JP3159013B2 - Optical fiber coupler and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber coupler for branching and coupling an optical signal in an optical communication network or the like using a plastic optical fiber as a transmission medium, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 2 is a diagram showing an example of the structure of a conventional equal distribution type optical fiber coupler. The optical fiber coupler 10 is formed by joining a part of a pair of plastic optical fibers 11 and 12 by an ultrasonic welding method. In this optical fiber coupler 10, the input port I
The light incident on P1 is distributed from both output ports OP1 and OP2 and emitted. At this time, both output ports OP1, OP2
Are set such that their distribution ratios are equal and the loss is small. The light incident on the input port IP2 also exits from both output ports OP1 and OP2. At this time, the light emitted from these output ports OP1 and OP2 is also set to have a low loss at an equal distribution ratio.

[0003]

However, in the optical fiber coupler 10 as described above, since the incident light is evenly distributed, for example, the light incident on the input port IP1 is emitted only from the output port OP1. And the light incident on the input port IP2 is output from both output ports OP2 and OP2.
It was not possible to give directionality to the light coupling / branching such as emission from 1.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical fiber coupler having a directivity in branching and coupling of light and a method of manufacturing the same.

[0005]

According to a first aspect of the present invention, an optical fiber coupler includes a plastic optical fiber portion for a trunk line and a plastic optical fiber portion for a branch line. the transmitted and has light an optical fiber coupler for coupling to a plastic optical fiber trunk, the cladding refractive index of the trunk for a plastic optical fiber portion, the refractive index of the core of the branch line for a plastic optical fiber portion and the like properly, linear The cladding of the plastic optical fiber part for trunk, which is maintained in the shape, and the core exposed at a predetermined region of the plastic optical fiber part for branch having a predetermined curvature are joined.

A second aspect of the present invention is a method of manufacturing an optical fiber coupler for coupling light transmitted to a branch plastic optical fiber to a main plastic optical fiber. prepare a branch for a plastic optical fiber portion comprising a core with a cladding equal refractive index of the trunk for a plastic optical fiber portion and trunk for a plastic optical fiber portion, exposing the core at a predetermined region of the branch line for a plastic optical fiber section At the same time, the plastic optical fiber part for the trunk line is kept straight, and the plastic optical fiber part for the branch line is maintained at a predetermined curvature, so that the cladding of the plastic optical fiber part for the trunk line and the core of the plastic optical fiber part for the branch line are connected. It is characterized by joining.

According to a third aspect of the invention, there is provided a method of manufacturing an optical fiber coupler, wherein the cladding of the plastic optical fiber portion for the trunk line is set thicker in advance than the cladding of the plastic optical fiber portion for the branch line, and the trunk line is kept straight. The plastic optical fiber portion for a branch and the plastic optical fiber portion for a branch line maintained at a predetermined curvature are partially ultrasonically welded.

[0008]

In [Action and Effect of the Invention An optical fiber coupler according to claim 1, the refractive index of the cladding of the trunk for a plastic optical fiber portion, the refractive index of the core of the branch line for a plastic optical fiber portions is maintained equal properly, straight Since the clad of the main plastic optical fiber portion and the core exposed in a predetermined region of the branch plastic optical fiber portion having a predetermined curvature are joined, light transmitted through the core of the main plastic optical fiber portion is It does not leak to the periphery of the plastic optical fiber for the trunk line or branch into the core of the plastic optical fiber portion for the branch line. On the other hand, light transmitted through the core of the plastic optical fiber part for branch lines is incident on the core of the plastic optical fiber part for trunk lines via the region where the above-mentioned junction is formed. Therefore, light transmitted through the core of the branch plastic optical fiber can be coupled to the core of the main plastic optical fiber without attenuating light transmitted through the core of the plastic optical fiber for trunk.

According to a second aspect of the present invention, there is provided a method of manufacturing an optical fiber coupler, comprising the steps of: providing a plastic optical fiber portion for a trunk line and a core having a refractive index equal to the cladding of the plastic optical fiber portion for the trunk line. An optical fiber portion is prepared, a core is exposed in a predetermined region of the plastic optical fiber portion for branch line, the plastic optical fiber portion for trunk is kept straight, and the plastic optical fiber portion for branch line is formed to a predetermined curvature. Keep
Since the cladding of the plastic optical fiber portion for the trunk line and the core of the plastic optical fiber portion for the branch line are joined, the plastic optical fiber portion for the branch line can be easily applied without attenuating the light transmitted by the core of the plastic optical fiber portion for the trunk line. The optical fiber coupler which can couple the light from the core to the core of the plastic optical fiber part for trunk can be provided.

