber onto the photocurable resin, and light of the wavelength is irradiated onto the photocurable resin from the detachable end face side via a photomask or a focusing lens, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

This disclosure provides an optical connector capable of connecting optical fibers with low loss, and a method for manufacturing an optical connector plug.

FIG. 1 is a diagram showing the structure of an optical connector plug of an optical connector. FIG. 2 is an enlarged view of a portion of the optical connector plug shown in FIG. FIG. 3 shows a modified example of the sealing material of the optical connector plug. FIG. 4 is a diagram showing an example of the arrangement of a plurality of optical fibers in an optical connector plug. FIG. 5 is a diagram showing a modified example of the optical connector plug arrangement member. FIG. 6 is a diagram showing an example of a connection configuration of an optical connector. FIG. 7 is a diagram showing another example of the connection configuration of the optical connector. 8A to 8C are diagrams illustrating a first method for producing an optical connector plug. FIG. 9 is a diagram showing a modification of the first method for producing an optical connector plug. FIG. 10 is a diagram showing an example of the relationship between the amount of axial misalignment D of an optical fiber and the excess loss TD. FIG. 11 is a diagram illustrating a second method for producing an optical connector plug. FIG. 12 is an enlarged view of a portion of the optical connector plug shown in FIG. 13A to 13C are diagrams illustrating a third method for producing an optical connector plug. FIG. 14 is a diagram illustrating a method for producing an optical connector plug for connecting a multi-core fiber. FIG. 15 is an enlarged view of a portion of the optical connector plug shown in FIG. FIG. 16 is a diagram showing an example of a connector plug structure of a single-fiber optical connector. FIG. 17 is a diagram showing a modified example of the sealing material of the single-fiber optical connector plug. FIG. 18 is a diagram showing an example of a connection configuration of a single-fiber optical connector. FIG. 19 is a diagram illustrating a first method for producing a single-fiber optical connector plug. FIG. 20 is a diagram illustrating a second method for producing a single-fiber optical connector plug. FIG. 21 is an enlarged view of a portion of the single-fiber optical connector plug shown in FIG. FIG. 22 is a diagram illustrating a third method for producing a single-fiber optical connector plug. FIG. 23 is a diagram illustrating a method for producing a single-core optical connector plug for connecting a multi-core fiber. FIG. 24 is an enlarged view of a portion of the optical connector plug shown in FIG.

Next, several embodiments will be described in detail with reference to the drawings. In the description, identical components will be assigned the same reference numerals and duplicate explanations will be omitted.

The first and second embodiments describe single-mode embodiments, and the third and fourth embodiments describe multi-mode embodiments.

[First embodiment]
Fig. 1 is a diagram showing an example of the structure of a connector plug of an optical connector according to a first embodiment. Fig. 1 is a cross-sectional view (side cross-sectional view) of an optical connector plug 100 taken along a plane parallel to the longitudinal direction of an optical fiber 10.

The optical connector of this embodiment includes an optical connector plug 100, which has a waveguide formed using photocurable resin 13, one end of which is connected to the core end face of an optical fiber 10 inserted and fixed in the optical connector plug 100 and capable of transmitting an optical signal from the core of the optical fiber 10 to the other end, with the end face of the other end being tapered and larger than the end face of the one end. The optical connector plug 100 may also have a ferrule 11 capable of holding the connection end of the optical fiber 10 and the photocurable resin 13, and a sealant 14 that forms the detachable end face of the ferrule 11 and prevents the photocurable resin from leaking out. The photocurable resin 13 is filled within the ferrule 11 so as to abut against the connection end of the optical fiber 10.

The optical connector plug 100 shown in the figure comprises the connection ends of multiple optical fibers 10 inserted and fixed into the ferrule 11, the ferrule 11, adhesive 12, a photocurable resin 13 that forms a self-forming optical waveguide (hereinafter referred to as "waveguide"), a sealing material 14, and an alignment member 16. The end face 15 of the ferrule 11 may be formed at an angle.

The optical connector plug 100 is a multi-core optical connector plug, and may be, for example, an F12-type multi-core optical fiber connector (MT connector). The optical connector plug 100 may also be an F13-type multi-core optical fiber connector (MPO connector). In this case, the end face of the MT ferrule may be formed at an angle. The MT ferrule is housed in an MPO plug housing, and the MPO plug is connected within an MPO adapter. The multi-core optical connector is not limited to MT connectors or MPO connectors, as long as it can connect multiple optical fibers in a detachable manner.

Figure 2 is an enlarged view of a portion of the cross-sectional view of the optical connector plug 100 shown in Figure 1. As shown, the photocurable resin 13 is connected to the optical fiber 10 inside the ferrule 11. A tapered waveguide 20 capable of transmitting optical signals is formed in the photocurable resin 13. The ferrule 11 is filled with the photocurable resin 13.

The sealing material 14 is provided on the ferrule end surface 15 and prevents the photocurable resin 13 from leaking out of the ferrule 11. The sealing material 14 holds the photocurable resin 13 inside the ferrule 11. The sealing material 14 forms the detachable end surface of the ferrule 11. The sealing material 14 is also referred to as the detachable end surface 14.

The sealing material 14 may be arranged so as to protrude from the ferrule end face 15, as shown in Figures 1 and 2. Alternatively, as shown in Figure 3, a portion of the ferrule end face 15 may be recessed, and the sealing material 14 may be embedded in the ferrule end face 15. The sealing material 14 may be arranged in any shape and in any manner, as long as it is possible to prevent the photocurable resin 13 from leaking out of the ferrule end face 15.

The sealing material 14 can be made of, for example, glass or resin. The sealing material 14 may have any shape that allows it to emit light propagating through the waveguide 20 formed in the photocurable resin 13, or to propagate incident light into the waveguide 20. The sealing material 14 may also be formed with a waveguide that can transmit optical signals in conjunction with the waveguide 20.

Figure 4 is a diagram illustrating multiple optical fibers 10 arranged in an optical connector plug 100. Figure 4 is a cross-sectional view of the optical connector plug 100 cut along a plane perpendicular to the longitudinal direction of the optical fibers 10. The cross-sectional view shown is a cross-sectional view of the area where the adhesive 12 and the alignment member 16 are present.

Multiple optical fibers 10 are arranged at equal intervals by an alignment member 16 toward the ferrule end face 15, and are fixed to the ferrule 11 with adhesive 12. The adhesive 12 is injected through a hole (not shown) provided in the top of the ferrule 11.

In order to arrange the optical fibers 10 at equal intervals, the arrangement member 16 is formed with, for example, V-grooves, semicircular grooves, circular holes, etc. The shape of the arrangement member 16 may be any shape that allows the optical fibers 10 to be arranged at equal intervals. In the example shown in Figure 4, eight optical fibers 10 are arranged, but the number of optical fibers 10 is not limited to eight, as long as it is two or more.

As shown in Figure 5, the alignment member 16 may have a tapered shape to make it easier to insert the optical fiber 10. The optical fiber 10 may be, for example, a single-core fiber, a multi-core fiber, or a polarization-maintaining fiber, as long as it is an optical fiber that transmits light of any wavelength.

