WO2018074010A1 - Optical transmission module - Google Patents

Abstract

The optical transmission module according to the present invention is provided with: a signal light generating unit for generating first signal light and second signal light; and an optical multiplexer for multiplexing the first signal light and the second signal light, the optical multiplexer being optically coupled to the signal light generating unit. The optical multiplexer has: a light selection filter for multiplexing the first signal light and the second signal light by reflecting the first signal light and transmitting the second signal light; and an etalon for compensating for wavelength dispersion of the first signal light and/or the second signal light after multiplexing, the etalon being disposed on an optical path between the light selection filter and a light emission point of the optical multiplexer.

Description

Optical transmission module

The present invention relates to an optical transmission module.
This application claims priority based on Japanese Patent Application No. 2016-203577 filed on Oct. 17, 2016, and incorporates all the content described in the above Japanese application.

Patent Document 1 discloses a wavelength division multiplexing optical transmission module including a plurality of semiconductor laser elements. In this optical transmission module, of the four signal lights having different wavelengths output from the four semiconductor laser elements, the two signal lights are combined with each other by the wavelength filter, and the other two signal lights are different wavelength filters. Are combined with each other. Then, after the polarization direction of one combined light is rotated, the one combined light and the other combined light are combined by a polarization beam combiner.

Patent Document 2 discloses a wavelength division multiplexing optical transmission module including a plurality of semiconductor laser elements. In this optical transmission module, four signal lights having different wavelengths output from four semiconductor laser elements are combined with each other in a WDM block having three wavelength filters.

Patent Document 3 discloses a chromatic dispersion compensation device. This chromatic dispersion compensation device has a flat plate-like etalon in which reflection films each having a predetermined light reflectance are formed on both surfaces. The reflective film has a filter characteristic in which the transmittance changes sharply for light in a certain wavelength range. In this chromatic dispersion compensating device, the reflectance is varied according to the incident angle of light by using such filter characteristics.

Patent Document 4 discloses a tunable dispersion compensator. This tunable dispersion compensator has a first etalon whose group delay characteristic with respect to a wavelength within the use wavelength range can be approximated by a downward convex quadratic function, and a group delay characteristic with a convex 2 upward with respect to the wavelength within the use wavelength range. A second etalon that can be approximated by a quadratic function, a Peltier element provided on the reflection side of the first etalon, and a power source and a temperature control unit that control heating or cooling of the Peltier element. By heating or cooling the Peltier element controlled by the temperature control unit, the optical thickness of the etalon plate is changed to shift the wavelength of the group delay characteristic of the first etalon, and by the passage of the optical signal, the first and second etalon Each group delay characteristic is synthesized and variable dispersion compensation is performed.

Patent Document 5 discloses an optical dispersion compensator. This optical dispersion compensator includes an optical component having a reflector and a filter layer arranged in parallel with a light transmission layer interposed therebetween.

Japanese Patent Laying-Open No. 2015-096944 U.S. Pat. No. 09350454 JP 2007-298968 A JP 2003-264505 A JP 2002-267834 A

An optical transmission module according to an embodiment is optically coupled to a signal light generation unit that generates a first signal light and a second signal light, and the signal light generation unit, and combines the first signal light and the second signal light. And an optical multiplexer that waves. The optical multiplexer reflects the first signal light and transmits the second signal light, thereby combining the first signal light and the second signal light, and the light of the light selection filter and the optical multiplexer. And an etalon for compensating for chromatic dispersion of at least one of the first signal light and the second signal light after being combined, which is disposed on the optical path between the emission point.

FIG. 1 is a plan view showing the internal structure of the optical transmission module according to the first embodiment. FIG. 2 is a side view schematically showing a part of the internal structure of the optical transmission module. FIG. 3 is an enlarged plan view showing the configuration of the polarization beam combiner. FIG. 4 is a graph showing an example of the group delay characteristic of the etalon. FIG. 5 is a graph showing an example of wavelength dispersion characteristics of an etalon. FIG. 6 is a graph showing an example of wavelength dispersion characteristics of an etalon. FIG. 7 is a graph showing an example of wavelengths used in the wavelength division multiplexing optical communication system. FIG. 8 is a plan view showing the configuration of the polarization beam combiner according to the first modification. FIG. 9 is a plan view showing the configuration of the polarization beam combiner according to the second modification. FIG. 10 is a plan view showing the internal structure of the optical transmission module according to the second embodiment of the present invention. FIG. 11 is an enlarged plan view showing the configuration of the WDM block. FIG. 12 is a plan view showing a configuration of a WDM block according to the third modification. FIG. 13 is a plan view showing a configuration of a WDM block according to a fourth modification.

With the recent increase in capacity of optical communication, so-called wavelength multiplexing optical communication technology for transmitting a plurality of signal lights having different wavelengths from each other is used. The optical transmission module combines and outputs a plurality of signal lights respectively output from the plurality of light emitting elements. As a multiplexing method, for example, there are a method using a polarization combining filter as described in Patent Document 1 and a method using a wavelength filter as described in Patent Document 2.

On the other hand, it is also considered that the wavelength of upstream signal light and the wavelength of downstream signal light are made different from each other in order to adapt to further increase in capacity of optical communication. In the conventional optical communication system, the upstream signal light and the downstream signal light use wavelengths such as 1295 nm, 1300 nm, 1305 nm, and 1310 nm that are close to the zero dispersion wavelength (1300 to 1324 nm) of the optical fiber (IEEE 802.3). Transmission of about 20 km is possible while suppressing deterioration of the waveform due to dispersion. However, if the wavelength differs between the upstream signal light and the downstream signal light, inevitably, at least one of the upstream signal light and the downstream signal light is separated from the zero dispersion wavelength. Therefore, the optical transmission waveform after transmission is distorted due to the influence of chromatic dispersion caused by the optical fiber. For example, when the signal light has a wavelength of 1340 nm, 1345 nm, 1350 nm, and 1355 nm and is transmitted for 20 km, the wavelength dispersion by the optical fiber is 50 ps / nm to 90 ps / nm.

It is also conceivable to compensate for chromatic dispersion using a dispersion compensator as described in Patent Documents 3 to 5. However, as the optical communication capacity increases, the number of optical components such as light emitting elements increases. On the other hand, since the dimensions of the optical transmission module are determined by the standard, it is not preferable to increase the number of components of the optical transmission module.

Therefore, it is an object of the present disclosure to provide an optical transmission module that can compensate for chromatic dispersion caused by an optical fiber while suppressing an increase in the number of components of the optical transmission module.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described. An optical transmission module according to an embodiment is optically coupled to a signal light generation unit that generates a first signal light and a second signal light, and the signal light generation unit, and combines the first signal light and the second signal light. And an optical multiplexer that waves. The optical multiplexer reflects the first signal light and transmits the second signal light, thereby combining the first signal light and the second signal light, and the light of the light selection filter and the optical multiplexer. And an etalon for compensating for chromatic dispersion of at least one of the first signal light and the second signal light after being combined, which is disposed on the optical path between the emission point.

