WO2012121006A1 - Optical interconnection device - Google Patents

Abstract

An optical interconnection device (1) is provided with a ferulle-equipped mechanical splice (2) for mechanically connecting and affixing optical fibers to one another. The mechanical splice (2) has a base part (5) having a fiber groove for housing an optical fiber (3), and a cap part (6) for pushing the optical fiber (3) toward the base part (5). The base part (5) and the cap part (6) configure a fiber connection member (8). A ferrule (9) for holding a short internal fiber (10) is affixed to the front-end section of the base part (5). The fiber connection member (8) is formed from non-crystalline resin to which a fiber-shaped filler has been added. The fiber-shaped filler to be used has a Mohs hardness that is less than that of the quartz glass for forming the optical fiber (3), and preferably has a Mohs hardness that is less than five.

Description

Optical connector

The present invention relates to an optical connector for connecting optical fibers.

As a conventional optical connector, for example, an optical connector described in Patent Document 1 is known. The optical connector described in Patent Document 1 includes a ferrule holding a built-in optical fiber, and a connection mechanism (mechanical splice) extending to the opposite side of the connection end face of the ferrule. The connection mechanism includes a base on which a positioning groove for positioning an optical fiber to be connected to the built-in optical fiber is formed, a lid portion facing the base, and a C-shaped flat spring which elastically clamps the base and the lid portion. And consists of. The base and the lid are formed of a 40% glass fiber polyetherimide resin.

JP, 2010-186058, A

However, the following problems exist in the above-mentioned prior art. That is, when two optical fibers are mechanically connected and fixed by mechanical splice, the glass fibers (fillers) present on the surface of the resin molded product (base and lid) come into contact with the optical fibers. The glass fiber and the optical fiber are both formed of quartz glass. For this reason, when the glass fiber comes in contact with the optical fiber, the surface of the optical fiber may be finely scratched, which leads to a reduction in the strength of the optical fiber.

An object of the present invention is to provide an optical connector capable of suppressing a reduction in the strength of optical fibers when mechanically connecting the optical fibers.

An optical connector according to the present invention is an optical connector provided with a fiber connection member for mechanically connecting optical fibers. In this optical connector, the fiber connection member is formed of an amorphous resin to which a fibrous filler having a Mohs hardness smaller than that of the material forming the optical fiber is added.

In such an optical connector, a filler is added to the resin material forming the fiber connection member in order to improve mechanical properties and thermal properties. At this time, when a non-crystalline resin is used as a resin material for forming the fiber connection member, the filler tends to appear on the surface of the fiber connection member. Therefore, in the present invention, the fibrous filler is softer than the optical fiber by forming the fiber connection member with the non-crystalline resin to which the fibrous filler having a smaller Mohs hardness than the material forming the optical fiber is added. Therefore, when mechanically connecting the optical fibers with each other by the fiber connection member, even if the fibrous filler present on the surface of the fiber connection member contacts the optical fiber, the surface of the optical fiber is not easily damaged. Thereby, the strength of the optical fiber can be secured.

Preferably, the Mohs hardness of the fibrous filler is less than 5. The Morse hardness of quartz glass is about 7. Therefore, when the optical fiber is formed of quartz glass, the fibrous filler becomes sufficiently softer than the optical fiber by setting the Mohs hardness of the fibrous filler to less than 5.

Preferably, the non-crystalline resin is a polyetherimide or polyether sulfone. In this case, the heat resistance of the noncrystalline resin can be increased.

Preferably, the fibrous filler comprises only potassium titanate or a mixture of potassium titanate and wollastonite. In this case, a fibrous filler having a Mohs hardness of less than 5 can be obtained.

At this time, the filling ratio of the fibrous filler to the non-crystalline resin is preferably 25 to 35%. In this case, the coefficient of linear expansion and the amount of bending and breaking deflection of the fiber connection member can be set to appropriate values.

Preferably, the fiber connection member has a base portion having a fiber groove for accommodating the optical fiber, and a lid portion for holding the optical fiber accommodated in the fiber groove against the base portion, and the base portion includes the optical fiber The ferrule holding the built-in fiber that constitutes one of the two is fixed. In this case, the optical connector can be used as a field mounted optical connector.