Figure 6 shows an example of the connection configuration of the optical connector 200 of this embodiment. Here, axial alignment is performed by inserting a guide pin (not shown) into a guide hole (not shown) located on the ferrule end face 15, and a spring (not shown) applies pressure to the opposing optical connector plugs 100, causing the sealing materials 14 (attachment/detachment end faces) to tightly adhere to each other, thereby forming the optical connector 200. This allows the optical fiber 10 inserted and fixed in the opposing optical connector plugs 100 to be connected with low loss.

To reduce return loss, as shown in Figure 7, a refractive index matching material 18 may be applied between the opposing sealing materials 14. The refractive index matching material 18 may be in a gel or solid state. If a solid refractive index matching material 18 is used, there is no need to remove and reapply the refractive index matching material 18 when connecting or disconnecting the optical connector, which reduces the amount of work required to connect or disconnect the optical connector.

Figure 8 is a diagram illustrating a first manufacturing method for the optical connector plug 100 used in the optical connector of this embodiment. In the first manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

Specifically, photocurable resin 13 is filled into the hollow space connecting the end face of the optical fiber placed in the ferrule 11 and the ferrule end face 15 (detachable end face 14). Then, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100, and light of that wavelength is irradiated onto the photocurable resin 13 from the core 10a of the optical fiber. This increases the refractive index of the irradiated portion of the photocurable resin 13 and hardens it, forming a tapered waveguide 20 as shown in Figure 2. After the waveguide 20 is formed, the light source 19 is removed, and the optical connector plug 100 is completed.

Alternatively, as shown in Figure 9, a cladding 21 may be formed around the waveguide 20. After forming the waveguide 20, the photocurable resin 13 may be removed from the portion where the waveguide 20 is not formed, and the ferrule 11 may be filled with another photocurable resin 13b capable of forming a cladding with a lower refractive index than the waveguide 20. Light of a wavelength that causes the other photocurable resin 13b to harden may be irradiated from the ferrule end face 15 side, thereby hardening the other photocurable resin 13b and forming a cladding 21 around the waveguide 20.

Specifically, the photocurable resin 13 is removed from the injection port 22 provided in the ferrule 11, and instead photocurable resin 13b is injected, which can form a cladding 21 with a lower refractive index than the waveguide 20 when irradiated with light. Then, a light source 37 with a wavelength that causes the photocurable resin 13b to harden is prepared, and the cladding 21 can be formed by irradiating light 37a of that wavelength from the light source 37. An injection port 22 may be provided in advance in the ferrule 11 to remove the photocurable resin 13 and inject the photocurable resin 13b.

If the optical fiber 10 is a single-mode optical fiber as defined in Recommendation G.654 of the International Telecommunications Union's Telecommunications Standardization Sector (ITU-T), for example, the mode field diameter, which corresponds to the core diameter of the single-mode fiber, can be in the range of 9.5 μm to 15 μm. Therefore, the mode field diameter of the core 10a of the optical fiber 10 can be selected in the range of 9.5 μm to 15 μm. If axial misalignment occurs during optical connector connection, the larger the mode field diameter, the lower the excess loss caused by axial misalignment.

Figure 10 shows an example of the relationship between the amount of axial misalignment D of the optical fiber and the excess loss TD. The relationship between the amount of axial misalignment D of the optical fiber and the excess loss TD can be expressed by the following equation.

W1 and W2 are the mode field diameters of the cores (waveguides 20) of the opposing ferrule end faces 15 of the two optical connector plugs 100 that make up the optical connector 200. Figure 10 shows the loss when the mode field diameters of the two cores are both 9.5 μm and the loss when the mode field diameters of the two cores are both 15 μm.

For example, when the axial misalignment D is 2.0 μm, the mode field diameter of the core at the ferrule end face 15 in the tapered waveguide 20 is expanded to 15 μm. This reduces the excess loss TD from approximately 0.77 dB when the mode field diameter is 9.5 μm to approximately 0.31 dB. Note that the optical fiber 10 is not limited to the specified single-mode optical fiber, as long as it is capable of transmitting light at the desired wavelength.

Figure 11 is a diagram illustrating a second manufacturing method for the optical connector plug 100 used in the optical connector 200 of this embodiment. In the second manufacturing method, the core end face of another optical fiber 30 inserted and fixed in another optical connector plug 300 for manufacturing a waveguide is placed opposite the detachable end face 14 of the ferrule 11, and light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated from the core of the optical fiber 10 onto the photocurable resin 13, while light of the same wavelength is irradiated onto the photocurable resin 13 from the core of the other optical fiber 30, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

Specifically, another optical connector plug 300 (a connector plug for waveguide fabrication) for fabricating a waveguide is connected to the optical connector plug 100 of the optical connector 200. The other optical connector plug 300 includes a plurality of optical fibers 30, a ferrule 31, an adhesive 32, and an alignment member 36.

The core 30a of the optical fiber 30 inserted and fixed into the other optical connector plug 300 has the same cutoff wavelength characteristics as the core 10a of the optical fiber 10 in the optical connector plug 100, and has a larger diameter than the core 10a. Light sources 19, 39 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are connected to the optical fiber 10 in the optical connector plug 100 and the optical fiber 30 in the other optical connector plug 300, respectively. Light of this wavelength is then irradiated from the cores 10a, 30a of each optical fiber 10, 30. This increases the refractive index of the irradiated portion of the photocurable resin 13 and hardens it, creating a tapered waveguide 20 as shown in Figure 12. After creating the waveguide 20, the other optical connector plug 300 and the light source 19 are removed, completing the optical connector plug 100. The optical fiber 30 has a core 30a and a cladding 30b.

The other optical connector plug 300 may be an optical connector plug used in a high-precision optical connector manufactured with minimal deviation from the design target of the optical connector. For example, a standard connector specified by the IEC (International Electrotechnical Commission) may be used.

In the case of a multi-core fiber connector without a reference connector, an optical connector with low connection loss may be selected, for example, using the following procedure. A plurality of optical connectors are fabricated in which the core positions are aligned using image alignment or other methods to minimize error from the design target, and those with the smallest error are selected from these to extract sample group A. Another plurality of optical connectors are fabricated in which the core positions are aligned, and those with the smallest error are selected from these to extract sample group B, which is different from sample group A. A plurality of optical connectors are fabricated in which the core positions are aligned, and those with the smallest error are selected from these to extract sample group C, which is different from sample groups A and B. The optical connectors of sample groups A, B, and C are then connected together to select an optical connector that achieves even lower connection loss. The optical connector plugs of the optical connectors selected in this manner may be used as other optical connector plugs 300.

Figure 13 is a diagram illustrating a third manufacturing method for the optical connector plug 100 of the first embodiment. In the third manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, and light of the same wavelength is irradiated onto the photocurable resin 13 from the attachment/detachment end face 14 side through a photomask 42, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

Specifically, in the third manufacturing method, instead of using another optical connector plug 300, photolithography technology using a photomask 42 and a light source 38 is used. The photomask 42 and a light source 38 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are placed near the ferrule end face 15 of the optical connector plug 100. In addition, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100.

By irradiating the photocurable resin 13 with light of a wavelength that increases the refractive index and hardens it from the core 10a of the optical fiber 10 and the photomask 42, the refractive index of the irradiated portion of the photocurable resin 13 increases and hardens, creating the waveguide 20.

The mode field diameter of the light emitted from the light source 38 can be adjusted by changing the shape of the photomask 42. By irradiating the photocurable resin 13 with light that has a mode field diameter larger than the core 10a of the optical fiber 10 using the photomask 42, it is possible to create a tapered waveguide 20. After creating the waveguide 20, the photomask 42 and light sources 19 and 38 are removed, and the optical connector plug 100 is produced.