In this optical transmission module, the etalon for compensating the chromatic dispersion of at least one of the first signal light and the second signal light after the combination includes an optical selection filter in the optical multiplexer and a light emission point of the optical multiplexer. Is provided on the optical path between. Thereby, chromatic dispersion due to the optical fiber can be suitably compensated. By providing the etalon as a part of the optical multiplexer in this way, an increase in the number of parts of the optical transmission module can be suppressed as compared with the case where the dispersion compensator is arranged as an independent component in the optical transmission module. Can do.

In the above optical transmission module, the optical multiplexer further includes a light transmissive member, the light selective filter is provided on the surface of the light transmissive member, and the etalon is a light selective filter on the surface of the light transmissive member. They may be provided at different positions. Thereby, the light transmissive member of the optical multiplexer, the optical selection filter, and the etalon are integrated, and can be easily arranged in the optical transmission module.

In the above optical transmission module, the light transmissive member has a first surface and a second surface that face each other, a light selection filter is provided on the first surface, an etalon is provided on the second surface, The first signal light and the second signal light output from the light generation unit may be incident on the first surface, and the combined first signal light and second signal light may be emitted from the second surface.

The optical transmission module further includes a base member having a flat mounting surface, and each optical component and optical multiplexer constituting the signal light generation unit are two-dimensionally arranged along the mounting surface, The optical axes of the first signal light and the second signal light output from the light generation unit may be parallel to each other. Thereby, the optical transmission module can be reduced in size with a simple structure.

In the above optical transmission module, even if the etalon or another etalon for compensating for dispersion of the first signal light is arranged on the optical path of the first signal light before being combined with the second signal light. Good. Thereby, the dispersion compensation amounts of the first signal light and the second signal light can be made different from each other. In this case, the optical multiplexer may further include a light transmissive member, and the etalon and the another etalon may be arranged side by side on the same surface of the light transmissive member. Thereby, the said etalon and said another etalon can be easily affixed on a light transmissive member.

In the above optical transmission module, the polarization direction of the first signal light and the polarization direction of the second signal light may be different from each other, and the light selection filter may be a polarization beam synthesis filter. Alternatively, the wavelength of the first signal light and the wavelength of the second signal light may be different from each other, and the light selection filter may be a wavelength filter.

As described above, according to the optical transmission module according to the present disclosure, it is possible to compensate for chromatic dispersion caused by the optical fiber while suppressing an increase in the number of components of the optical transmission module.

[Details of the embodiment of the present invention]
A specific example of the optical transmission module according to the embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to these exemplifications, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and redundant descriptions are omitted.

(First embodiment)
FIG. 1 is a plan view showing the internal structure of the optical transmission module 1A according to the first embodiment. FIG. 2 is a side view schematically showing a part of the internal structure of the optical transmission module 1A. 1 A of optical transmission modules are TOSA (Transmitter Optical SubAssembly) provided with the rectangular parallelepiped housing | casing 2 and the cylindrical optical coupling part 3 which has a flange.

A signal light generator 10A and a polarization beam combiner 20A are provided inside the optical transmission module 1A. The signal light generating unit 10A includes N (N is an integer of 2 or more) light emitting units 11a to 11d, N first lenses 12a to 12d, N second lenses 15a to 15d, a first WDM filter 16, a first WDM filter 16, and a first WDM filter 16. 2 WDM filter 17, mirror 18, and wave plates 19 a and 19 b are included. In one example, the optical transmission module 1A is a four-channel (N = 4) light emitting module. The light emitting units 11a to 11d, the first lenses 12a to 12d, the second lenses 15a to 15d, the first WDM filter 16, the second WDM filter 17, the mirror 18, the wave plates 19a and 19b, and the polarization beam combiner 20A Are mounted on the flat mounting surface 7a of the base member 7 provided inside the two, and are two-dimensionally arranged along the mounting surface 7a. A Peltier element as a temperature control element is provided between the back surface of the base member 7 and the bottom surface of the housing 2. A carrier member 13 and N semiconductor light receiving elements (photodiodes) 14a to 14d are further provided on the mounting surface 7a inside the optical transmission module 1A.

In the optical transmission module 1A, the light emitting units 11a to 11d functioning as light sources are independently driven, and the light emitting units 11a to 11d individually output the signal lights La to Ld. Drive signals to the light emitting units 11a to 11d are provided from the outside of the optical transmission module 1A. The signal lights La to Ld are light modulated according to the drive signal. Each of the light emitting units 11a to 11d includes a semiconductor optical integrated element 9 in which a laser diode and a semiconductor optical modulator are integrated. Each wavelength of the signal light La to Ld is, for example, a 1.3 μm band and is different from each other. In one example, the wavelengths of the signal lights La to Ld are 1345 nm, 1340 nm, 1335 nm, and 1330 nm, respectively.

The first lenses 12a to 12d are optically coupled to the light emitting portions 11a to 11d, respectively. The signal lights La to Ld output from the light emitting units 11a to 11d are input to the first lenses 12a to 12d, respectively. The distance between the semiconductor optical integrated element 9 of each light emitting part 11a to 11d and the corresponding first lens 12a to 12d is longer than the focal length of the first lens 12a to 12d. Therefore, as shown in FIG. 2, the first lenses 12a to 12d convert the signal lights La to Ld, which are divergent lights, into convergent lights.

The carrier member 13 is a rectangular parallelepiped member extending in the direction intersecting with each optical axis of the signal light La to Ld as a longitudinal direction, and on the optical path between the first lens 12a to 12d and the second lens 15a to 15d. Has been placed. As shown in FIG. 2, the carrier member 13 includes a dielectric multilayer film (beam splitter) 13b that is inclined with respect to the optical axes of the signal lights La to Ld. The dielectric multilayer film 13b When the signal lights La to Ld pass through, a part of each of the signal lights La to Ld is branched. The semiconductor light receiving elements 14a to 14d are arranged on the mounting surface 13a of the carrier member 13, and detect the light intensities of the signal lights La to Ld by receiving a part of the branched signal lights La to Ld. The semiconductor light receiving elements 14a to 14d are mounted on the carrier member 13 so that their back surfaces and the mounting surface 13a of the carrier member 13 face each other.

The second lenses 15a to 15d are optically coupled to the first lenses 12a to 12d with the carrier member 13 interposed therebetween. The signal lights La to Ld output from the first lenses 12a to 12d pass through the carrier member 13, form a beam waist, and then enter the second lenses 15a to 15d while spreading again. The distances between the second lenses 15a to 15d and the beam waists of the signal lights La to Ld coincide with the focal lengths of the second lenses 15a to 15d. Therefore, the second lenses 15a to 15d convert the signal lights La to Ld that are incident while spreading into collimated light.

