JP2003241022A - Optical fiber connection member - Google Patents

Abstract

(57) [Problem] To connect an optical fiber without applying a local stress to the optical fiber when connecting the optical fiber using an optical fiber connecting member. Further, even in the case of an optical fiber such as a polarization maintaining optical fiber that is easily affected by the side pressure on the optical transmission characteristics, the connection can be made without deteriorating the optical transmission characteristics, and the polarization direction can be easily adjusted. SOLUTION: An optical fiber insertion hole 2 is provided in a ferrule 1.
Is provided, and the cross section of the optical fiber insertion hole 2 has a substantially elliptical shape. Therefore, even when the polarization maintaining optical fiber 3 having a substantially elliptical cross section is inserted,
The thickness of the adhesive 8 provided between the inner wall of the optical fiber insertion hole 2 and the outer periphery of the polarization maintaining optical fiber 3 does not become uneven, and local stress is hardly applied to the polarization maintaining optical fiber 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber connecting member such as an optical connector attached to a terminal of an optical fiber when connecting optical fibers used in an optical communication system with each other or with an optical component. It is about.

[0002]

2. Description of the Related Art As a method for connecting optical fibers to each other,
A connection method using an optical connector is widely used. In general, a single-core optical connector is composed of a ferrule having a through hole for inserting an end of an optical fiber, and a housing provided on the outer periphery of the ferrule and having a function of fitting with an adapter. The optical fiber is inserted into the fiber insertion hole of the ferrule and fixed with an adhesive after the coating of the end is removed by a certain length.

Further, in an optical fiber array in which a plurality of optical fibers are arranged in parallel and a multi-core optical fiber is collectively connected, a plurality of V-shaped V-shaped cross sections for positioning and fixing the optical fibers are arranged in parallel. A fiber insertion hole having a triangular cross-sectional shape is formed on the substrate by laminating the upper substrate. The optical fiber is inserted into the fiber insertion hole and then fixed with an adhesive.

When the optical fiber is positioned and connected to the optical component with high accuracy, the optical fiber is inserted into the fiber insertion hole of the ferrule having a metal pipe on the outer periphery and fixed with an adhesive, and then the position of the ferrule is fixed. Is positioned at an optimum position with respect to the optical component, and the metal pipe on the outer periphery and a part of the optical component are fixed by YAG welding.

In any of the above-mentioned cases, the optical fiber is inserted and fixed in a fiber insertion hole which is machined so that the inner dimension of the optical fiber is adjusted to the outer diameter with high accuracy.

[0006]

When the optical fiber is not a perfect circle but a slightly elliptical shape, if it is inserted into the circular optical fiber insertion hole, the thickness of the adhesive around the optical fiber will not be uniform. However, there is a problem that the stress at the time of curing the adhesive remains and local stress is easily applied to the optical fiber.

In particular, when the optical fiber is a polarization maintaining optical fiber, if local stress is applied to the optical fiber during optical transmission, birefringence increases, so that the polarization extinction ratio of emitted light deteriorates. To do. Further, when connecting a polarization maintaining optical fiber, it is necessary to match the polarization directions of the opposing optical fibers, but it is easy to shift the position of the optical fiber in the direction of rotation with respect to the fiber insertion hole. Therefore, there is a problem that it is difficult to match the polarization directions.

FIG. 5 is a cross-sectional view of a ferrule housed inside a conventional optical connector for connecting a polarization maintaining optical fiber. Since the stress imparting portions 46 are arranged at both ends of the core 44 of the polarization maintaining optical fiber 43 and the stress distribution is formed non-axisymmetrically, it is possible to preserve and transmit the polarization plane of the propagating light. it can. Ferrule 4 made of zirconia
A protrusion 47 is provided on the outer circumference of the ferrule 41, and the ferrule 41 is fitted by fitting the groove 47 provided in the adapter.
The position can be determined without rotating with respect to the axis. The polarization-maintaining optical fiber 43 is fixed with an adhesive 48 so that the convex portion 47 is located on an extension line of the arrangement direction of the stress applying portions 46. By fixing the protrusion 47 along the groove in the housing, the polarization-maintaining optical fiber 43 is fixed in a fixed direction in the plug, so that the polarization directions can be aligned and connected.