In the first manufacturing method described above, the optical connector plug 100 is irradiated with light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it; in the second manufacturing method, another connector plug 300 is used to manufacture the waveguide; and in the third manufacturing method, photolithography technology is used to irradiate the photocurable resin 13 with light of the wavelength. Note that the manufacturing method for the optical connector plug 100 is not limited to these, and any method that can manufacture a tapered waveguide 20 may be used.

Figure 14 is a diagram illustrating a method for fabricating an optical connector plug 100 for connecting a multicore fiber. Here, a method for fabricating the optical connector plug 100 using the second fabrication method described above is described as an example. Another optical connector plug 300 is connected to the optical connector plug 100. The core 30a of the optical fiber 30 of the other optical connector plug 300 has the same cutoff wavelength characteristics as the core 10a of the optical fiber 10 of the optical connector plug 100, and has a larger diameter than the core 10a. The optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of the other optical connector plug 300 are each connected to a single-core fiber 40 via a fan-out 41. Light sources 19, 39 with a wavelength that increases the refractive index and hardens the photocurable resin 13 are connected to each single-core fiber 40, and light of that wavelength is irradiated from the cores 10a, 30a of the optical fibers 10, 30.

This causes the refractive index of the photocurable resin 13 in the irradiated area to increase and harden, forming multiple tapered waveguides 20 as shown in Figure 15. After the waveguides 20 are created, the other optical connector plugs 300 and the fan-out 41 are removed to produce the optical connector plug 100. Figures 14 and 15 show an example of a multicore fiber with four cores, but the number of cores in the multicore fiber may be two or more, and the core arrangement may be any desired arrangement.

Second Embodiment
Fig. 16 is a diagram showing an example of a connector plug structure of an optical connector according to the second embodiment. Fig. 16 is a cross-sectional view (side cross-sectional view) of an optical connector plug 500 taken along a plane parallel to the longitudinal direction of the optical fiber 50.

The optical connector plug 500 of this embodiment has a waveguide formed using photocurable resin 53, one end of which is connected to the core end face of an optical fiber 50 inserted and fixed in the optical connector plug 500, and which is capable of transmitting an optical signal from the core of the optical fiber 50 to the other end, with the end face of the other end being tapered and larger than the end face of the one end. The optical connector plug 500 may also have a ferrule 51 that can hold the connection end of the optical fiber 50 and the photocurable resin 53, and a sealant 54 that forms the detachable end face of the ferrule 51 and prevents the photocurable resin from leaking out. The photocurable resin 53 is filled into the ferrule 51 so as to abut against the connection end of the optical fiber 50.

The optical connector plug 500 of this embodiment is a single-core optical connector plug, and includes the connection end of a single optical fiber 50 inserted and fixed into the ferrule 51, the ferrule 51, a plug frame 52, a photocurable resin 53 that forms a self-forming optical waveguide (waveguide), a sealant 54, a tab 56, a flange 57, a spring 58, and a stop ring 59. The sealant 54 is placed on the ferrule end face 55 to prevent the photocurable resin 53 filled in the ferrule 51 from leaking out.

The single-core optical connector plug 500 may be an F04 type optical fiber connector (SC connector). Also, instead of an SC connector, the optical connector plug 500 may be an F14 type optical fiber connector (MU connector).

The optical connector plug 500 may have any shape that allows the single-core optical fiber 50 adhesively fixed to the ferrule 51 to be connected to an opposing optical fiber via an adapter (not shown). In other words, the presence or absence of the flange 57, spring 58, stop ring 59, plug frame 52, and knob 56, as well as their shapes, are not limited to those shown in Figure 16. The single-core optical connector of this embodiment is not limited to an SC connector or an MU connector, as long as it can connect a single-core optical fiber in a detachable manner.

The photocurable resin 53 is connected to the optical fiber 50 inside the ferrule 51, and is used to form a tapered, self-forming optical waveguide capable of transmitting optical signals. The photocurable resin 53 is prevented from flowing out of the ferrule end face 55 by the sealing material 54, and is held inside the ferrule 51.

The sealing material 54 may be arranged so as to protrude from the ferrule end face 55 as shown in FIG. 16, or may be arranged so as to be embedded in the ferrule end face 55 by making the ferrule end face 55 concave as shown in FIG. 17. The sealing material 54 may be of any shape and arrangement as long as it can prevent the photocurable resin 53 from leaking out from the ferrule end face 55. The sealing material 54 is also referred to as the detachable end face 54. For example, glass or resin may be used for the sealing material 54. The sealing material 54 may have any shape as long as it can emit light propagating through the waveguide formed in the photocurable resin 53 or propagate incident light into the waveguide. A waveguide capable of transmitting optical signals together with the waveguide formed in the photocurable resin 53 may be formed in the sealing material 54.

The single-core optical fiber 50 may be, for example, a single-core fiber, a multi-core fiber, or a polarization-maintaining fiber, as long as it is an optical fiber capable of transmitting light of any wavelength.

Figure 18 shows an example of a connection configuration for an optical connector according to the second embodiment. Axial alignment is achieved by inserting two opposing ferrules 51 into a sleeve 63 attached to an adapter (not shown). Then, a pressing force is applied to the optical fiber 50 and the ferrule end face 55 by a spring 58, forming an optical connector 600 in which the sealing materials 54 are in close contact with each other, and connecting the optical fiber 50.

To reduce return loss, a refractive index matching material (not shown) may be applied between the sealing materials 54. The refractive index matching material may be in gel or solid form. If a solid refractive index matching material is used, there is no need to remove and reapply the matching material when connecting or disconnecting the optical connector, which reduces the amount of work required to connect or disconnect the optical connector.

Figure 19 is a diagram illustrating a first manufacturing method for the optical connector plug 500 of the second embodiment. In the first manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide.

Specifically, a light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is connected to the optical fiber 50 of the optical connector plug 500, and light of that wavelength is irradiated onto the photocurable resin 53 from the core 50a of the optical fiber 50. This increases the refractive index of the irradiated portion of the photocurable resin 53 and hardens it, creating a tapered waveguide. After the tapered waveguide is created, the light source 69 is removed, and the optical connector plug 500 is completed.

After the waveguide is created, the cladding may be formed in the same manner as in the first manufacturing method of the first embodiment. Specifically, after the waveguide is created, the photocurable resin 53 is removed from an injection port (not shown) formed in the ferrule 51, and instead a photocurable resin capable of forming a cladding with a lower refractive index than the waveguide by light irradiation is injected. A light source with a wavelength that causes the photocurable resin for the cladding to harden may be prepared, and the cladding may be formed by irradiating light from the light source.

If the optical fiber 50 is a single-mode optical fiber as defined in Recommendation G.654 of the International Telecommunications Union's Telecommunications Standardization Sector (ITU-T), for example, the mode field diameter, which corresponds to the core diameter of the single-mode fiber, can be in the range of 9.5 μm to 15 μm, and the mode field diameter with the core 50a can be selected in the range of 9.5 μm to 15 μm. If axial misalignment occurs during optical connector connection, the larger the mode field diameter, the lower the excess loss due to axial misalignment. For example, if the axial misalignment amount D is 2.0 μm, the mode field diameter of the core (waveguide 60) at the ferrule end face 55 in a tapered waveguide is expanded to 15 μm. This reduces the excess loss TD from approximately 0.77 dB when the mode field diameter is 9.5 μm to approximately 0.31 dB. The optical fiber 10 is not limited to the defined single-mode optical fiber, as long as it is capable of transmitting light at the desired wavelength.