The mirror 18 is optically coupled to the second lenses 15a and 15b. The light reflecting surface of the mirror 18 is located on the optical axes of the second lenses 15a and 15b, and is inclined with respect to these optical axes. The mirror 18 reflects the signal lights La and Lb in a direction crossing these optical axes. The first WDM filter 16 is optically coupled to the second lens 15c. The wavelength selection surface of the first WDM filter 16 is located on the optical axis of the second lens 15c and is inclined with respect to the optical axis. The first WDM filter 16 transmits the signal light Lc from the second lens 15 c and reflects the signal light La reflected by the mirror 18. Thereby, the optical paths of the signal lights La and Lc coincide with each other, and the signal lights La and Lc are combined with each other to become the signal light Le (first signal light). The second WDM filter 17 is optically coupled to the second lens 15d. The wavelength selection surface of the second WDM filter 17 is located on the optical axis of the second lens 15d and is inclined with respect to the optical axis. The second WDM filter 17 transmits the signal light Ld from the second lens 15d and reflects the signal light Lb reflected by the mirror 18. Thereby, the optical paths of the signal lights Lb and Ld coincide with each other, and the signal lights Lb and Ld are combined with each other to become the signal light Lf (second signal light).

The wave plate 19 a is optically coupled to the first WDM filter 16. The wave plate 19 b is optically coupled to the second WDM filter 17. The wave plate 19a rotates the polarization direction of the signal light Le by a certain angle (for example, 45 °). The wave plate 19b rotates the polarization direction of the signal light Lf by a certain angle (for example, 45 °) in the opposite direction to the wave plate 19a. As a result, the polarization direction of the signal light Le and the polarization direction of the signal light Lf are different from each other. In one example, the polarization direction of the signal light Le and the polarization direction of the signal light Lf are different from each other by 90 °. Thereafter, the signal lights Le and Lf are output from the signal light generator 10A along two optical axes that are included in an imaginary plane parallel to the mounting surface 7a and parallel to each other.

The polarization beam combiner 20A is an example of an optical multiplexer in the present embodiment. The polarization beam combiner 20A is optically coupled to the signal light generator 10A and combines the signal light Le and Lf to generate the signal light Lg. The signal light Lg is output from the polarization beam combiner 20 </ b> A and output to the outside of the housing 2 through a window provided on the side wall 2 </ b> A of the housing 2.

The optical coupling unit 3 is a coaxial module having a lens 52 (see FIG. 2) and a fiber stub. The lens 52 is optically coupled to the polarization beam combiner 20A. The fiber stub holds the optical fiber F (see FIG. 2). The lens 52 collects the signal light Lg and guides it to the end face of the optical fiber F. The optical coupling unit 3 is aligned with the optical axis of the signal light Lg and then fixed to the side wall 2A of the housing 2 by welding. The optical coupling unit 3 may further include an optical isolator that blocks light from the outside in addition to the lens 52 and the fiber stub.

FIG. 3 is an enlarged plan view showing the configuration of the polarization beam combiner 20A. The polarization beam combiner 20 </ b> A includes a light transmissive member 21, an antireflection film 22, a polarization wave synthesis filter 23 (light selection filter), a light reflection film 24, a light reflection film 25, an antireflection film 26, and an etalon 27. The light transmissive member 21 is a flat member and is made of a material that is transparent with respect to the wavelengths of the signal lights La to Ld, such as glass. The light transmissive member 21 has a first surface 21a and a second surface 21b that face each other in the thickness direction. The first surface 21a and the second surface 21b are parallel to each other and are flat. The first surface 21a and the second surface 21b are arranged perpendicular to the mounting surface 7a and are inclined with respect to the optical axes of the signal lights Le and Lf incident on the polarization beam combiner 20A.

The first surface 21a includes three regions 21a1, 21a2, and 21a3. The regions 21a1, 21a2, and 21a3 are arranged in this order in a direction parallel to the mounting surface 7a. An antireflection film 22 is provided on the region 21a1. A polarization beam synthesis filter 23 is provided on the region 21a2. A light reflecting film 24 is provided on the region 21a3.

The second surface 21b includes three regions 21b1, 21b2, and 21b3. The regions 21b1, 21b2, and 21b3 are arranged in this order in a direction parallel to the mounting surface 7a. The region 21b1 is opposed to the region 21a1, the region 21b2 is opposed to the region 21a2, and the region 21b3 is opposed to the region 21a3. A light reflecting film 25 is provided on the region 21b1. An antireflection film 26 is provided on the region 21b2 and the region 21b3. Further, an etalon 27 is provided on the light reflection film 25 and the antireflection film 26 extending from the region 21b1 to the region 21b2. Thus, on the surface of the light transmissive member 21, the polarization combining filter 23 and the etalon 27 are provided at different positions.

The antireflection film 22 transmits the signal light Le incident from the signal light generation unit 10 </ b> A toward the inside of the light transmissive member 21. The light reflection film 25 totally reflects the signal light Le that has passed through the antireflection film 22. The polarization beam combining filter 23 reflects the signal light Le that has arrived from the light reflecting film 25, and simultaneously transmits the signal light Lf incident from the signal light generation unit 10A and having a polarization direction different from that of the signal light Le. Permeate toward the inside of the. At this time, the optical axis of the signal light Le and the optical axis of the signal light Lf coincide with each other. As a result, the signal lights Le and Lf are combined to generate the signal light Lg. The antireflection film 26 on the region 21 b 2 transmits the signal light Lg that has arrived from the polarization beam combining filter 23 toward the outside of the light transmissive member 21. Since the etalon 27 is provided outside the antireflection film 26 on the region 21 b 2, the signal light Lg is incident on the etalon 27.

The etalon 27 is disposed on the optical path between the polarization beam combining filter 23 and the light output point P1 of the polarization beam combiner 20A. The etalon 27 is provided on a light transmissive plate member 27a (for example, a quartz plate), a partial reflection film 27b provided on one plate surface of the plate member 27a, and the other plate surface of the plate member 27a. And a total reflection film 27c. The etalon 27 has a periodic group delay characteristic corresponding to the wavelength of incident light, and the chromatic dispersion characteristic obtained by wavelength differentiation of the group delay characteristic also changes periodically with respect to the wavelength. Using this wavelength dispersion characteristic, it is possible to compensate for the wavelength dispersion of the combined signal lights Le and Lf, that is, the signal light Lg.

Here, the dispersion compensation action of the etalon 27 will be described in detail. In the etalon 27, the incident signal light Lg is multiple-reflected between the partial reflection film 27b and the total reflection film 27c. The light reflectivity of the total reflection film 27c is 100%, and the light reflectivity of the partial reflection film 27b is about several% to several tens%.

The signal light Lg enters from the partial reflection film 27b side, is totally reflected by the total reflection film 27c, a part of the reflected light is transmitted to the outside of the etalon 27, and the remaining signal light Lg is further totally reflected by the total reflection film 27c. Is done. Thus, since the input signal light Lg is always totally reflected by the total reflection film 27c, all energy of the signal light Lg is returned to the input side. However, the signal light Lg has a periodic phase delay in a wavelength period determined by the optical thickness of the plate-like member 27a, that is, a group delay characteristic with respect to the wavelength. In other words, the etalon 27 has a function as an all-pass filter that reflects all the signal light Lg and changes only the phase. The thickness of the plate member 27a is, for example, 100 μm.