When the polarization-maintaining optical fiber 43 has a substantially elliptical shape, when the polarization-maintaining optical fiber 43 is inserted into the circular optical fiber insertion hole 42, the thickness of the adhesive 48 varies in the major axis direction and the minor axis direction of the polarization-maintaining optical fiber 43. Polarization-maintaining optical fiber 43 because it is different
Is likely to be locally stressed. Further, when the polarization-maintaining optical fiber 43 rotates inside the optical fiber insertion hole 42 of the ferrule 41, the position with respect to the protrusion 47 is displaced, so that the polarization directions cannot be aligned and connected.

An object of the present invention is to provide an optical fiber connecting member which can be connected without applying a local stress to the optical fiber when connecting the optical fiber using the optical fiber connecting member. Further, even in the case of an optical fiber such as a polarization-maintaining optical fiber, which is easily affected by lateral pressure on the optical transmission characteristic, the optical fiber can be connected without deteriorating the optical transmission characteristic and the polarization direction can be easily adjusted.

[0011]

The optical fiber connecting member of the present invention has at least one optical fiber insertion hole, and the cross section of the optical fiber insertion hole is substantially elliptical.

The optical fiber having a substantially elliptical cross section inserted into the substantially elliptical optical fiber insertion hole is fixed so that the major axis direction of the optical fiber cross section is aligned with the major axis direction of the optical fiber insertion hole cross section. Is preferably provided.

When the optical fiber is a polarization maintaining optical fiber,
The gap between the optical fiber insertion hole and the optical fiber is preferably 1 μm or less over the outer circumference of the optical fiber.

The major axis of the cross section of the optical fiber is preferably larger than the minor axis of the cross section of the optical fiber insertion hole. Since the rotation of the optical fiber inside the optical fiber insertion hole can be prevented, when the optical fiber is a polarization maintaining optical fiber, the deviation of the polarization direction is unlikely to occur.

Further, the optical fiber connecting member of the present invention has at least one optical fiber insertion hole, and the optical fiber insertion hole is a transverse groove formed by the V groove and the upper substrate arranged thereon. The surface has a triangular shape. The depth of the V groove is larger than the width of the opening that is in contact with the upper substrate.

A substantially elliptical optical fiber is fixed in the optical fiber insertion hole having a triangular cross section, and the optical fiber is fixed so that the major axis direction of the optical fiber is aligned with the depth direction of the V groove. preferable. When the optical fiber is a polarization-maintaining optical fiber, the optical fiber does not easily rotate, so that the polarization direction is less likely to shift.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the optical fiber connecting member of the present invention. A polarization maintaining optical fiber 3 having a substantially elliptical cross section is inserted into the optical fiber insertion hole 2 having a substantially elliptical cross section of the ferrule 1 and fixed with an adhesive 8. The polarization-maintaining optical fiber 3 is composed of a core 4, a clad 5, and two stress applying portions 6 arranged along both sides of the core. Further, a protrusion 7 that can be fitted with the adapter is provided on the outer periphery of the ferrule 1.

The major axis c of the optical fiber insertion hole 2 having a substantially elliptical cross section and the major axis a of the polarization maintaining optical fiber 3 are inserted in the same direction. Since the adhesive 8 has a substantially uniform thickness over the outer circumference of the polarization-maintaining optical fiber 3, local stress is unlikely to be applied to the polarization-maintaining optical fiber 3 when the adhesive 8 is cured. Furthermore, by setting the thickness of the adhesive 8 to 1 μm or less, the stress applied to the polarization maintaining optical fiber 3 can be reduced, and the polarization extinction ratio is less likely to deteriorate during optical transmission.