Figure 20 is a diagram illustrating a second method for manufacturing the optical connector plug 500 of the second embodiment. In the second manufacturing method, the core end face of another optical fiber 70 inserted and fixed into another optical connector plug 700 for manufacturing a waveguide is positioned opposite the detachable end face 54 of the ferrule 51, and light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated from the core of the optical fiber 50 onto the photocurable resin 53, while light of the same wavelength is irradiated onto the photocurable resin 53 from the core of the other optical fiber 70, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

Specifically, another optical connector plug 700 for creating a waveguide is connected to the optical connector plug 500. The core 70a of the optical fiber 70 of the other optical connector plug 700 has the same cutoff wavelength characteristics as the core 50a of the optical fiber 50 of the optical connector plug 500, and has a larger diameter than the core 50a. Light sources 69 and 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to the optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of the other optical connector plug 700, respectively, and light of that wavelength is irradiated onto the photocurable resin 53 from the cores 50a and 70a of the optical fibers 50 and 70. This increases the refractive index of the irradiated portion of the photocurable resin 53 and hardens it, forming a tapered waveguide 60 as shown in Figure 21. After the waveguide 60 is created, the other optical connector plug 700 and the light source 69 are removed, completing the optical connector plug 500.

The other optical connector plug 700 may be a high-precision connector manufactured with minimal error from the optical connector's design targets. For example, a standard connector specified by the IEC (International Electrotechnical Commission) may be used.

In the case of a multi-core fiber connector without a reference connector, an optical connector with low connection loss may be selected, for example, using the following procedure. A plurality of optical connectors are fabricated in which the core positions are aligned using image alignment or other methods to minimize error from the design target, and those with the smallest error are selected from these to extract sample group A. Another plurality of optical connectors are fabricated in which the core positions are aligned, and those with the smallest error are selected from these to extract sample group B, which is different from sample group A. A plurality of optical connectors are fabricated in which the core positions are aligned, and those with the smallest error are selected from these to extract sample group C, which is different from sample groups A and B. The optical connectors of sample groups A, B, and C are then connected together to select an optical connector that achieves even lower connection loss. The optical connector plugs of the optical connectors selected in this manner may be used as other optical connector plugs 300.

Figure 22 is a diagram illustrating a third manufacturing method for the optical connector plug 500 of the second embodiment. In the third manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, and light of the same wavelength is irradiated onto the photocurable resin 53 from the attachment/detachment end face 54 side through a photomask 62, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

Specifically, instead of using another optical connector plug 700, photolithography technology is used with a photomask 62 and a light source 88. The photomask 62 and a light source 88 with a wavelength that increases the refractive index and hardens the photocurable resin 53 are placed near the ferrule end face 55 of the optical connector plug 500. In addition, a light source 69 with a wavelength that increases the refractive index and hardens the photocurable resin 53 is connected to the optical fiber 50 of the optical connector plug 500.

By irradiating the photocurable resin 53 with light of a wavelength that increases the refractive index and hardens it from the core 50a of the optical fiber 50 and the photomask 62, the refractive index of the irradiated portion of the photocurable resin 53 increases and hardens, creating a tapered waveguide 60.

The mode field diameter of the light 88a emitted from the light source 88 can be adjusted by changing the shape of the photomask 62. By irradiating the photocurable resin 53 with light that has a mode field diameter larger than the core 50a of the optical fiber 50 using the photomask 62, it is possible to create a tapered waveguide 60. After creating the waveguide 60, the photomask 62 and light sources 69 and 88 are removed, and the optical connector plug 500 is produced.

In the first manufacturing method described above, the optical connector plug 500 is irradiated with light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it; in the second manufacturing method, another connector plug 700 is used to manufacture the waveguide; and in the third manufacturing method, photolithography technology is used to irradiate the photocurable resin 53 with light of the wavelength. Note that the manufacturing method for the optical connector plug 500 is not limited to these, and any method that can manufacture a tapered waveguide 60 may be used.

Figure 23 is a diagram illustrating a method for manufacturing an optical connector plug 500 for connecting a multicore fiber. Here, a method for manufacturing the optical connector plug 500 using the second manufacturing method described above is described as an example. Another optical connector plug 700 is connected to the optical connector plug 500. The core 70a of the optical fiber 70 of the other optical connector plug 700 has the same cutoff wavelength characteristics as the core 50a of the optical fiber 50 of the optical connector plug 500, and has a diameter larger than the diameter of the core 50a.

The optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of another optical connector plug 700 are each connected to a single-core fiber 80 via a fan-out 61. Light sources 69, 89 with a wavelength that increases the refractive index and hardens the photocurable resin 53 are connected to each single-core fiber 80, and light of that wavelength is irradiated onto the photocurable resin 53 from the cores 50a, 70a of the optical fibers 50, 70.

This causes the refractive index of the photocurable resin 13 in the irradiated area to increase and harden, creating multiple tapered waveguides 60 as shown in Figure 24. After the waveguides 60 are created, the other optical connector plugs 700 and the fan-out 61 are removed to create the optical connector plug 500. While Figures 23 and 24 show an example of a multicore fiber with four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any arrangement.

[Third embodiment]
FIG. 16 is a diagram showing an example of a connector plug structure of an optical connector according to a third embodiment. The connector plug structure 9 of this embodiment is similar to the connector plug structure of the second embodiment described above. That is, the optical connector plug 500 of this embodiment has a waveguide formed using a photocurable resin 53, one end of which is connected to the core end face of an optical fiber 50 inserted and fixed into the optical connector plug 500, and which is capable of transmitting an optical signal from the core of the optical fiber 50 to the other end, with the end face of the other end being tapered larger than the end face of the one end. The optical connector plug 500 may also have a ferrule 51 capable of holding the connection end of the optical fiber 50 and the photocurable resin 53, and a sealant 54 that forms the detachable end face of the ferrule 51 and prevents the photocurable resin from leaking out. The photocurable resin 53 is filled in the ferrule 51 so as to abut against the connection end of the optical fiber 50.

The optical connector plug 500 shown is a single-core optical connector plug, and includes the connection end of a single optical fiber 50 inserted and fixed into the ferrule 51, the ferrule 51, a plug frame 52, a photocurable resin 53 that forms a self-forming optical waveguide (waveguide), a sealant 54, a knob 56 (housing), a flange 57, a spring 58, and a stop ring 59. The sealant 54 is placed on the ferrule end face 55 to prevent the photocurable resin 53 filled in the ferrule 51 from leaking out. The sealant 54 is also referred to as the detachable end face 54. The single-core optical connector plug 500 can be, for example, an SC connector, an MU connector, or other optical connector plug, but is not limited to these.

The optical connector plug 500 may have any shape that allows the single-core optical fiber 50 adhesively fixed to the ferrule 51 to be connected to an opposing optical fiber via an adapter (not shown). In other words, the presence or absence of the flange 57, spring 58, stop ring 59, plug frame 52, and knob 56, as well as their shapes, are not limited to those shown in Figure 16. The single-core optical connector of this embodiment is not limited to an SC connector or an MU connector, as long as it can connect a single-core optical fiber in a detachable manner.