In the method for manufacturing an optical fiber coupler according to a third aspect of the present invention, the cladding of the plastic optical fiber portion for the trunk line is set to be thicker than the cladding of the plastic optical fiber portion for the branch line in advance, and the trunk line is kept straight. The plastic optical fiber part for the branch and the plastic optical fiber part for the branch line maintained at a predetermined curvature are partially ultrasonically welded, so that the cladding of the plastic optical fiber part for the trunk line is left by adjusting the degree of ultrasonic welding. The cladding of the plastic optical fiber portion for branch lines can be removed. Therefore, there is no need to provide a special step of exposing the core of the plastic optical fiber portion for branch lines, and the manufacture of the optical fiber coupler is further simplified.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical fiber coupler according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram illustrating the structure of an optical fiber coupler according to an embodiment. The optical fiber coupler 2 includes a main optical fiber portion 21 made of a GI plastic optical fiber and a branch optical fiber portion 22 made of an SI plastic optical fiber. As shown in the figure, the trunk optical fiber portion 21 and the branch optical fiber portion 22 are to maintain the trunk optical fiber portion 22 side at a predetermined curvature while keeping the trunk optical fiber portion 21 side straight. Butts are joined by ultrasonic welding. By such an ultrasonic welding method, the core 22a of the branch optical fiber portion 22 is exposed at the welded portion, and the clad 21b of the trunk optical fiber portion 21 and the core 22a of the branch optical fiber portion 22 are directly joined. .

Here, since the plastic optical fibers are joined to each other by the ultrasonic welding method, the branch optical fiber portion 2 is formed.
When the light from the optical fiber 2 is coupled to the trunk optical fiber portion 21, the loss at the branch coupling portion can be minimized.
In addition, the cladding 21b of the trunk optical fiber portion 21 and the core 22a of the branch optical fiber portion 22 are made of the same material, so that light can enter the trunk optical fiber portion 21 from the branch optical fiber portion 22 efficiently. It can be a typical thing. Further, the cladding 21b of the trunk optical fiber portion 22 is replaced with the cladding 22b of the branch optical fiber portion 22.
b, the main optical fiber portion 2
1 can be prevented from leaking to the branch optical fiber portion 22. Further, by slightly converting the transmission mode of the light from the branch optical fiber portion 22 to a higher order side, the light coupling efficiency can be increased.

Hereinafter, specific embodiments will be described.
The optical fiber constituting the optical fiber portion 21 for the trunk line includes a clad 21b made of PMMA having a refractive index of 1.495, and has a diameter of 1.0 mm and a core diameter of 0.7 mm. The optical fiber constituting the branch optical fiber portion 22 has a core 22 made of PMMA having a refractive index of 1.495.
a having a diameter of 1.0 mm and a core diameter of 0.97
mm.

The connection between the main optical fiber portion 21 and the branch optical fiber portion 22 will be described. A pair of optical fibers constituting each of the optical fiber portions 21 and 22 are arranged in the longitudinal direction, and a part thereof is ultrasonically bonded under the following conditions.

First, the optical fiber on the trunk optical fiber portion 21 side is held linearly and fixed to a fixing jig provided on the ultrasonic bonding anvil side, and the optical fiber on the branch optical fiber portion 22 side is fixed to a predetermined position. And fixed to a jig with curvature provided on the ultrasonic horn side. At this time, the bending portion of the optical fiber on the side of the branch optical fiber portion 22 has a radius of 200.
mm arc, and at its vertex, the optical fiber part 2 for the trunk line
It touches the optical fiber on one side.

The fixing jig provided on the ultrasonic bonding anvil side and the jig with curvature provided on the ultrasonic horn side have a smooth contact surface with the optical fiber, and the side surface of the optical fiber is not damaged. Prevents transfer.

The ultrasonic energy in the ultrasonic bonding is
21 KHz, 100 W or less. The bonding time is 1
Set within 0 seconds. Furthermore, the joining form is 1 in compression ratio.
0%. This compression ratio prevents the light from the core 22a of the branch optical fiber portion 22 from being directly coupled to the core 21a of the trunk optical fiber portion 21 by removing the cladding 21b of the trunk optical fiber portion 21. Must be set to

By ultrasonic bonding under the above conditions,
Optical fiber portion 21 for trunk line and optical fiber portion 22 for branch line
Were bonded over a bonding length of 20 mm. That is, the branch optical fiber portion 22 has a length of 20 mm and a cladding 2.
2b was removed to expose the core 22a, and the exposed core 22a and the optical fiber portion 21 for the trunk were welded.
At this time, the branch optical fiber portion 22 was bonded to the main optical fiber portion 21 while being bent by the ultrasonic horn and the jig having a curvature.