The major axis a of the polarization maintaining optical fiber 3 having a substantially elliptical cross section is larger than the minor diameter d of the substantially elliptical optical fiber insertion hole 2. Since the polarization-maintaining optical fiber 3 cannot rotate inside the optical fiber insertion hole 2, the line connecting the core 4 and the stress applying portion 6 is fixed at a substantially constant value. Therefore, when the polarization maintaining optical fiber 3 is connected to another polarization maintaining fiber, the polarization directions can be aligned and connected. Further, when inserting the polarization maintaining optical fiber 3 into the optical fiber insertion hole 2, the polarization maintaining optical fiber 3 is inserted with the orientation thereof aligned with reference to the position of the protrusion 7 on the outer periphery of the ferrule 1. , The major axis a of the polarization maintaining optical fiber 3
Is larger than the minor diameter d of the optical fiber insertion hole 2, it cannot be inserted in different directions, so that the direction is not mistakenly inserted.

As the ferrule 1, ceramics such as zirconia, metals such as stainless steel and steel, liquid crystal polymers, plastics such as polyphenylene sulfide, and crystallized glass are used. Zirconia is particularly preferable in terms of strength and workability. Further, the projection 7 is not always necessary if the polarization direction is determined by optical measurement or the like at the time of connection.

The polarization maintaining optical fiber 3 inserted into the optical fiber insertion hole 2 has a major axis a of a substantially elliptical cross section of 125 μm.
<A ≦ 150 μm, minor axis b is 100 μm ≦ b <125 μ
m is satisfied. The major axis c of the optical fiber insertion hole 2 into which the polarization maintaining optical fiber 3 is inserted is larger than the major axis a of the polarization maintaining optical fiber insertion hole 2 and is preferably a + 1 μm or less. The minor axis d of the optical fiber insertion hole 2 is
Larger than the minor axis b of the polarization maintaining optical fiber, b + 1 μm
The following is preferable. The substantially elliptical optical fiber insertion hole 2 may be molded by using a substantially elliptical molding pin at the time of molding, or after the circular hole is molded, it may be ground by post-processing to be elliptical. .

FIG. 2 shows an optical fiber connecting member of the present invention as J
SC specified as IS C5973 F04 type
It is a perspective view when applied to a connector. The ferrule 1 in which the coating of the end of the optical fiber core wire 14 is removed to a certain length and the polarization maintaining optical fiber 3 is inserted is housed inside a housing 11 and assembled as a plug 13. Plug 1
3 are connected via an adapter 12 so that the polarization direction is set to one direction and fitted. As the optical connector, an FC connector, an LC connector, and other optical connectors can be used in addition to the SC connector.

FIG. 3 is a perspective view showing another embodiment of the optical fiber connecting member of the present invention. The ferrule 1 made of zirconia is press-fitted into the tip of the stainless steel pipe 21. The ferrule 1 is provided with a substantially elliptical optical fiber insertion hole, and the substantially elliptical polarization maintaining optical fiber 3 is inserted therein. This optical fiber connecting member is aligned at the position where the connection loss is minimized in connection with the optical component, and after the polarization directions are aligned, the stainless pipe 21 and a part of the optical component are fixed by YAG welding. It

FIG. 4 is a sectional view showing another embodiment of the optical fiber connecting member of the present invention. The lower substrate 31 has a cross section of V
Four V-shaped V-shaped grooves 32 are provided at a constant pitch, and by bonding the upper substrate 33 to each other, four optical fiber insertion holes each having a triangular cross section are formed. A substantially elliptical polarization-maintaining optical fiber 3 is inserted into each of the optical fiber insertion holes, and is fixed with an adhesive 35.