The photocurable resin 53 is connected to the optical fiber 50 inside the ferrule 51, and is used to form a tapered, self-forming optical waveguide capable of transmitting optical signals. The photocurable resin 53 is prevented from flowing out of the ferrule end face 55 by the sealing material 54, and is held inside the ferrule 51.

One end of the tapered waveguide is connected to the core end face of the optical fiber 50, and the other end is connected to the sealing material 54, which is the detachable end face. The cross-sectional size of the tapered waveguide is larger at the connection point with the sealing material 54 than at the connection point with the core end face of the optical fiber. The sealing material 54 may be arranged so as to protrude from the ferrule end face 55 as shown in Figure 16, or may be arranged so as to be embedded in the ferrule end face 55 with the ferrule end face 55 having a concave shape as shown in Figure 17. The sealing material 54 may have any shape and arrangement as long as it can prevent the photocurable resin 53 from leaking out from the ferrule end face 55. For example, glass, resin, etc. can be used for the sealing material 54. The sealing material 54 may have any shape as long as it can emit light propagating through the waveguide formed in the photocurable resin 53, or propagate incident light into the waveguide. A waveguide capable of transmitting optical signals may be formed in the sealing material 54 in conjunction with the waveguide formed in the photocurable resin 53.

The single-core optical fiber 50 of this embodiment may be, for example, a single-core multimode fiber or a multi-core multimode fiber, as long as it is an optical fiber that transmits light of any wavelength in multiple propagation modes. In this embodiment, we will explain the case where a multi-core multimode fiber is used.

A first manufacturing method for the optical connector plug of this embodiment will be described using Figure 19. In the first manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide.

Specifically, a light source 69 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is connected to the optical fiber 50 of the optical connector plug 500 according to this embodiment, and light of this wavelength is irradiated onto the photocurable resin 53 from the core 50a of the optical fiber 50. This causes the irradiated light to spread in a tapered shape within the photocurable resin 53, increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide. After the tapered waveguide is formed, the light source 69 is removed, and the optical connector plug 500 is completed.

The light source 69 has the same wavelength as the communication light to be transmitted through the optical connector, and the light is propagated in the same propagation mode as the propagation mode used for communication, creating a tapered waveguide. For example, when connecting a multimode fiber that uses the three propagation modes of LP01, LP11, and LP02, the light output from the light source 69 can first propagate in the optical fiber 50 in LP01 mode to harden the photocurable resin 53, then propagate in LP11 mode to harden the photocurable resin 53, and then propagate in LP02 mode to harden the photocurable resin 53.

After creating the waveguide, it is also possible to remove the photocurable resin 53, inject a photocurable resin that can be irradiated with light to form a cladding with a lower refractive index than the waveguide, prepare a light source with a wavelength that will harden the injected photocurable resin, and irradiate the injected photocurable resin with light of a wavelength that will harden the injected photocurable resin to form the cladding.

Alternatively, a photocurable resin 53 that is cured at two or more different wavelengths may be used, and after forming the waveguide, a cladding with a low refractive index may be formed by curing the remaining uncured photocurable resin 53 using a light source with a wavelength different from that used when forming the waveguide.

The refractive index of the cladding changes depending on whether or not the cladding is cured, and if it is cured, the physical properties of the photocurable resin injected and the wavelength used for curing. If the refractive index of the cladding changes, the mode field diameter of the light propagating through the formed waveguide changes. This can be used to measure the loss and mode conversion state after forming the waveguide, and by changing the refractive index of the cladding as necessary, the mode field diameter of the waveguide can be changed and the loss and mode conversion state can be improved.

The formed waveguide has an extremely fine structure and is at risk of being destroyed when external forces are applied. However, in this embodiment, the waveguide is formed within the ferrule 51 and sealing material 54, and is therefore protected from external forces by the ferrule 51. The ferrule 51 is protected from external forces by the plug frame 52. The plug frame 52 is protected from external forces by the knob 56. In this way, this embodiment can provide an optical connector in which the waveguide is less likely to be damaged.

Figure 18 shows an example of a connection configuration for an optical connector according to the third embodiment. Axial alignment is achieved by inserting two opposing ferrules 51 into a sleeve 63 attached to an adapter (not shown). Then, a spring 58 applies a pressing force to the optical fiber 50 and ferrule end face 55, forming an optical connector 600 in such a way that the detachable end faces 54 are in close contact with each other, and connecting the optical fiber 50. A refractive index matching material may be applied between the detachable end faces 54 to reduce return loss.

When using the sleeve 63 and ferrule 51, if components complying with the international standard IEC 61755-3-1 are used, the maximum optical fiber core misalignment will be 2.0 μm.

For example, suppose the mode field diameter of a particular propagation mode in optical fiber 50 is 10 μm. Suppose this mode field diameter expands to, say, 20 μm at the detachable end face 54 due to the tapered waveguide. If axial misalignment occurs during optical connector connection, the greater the mode field diameter, the lower the loss and mode conversion caused by axial misalignment. The relationship between the amount of axial misalignment D of the optical fiber and the proportion T of propagating light that passes through without loss or mode conversion can be expressed by the following equation:

W1 and W2 are the mode field radii of the propagating light at the detachable end faces 54 of the two optical connector plugs 500 of the optical connector 600. If the optical fiber core axis misalignment when the connector is connected is 2.0 μm, the above formula shows that the proportion of light that transmits without loss or mode conversion when the mode field diameter is 10 μm is 85.2%, and when the mode field diameter is 20 μm it is 96.1%. Therefore, by increasing the mode field diameter using a tapered waveguide, loss and mode conversion can be significantly reduced.

For example, in a typical single-mode fiber for communications, the angle of light emitted from the end of the optical fiber is approximately 10 degrees, and a tapered waveguide of only 30 μm is sufficient to widen the mode field diameter to 20 μm. Because the tapered waveguide is short, there is almost no optical loss due to propagation through the tapered waveguide.

As the number of propagation modes increases from 1, the numerical aperture of the optical fiber increases, resulting in a larger output angle and a shorter required length of tapered waveguide.

As described above, by using the optical connector 600 of the third embodiment, it is possible to reduce the amount of axial misalignment of the optical fiber 50. As a result, the length of the tapered waveguide in the optical connector plug 500 can be shortened, and optical loss in the tapered waveguide can be suppressed.

Furthermore, in this embodiment, a tapered waveguide is formed using light with the same wavelength and propagation mode as the communication light emitted from the core of the optical fiber 50. This results in a tapered waveguide with a shape that matches the shape of the communication light, thereby suppressing propagation mode conversion within the tapered waveguide.

A second method for manufacturing the optical connector plug of this embodiment will be described using Figure 20. In the second manufacturing method, the core end face of another optical fiber 70 inserted and fixed into another optical connector plug 700 for manufacturing a waveguide is placed opposite the detachable end face 54 of the ferrule 51, and light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated from the core of the optical fiber 50 onto the photocurable resin 53, while light of the same wavelength is irradiated onto the photocurable resin 53 from the core of the other optical fiber 70, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

Specifically, another optical connector plug 700 (a connector plug for producing a waveguide) is connected to the optical connector plug 500. The diameter of the core 70a of the optical fiber 70 of the other optical connector plug 700 is larger than the diameter of the core 50a of the optical fiber 50 of the optical connector plug 500. Light sources 69 and 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to the optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of the other optical connector plug 700, respectively, and light of that wavelength is irradiated onto the photocurable resin 53 from the cores 50a and 70a of each optical fiber 50 and 70.