According to the present invention, it is possible to suppress the decrease in the strength of the optical fiber when mechanically connecting the optical fibers. This makes it possible to improve the reliability of the optical fiber while securing the characteristics required for mechanically connecting the optical fibers.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an optical connector. It is sectional drawing which shows the switching state of the mechanical splice with a ferrule shown in FIG. It is a graph which shows an example of the Weibull plot of fiber breaking strength. It is a graph which shows an example of correlation with the filling factor of a fibrous filler, the linear expansion coefficient of a PEI molded article, and the amount of bending fracture bending | flexion. It is a graph which shows an example of correlation with the surface roughness Rz of the filling rate of a fibrous filler, and a PEI molded article, and a fiber drawing force.

Hereinafter, preferred embodiments of an optical connector according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an optical connector. In the figure, the optical connector 1 of the present embodiment is an optical connector of mechanical splice type.

The optical connector 1 includes a ferrule-attached mechanical splice 2 that mechanically connects and fixes the optical fibers, and a housing (not shown) that covers the ferrule-attached mechanical splice 2.

The mechanical splice 2 with ferrule is housed in the fiber groove 4 as shown in FIG. 1 and FIG. A cover 6 for holding the optical fiber 3 against the base 5 and a clamp spring 7 having a U-shaped cross section sandwiching the base 5 and the cover 6 are provided. The base 5 and the lid 6 constitute a fiber connection member 8 made of resin. The tip portion of the optical fiber 3 is stripped and the bare fiber 3a is exposed. Bare fiber 3a is formed of quartz glass.

A ferrule 9 is fixed to the front end of the base 5. The ferrule 9 holds a short internal fiber 10. The built-in fiber 10 has the same configuration as the above-described bare fiber 3 a, and extends from the front end face (connection end face) of the ferrule 9 to the fiber groove 4 of the fiber connection member 8.

At the boundary between the base 5 and the lid 6 in the fiber connection member 8, a plurality of wedge insertion recesses 12 into which the wedge member 11 is inserted are provided. The fiber connection member 8 is sandwiched by the clamp spring 7 from the opposite side of the wedge insertion recess 12.

In such an optical connector 1, when connecting the optical fiber 3 to the built-in fiber 10 held by the ferrule 9, as shown in FIG. 2 (b), the wedge member 11 is inserted into the wedge insertion recess of the fiber connection member 8. Insert in 12 Then, the base portion 5 and the lid portion 6 are opened against the biasing force of the clamp spring 7.

Then, as shown in FIG. 1, the optical fiber 3 is introduced into the fiber connection member 8 from the rear side of the ferrule-equipped mechanical splice 2, and the tip end face of the optical fiber 3 is abutted against the built-in fiber 10. The inside of the fiber connection member 8 is filled with a refractive index matching agent S for eliminating an optical discontinuity between the optical fiber 3 and the built-in fiber 10.

In this state, as shown in FIG. 2C, the wedge member 11 is removed from the wedge insertion recess 12. Then, the base portion 5 and the lid portion 6 are closed by the biasing force of the clamp spring 7 and the optical fiber 3 and the built-in fiber 10 are optically connected to each other via the refractive index matching agent S. It will be pressed and fixed by the cover 5 and the cover 6.

The base portion 5 and the lid portion 6 (fiber connection member 8) are formed of a non-crystalline resin to which a fibrous filler is added. As the non-crystalline resin, it is preferable to use an engineering plastic resin such as polyetherimide (PEI) or polyether sulfone (PES) having high heat resistance.

As the fibrous filler, one having a Mohs hardness smaller than that of the quartz glass forming the optical fiber 3, preferably one having a Mohs hardness smaller than 5 is used. The Mohs hardness is an index showing the hardness of a substance, and the smaller the hardness, the smaller the hardness when the minerals are rubbed against each other.

Representative examples of such fibrous fillers include potassium titanate whiskers (KTW). Further, as the fibrous filler, in addition to KTW, needle-like fillers such as wollastonite, aluminum borate, basic magnesium sulfate (MOS), zonolite, zinc oxide and the like may be used, and other properties are imparted. In order to do this, a plate-like or spherical filler having a low Mohs hardness may be added.

Here, the fiber connection member was formed of PEI whisker resin obtained by adding potassium titanate whisker to polyetherimide, and various characteristics were actually evaluated. The evaluation results are described below.

