JPH11202155A - Optical fiber connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical fiber connector which has a small loss increase at low temperature. SOLUTION: The optical fiber has its coating part 3b mounted on a coating mount part 1b and a coating-removed bare fiber 3a arranged in a V groove 1a, pressed by a depression member 2, and fixed with an adhesive 4. A step of the coating mount part is made short so that the optical fiber behind the depression part can be bent downward. When the optical fiber is fixed with the adhesive 4, the optical fiber is bent downward, so the coating mount part 1b is bent upward by shrinkage at the time of the solidification of the adhesive and shrinkage due to low temperature after the solidification, but stress applied to the optical fiber is reduced since the optical fiber is previously bent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber connector used for connecting an optical fiber to an optical device such as an optical waveguide.

[0002]

2. Description of the Related Art Japanese Patent No. 2557164 discloses that a coating of an optical fiber is removed by using a substrate having a V-groove at the front and a coating mounting portion for mounting a coating portion at the rear. There is described an optical fiber connector in which exposed bare fibers are aligned with a V-groove, the bare fibers are pressed against the V-groove by a pressing member, and the optical fibers are fixed with an adhesive.
The step of the coating mounting portion with respect to the V groove is about の of the diameter of the coating portion of the optical fiber, and when the optical fiber is mounted on the coating mounting portion formed as the rear step portion, the optical fiber Is located at the center of the V-groove.

FIG. 7 is a view for explaining such an optical fiber connector. FIG. 7A is a perspective view before an optical fiber is arranged, and FIG. 7B is a state in which the optical fiber is gripped. FIG. 7 (C) is a longitudinal sectional view through the center of the optical fiber. In the figure, 1 is a substrate, 1a is a V-groove, 1b is a coating mounting portion, 2 is a pressing member, 3 is an optical fiber, 3a is a bare fiber, 3b is a coating portion, and 4 is an adhesive. FIG.
In (B), the illustration of the adhesive is omitted.

As shown in FIG. 7 (A), a V-groove 1a is formed on the upper surface in front of the substrate 1, and a cover mounting portion 1b is formed with a step behind it. The bare fibers exposed by removing the coating of the optical fiber 3 are arranged in the V-groove 1a, and as shown in FIG. 7B, the V-groove 1a and the pressing member are pressed by the pressing member 2 from above. The adhesive 4 is injected around the bare fiber and the optical fiber placed on the coating placing part to fix the optical fiber 3. For example, the outer diameter of the bare fiber 3a is 125
μm, and the outer diameter of the coating portion 3b is 250 μm. V groove 1a
Of the bare fiber 3a and the coating placement part 1
As shown in FIG. 7 (C), in the optical fiber connector, the step difference from the upper surface of b is 125 μm, from the bare fiber 3a placed in the V-groove 1a to the coating 3b.
The center of the optical fiber is positioned so as to be substantially straight. Note that the end face of the front end is polished for connection with a waveguide or the like. Normally, it is polished at an angle of 8 ° to reduce reflected return light.

An example of connection between an optical fiber connector and a waveguide will be described. FIG. 8 is a view for explaining an example of a use state of the optical fiber connector.
8A is a side view, and FIG. 8B is a plan view. In addition, in order to make it easy to see the inside, it is illustrated by thin lines. In the figure, 11,
11 'is an optical fiber connector, 12.12' is an eight-core optical fiber ribbon, 13 is a waveguide chip, and 14 is a waveguide. Both end surfaces of the waveguide chip 13 are polished at an inclination angle of 8 °, are aligned from both sides, and the optical fiber connectors 11 and 11 ′ are bonded. The waveguide chip 13 includes:
Four sets of couplers are formed by the waveguide 14, and 8 couplers on both sides are formed.
Optical ports 11 on each side
11 'is coupled to the tape-shaped optical fiber core wires 12 and 12', and performs multiplexing and demultiplexing.

Returning to FIG. 7, the description will be continued. As shown in FIG. 7C, in the state where each member of the optical fiber connector and the optical fiber are fixed with an adhesive, the center of the optical fiber has been described as being substantially linear, but in practice, the adhesive is The adhesive shrinks when cured. In addition, when the ambient temperature changes, the adhesive expands and contracts. Such a change in the volume of the adhesive causes deformation of each component of the optical fiber connector, applies stress to the optical fiber, and deteriorates the temperature characteristics of a device such as an optical waveguide to which the optical fiber connector is connected.