This causes the refractive index of the irradiated portion of the photocurable resin 53 to increase and harden, creating a tapered waveguide 60 as shown in Figure 21. After the waveguide 60 is created, the other optical connector plug 700 and the light source 69 are removed, creating the optical connector plug 500. The other optical connector plug 700 may be a high-precision connector manufactured with minimal error from the optical connector design target.

A third manufacturing method for the optical connector plug of this embodiment will be described using Figure 22. In this third manufacturing method, a condenser lens 62 is used instead of the photomask 62 described in the third manufacturing method of the second embodiment. In this third manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 53 and hardens it is irradiated onto the photocurable resin 53 from the core of the optical fiber 50, and light of this wavelength is irradiated onto the photocurable resin 53 from the attachment/detachment end face 54 side via the condenser lens 62, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 53, thereby forming a tapered waveguide 60.

Specifically, as shown in FIG. 22, a condenser lens 62 and a light source 88 with a wavelength that increases the refractive index and hardens the photocurable resin 53 are placed near the ferrule end face 55 of the optical connector plug 500. A light source 69 with a wavelength that increases the refractive index and hardens the photocurable resin 53 is connected to the optical fiber 50 of the optical connector plug 500. Light with the wavelength is then irradiated from the core 50a of the optical fiber and the condenser lens 62, respectively, causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 53, creating a tapered waveguide 60.

The shape of the condenser lens 62 makes it possible to adjust the mode field diameter and convergence angle of the light 88a emitted from the light source 88. By using the condenser lens 62 to irradiate the photocurable resin 53 with light that has a mode field diameter larger than the core 50a of the optical fiber 50, it is possible to create a tapered waveguide 60. After creating the waveguide 60, the condenser lens 62 and light sources 69 and 88 are removed to produce the optical connector plug 500.

Figure 23 is a diagram illustrating a method for manufacturing an optical connector plug 500 for connecting a multicore fiber. Here, as an example, a method for manufacturing the optical connector plug 500 using the second manufacturing method described above is described. Another optical connector plug 700 is connected to the optical connector plug 500.

The optical fiber 50 of the optical connector plug 500 and the optical fiber 70 of another optical connector plug 700 are each connected to a single-core fiber 80 via a fan-out 61. Light sources 69, 89 with a wavelength that increases the refractive index of the photocurable resin 53 and hardens it are connected to each single-core fiber 80, and light of that wavelength is irradiated onto the photocurable resin 53 from the cores 50a, 70a of the optical fibers 50, 70. The diameter of the core 70a of the optical fiber 70 of the other optical connector plug 700 is larger than the diameter of the core 50a of the optical fiber 50 of the optical connector plug 500.

This causes the refractive index of the photocurable resin 53 in the irradiated area to increase and harden, creating multiple tapered waveguides 60 as shown in Figure 24. After the waveguides 60 are created, the other optical connector plugs 700 and the fan-out 61 are removed to create the optical connector plug 500. While Figures 23 and 24 show an example of a multicore fiber with four cores, the number of cores in the multicore fiber may be two or more, and the core arrangement may be any desired arrangement.

[Fourth embodiment]
FIG. 1 is a diagram showing an example of a connector plug structure of an optical connector according to a fourth embodiment. The optical connector plug 100 of this embodiment is a multi-fiber optical connector plug similar to the optical connector plug 100 of the first embodiment. The optical connector plug 100 of this embodiment has a waveguide formed using a photocurable resin 13, one end of which is connected to a core end face of an optical fiber 10 inserted and fixed into the optical connector plug 100 and capable of transmitting an optical signal from the core of the optical fiber 10 to the other end, and the end face of the other end is tapered larger than the end face of the one end. The optical connector plug 100 may also have a ferrule 11 capable of holding the connection end of the optical fiber 10 and the photocurable resin 13, and a sealant 14 that forms the detachable end face of the ferrule 11 and prevents the photocurable resin from leaking out. The photocurable resin 13 is filled in the ferrule 11 so as to abut against the connection end of the optical fiber 10.

The optical connector plug 100 shown in the figure has connection ends of multiple optical fibers 10 inserted and fixed into a ferrule 11, the ferrule 11, adhesive 12, a photocurable resin 13 that forms a self-forming optical waveguide, a sealing material 14, and an alignment member 16. The sealing material 14 is also referred to as a detachable end face 14. A multi-fiber optical connector is not limited to multi-fiber optical connectors such as MT connectors and MPO connectors, as long as it can connect multiple optical fibers in a detachable manner.

As shown in Figure 2, the photocurable resin 13 is connected to the optical fiber 10 inside the ferrule 11, and a tapered waveguide 20 capable of transmitting optical signals is formed in the photocurable resin 13. One end of the tapered waveguide 20 is connected to the end face of the core 10a of the optical fiber 10, and the other end is connected to the detachable end face 14. The cross-sectional size of the waveguide 20 is larger at the connection position with the detachable end face 14 than at the connection position with the optical fiber end face.

The sealing material 14 may be arranged so as to protrude from the ferrule end face 15 as shown in FIG. 1, or may be arranged so as to be embedded in the ferrule end face 15 by making the ferrule end face 15 concave as shown in FIG. 2. The sealing material 14 may have any shape that prevents the photocurable resin 13 from leaking out from the ferrule end face 15. The sealing material 14 may be made of, for example, glass or resin, and may have any shape that allows light propagating through the waveguide 20 formed in the photocurable resin 13 to be emitted, or allows incident light to propagate through the waveguide 20 formed in the photocurable resin 13. When glass is used for the sealing material 14, a waveguide may be formed inside the glass material by laser drawing or the like.

As shown in Figure 4, multiple optical fibers 10 are arranged at equal intervals by an arranging member 16 toward the ferrule end face 15, and are adhered and fixed to the ferrule 11 by adhesive 12 injected through a hole (not shown) provided in the top of the ferrule 11. In order to arrange the optical fibers 10 at equal intervals, the arranging member 16 is provided with, for example, a V-groove, a semicircular groove, or a circular hole. However, the grooves and holes provided in the arranging member 16 may have any shape as long as they can arrange the optical fibers 10 at equal intervals. In Figure 4, eight optical fibers are arranged, but the number of optical fibers 10 is not limited to eight, as long as it is two or more.

The multiple optical fibers 10 may be, for example, single-core multimode fibers or multi-core multimode fibers, and may be optical fibers that transmit light of any wavelength in multiple propagation modes. In this embodiment, we will explain the case where a multi-core multimode fiber is used.

A first manufacturing method for the optical connector plug of this embodiment will be described using Figure 8. In the first manufacturing method, light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

Specifically, a light source 19 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to the optical fiber 10 of the optical connector plug 100, and light of that wavelength is irradiated onto the photocurable resin 13 from the core 10a of the optical fiber 10. As a result, the light from the core 10a spreads in a tapered shape within the photocurable resin 13, increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, forming a tapered waveguide 20. After the waveguide 20 is formed, the light source 19 is removed, and the optical connector plug 100 is completed.

The light from the light source 19 has the same wavelength as the communication light to be transmitted through the optical connector, and the light is propagated in the same propagation mode as that used for communication to generate the waveguide 20.