First, the breaking strength of the optical fiber was evaluated. Specifically, with the optical fiber from which the coating on the middle part has been removed set in the fiber groove of the fiber connection member and the cover held down by the cover against the base, a constant load (approximately 5 N) by the clamp spring Add Thereafter, the optical fiber was removed from the fiber connection member, the optical fiber was set in a fiber tensile tester, and a tensile force was applied to the optical fiber to measure the load when the optical fiber broke (fiber break strength).

At this time, as the resin material for forming the fiber connection member, the above-mentioned PEI whisker resin, PEI / GF resin formed by adding glass fiber (GF) to polyetherimide, and PEI-N not adding filler to polyetherimide Three types of (natural) resin were used. The Weibull plot of the fiber breaking strength at that time is shown in FIG.

The 50% breaking strength of the optical fiber was 20 to 30 N for PEI whisker resin, about 5 N for PEI · GF resin, and about 30 N for PEI-N resin. It is considered that the surface of the optical fiber is scratched by the glass fiber because the breaking strength of the PEI / GF resin is smaller than that of the PEI whisker resin and the PEI-N resin. Since the breaking strengths of the PEI whisker resin and the PEI-N resin are almost equal, it is understood that the potassium titanate whisker having a low Mohs hardness hardly damages the optical fiber.

Accordingly, it is apparent that it is preferable to use a non-crystalline resin to which a fibrous filler having a Mohs hardness smaller than that of quartz glass is added as a resin material for forming a fiber connection member.

At this time, the filling ratio (blending amount) of the fibrous filler to the non-crystalline resin is preferably 25 to 35 wt%. In the above-mentioned PEI whisker resin, the blending amount of potassium titanate whisker is 30 wt%. The ground that the blending amount of the fibrous filler is preferably 25 to 35 wt% is as follows.

FIG. 4A shows the correlation between the filling ratio of the fibrous filler to the non-crystalline resin and the linear expansion coefficient of the PEI molded product (fiber connection member). In mechanical splices, it is common for the resin to flow and be oriented along the longitudinal direction of the fiber groove during molding. Therefore, FIG. 4A shows the linear expansion coefficient in the resin flow direction (MD) of the PEI molded product. As can be seen from FIG. 4A, since the linear expansion coefficient tends to be saturated when the filling factor of the fibrous filler is 25% or more, from the viewpoint of the linear expansion coefficient, the filling of the fibrous filler to the noncrystalline resin The rate is preferably 25% or more. The linear expansion coefficient of the fiber connection member is, for example, 1 × 10 ⁻⁵ to 3 × 10 ⁻⁵ / K.

Moreover, there is an impact test as one of the connector specification tests. For example, with the mechanical splice housed in the housing, the optical connector is dropped from a certain height, and the presence or absence of appearance abnormality and the optical characteristics (loss fluctuation amount) are evaluated at that time. Tensile strength, bending strength, etc. are one of the indications of mechanical strength.

FIG. 4 (b) shows the correlation between the filling ratio of the fibrous filler to the non-crystalline resin and the bending fracture deflection amount of the PEI molded product (fiber connection member). As can be seen from FIG. 4 (b), since the bending fracture deflection amount decreases (toughness decreases) as the addition amount of the fibrous filler increases, the impact resistance decreases. When the connector drop test was conducted, breakage was observed in a part of the mechanical splices in 1/10 of the samples in which the filling factor of the fibrous filler was more than 35%. Therefore, from the viewpoint of mechanical strength, the filling ratio of the fibrous filler to the non-crystalline resin is preferably 35% or less. The bending rupture deflection of the fiber connection member is, for example, 1 to 4%.

FIG. 5A shows the correlation between the filling ratio of the fibrous filler to the non-crystalline resin and the surface roughness Rz of the PEI molded product (fiber connection member). As can be seen from FIG. 5 (a), the larger the amount of fibrous filler added, the larger (rougher) the surface roughness. FIG. 5 (b) shows the correlation between the filling ratio of the fibrous filler to the non-crystalline resin and the fiber drawing force of the PEI molded article (fiber connecting member). As can be seen from FIG. 5 (b), the fiber drawing power (fiber holding power) increases as the addition amount of the fibrous filler increases. Therefore, it can be said that as the surface roughness of the fiber connection member becomes rougher, the fiber drawing force becomes higher. The surface roughness Rz of the portion of the fiber connection member in contact with the glass fiber is, for example, 1 to 8 μm.