FIG. 9 is a schematic view showing how the optical fiber connector is deformed at low and high temperatures. At a low temperature, the adhesive 4 contracts, and as shown in FIG.
A local stress is applied to the bare fiber 3a at a portion A which is a rear corner of the bare fiber 3a. At high temperatures, FIG.
As shown in (B), at the B portion which is the corner of the V groove,
Local stress is applied to the bare fiber 3a. According to the model calculation, if there is a temperature change from room temperature to 60 ° C., a stress of about 2 kg / mm ² is applied to the bare fiber 3a in the portion A or the portion B. In fact, due to the general properties of the adhesive, the Young's modulus increases as the temperature decreases, so the stress generated at low and high temperatures is applied to the bare fiber at the low temperature where the Young's modulus is large. Stress increases. Furthermore, since shrinkage due to curing of the adhesive is always involved,
It is important to reduce the stress applied to the portion A.

The above-mentioned deformation is also caused by the fact that the components of the optical fiber connector are asymmetric with respect to the adhesive. As shown in FIG. 4 of JP-A-2-280124, in a structure in which a V-groove is formed in both an upper member and a lower member to press the bare fiber symmetrically in the vertical direction,
Even if the adhesive is injected and fixed, the deformation due to the expansion and contraction of the adhesive is small, and the stress applied to the bare fiber does not matter much. However, as shown in FIG. 7, when the components of the optical fiber connector are asymmetric with respect to the adhesive, the stress applied to the bare fiber is problematic.
In particular, the problem is significant at low temperatures.

As shown in FIG. 10, even if the second pressing member 8 is provided behind the V-groove portion of the substrate 1, the V-groove portion of the substrate 1 and the coating placing portion are integrated. On the other hand, since the pressing members 2 and 8 are divided, it has been found by calculation that stress is applied to the portion A in FIG. 9A when the adhesive contracts.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical fiber connector having a small increase in loss particularly at low temperatures.

[0011]

According to a first aspect of the present invention, the bare fiber exposed by removing the coating of the optical fiber is aligned with a substrate having a V-groove, and the bare fiber is placed in the first position.
In the optical fiber connector in which the optical fiber is pressed against the V-groove by the pressing member and the optical fiber is fixed by the adhesive, the optical fiber is opposite to the direction in which the optical fiber behind the pressing member is bent when the adhesive contracts. Characterized by being bent in advance in the direction of.

According to a second aspect of the present invention, a V
The bare fiber exposed by removing the coating of the optical fiber is aligned with the V-groove of the substrate having the groove and having the coating mounting portion in the rear, and the bare fiber is pressed against the V-groove by a first pressing member, In an optical fiber connector in which an optical fiber is fixed by an adhesive, the optical fiber is bent downward in the vicinity of a pressing member behind the pressing member and is mounted on the coating mounting portion. It is.

According to a third aspect of the present invention, in the optical fiber connector according to the first or second aspect, the radius of curvature of the bent portion is 20 mm or more.

According to a fourth aspect of the present invention, in the optical fiber connector according to any one of the first to third aspects, the lower surface of the rear end of the first pressing member is subjected to chamfering or curved surface processing. It is characterized by having been done.

According to a fifth aspect of the present invention, in the optical fiber connector according to any one of the first to fourth aspects, the substrate is formed of silicon, and the first pressing member is made of an ultraviolet transmitting material. It is characterized by being formed.

According to a sixth aspect of the present invention, in the optical fiber connector according to any one of the first to fourth aspects, a second pressing member is provided behind the first pressing member. It is characterized by the following.

According to a seventh aspect of the present invention, in the optical fiber connector according to the sixth aspect, the substrate is formed of silicon, and the first pressing member and the second pressing member are made of an ultraviolet transmitting material. It is characterized by being formed.

[0018]

FIG. 1 is a view for explaining a first embodiment of an optical fiber connector according to the present invention.
FIG. 1A is a perspective view of a substrate, FIG. 1B is a longitudinal sectional view centering on the optical fiber, and FIG. 1C is an explanatory view showing the arrangement of bare fibers in a V-groove. In the figure, the same parts as those in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the covering portion 3 of the optical fiber placed on the covering placing portion 1b is used.
b, the optical fiber behind the pressing member is pre-bent so that the optical fiber connector component exerts stress on the optical fiber when the adhesive forming the optical fiber connector shrinks. I tried to keep it.
That is, referring to FIG. 9, a downward stress is applied to the optical fiber at the portion A, but the covering portion 3b of the optical fiber is placed at a low position, and a downward stress is applied near the pressing member behind the pressing member 2. Was pre-bent.