FIG. 4 is a graph showing an example of the group delay characteristic of the etalon 27. In FIG. 4, the horizontal axis indicates the wavelength, and the vertical axis indicates the group delay amount. As shown in FIG. 4, the etalon 27 has a periodic group delay characteristic with a certain wavelength period T1. 5 and 6 are graphs showing an example of the chromatic dispersion characteristic of the etalon 27 obtained by wavelength differentiation of the group delay characteristic shown in FIG. 5 and 6, the horizontal axis indicates the wavelength, and the vertical axis indicates the chromatic dispersion amount. As shown in FIGS. 5 and 6, the etalon 27 has a periodic chromatic dispersion characteristic at a certain wavelength period T1. On the other hand, FIG. 7 is a graph showing examples of wavelengths used in the wavelength division multiplexing optical communication system. In FIG. 7, the horizontal axis indicates the wavelength (unit: nm), and the vertical axis indicates the light intensity (unit: dB). As shown in FIG. 7, for example, a wavelength band shorter than the zero dispersion wavelength band A0 (A1 in the figure, for example, 1260 nm to 1300 nm) is used for upstream signal light, and zero for downstream signal light. A wavelength band longer than the dispersion wavelength band A0 (A2 in the figure, eg, 1320 nm to 1360 nm) is used. Then, the wavelengths of the upstream signal light are λa ₁ , λa ₂ , λa ₃ , and λa ₄ (λa ₁ > λa ₂ > λa ₃ > λa ₄ ), and the wavelengths of the downstream signal light are λb ₁ , λb ₂ , λb ₃ and λb ₄ (λb ₁ > λb ₂ > λb ₃ > λb ₄ ). At this time, the wavelengths λa ₁ , λa ₂ , λa ₃ , and λa ₄ are included in each of the plurality of wavelength bands A3 shown in FIG. 5, and the wavelength is set in each of the plurality of wavelength bands A4 shown in FIG. The thickness of the plate-like member 27a is determined so that each of λb ₁ , λb ₂ , λb ₃ , and λb ₄ is included.

Each of the plurality of wavelength bands A3 indicates a wavelength band between each of the plurality of peak wavelengths λp in the wavelength dispersion characteristic and the wavelength λ0 where the wavelength dispersion adjacent to the short wavelength side is zero. In other words, each of the plurality of wavelength bands A3 is a portion where the amount of chromatic dispersion is positive on the short wavelength side of the plurality of peak waveforms in the chromatic dispersion characteristics. Each of the plurality of wavelength bands A4 indicates a wavelength band between each of the plurality of bottom wavelengths λb in the wavelength dispersion characteristic and the wavelength λ0 adjacent to the longer wavelength side where the chromatic dispersion amount is 0. In other words, each of the plurality of wavelength bands A4 is a portion where the amount of chromatic dispersion is negative on the long wavelength side of the plurality of bottom waveforms in the chromatic dispersion characteristics.

With the above configuration, dispersion compensation of the signal light Lg including the plurality of signal lights La to Ld having different wavelengths can be suitably performed. Dispersion compensation of the signal light Lg including the plurality of signal lights La to Ld having different wavelengths can be collectively performed by one etalon 27.

The chromatic dispersion after 80 km transmission of the conventional C band (1.55 μm band) is 1600 ps / nm. On the other hand, for example, the chromatic dispersion after 20 km transmission at a wavelength of 1340 nm is 50 ps / nm, and the chromatic dispersion after 20 km transmission at a wavelength of 1280 nm is −50 ps / nm. Thus, when compensating for a relatively small amount of chromatic dispersion, the dispersion compensation action by the etalon 27 is particularly effective.

In the example shown in FIG. 7, a peak waveform including a wavelength band A3 including a certain wavelength (for example, λa ₁ ) and a peak waveform including a wavelength band A3 including a wavelength adjacent to the wavelength (for example, λa ₂ ) are mutually They may be adjacent or not adjacent to each other. Similarly, in the example shown in FIG. 7, a peak waveform including a wavelength band A4 including a certain wavelength (for example, λb ₁ ) and a wavelength band A4 including a wavelength adjacent to the wavelength (for example, λb ₂ ). May be adjacent to each other or may not be adjacent to each other.

Refer to FIG. 3 again. The signal light Lg that has reached the etalon 27 is reflected by the etalon 27 and reaches the light reflecting film 24. The light reflecting film 24 totally reflects the signal light Lg that has arrived from the etalon 27. The antireflection film 26 on the region 21b3 transmits the signal light Lg that has arrived from the light reflection film 24. Accordingly, the signal light Lg is emitted from the second surface 21b toward the outside of the polarization beam combiner 20A. The light emission point P1 described above is located on the outer surface of the antireflection film 26 on the region 21b3.

The antireflection films 22 and 26, the light reflection films 24 and 25, and the polarization wave synthesis filter 23 are made of, for example, a dielectric multilayer film. The dielectric multilayer film may be formed on the surface of the light transmissive member 21 or may be attached to the surface of the light transmissive member 21. The etalon 27 is pasted on the light reflection film 25 and the antireflection film 26 after the partial reflection film 27b and the total reflection film 27c are formed on both plate surfaces of the plate member 27a.

The effects obtained by the optical transmission module 1A of the present embodiment described above will be described. In the optical transmission module 1A of the present embodiment, the etalon 27 for compensating the chromatic dispersion of the combined signal light Le and signal light Lf (that is, the signal light Lg) is a polarization combining filter 23 in the polarization combiner 20A. And a light exit point P1 of the polarization beam combiner 20A. Thereby, chromatic dispersion due to the optical fiber can be suitably compensated. Thus, by providing the etalon 27 as a part of the polarization beam combiner 20A, the number of components of the optical transmission module 1A is increased as compared with the case where the dispersion compensator is disposed as an independent component in the optical transmission module. Can be suppressed. Furthermore, since it is easy to make the optical axis direction on the input side and the optical axis direction on the output side parallel to each other, replacement (implementation) from a conventional polarization beam combiner is easy.

As in the present embodiment, the polarization beam combiner 20 </ b> A further includes the light transmissive member 21, the polarization beam combining filter 23 is provided on the surface of the light transmissive member 21, and the etalon 27 is the light transmissive member 21. It may be provided at a position different from the polarization combining filter 23 on the surface. As a result, the light transmissive member 21, the polarization beam combining filter 23, and the etalon 27 of the polarization beam combiner 20A can be integrated and easily arranged in the optical transmission module 1A.

As in the present embodiment, the optical transmission module 1A further includes a base member 7 having a flat mounting surface 7a, and each optical component and the polarization beam combiner 20A constituting the signal light generation unit 10A are provided on the mounting surface 7a. The optical axes of the signal light Le and the signal light Lf output from the signal light generation unit 10A may be parallel to each other. Thereby, the optical transmission module 1A can be reduced in size with a simple structure.