When using a resin material obtained by adding a non-crystalline resin to a fibrous filler having a Mohs hardness smaller than that of quartz glass as in this embodiment, the surface roughness of the fiber connection member is large, and the optical fiber and the fiber are used. Even if the frequency of contact with the fibrous filler is high, the strength of the optical fiber is hardly affected, so the degree of freedom of the amount of the fibrous filler is increased. Therefore, it becomes possible to fill many fibrous fillers with respect to non-crystalline resin.

In the above characteristic evaluation, the fibrous filler is made of only potassium titanate whiskers, but, for example, a mixture of potassium titanate whiskers and wollastonite as the fibrous filler in order to suppress the occurrence of warpage of a resin molded product. May be used.

By the way, in mechanical splices, the dimensional accuracy of the fiber connection member (base and lid), which is a resin molded product, increases as the filler filling amount with resin increases, and the dimensional change at the time of temperature change is small. The optical properties of are stabilized. On the other hand, when the filling amount of the filler is large, the proportion of the filler appearing on the surface of the resin molded product is high. Here, when glass fiber is used as the filler, Moss hardness is almost equal (about 7) between glass fiber and quartz glass, so the following problems occur.

That is, since the optical fiber is pressed and fixed by the mechanical splice, the filler present on the surface of the fiber connection member may damage the bare fiber. In particular, in the case of the locally mounted optical connector, a pulling force may act on the optical fiber due to the use environment. Therefore, it is possible that the fine flaws on the surface of the optical fiber are the starting point, the strength of the optical fiber is deteriorated, and in the worst case, the optical fiber is broken.

On the other hand, in the present embodiment, since the base portion 5 and the lid portion 6 as the fiber connection member 8 are formed of the non-crystalline resin to which the fibrous filler having a Mohs hardness smaller than that of the quartz glass is added Is sufficiently softer than the bare fiber 3a of the optical fiber 3. For this reason, when the optical fiber 3 is pressed and fixed by the mechanical splice 2 with a ferrule, the filler present on the surface of the fiber connection member 8 is unlikely to damage the bare fiber 3a. Therefore, the mechanical strength of the optical fiber 3 is secured even if the pulling force acts on the optical fiber 3. Thereby, even if the filling amount of the fibrous filler is increased, the strength reliability of the optical fiber 3 is improved while securing the properties (optical property, mechanical strength, optical fiber holding power) necessary for the mechanical splice 2 with ferrule. be able to.

The present invention is not limited to the above embodiment. For example, although the optical connector 1 of the above embodiment is a mechanical splice type optical connector for connecting the optical fiber 3 to the built-in fiber 10, the present invention introduces two optical fibers into the mechanical splice from both sides. It is applicable also to the thing of a connection and fixation type.

The present invention is also applicable to optical connectors such as MT connector ferrules and optical positioning members, in addition to mechanical splices in which optical fibers are mechanically connected and fixed.

DESCRIPTION OF SYMBOLS 1 ... Optical connector, 3 ... Optical fiber, 4 ... Fiber groove, 5 ... Base part, 6 ... Lid part, 8 ... Fiber connection member, 9 ... Ferrule, 10 ... Built-in fiber.

Claims (6)

In an optical connector provided with a fiber connection member for mechanically connecting optical fibers with each other,
The optical connector, wherein the fiber connection member is formed of an amorphous resin to which a fibrous filler having a Mohs hardness smaller than that of a material forming the optical fiber is added. The optical connector according to claim 1, wherein the Mohs hardness of the fibrous filler is less than 5. The optical connector according to claim 1, wherein the noncrystalline resin is polyetherimide or polyethersulfone. The optical connector according to any one of claims 1 to 3, wherein the fibrous filler comprises only potassium titanate or a mixture of potassium titanate and wollastonite. The optical connector according to claim 4, wherein a filling ratio of the fibrous filler to the non-crystalline resin is 25 to 35%. The fiber connection member has a base portion having a fiber groove for accommodating the optical fiber, and a lid portion for pressing the optical fiber accommodated in the fiber groove against the base portion.
The optical connector according to any one of claims 1 to 5, wherein a ferrule holding an incorporated fiber that constitutes one of the optical fibers is fixed to the base portion.

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