Although the manufacturing process will be described together with specific examples, the present invention is not limited to specific examples. FIG.
In the case of using an optical fiber having a coating outer diameter of 250 μm, the step between the center of the bare fiber 3a and the upper surface of the coating mounting portion 1b was 125 μm. When a fiber was used, the step between the top of the V-groove and the upper surface of the coating placement section was 300 μm. But,
The size of the step is not limited to this value.

The substrate 1 shown in FIG. 1A is obtained by forming one or a plurality of V grooves on a silicon substrate. The V-groove can be easily and accurately produced by processing with a dicer. As shown in FIG. 1C, the shape of the V-groove was such that when the bare fiber 3a was placed in contact with both side surfaces of the V-groove, the center of the bare fiber was lowered by about 50 μm from the top of the V-groove. .

A description will be given with reference to FIG. The coating of one or a plurality of single-core optical fibers is removed to expose the bare fiber 3a, and the bare fiber 3a is aligned in the V premises. At the same time, the bare fiber 3a is pressed by the pressing member 2 made of quartz glass.
, And fixed in the V premises so that the bare fiber 3 a contacts the pressing member 2. Next, the adhesive 4 is poured, and the substrate 1, the pressing member 2, and the bare fiber 3a are bonded together.
Cover mounting portion 1b formed as a step portion behind substrate 1
Of the optical fiber placed on the substrate 1 is adhered to the substrate 1. The height difference (shift amount) between the center of the bare fiber 3a gripped by the V-groove and the center of the optical fiber in the fixed covering portion is 300-50-125 = 125 μm. The optical fiber is bent down behind the V-groove. The bending amount of the optical fiber varies depending on the size of the step and the length of the coating mounting portion behind the V-groove substrate, but when the length of the coating mounting portion is about 4 mm, the optical fiber held in the V-groove is used. It is preferable that the center axis of the optical fiber and the center of the optical fiber at the distal end position of the coating portion have a deviation amount of about 10 to 150 μm.

The optical fiber gripped by the optical fiber connector is not limited to a single-core optical fiber as described above, but may be a tape-like optical fiber in which a plurality of optical fibers are arranged in parallel to form a common coating. Optical fibers can also be used. When the thickness of the common coating is 320 μm, the displacement amount is 300-50-1 in the substrate of the specific example described above.
60 = 90 μm. In the case where the amount of displacement is the same as in the case of a single-core optical fiber, the step between the top of the V-groove and the upper surface of the coating mounting portion may be 335 μm.

The front end of the substrate 1 to which each member and the optical fiber are fixed by the adhesive 4 is polished together with the front surface of the pressing member 2 to connect to a waveguide or the like. Normally, it is polished at an angle of 8 ° to reduce reflected return light.

FIG. 2 shows an example of a mode of use of the optical fiber connector manufactured as described above. In the figure, 5, 5 '
Is an optical fiber connector, 6, 6 'are tape-shaped optical fibers, and 7 is a waveguide chip. Optical fiber tape 6,
6 'uses an eight-core tape-shaped optical fiber in this example. The waveguide chip 7 was a 1 × 8 branch waveguide. Light is input from one optical fiber of the tape-shaped optical fiber 6, light passing through the branch waveguide of the waveguide chip 7 is received by the eight-core optical fiber connector 5 ', and the optical axes of the waveguide and the optical fiber are aligned. Adjust and align for maximum power. After the alignment, an adhesive having a matching refractive index is poured into the connection portion between the waveguide chip 7 and the optical fiber connectors 5 and 5 ', and the mixture is cured and fixed, whereby a waveguide module can be manufactured.

FIG. 3 shows the temperature characteristics of the waveguide module manufactured as described above. The figure also shows, as a comparative example, the results of a waveguide module manufactured with an optical fiber connector having a conventional structure. Each is the average value of eight hearts.
In a waveguide module using an optical fiber connector with a conventional structure, stress is applied due to shrinkage of the adhesive, especially on the low temperature side.
Although a loss fluctuation of 0.3 to 0.4 dB is observed, the loss fluctuation is reduced to about 0.1 dB in the waveguide module using the optical fiber connector of the present invention. In the optical fiber connector of the present invention, the bending amount is further increased due to the expansion of the adhesive at a high temperature, and it is expected from the model calculation that a large stress is applied. However, the Young's modulus of the adhesive is low at a high temperature. In addition, since the compressive stress received by the curing shrinkage when the optical fiber connector is manufactured is released, a large increase in loss does not occur.