(First modification)
FIG. 8 is a plan view showing a configuration of a polarization beam combiner 20B according to a first modification of the first embodiment. The polarization beam combiner 20B includes a light transmissive member 21, an antireflection film 22, a polarization wave synthesis filter 23 (light selection filter), a light reflection film 24, an antireflection film 28, a polarization wave synthesis filter 29, an antireflection film 30, It has etalons 31 and 32. Among these, the configurations of the light transmissive member 21, the antireflection film 22, the polarization synthesis filter 23, and the light reflection film 24 are the same as those in the above embodiment.

The antireflection film 28, the polarization synthesis filter 29, and the antireflection film 30 are provided on the region 21b1, the region 21b2, and the region 21b3, respectively. The etalon 31 is provided on the antireflection film 28. The etalon 32 is provided on the polarization combining filter 29. Thus, also in this modification, the polarization beam combining filter 23 and the etalons 31 and 32 are provided at different positions on the surface of the light transmissive member 21.

In the present modification, the antireflection film 22 transmits the signal light Le incident from the signal light generation unit 10 </ b> A toward the inside of the light transmissive member 21. The antireflection film 28 transmits the signal light Le that has passed through the antireflection film 22. Since the etalon 31 is provided outside the antireflection film 28, the signal light Le enters the etalon 31. The etalon 31 is disposed on the optical path between the light incident point P2 of the signal light Le (the outer surface of the antireflection film 22) and the polarization beam combining filter 23 in the polarization beam combiner 20B. The configuration of the etalon 31 is the same as that of the etalon 27 described above except for the thickness of the plate member. The etalon 31 has a periodic chromatic dispersion characteristic corresponding to the wavelength of incident light, and can compensate for the chromatic dispersion of the signal light Le.

The signal light Le that has reached the etalon 31 is reflected by the etalon 31, passes through the antireflection film 28 again, and reaches the polarization combining filter 23. The polarization beam combining filter 23 reflects the signal light Le and simultaneously transmits the signal light Lf incident from the signal light generation unit 10 </ b> A and having a polarization direction different from that of the signal light Le toward the inside of the light transmissive member 21. By combining these, The polarization beam combining filter 29 reflects the signal light Le and transmits the signal light Lf out of the signal light Le and Lf arrived from the polarization beam combining filter 23. Since the etalon 32 is provided outside the polarization combining filter 29, the signal light Lf is incident on the etalon 32.

The etalon 32 is disposed on the optical path between the polarization beam combining filter 23 and the light output point P3 of the polarization beam combiner 20B. The configuration of the etalon 32 is the same as that of the etalon 27 described above except for the thickness of the plate member. The etalon 32 has a periodic chromatic dispersion characteristic corresponding to the wavelength of incident light, and can compensate for the chromatic dispersion of the signal light Lf.

The signal light Lf that has reached the etalon 32 is reflected by the etalon 32, and is combined again with the signal light Le to become the signal light Lg, which reaches the light reflecting film 24. The light reflecting film 24 totally reflects the signal light Lg. The antireflection film 30 transmits the signal light Lg that has arrived from the light reflection film 24 toward the outside of the light transmissive member 21. Thereby, the signal light Lg is emitted from the second surface 21b. The light emission point P3 described above is located on the outer surface of the antireflection film 30.

In this modification, in addition to the etalon 32 for compensating for the dispersion of the signal light Lf disposed on the optical path between the polarization beam combining filter 23 and the light emission point P3, before the multiplexing with the signal light Lf. An etalon 31 for compensating for the dispersion of the signal light Le is also disposed on the optical path of the signal light Le. In this way, the etalon 31 for dispersion compensation of the signal light Le and the etalon 32 for dispersion compensation of the signal light Lf are separately provided, so that the dispersion compensation amounts of the signal light Le and Lf are made different from each other. be able to. Therefore, even when the chromatic dispersion of the signal light Le and the chromatic dispersion of the signal light Lf are greatly different, the compensation amount can be optimized for these chromatic dispersions.

As in this modification, the etalon 31 and the etalon 32 may be arranged side by side on the same surface (second surface 21b) of the light transmissive member 21. Accordingly, the etalons 31 and 32 can be easily attached to the light transmissive member 21.

(Second modification)
FIG. 9 is a plan view showing a configuration of a polarization beam combiner 20C according to a second modification of the first embodiment. The polarization synthesizer 20C is different from the polarization synthesizer 20A of the above embodiment in that the light reflection film 25 is not provided and the antireflection film 26 extends to the region 21b1 instead.

The signal light Le passes through the antireflection film 22 and enters the light transmissive member 21, then passes through the antireflection film 26 and reaches the etalon 27. At this time, the etalon 27 compensates for a part of the chromatic dispersion of the signal light Le. Thereafter, the signal light Le is reflected by the etalon 27 and reaches the polarization beam combining filter 23. The polarization combining filter 23 reflects the signal light Le and simultaneously transmits the signal light Lf incident from the signal light generation unit 10 </ b> A toward the inside of the light transmissive member 21. As a result, the signal lights Le and Lf are combined to generate the signal light Lg. The signal light Lg passes through the antireflection film 26 and reaches the etalon 27. At this time, the etalon 27 compensates the remaining chromatic dispersion of the signal light Le included in the signal light Lg and the chromatic dispersion of the signal light Lf included in the signal light Lg. Thereafter, the signal light Lg is reflected by the etalon 27, is reflected again by the light reflecting film 24, passes through the antireflection film 26, and is output to the outside of the polarization beam combiner 20C.

In this modification, an etalon 27 for compensating for dispersion of the signal light Lg disposed on the optical path between the polarization beam combining filter 23 and the light emission point P1 is a signal before being combined with the signal light Lf. It is also arranged on the optical path of the light Le. Thereby, the signal light Le passes through the etalon 27 twice, and the dispersion compensation amounts of the signal light Le and Lf can be made different from each other. Therefore, even when the chromatic dispersion of the signal light Le and the chromatic dispersion of the signal light Lf are greatly different, the compensation amount can be optimized for these chromatic dispersions. The configuration of this modification is particularly effective when the wavelength interval between the signal light Le and the zero dispersion wavelength is longer than the wavelength interval between the signal light Lf and the zero dispersion wavelength.