The groove depth e of the V groove 32 is larger than the width f of the opening of the V groove 32. The major axis a of the polarization-maintaining optical fiber 3 is fixed in the direction of the groove depth e of the V groove 32. The adhesive 32 is the polarization maintaining optical fiber 3
Since the thickness can be reduced over the outer circumference of the polarization maintaining optical fiber 3, local stress is less likely to be applied to the polarization maintaining optical fiber 3 when the adhesive 35 is cured. Further, the stress applied to the polarization maintaining optical fiber 3 can be reduced, and the polarization extinction ratio is less likely to deteriorate during optical transmission.

Since the polarization-maintaining optical fiber 3 is fixed so that the long diameter a of the polarization-maintaining optical fiber 3 matches the direction of the groove depth e of the V groove 32, the polarization-maintaining optical fiber 3 is fixed.
It does not rotate inside the optical fiber insertion hole, and the polarization direction does not shift during connection.

For the upper substrate 33 and the lower substrate 31, silicon, a metal plate or the like is used. As the adhesive 35, a thermosetting adhesive such as epoxy resin or polyimide resin, solder or the like is used.

The groove depth e of the V groove 32 is preferably larger than the width f of the opening of the V groove 32 and smaller than 1.4 × f. Within this range, the amount of adhesive 35 applied can be reduced.

The number of V grooves 32 is not limited to four,
Any number may be used as long as it is one or more. Although the polarization maintaining optical fiber 3 may be inserted after the upper substrate 33 is bonded to the lower substrate 31, the polarization maintaining optical fibers 3 may be arranged in the V groove 32 of the lower substrate 31 and then the V groove may be formed. The upper substrate 33 may be attached so as to be pressed against 32.

[0030]

EXAMPLE An example of the present invention will be described with reference to FIG.
A ferrule 1 made of zirconia is formed at the center so as to form an optical fiber insertion hole having a circular cross section,
After that, the inside of the hole was ground so that the cross-sectional shape was substantially elliptical, and the optical fiber insertion hole 1 was processed. The major axis c of the elliptical cross section of the optical fiber insertion hole 1 was 126.5 μm and the minor axis d was 124.5 μm. The polarization maintaining optical fiber 3 was inserted into this, and an epoxy adhesive was filled and cured. The major axis a of the polarization maintaining optical fiber 3 is 126.0 μm,
The minor axis b was 124.0 μm. The thickness of the adhesive 8 is
It was 0.5 μm.

Using the ferrule 1 to which this polarization-maintaining optical fiber 3 was attached, an SC connector having the structure shown in FIG. 2 was assembled. When the polarization maintaining optical fiber 3 facing each other is connected via the adapter 12 using this SC connector,
The transmission characteristics such as transmission loss and polarization extinction ratio were good.

An embodiment of another aspect of the present invention will be described with reference to FIG. Lower substrate 31 cut out from a silicon wafer
Four V-grooves 32 were provided at a pitch of 125 μm by grinding. The upper substrate 33 is attached to this with an epoxy adhesive, and four optical fiber insertion holes 3 each having a triangular cross section are formed.
Created 4. The depth e of the V groove 32 is 200.5 μm,
The width f of the opening was 166.5 μm. One polarization-maintaining optical fiber 3 was inserted into each of the V grooves 32, and an epoxy adhesive was filled and cured. The polarization maintaining optical fiber 3 has a major axis a of 126.0 μm and a minor axis b of 124.0.
μm.

When the polarization maintaining optical fibers 3 facing each other are connected by abutting the optical fiber arrays with each other,
The transmission characteristics such as transmission loss and polarization extinction ratio were good.

[0034]

The optical fiber connecting member of the present invention has at least one optical fiber insertion hole, and since the optical fiber insertion hole has a substantially elliptical cross section, it has a substantially elliptical shape. Even when inserting the optical fiber
The thickness of the adhesive does not become uneven, and local stress is less likely to be applied to the optical fiber.