In the present invention, an optical fiber connector constituted by a V-groove substrate for aligning the optical fiber from which the coating has been removed and a pressing member for aligning the optical fiber by pressing the optical fiber into a V premises as described in FIG. In addition, the pressing member 2 and the V-groove of the substrate 1 are not symmetric but asymmetric, and the optical fiber behind the pressing member 2 is formed by the optical fiber connector constituting member when the adhesive constituting the optical fiber connector contracts. The optical fiber is characterized in that it is bent in advance in a direction in which stress is applied to the optical fiber. Regarding the bending direction, it can be said that the optical fiber behind the pressing member is bent in advance in the direction opposite to the direction in which the optical fiber is bent when the adhesive contracts.
Shrinkage of the adhesive occurs upon solidification and at low temperatures.

FIG. 4 shows the state of bending applied to the optical fiber in advance. As shown in FIG. 4, the straight portion 8 regulated by being held in the V-groove and the covering portion are fixed to the covering placing portion. The bent portion is regulated by the distance L between the straight portion 9 and the height difference H regulated by the curve. If the radius of curvature R of the bent portion is not more than 20 mm, the probability of breakage increases. Therefore, the radius of curvature R of the bent portion is desirably 20 mm or more. If the radius of curvature is 20 mm, if L is 2 mm, H is approximately 5
0 μm.

FIG. 5 is a view for explaining a second embodiment of the optical fiber connector according to the present invention. FIG. 5A is a perspective view of the optical fiber connector, and FIG. FIG. 5C is a perspective view of the pressing member, and FIG. 5C is a longitudinal sectional view centered on the optical fiber. In the figure, the same parts as those in FIG. 8 is a pressing member. In this embodiment, the second pressing member 8 is provided behind the pressing member 2 that presses the bare fiber disposed in the V-groove. By providing the pressing member 8, as shown in FIG. 5C, the adhesive 4 is not unnecessarily piled behind the pressing member 2, and the amount of the adhesive 4 can be reduced. The ability to reduce the amount of the adhesive 4 can reduce the amount of shrinkage of the adhesive 4 at a low temperature, reduce the stress applied to the optical fiber, and suppress an increase in loss. In addition, since the height of the pressing member 8 can be made constant, it is possible to always adhere with a fixed amount of adhesive, and it is possible to reduce variation in characteristics among samples. In one example, the pressing member 8
As shown in FIG. 5B, the amount of the adhesive can be reduced and made constant by providing the legs for regulating the height on both sides. Further, the pressing member 8 is formed in a flat plate shape without a leg portion, and a positioning member such as a side wall having a predetermined height is formed on both sides of the coating mounting portion, and the pressing member 8 is mounted thereon. Also, the height of the pressing member 8 can be made constant, and the amount of the adhesive 4 can be reduced, and can be made constant.

FIG. 6 is a longitudinal sectional view of the optical fiber connector according to a third embodiment of the present invention, illustrating the center of the optical fiber. In the figure, the same parts as those in FIG. 9 is a curved surface portion. In this embodiment, the lower end of the rear portion of the pressing member 2 is chamfered or curved. The optical fiber is bent downward in the vicinity of the pressing member behind the pressing member 2 as in the above-described embodiments, but the adhesive 4 shrinks due to the provision of the curved surface portion 9. When the optical fiber is bent upward, stress on the optical fiber can be reduced at the corner of the pressing member 2. Also in this embodiment, the pressing member 8 described in FIG. 5 may be used together.

As the material of the substrate, in addition to the above-mentioned silicon, any suitable material such as glass, molded resin, ceramic, etc. can be used as long as it can process the V-groove. However, a material having an expansion coefficient close to that of glass, which is a material of the optical fiber, is desirable. The same applies to the material of the pressing member. However, when an ultraviolet-curable adhesive is used, it is desirable that the pressing member be transparent to ultraviolet light. As the waveguide, a polymer waveguide, a semiconductor waveguide, or the like may be applied in addition to the quartz-based waveguide.

As the adhesive for fixing the optical fiber, the pressing member, and the like to the substrate, a thermosetting adhesive, a hot melt, and the like can be used in addition to an ultraviolet curable adhesive that can be quickly cured. Given the stress on the optical fiber,
It is preferable that the Young's modulus, expansion coefficient, and cure shrinkage ratio are as small as possible. The adhesive used for connection with the waveguide is preferably a UV-curable adhesive whose refractive index has been matched between the waveguide and the optical fiber, but a thermosetting adhesive can also be used.