(Second Embodiment)
FIG. 10 is a plan view showing the internal structure of the optical transmission module 1B according to the second embodiment of the present invention. The optical transmission module 1 </ b> B is a TOSA including a housing 2 and an optical coupling unit 3. Inside the optical transmission module 1B, a signal light generation unit 10B and a WDM block 20D are provided. The signal light generation unit 10B includes N (N is an integer of 2 or more) light emitting units 11a to 11d, N first lenses 12a to 12d, and N second lenses 15a to 15d. In one example, the optical transmission module 1B is a four-channel (N = 4) light emitting module. The light emitting units 11a to 11d, the first lenses 12a to 12d, the second lenses 15a to 15d, and the WDM block 20D are mounted on the flat mounting surface 7a of the base member 7, and two-dimensionally along the mounting surface 7a. Has been placed. Similar to the first embodiment, a carrier member 13 and N semiconductor light receiving elements (photodiodes) 14a to 14d are further provided on the mounting surface 7a inside the optical transmission module 1B. The configurations of the light emitting units 11a to 11d, the first lenses 12a to 12d, the carrier member 13, the N semiconductor light receiving elements 14a to 14d, and the second lenses 15a to 15d are the same as in the first embodiment.

The light emitting units 11a to 11d output signal lights La to Ld having different wavelengths. Examples of these wavelengths are as described in the first embodiment. The first lenses 12a to 12d convert the signal lights La to Ld, which are divergent light, into convergent light. The carrier member 13 branches each part of the signal lights La to Ld when the signal lights La to Ld pass through. The semiconductor light receiving elements 14a to 14d detect the light intensities of the signal lights La to Ld by receiving a part of the branched signal lights La to Ld. The second lenses 15a to 15d convert the signal lights La to Ld that are incident while spreading into collimated light. Thus, the signal lights La to Ld, which are collimated light, are output from the signal light generator 10B along four optical axes that are included in an imaginary plane parallel to the mounting surface 7a and parallel to each other. In the present embodiment, any one of the signal lights La to Ld is an example of the first signal light, and the other one is an example of the second signal light.

The WDM block 20D is an example of an optical multiplexer in the present embodiment. The WDM block 20D is optically coupled to the signal light generator 10B, and generates the signal light Lh by combining the signal lights La to Ld. The signal light Lh is output from the WDM block 20D and output to the outside of the optical transmission module 1B via the window provided on the side wall 2A of the housing 2 and the optical coupling unit 3.

FIG. 11 is an enlarged plan view showing the configuration of the WDM block 20D. The WDM block 20D includes a light transmissive member 33, an antireflection film 34, wavelength filters 35 to 37 (light selection filters), a light reflection film 38, a light reflection film 39, an antireflection film 40, and an etalon 41. The light transmissive member 33 is a flat member, and is made of a material that is transparent with respect to the wavelengths of the signal lights La to Ld, such as glass. The light transmissive member 33 has a first surface 33a and a second surface 33b facing each other in the thickness direction. The first surface 33a and the second surface 33b are parallel to each other and are flat. The first surface 33a and the second surface 33b are arranged perpendicular to the mounting surface 7a, and are inclined with respect to the optical axes of the signal lights La to Ld incident on the WDM block 20D.

The first surface 33a includes five regions 33a1 to 33a5. The regions 33a1 to 33a5 are arranged in this order along the direction parallel to the mounting surface 7a. An antireflection film 34 is provided on the region 33a1. A wavelength filter 35 is provided on the region 33a2. A wavelength filter 36 is provided on the region 33a3. A wavelength filter 37 is provided on the region 33a4. A light reflecting film 38 is provided on the region 33a5.

The second surface 33b includes five regions 33b1 to 33b5. The regions 33b1 to 33b5 are arranged in this order along the direction parallel to the mounting surface 7a. The regions 33b1 to 33b5 are opposed to the regions 33a1 to 33a5, respectively. A light reflecting film 39 is provided on the regions 33b1 to 33b3. An antireflection film 40 is provided on the regions 33b4 to 33b5. Further, an etalon 41 is provided on the light reflection film 39 and the antireflection film 40 extending from the region 33b1 to the region 33b4. Thus, on the surface of the light transmissive member 33, the wavelength filters 35 to 37 and the etalon 41 are provided at different positions.

The antireflection film 34 transmits the signal light La incident from the signal light generation unit 10 </ b> B toward the inside of the light transmissive member 33. The light reflection film 39 on the region 33b1 totally reflects the signal light La that has passed through the antireflection film 34. The wavelength filter 35 reflects the signal light La that has arrived from the light reflection film 39 and simultaneously transmits the signal light Lb incident from the signal light generation unit 10 </ b> B toward the inside of the light transmissive member 33. At this time, the optical axis of the signal light La and the optical axis of the signal light Lb coincide with each other. Thereby, the signal lights La and Lb are multiplexed. The light reflection film 39 on the region 33b2 totally reflects the signal lights La and Lb that have arrived from the wavelength filter 35. The wavelength filter 36 reflects the signal lights La and Lb that have arrived from the light reflecting film 39 and simultaneously transmits the signal light Lc incident from the signal light generating unit 10 </ b> B toward the inside of the light transmissive member 33. At this time, the optical axes of the signal lights La and Lb and the optical axis of the signal light Lc coincide with each other. Thereby, the signal lights La to Lc are multiplexed. The light reflecting film 39 on the region 33b3 totally reflects the signal lights La to Lc that have arrived from the wavelength filter. The wavelength filter 37 reflects the signal lights La to Lc that have arrived from the light reflecting film 39, and at the same time, transmits the signal light Ld incident from the signal light generator 10B toward the inside of the light transmissive member 33. At this time, the optical axes of the signal lights La to Lc and the optical axis of the signal light Ld coincide with each other. As a result, the signal lights La to Ld are combined to generate the signal light Lh.

The antireflection film 40 on the region 33b4 transmits the signal light Lh that has arrived from the wavelength filter 37. Since the etalon 41 is provided outside the antireflection film 40 on the region 33b4, the signal light Lh is incident on the etalon 41.

The etalon 41 is disposed on the optical path between the wavelength filter 37 and the light emission point P4 of the WDM block 20D. The etalon 41 is provided on a light transmissive plate member 41a (for example, a quartz plate), a partial reflection film 41b provided on one plate surface of the plate member 41a, and the other plate surface of the plate member 41a. And a total reflection film 41c. The etalon 41 has a periodic chromatic dispersion characteristic corresponding to the wavelength of the incident light, and can compensate for the chromatic dispersion of the combined signal light La to Ld, that is, the signal light Lh.

Thereafter, the signal light Lh is reflected by the etalon 41 and reaches the light reflecting film 38. The light reflecting film 38 totally reflects the signal light Lh that has arrived from the etalon 41. The antireflection film 40 on the region 33b5 transmits the signal light Lh that has arrived from the light reflection film 38. Thereby, the signal light Lh is emitted from the second surface 33b toward the outside of the WDM block 20D. The light emission point P4 described above is located on the outer surface of the antireflection film 40 on the region 33b5.

The antireflection films 34 and 40, the light reflection films 38 and 39, and the wavelength filters 35 to 37 are made of, for example, a dielectric multilayer film. The dielectric multilayer film may be formed on the surface of the light transmissive member 33 or may be attached to the surface of the light transmissive member 33. The etalon 41 is pasted on the light reflection film 39 to the antireflection film 40 after the partial reflection film 41b and the total reflection film 41c are formed on both plate surfaces of the plate-like member 41a.