When the optical fiber is a polarization-maintaining optical fiber, local stress due to the adhesive is unlikely to be applied, so that the polarization extinction ratio is less likely to deteriorate during optical transmission. Further, since the polarization maintaining optical fiber can be inserted in a fixed direction of the optical fiber insertion hole and the rotation can be suppressed even after the insertion, the polarization directions can be aligned and connected at the time of connection.

Further, the optical fiber connecting member of the present invention has a triangular optical fiber insertion hole formed by a lower substrate having at least one V-shaped groove having a V-shaped cross section and an upper substrate bonded thereon. Since the depth of the V-groove is larger than the width of the opening of the V-groove, the thickness of the adhesive is nonuniform even when an optical fiber having a substantially elliptical cross section is inserted. Therefore, local stress is less likely to be applied to the optical fiber.

When the optical fiber is a polarization maintaining optical fiber, local stress due to the adhesive is unlikely to be applied, so that the polarization extinction ratio is unlikely to deteriorate during optical transmission. Further, since the polarization maintaining optical fiber can be inserted in a fixed direction of the optical fiber insertion hole and the rotation can be suppressed even after the insertion, the polarization directions can be aligned and connected at the time of connection.

[Brief description of drawings]

FIG. 1 is a transverse sectional view showing an embodiment of an optical fiber connecting member of the present invention.

FIG. 2 is a perspective view showing a configuration when the optical fiber connecting member of the present invention is applied as an optical connector.

FIG. 3 is a perspective view showing an embodiment of another configuration of the optical fiber connecting member of the present invention.

FIG. 4 is a cross-sectional view showing an embodiment of another aspect of the optical fiber connecting member of the present invention.

FIG. 5 is a cross-sectional view showing a conventional optical fiber connecting member.

[Explanation of symbols]

1 ferrule 2 Optical fiber insertion hole 3 Polarization-maintaining optical fiber 4 core 5 clad 6 Stress applying part 7 Projection 8 adhesive 11 housing 12 Adapter 13 plugs 14 Optical fiber core 21 stainless steel pipe 31 Lower substrate 32 V groove 33 Upper substrate 35 Adhesive 41 Ferrule 42 Optical fiber insertion hole 43 Polarization-maintaining optical fiber 44 core 45 clad 46 stress applying section 47 Projection 48 Adhesive a Long diameter of polarization-maintaining optical fiber b Short diameter of polarization maintaining optical fiber c Optical fiber insertion hole major axis d Short diameter of optical fiber insertion hole e V groove depth f V groove opening width

Claims (6)

[Claims] 1. An optical fiber connecting member having at least one optical fiber insertion hole, wherein the cross-sectional shape of the optical fiber insertion hole is substantially elliptical. 2. An optical fiber having a substantially elliptical cross-section is inserted into the optical fiber insertion hole, and a major axis direction of the optical fiber insertion hole cross section and a major axis direction of the optical fiber cross section are defined. The optical fiber connecting member according to claim 1, wherein the optical fibers are inserted in the same direction. 3. The optical fiber is a polarization-maintaining optical fiber, and the gap between the inner wall of the optical fiber insertion hole and the optical fiber is 1 μm or less along the outer circumference of the optical fiber. 2. The optical fiber connecting member according to 2. 4. The optical fiber connecting member according to claim 3, wherein the major axis of the cross section of the optical fiber is larger than the minor axis of the cross section of the optical fiber insertion hole. 5. An optical fiber insertion hole having a triangular cross section formed by a lower substrate having at least one V-shaped groove having a V-shaped cross section and an upper substrate bonded thereon. An optical fiber connecting member, wherein the depth of the V groove is larger than the width of the opening of the V groove. 6. A substantially elliptical polarization-maintaining optical fiber is inserted into the optical fiber insertion hole, and the major axis direction of the cross section of the polarization-maintaining optical fiber and the depth direction of the V groove are in the same direction. The optical fiber connecting member according to claim 5, wherein the polarization maintaining optical fiber is fixed so that