Alternatively, as shown in FIG. 9, a cladding 21 may be formed around the waveguide 20. Specifically, after the waveguide 20 is created, the photocurable resin 13 is removed through an injection port 22 provided in the ferrule 11, and instead photocurable resin 13b is injected, which can form a cladding 21 with a lower refractive index than the waveguide 20 when irradiated with light. Then, a light source 37 with a wavelength that hardens the photocurable resin 13b is prepared, and the cladding 21 may be formed by irradiating light 37a of said wavelength from the light source 37. An injection port 22 may be provided in advance in the ferrule 11 for removing the photocurable resin 13 and injecting the photocurable resin 13b.

Figure 6 shows an example of the connection configuration of an optical connector according to the fourth embodiment. Axial alignment is achieved by inserting a guide pin (not shown) into a guide hole 17 located on the ferrule end face 15, and a spring (not shown) applies pressure to the opposing optical connector plugs, forming an optical connector 200 in such a way that the detachable end faces 14 are in close contact with each other, thereby connecting the optical fibers. To reduce return loss, a refractive index matching material 18 may be applied between the detachable end faces 14 (see Figure 7).

Let's say that the diameter of a particular propagation mode field of the optical fiber 10 is, for example, 10 μm. Let's say that this is widened to, for example, 20 μm at the detachable end face 14 by the tapered waveguide 20. When axial misalignment occurs during optical connector connection, the larger the mode field diameter, the lower the loss and mode conversion caused by the axial misalignment. The relationship between the amount of axial misalignment D of the optical fiber 10 and the proportion T of propagating light that passes through without loss or mode conversion can be expressed by the following equation.

W1 and W2 are the mode field radii of the cores (waveguides 20) of the opposing ferrule end faces 15 of the two optical connector plugs 100 that make up the optical connector 200. If the optical fiber core axis misalignment when the connector is connected is 2.0 μm, the above formula shows that the transmittance is 85.2% when the mode field diameter is 10 μm, and 96.1% when the mode field diameter is 20 μm. Increasing the mode field diameter with the waveguide 20 significantly reduces loss and mode conversion.

Furthermore, because the waveguide 20 is formed with light of the same wavelength and propagation mode as the communication light emitted from the core 10a of the optical fiber 10, a tapered waveguide is created based on that propagation state. This suppresses propagation mode conversion within the tapered waveguide 20.

A second method for manufacturing the optical connector plug of the fourth embodiment will be described using Figure 11. In the second manufacturing method, the core end face of another optical fiber 30 inserted and fixed in another optical connector plug 300 for manufacturing a waveguide is placed opposite the detachable end face 14 of the ferrule 11, and light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated from the core of the optical fiber 10 onto the photocurable resin 13, while light of the same wavelength is irradiated onto the photocurable resin 13 from the core of the other optical fiber 30, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, thereby forming a tapered waveguide 20.

Specifically, another optical connector plug 300 (a connector plug for waveguide fabrication) for use in fabricating a waveguide is connected to the optical connector plug 100. The other optical connector plug 300 comprises multiple optical fibers 30, a ferrule 31, an adhesive 32, and an alignment member 36. The diameter of the core 30a of the optical fiber 30 in the other optical connector plug 300 is larger than the diameter of the core 10a of the optical fiber 10 in the optical connector plug 100. Light sources 19, 39 of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it are connected to the optical fiber 10 in the optical connector plug 100 and the optical fiber 30 in the other optical connector plug 300, respectively, and light of that wavelength is irradiated onto the photocurable resin 13 from the cores 10a, 30a of the optical fibers 10, 30.

This causes the refractive index of the light-irradiated portion of the photocurable resin 13 to increase and harden, forming a tapered waveguide 20 as shown in Figure 12. After the waveguide 20 is created, the other optical connector plug 300 and the light source 19 are removed, thereby producing the optical connector plug 100. The other optical connector plug 300 may be a high-precision connector manufactured with minimal error from the optical connector design target.

A third manufacturing method for the optical connector plug 100 of the fourth embodiment will be described using Figure 13. In this third manufacturing method, instead of using another optical connector plug 300, a condenser lens 42 is used. That is, light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is irradiated onto the photocurable resin 13 from the core of the optical fiber 10, and light of the same wavelength is irradiated onto the photocurable resin 13 from the detachable end face 14 side via the condenser lens 42, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin 13, and forming a tapered waveguide 20.

Specifically, as shown in FIG. 13, a condenser lens 42 and a light source 38 with a wavelength that increases the refractive index and hardens the photocurable resin 53 are placed near the ferrule end face 15 of the optical connector plug 100. A light source 19 with a wavelength that increases the refractive index and hardens the photocurable resin 13 is connected to the optical fiber 10 of the optical connector plug 100. Light with the wavelength is then irradiated from the core 10a of the optical fiber and the condenser lens 42, respectively, causing an increase in the refractive index and hardening of the irradiated portion of the photocurable resin 13, creating a tapered waveguide 20.

The shape of the condenser lens 42 makes it possible to adjust the mode field diameter and convergence angle of the light 38a emitted from the light source 38. By using the condenser lens 42 to irradiate the photocurable resin 13 with light that has a mode field diameter larger than the core 10a of the optical fiber 10, it is possible to create a tapered waveguide 20. After creating the waveguide 20, the condenser lens 42 and light sources 19 and 38 are removed to produce the optical connector plug 100.

In the first manufacturing method described above, the optical connector plug 100 was irradiated with light of a wavelength that increases the refractive index of the photocurable resin 13 and hardens it; in the second manufacturing method, another connector plug 300 for waveguide manufacturing was used; and in the third manufacturing method, a condenser lens 42 was used to irradiate the photocurable resin 13 with light of the wavelength. Note that the manufacturing methods for the optical connector plug 100 are not limited to these, and any method that can manufacture a tapered waveguide 20 may be used.

Using Figure 14, a method for manufacturing an optical connector plug 100 for connecting a multicore fiber will be described. Here, as an example, a method for manufacturing the optical connector plug 100 using the second manufacturing method described above will be described. Another optical connector plug 300 is connected to the optical connector plug 100. The core 30a of the optical fiber 30 of the other optical connector plug 300 has the same cutoff wavelength characteristics as the core 10a of the optical fiber 10 of the optical connector plug 100, and has a diameter larger than the diameter of the core 10a.

The optical fiber 10 of the optical connector plug 100 and the optical fiber 30 of another optical connector plug 300 are each connected to a single-core fiber 40 via a fan-out 41. A light source 19, 39 with a wavelength that increases the refractive index of the photocurable resin 13 and hardens it is connected to each single-core fiber 40, and light of that wavelength is irradiated onto the photocurable resin 13 from the cores 10a, 30a of the optical fibers 10, 30.

This causes the refractive index of the photocurable resin 13 in the irradiated area to increase and harden, forming multiple tapered waveguides 20 as shown in Figure 15. After the waveguides 20 are created, the other optical connector plugs 300 and the fan-out 41 are removed to produce the optical connector plug 100. Figures 14 and 15 show an example of a multicore fiber with four cores, but the number of cores in the multicore fiber may be two or more, and the core arrangement may be any desired arrangement.