The performance of the optical fiber coupler of the above embodiment was evaluated. At this time, a stabilized light source having a wavelength of 660 nm and 38 μW was used. Table 1 below summarizes the results.

[0021]

[Table 1]

In the above table, 1CH to 4CH indicate input / output channels and are arranged as shown in FIG.
Specifically, when 38 μW light from the stabilized light source is supplied to the input side channel 1CH, the output side channel 3
Light of 35 μW is output only from CH. At this time, the loss was 0.3 dB. Also, channel 2 on the input side
When light from a stabilized light source is supplied to CH, 10 μW and 20 μW are output from output channels 3CH and 4CH, respectively.
Is output. Furthermore, the input side channel 3CH
Is supplied from the stabilized light source, 34 μW light is output only from the channel 1CH on the output side. further,
When light from the stabilized light source is supplied to the input side channel 4CH, 8 μW and 19 μW light are output from the output side channels 1CH and 2CH, respectively.

Thus, the main channel 1CH,
When light is supplied to 3CH, the branch channel 4C
Since light does not leak to H and 2CH, the loss in the optical fiber coupler 2 is extremely small. On the other hand, when light is supplied to the channels 2CH and 4CH on the branch line, the light is coupled to the channels 3CH and 1CH on the trunk line. On this occasion,
Channels 2CH and 4CH on branch line to 3C on trunk line
Of the light supplied to H and 1CH, those that do not satisfy the condition of the transmission mode of the main optical fiber portion 21 are emitted to the outside as leakage light and cause loss. Therefore, it is necessary to appropriately adjust the mode of light transmitted through the trunk optical fiber portion 21 and the curvature of the trunk optical fiber portion 21 in advance.

When 38 μW light from the stabilized light source was supplied to both the channels 1CH and 2CH, 45 μW light was output from the output channel 3CH. It can be seen that part of the light from the branch line is coupled to the trunk side with little loss occurring on the trunk side. That is, according to the optical fiber coupler 2 of the embodiment, the optical signal transmitted from the branch line can be injected without substantially attenuating the optical signal transmitted on the trunk line. Therefore, in the LAN system, the minimum receiving sensitivity does not need to be increased, and it is useful for improving the S / N ratio. Therefore, an effect of mainly reducing the load on the receiving device can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure of an optical fiber coupler according to an embodiment.

FIG. 2 is a diagram illustrating a conventional optical fiber coupler.

[Explanation of symbols]

 2 Optical Fiber Coupler 21 Main Line Optical Fiber 21a Core 21b Cladding 22 Branch Optical Fiber 22a Core 22b Cladding

Claims (3)

(57) [Claims] An optical fiber coupler comprising a plastic optical fiber portion for a trunk line and a plastic optical fiber portion for a branch line, and coupling light transmitted to the plastic optical fiber portion for a branch line to the plastic optical fiber for a trunk line. Te, and the refractive index of the cladding of the main line for a plastic optical fiber portion, and the cladding of the main line for a plastic optical fiber portion in which the refractive index is kept equal properly, a linear core of the branch line for a plastic optical fiber portion, a predetermined An optical fiber coupler characterized by being joined to a core exposed at a predetermined region of the branch plastic optical fiber portion having a curvature of: 2. A method of manufacturing an optical fiber coupler for coupling light transmitted to a plastic optical fiber portion for a branch line to a plastic optical fiber for a main line, comprising: a plastic optical fiber portion for a main line; prepare and the branch line for plastic optical fiber portion comprising a core with a cladding equal refractive index of the plastic optical fiber portion, to expose the core at a predetermined area of the branch for a plastic optical fiber portion, said trunk for a plastic optical fiber The cladding of the plastic optical fiber portion for the trunk and the core of the plastic optical fiber portion for the branch line are joined by keeping the portion linear and maintaining the plastic optical fiber portion for the branch line at a predetermined curvature. Manufacturing method of an optical fiber coupler. 3. The cladding of said plastic optical fiber part for trunk is set thicker than the cladding of said plastic optical fiber part for branching in advance, and said plastic optical fiber part for trunk which is kept straight and said predetermined 3. The method for manufacturing an optical fiber coupler according to claim 2, wherein the plastic optical fiber portion for a branch line maintained at the curvature is partially ultrasonically welded.