The effects obtained by the optical transmission module 1B of the present embodiment described above will be described. In the optical transmission module 1B of the present embodiment, the etalon 41 for compensating the chromatic dispersion of the combined signal light La to signal light Ld (that is, the signal light Lh) includes the wavelength filter 37 and the WDM block 20D in the WDM block 20D. Is provided on the optical path between the light emitting point P4. Thereby, chromatic dispersion due to the optical fiber can be suitably compensated. Thus, by providing the etalon 41 as a part of the WDM block 20D, an increase in the number of parts of the optical transmission module 1B is suppressed as compared with the case where the dispersion compensator is arranged as an independent part in the optical transmission module. can do.

As in this embodiment, the WDM block 20D further includes a light transmitting member 33, wavelength filters 35 to 37 are provided on the surface of the light transmitting member 33, and the etalon 41 is on the surface of the light transmitting member 33. The wavelength filters 35 to 37 may be provided at different positions. As a result, the light transmissive member 33 and the wavelength filters 35 to 37 of the WDM block 20D and the etalon 41 are integrated, and can be easily disposed in the optical transmission module 1B.

As in the present embodiment, the optical transmission module 1B further includes a base member 7 having a flat mounting surface 7a, and each optical component and the WDM block 20D constituting the signal light generation unit 10B are arranged along the mounting surface 7a. The optical axes of the signal lights La to Ld output from the signal light generation unit 10B may be parallel to each other. Thereby, the optical transmission module 1B can be reduced in size with a simple structure.

(Third Modification)
FIG. 12 is a plan view showing a configuration of a WDM block 20E according to a third modification of the second embodiment. The WDM block 20E includes a light transmissive member 33, an antireflection film 34, wavelength filters 35 to 37 (light selection filters), a light reflection film 38, an antireflection film 42, wavelength filters 43 to 45, an antireflection film 46, and an etalon. 47-50. Among these, the configurations of the light transmissive member 33, the antireflection film 34, the wavelength filters 35 to 37, and the light reflection film 38 are the same as those in the above embodiment.

The antireflection film 42, the wavelength filters 43 to 45, and the antireflection film 46 are provided on the region 33b1, the regions 33b2 to 33b4, and the region 33b5, respectively. The etalon 47 is provided on the antireflection film 42. The etalons 48 to 50 are provided on the wavelength filters 43 to 45, respectively. Thus, also in this modification, the wavelength filters 35 to 37 and the etalons 47 to 50 are provided at different positions on the surface of the light transmissive member 33. The configuration of the etalons 47 to 50 is the same as that of the etalon 41 described above, except for the thickness of the plate member.

In this modification, the antireflection film 34 transmits the signal light La incident from the signal light generation unit 10B. The antireflection film 42 transmits the signal light La that has passed through the antireflection film 34. Since the etalon 47 is provided outside the antireflection film 42, the signal light La enters the etalon 47. The etalon 47 is disposed on the optical path between the light incident point P5 of the signal light La (the outer surface of the antireflection film 34) and the wavelength filter 35 in the WDM block 20E. The etalon 47 compensates for the chromatic dispersion of the signal light La.

The signal light La that has reached the etalon 47 is reflected by the etalon 47, passes through the antireflection film 42 again, and reaches the wavelength filter 35. The wavelength filter 35 combines the signal light La and Lb by reflecting the signal light La and simultaneously transmitting the signal light Lb incident from the signal light generation unit 10B. The wavelength filter 43 reflects the signal light La and transmits the signal light Lb among the signal lights La and Lb that have arrived from the wavelength filter 35. Since the etalon 48 is provided outside the wavelength filter 43, the signal light Lb is incident on the etalon 48.

The etalon 48 is disposed on the optical path between the light incident point P6 (the outer surface of the wavelength filter 35) of the signal light Lb and the wavelength filter 36 in the WDM block 20E. The etalon 48 compensates for the chromatic dispersion of the signal light Lb. The signal light Lb that has reached the etalon 48 is reflected by the etalon 48, passes through the wavelength filter 43 again, and reaches the wavelength filter 36. The wavelength filter 36 combines the signal lights La to Lc by reflecting the signal lights La and Lb and simultaneously transmitting the signal light Lc incident from the signal light generator 10B. The wavelength filter 44 reflects the signal lights La and Lb among the signal lights La to Lc that have arrived from the wavelength filter 36, and transmits the signal light Lc. Since the etalon 49 is provided outside the wavelength filter 44, the signal light Lc is incident on the etalon 49.

The etalon 49 is disposed on the optical path between the light incident point P7 of the signal light Lc (the outer surface of the wavelength filter 36) and the wavelength filter 37 in the WDM block 20E. The etalon 49 compensates for the chromatic dispersion of the signal light Lc. The signal light Lc that has reached the etalon 49 is reflected by the etalon 49, passes through the wavelength filter 44 again, and reaches the wavelength filter 37. The wavelength filter 37 multiplexes the signal light La to Ld by reflecting the signal light La to Lc and simultaneously transmitting the signal light Ld incident from the signal light generation unit 10B. The wavelength filter 45 reflects the signal lights La to Lc among the signal lights La to Ld that have arrived from the wavelength filter 37, and transmits the signal light Ld. Since the etalon 50 is provided outside the wavelength filter 45, the signal light Ld enters the etalon 50.

The etalon 50 is disposed on the optical path between the wavelength filter 37 and the light emission point P9 of the signal light Ld in the WDM block 20E (the outer surface of the antireflection film 46). The etalon 50 compensates for the chromatic dispersion of the signal light Ld. The signal light Ld that has reached the etalon 50 is reflected by the etalon 50, passes through the wavelength filter 45 again, and reaches the light reflecting film 38. The light reflecting film 38 totally reflects the signal light Lh including the signal lights La to Ld. The antireflection film 46 transmits the signal light Lh that has arrived from the light reflection film 38. Thereby, the signal light Lh is emitted from the second surface 33b toward the outside of the WDM block 20E.

In this modification, in addition to the etalon 50 arranged on the optical path between the wavelength filter 37 and the light emission point P9 for compensating dispersion of the signal light Ld, the signal before being combined with the signal light Ld Etalons 47 to 49 for compensating dispersion of the signal lights La to Lc are arranged on the optical paths of the lights La to Lc. Thus, by providing the etalons 47 to 50 for dispersion compensation of the signal lights La to Ld individually, the dispersion compensation amounts of the signal lights La to Ld can be made different from each other. Therefore, even when the chromatic dispersions of the signal lights La to Ld are greatly different from each other, the compensation amount can be optimized for these chromatic dispersions.

As in this modification, the etalons 47 to 50 may be arranged side by side on the same surface (second surface 33b) of the light transmissive member 33. Thereby, the etalons 47 to 50 can be easily attached to the light transmissive member 33.