[0032]

As is apparent from the above description, according to the first to third aspects of the present invention, the stress on the optical fiber caused by the shrinkage of the adhesive can be reduced, and the optical fiber connector having good temperature characteristics. Can be provided.

According to the invention described in claim 4, the first V
Since the lower surface of the rear end of the pressing member for the groove is subjected to chamfering or curved surface processing, local stress on the optical fiber can be further reduced.

According to the sixth aspect of the present invention, the amount of the adhesive can be reduced, the amount of the adhesive can be kept constant, and the characteristic variation between samples can be reduced.

According to the fifth and seventh aspects of the present invention, it is possible to use a suitable ultraviolet curable adhesive as an adhesive when manufacturing an optical fiber connector.

[Brief description of the drawings]

FIG. 1 is a view for explaining a first embodiment of an optical fiber connector of the present invention, wherein (A) is a perspective view of a substrate,
(B) is a longitudinal sectional view through the center of the optical fiber, and (C) is an explanatory view showing the arrangement of bare fibers in a V-groove.

FIG. 2 is an explanatory diagram of an example of a mode of use of the optical fiber connector of the present invention.

FIG. 3 is a diagram showing temperature characteristics of the waveguide module of FIG. 2;

FIG. 4 is an explanatory diagram of a state of bending given to an optical fiber.

5A and 5B are views for explaining a second embodiment of the optical fiber connector according to the present invention, wherein FIG. 5A is a perspective view of the optical fiber connector, FIG. 5B is a perspective view of a second pressing member, and FIG. C)
FIG. 2 is a longitudinal sectional view through the center of the optical fiber.

FIG. 6 is a view for explaining a third embodiment of the optical fiber connector of the present invention, and is a longitudinal sectional view centered on the optical fiber.

7A and 7B are views for explaining a conventional optical fiber connector, and FIG. 7A is a perspective view before an optical fiber is arranged;
(B) is a perspective view of a state in which the optical fiber is gripped, and (C) is a longitudinal sectional view centered on the optical fiber.

8A and 8B are diagrams for explaining an example of a use state of the optical fiber connector, wherein FIG. 8A is a side view and FIG. 8B is a plan view.

FIG. 9 is a schematic diagram showing a state of deformation of the optical fiber connector at low and high temperatures.

FIG. 10 is a perspective view of an example of a conventional optical fiber connector provided with a pressing member for a covering portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Board, 1a ... V groove, 1b ... Coating mounting part, 2 ... Pressing member, 3 ... Optical fiber, 3a ... Bare fiber, 3b ... Coating part, 4 ... Adhesive, 5, 5 '... Optical fiber connector, 6,
6 ': tape-shaped optical fiber, 7: waveguide chip, 8: pressing member, 9: curved surface portion.

Claims (7)

[Claims] 1. A bare fiber exposed by removing a coating of an optical fiber is aligned with a substrate having a V groove, the bare fiber is pressed against the V groove by a first pressing member, and the optical fiber is fixed by an adhesive. In the optical fiber connector described above, the optical fiber is characterized in that the optical fiber is previously bent in a direction opposite to a direction in which an optical fiber behind the first pressing member is bent when the adhesive contracts. Optical fiber connector. 2. A bare fiber having a V-groove on a front upper surface and a coating having an optical fiber coating removed and aligned with a V-groove of a substrate having a coating mounting portion on the rear side, and the bare fiber is placed in the first groove. In the optical fiber connector in which the optical fiber is pressed against the V-groove by the pressing member and the optical fiber is fixed by the adhesive, the optical fiber is bent downward near the pressing member behind the first pressing member, and An optical fiber connector mounted on a part. 3. The optical fiber connector according to claim 1, wherein a radius of curvature of the bent portion is 20 mm or more. 4. The optical fiber connector according to claim 1, wherein a rear end lower surface of the first pressing member is subjected to a chamfering process or a curved surface processing. 5. The optical fiber connector according to claim 1, wherein said substrate is formed of silicon, and said first pressing member is formed of an ultraviolet transmitting material. . 6. The optical fiber connector according to claim 1, wherein a second pressing member is provided behind the first pressing member. 7. The optical fiber connector according to claim 6, wherein the substrate is formed of silicon, and the first pressing member and the second pressing member are formed of an ultraviolet transmitting material. .