The optical connectors of the first to fourth embodiments described above are optical connectors that include an optical connector plug, and the optical connector plug has a waveguide formed using a photocurable resin, one end of the waveguide is connected to the core end face of an optical fiber inserted and fixed into the optical connector plug, and is a waveguide that can transmit an optical signal from the core of the optical fiber to the other end, and the end face of the other end is tapered so that it is larger than the end face of the one end.

In addition, a first method for producing (manufacturing) an optical connector plug for use in the optical connectors of the first to fourth embodiments includes an optical connector plug having a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut the connection end of the optical fiber, and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out, and by irradiating the photocurable resin with light from the core of the optical fiber at a wavelength that increases the refractive index of the photocurable resin and hardens it, the irradiated portion of the photocurable resin increases the refractive index and hardens, thereby forming a tapered waveguide.

A second manufacturing method (manufacturing method) for an optical connector plug used in the optical connectors of the first to fourth embodiments is a manufacturing method for an optical connector plug used in an optical connector, wherein the optical connector plug comprises a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber, and a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out. The detachable end face of the ferrule is opposed to the core end face of another optical fiber inserted and fixed in another optical connector plug used to fabricate a waveguide, and light of a wavelength that increases the refractive index of the photocurable resin and hardens it is irradiated from the core of the optical fiber onto the photocurable resin, and light of the same wavelength is irradiated from the core of the other optical fiber onto the photocurable resin, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

A third manufacturing method (production method) for an optical connector plug used in the optical connectors of the first to fourth embodiments is a method for manufacturing an optical connector plug used in an optical connector, wherein the optical connector plug has a ferrule capable of holding a connection end of an optical fiber and photocurable resin, the connection end of the optical fiber inserted and fixed within the ferrule, photocurable resin filled within the ferrule so as to abut against the connection end of the optical fiber, and a sealant that forms the detachable end face of the ferrule and prevents the photocurable resin from leaking out. Light of a wavelength that increases the refractive index of the photocurable resin and hardens it is irradiated from the core of the optical fiber onto the photocurable resin, and light of the wavelength is irradiated onto the photocurable resin from the detachable end face side via a photomask or a focusing lens, thereby increasing the refractive index and hardening the irradiated portion of the photocurable resin, thereby forming a tapered waveguide.

The optical connector of this embodiment can provide a low-loss optical connector when used in combination with fibers that have core placement errors due to manufacturing accuracy, even in optical connectors manufactured to standardized specifications.

Furthermore, the method for manufacturing the optical connector plug of this embodiment eliminates the need for precise core alignment when combining fibers with core placement errors due to manufacturing accuracy in optical connectors manufactured to standardized specifications, making it possible to easily manufacture low-loss optical connectors, thereby reducing costs.

Furthermore, by emitting the light that causes curing from the optical fiber core, a tapered waveguide is reliably formed at the position of the light emitted from the optical fiber core. This allows the optical fiber core and tapered waveguide to be connected with low loss.

Note that this disclosure is not limited to the above embodiments, and various modifications and combinations are possible.

10, 30, 50, 70 Optical fiber 10a, 30a, 50a, 70a Core 10b, 30b, 50b, 70b Cladding 100, 500 Optical connector plug 11, 31, 51, 71 Ferrule 12, 32 Adhesive 13, 13b, 53 Photocurable resin 14, 54 Sealant (detachable end face)
15, 55 Ferrule end face 16, 36 Arrangement member
18 Refractive index matching material 19, 37, 38, 39, 69, 88, 89 Light source 20, 60 Waveguide (self-forming optical waveguide)
200, 600 Optical connector 21 Cladding 22 Inlet 300, 700 Other optical connector plug (connector plug for waveguide fabrication)
37a 38a, 88a Light 40, 80 Single-core fiber 41, 61 Fan-out 42, 62 Photomask, condenser lens 52, 72 Plug frame 56, 76 Knob 57, 77 Flange 58, 78 Spring 59, 79 Stop ring 63 Sleeve

Claims (8)

An optical connector including an optical connector plug,
The optical connector plug comprises:
a waveguide formed using a photocurable resin;
The waveguide has one end connected to the core end face of an optical fiber inserted and fixed in the optical connector plug, and is capable of transmitting an optical signal from the core of the optical fiber to the other end, and the end face of the other end is tapered and larger than the end face of the one end. The optical connector plug comprises:
a ferrule capable of holding the connection end of the optical fiber and the photocurable resin;
The optical connector according to claim 1 , further comprising: a sealant that forms a detachable end face of the ferrule and prevents the photocurable resin from leaking out. A method for manufacturing an optical connector plug for use in an optical connector, comprising:
The optical connector plug comprises:
a ferrule capable of holding a connection end of an optical fiber and a photocurable resin;
a connection end of the optical fiber inserted and fixed in the ferrule;
a photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber;
a sealing material that forms a detachable end surface of the ferrule and prevents the photocurable resin from leaking out,
A method for manufacturing an optical connector plug, comprising: irradiating the photocurable resin with light of a wavelength that increases the refractive index of the photocurable resin and hardens the resin from the core of the optical fiber, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening the resin, thereby forming a tapered waveguide. After forming the waveguide, the photocurable resin is removed from a portion where the waveguide is not formed, and another photocurable resin capable of forming a clad having a refractive index lower than that of the waveguide is filled into the ferrule;
4. The method for manufacturing an optical connector plug according to claim 3, wherein the cladding is formed around the waveguide by irradiating the other photocurable resin with light of a wavelength that causes the other photocurable resin to harden from the detachable end face side. A method for manufacturing an optical connector plug for use in an optical connector, comprising:
The optical connector plug comprises:
a ferrule capable of holding a connection end of an optical fiber and a photocurable resin;
a connection end of the optical fiber inserted and fixed in the ferrule;
a photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber;
a sealing material that forms a detachable end surface of the ferrule and prevents the photocurable resin from leaking out,
a core end face of another optical fiber inserted and fixed in another optical connector plug for fabricating a waveguide is arranged opposite the detachable end face of the ferrule;
A method for manufacturing an optical connector plug, comprising: irradiating the photocurable resin with light of a wavelength that increases the refractive index of the photocurable resin and hardens it from the core of the optical fiber; and irradiating the photocurable resin with light of the same wavelength from the core of the other optical fiber, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening it, thereby forming a tapered waveguide. The method for manufacturing an optical connector plug according to claim 5 , wherein the diameter of the core of the other optical fiber is larger than the diameter of the core of the optical fiber. A method for manufacturing an optical connector plug for use in an optical connector, comprising:
The optical connector plug comprises:
a ferrule capable of holding a connection end of an optical fiber and a photocurable resin;
a connection end of the optical fiber inserted and fixed in the ferrule;
a photocurable resin filled in the ferrule so as to abut against the connection end of the optical fiber;
a sealing material that forms a detachable end surface of the ferrule and prevents the photocurable resin from leaking out,
A method for manufacturing an optical connector plug, comprising: irradiating the photocurable resin with light of a wavelength that increases the refractive index of the photocurable resin and hardens it from the core of the optical fiber; and irradiating the photocurable resin with light of the wavelength from the detachable end face side through a photomask or a focusing lens, thereby increasing the refractive index of the irradiated portion of the photocurable resin and hardening it, thereby forming a tapered waveguide. The method for manufacturing an optical connector plug described in any one of claims 4 to 7, wherein the light irradiated from the core of the optical fiber to the photocurable resin has the same wavelength and propagation mode as the communication light to be transmitted through the optical connector.