(Fourth modification)
FIG. 13 is a plan view showing a configuration of a WDM block 20F according to a fourth modification of the second embodiment. The difference between the WDM block 20F and the WDM block 20D of the above embodiment is that the light reflection film 39 is not provided and the antireflection film 40 extends to the region 33b1 instead.

The signal light La passes through the antireflection film 34 and enters the light transmissive member 33, then passes through the antireflection film 40 and reaches the etalon 41. At this time, the etalon 41 compensates for a part of the chromatic dispersion of the signal light La. Thereafter, the signal light La is reflected by the etalon 41 and reaches the wavelength filter 35. The wavelength filter 35 reflects the signal light La and simultaneously transmits the signal light Lb incident from the signal light generation unit 10B. Thereby, the signal lights La and Lb are multiplexed. The signal lights La and Lb pass through the antireflection film 40 and reach the etalon 41. At this time, the etalon 41 compensates for each part of the chromatic dispersion of the signal lights La and Lb. Thereafter, the signal lights La and Lb are reflected by the etalon 41 and reach the wavelength filter 36. The wavelength filter 36 reflects the signal lights La and Lb and simultaneously transmits the signal light Lc incident from the signal light generator 10B. Thereby, the signal lights La to Lc are multiplexed. The signal lights La to Lc pass through the antireflection film 40 and reach the etalon 41. At this time, the etalon 41 compensates for each part of the chromatic dispersion of the signal lights La to Lc. Thereafter, the signal lights La to Lc are reflected by the etalon 41 and reach the wavelength filter 37. The wavelength filter 37 reflects the signal lights La to Lc and simultaneously transmits the signal light Ld incident from the signal light generator 10B. As a result, the signal lights La to Ld are combined to generate the signal light Lh. The signal light Lh passes through the antireflection film 40 and reaches the etalon 41. At this time, the etalon 41 compensates each remaining portion of the chromatic dispersion of the signal light La to Lc included in the signal light Lh and the chromatic dispersion of the signal light Ld included in the signal light Lh. Thereafter, the signal light Lh is reflected by the etalon 41, is reflected again by the light reflecting film 38, passes through the antireflection film 40, and is output to the outside of the WDM block 20F.

In this modification, the etalon 41 that is arranged on the optical path between the wavelength filter 37 and the light emission point P4 and compensates for the dispersion of the signal light Lh is the signal light La before being combined with the signal light Ld. Also arranged on the optical path of .about.Lc, on the optical path of the signal lights La and Lb before being combined with the signal light Lc, and on the optical path of the signal light La before being combined with the signal light Lb. Accordingly, the signal lights La to Lc pass through the etalon 41 four times, three times, and twice, respectively, and the dispersion compensation amounts of the signal lights La to Ld can be made different from each other. Therefore, even when the chromatic dispersions of the signal lights La to Ld are greatly different from each other, the compensation amount can be optimized for these chromatic dispersions. The configuration of this modification is particularly effective when the lengths of the wavelength intervals Δλa to Δλd between the respective wavelengths of the signal light La to Ld and the zero dispersion wavelength satisfy Δλa> Δλb> Δλc> Δλd.

The optical transmission module according to the present invention is not limited to the above-described embodiment, and various other modifications are possible. For example, you may combine each embodiment and each modification which were mentioned above according to the required objective and effect. In each of the embodiments described above, the case where the light selection filter is a polarization combining filter and the case where the light selection filter is a wavelength filter have been described. However, the light selection filter according to the present invention is for multiplexing signal light. Other filters may be used as long as they are filters.

DESCRIPTION OF SYMBOLS 1A, 1B ... Optical transmission module, 2 ... Housing | casing, 2A ... Side wall, 3 ... Optical coupling part, 7 ... Base member, 7a ... Mounting surface, 9 ... Semiconductor optical integrated element, 10A, 10B ... Signal light generation part, 11a 11d ... light emitting part, 12a-12d ... lens, 13 ... carrier member, 13a ... mounting surface, 13b ... dielectric multilayer film, 14a-14d ... semiconductor light receiving element, 15a-15d ... lens, 16, 17 ... WDM filter, 18 ... Mirror, 19a, 19b ... Wave plate, 20A-20C ... Polarization combiner, 20D-20F ... WDM block, 21, 33 ... Light transmissive member, 21a, 33a ... First surface, 21a1-21a3, 33a1 ... 33a5 ... area, 21b, 33b ... second surface, 21b1 to 21b3, 33b1 to 33b5 ... area, 22, 26, 28, 34, 40, 42, 46 ... antireflection film, 23 ... polarization Synthetic filter, 24, 25, 38, 39 ... light reflecting film, 27, 31, 32, 41, 47-50 ... etalon, 27a, 41a ... plate member, 27b, 41b ... partially reflecting film, 27c, 41c ... all Reflection film, 29 ... Polarization synthesis filter, 30 ... Antireflection film, 35-37, 43-45 ... Wavelength filter, 52 ... Lens, F ... Optical fiber, La-Lh ... Signal light, P1, P3, P4, P9 ... light exit points, P2, P5, P6, P7 ... light incident points.

Claims (8)

A signal light generator for generating the first signal light and the second signal light;
An optical multiplexer that is optically coupled to the signal light generator and combines the first signal light and the second signal light;
With
The optical multiplexer is
An optical selection filter that combines the first signal light and the second signal light by reflecting the first signal light and transmitting the second signal light;
It is disposed on an optical path between the light selection filter and the light output point of the optical multiplexer, and compensates for chromatic dispersion of at least one of the first signal light and the second signal light after multiplexing. With etalon,
An optical transmission module. The optical multiplexer further includes a light transmissive member, the light selective filter is provided on a surface of the light transmissive member, and the etalon is different from the light selective filter on the surface of the light transmissive member. The optical transmission module according to claim 1, wherein the optical transmission module is provided at a position. The light transmissive member has a first surface and a second surface facing each other, the light selection filter is provided on the first surface, and the etalon is provided on the second surface,
The first signal light and the second signal light output from the signal light generation unit are incident on the first surface, and the combined first signal light and the second signal light are from the second surface. The optical transmission module according to claim 2, which emits light. A base member having a flat mounting surface;
Each optical component constituting the signal light generation unit and the optical multiplexer are two-dimensionally arranged along the mounting surface,
4. The optical transmission module according to claim 1, wherein optical axes of the first signal light and the second signal light output from the signal light generation unit are parallel to each other. 5. The etalon or another etalon for compensating chromatic dispersion of the first signal light is also disposed on the optical path of the first signal light before being combined with the second signal light. 2. The optical transmission module according to 1. The optical multiplexer further includes a light transmissive member,
The optical transmission module according to claim 5, wherein the etalon and the another etalon are arranged side by side on the same surface of the light transmissive member. The polarization direction of the first signal light and the polarization direction of the second signal light are different from each other.
The optical transmission module according to claim 1, wherein the optical selection filter is a polarization beam combining filter. The wavelength of the first signal light and the wavelength of the second signal light are different from each other,
The optical transmission module according to claim 1, wherein the optical selection filter is a wavelength filter.

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