JP3106932B2 - Optical splitter - 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 branching device for distributing an optical signal as a signal transmission medium or an optical network component of an optical communication network.

[0002]

2. Description of the Related Art A conventional optical splitter is disclosed in, for example,
There is one disclosed in JP-A-6-64010. This optical splitter is an optical fiber bundle in which a plurality of optical fibers whose cores are exposed at the distal end are bundled so as to be in contact with the distal end, a spherical transparent resin portion surrounding the distal end of the optical fiber bundle, And a metal reflection film that covers the surface of the transparent resin portion. In this optical branching device, the signal light emitted from the tip of one optical fiber constituting the optical fiber bundle is reflected and diffused on the inner surface of the metal reflection film which is an optical mirror surface arranged opposite thereto, The light is re-incident on each optical fiber constituting the optical fiber bundle. As a result, the signal light from the original optical fiber is appropriately distributed to all other optical fibers.

[0003]

However, in the optical branching device described above, the signal light is emitted from the core material of the optical fiber to another medium (specifically, a transparent resin), and the emitted light is appropriately transmitted. After processing, the structure is such that the light enters the core material of the optical fiber again, so that the influence of reflection loss, diffusion noise, and the like at the interface between different media cannot be avoided. Therefore,
In such an optical branching device, the excess loss value becomes large, and the level diagram when the optical signal from the optical transmitting unit reaches the optical receiving unit falls within the allowable sensitivity of the receiving IC for porting to an optical network. It is a level transition graph for judging whether or not this is the case.)
As described above, it is necessary for the optical splitter to simultaneously reduce the insertion loss as well as its distribution performance.

Accordingly, an object of the present invention is to provide an optical branching device which has a low insertion loss while maintaining distribution performance.

[0005]

In order to solve the above-mentioned problems, an optical splitter according to the first aspect of the present invention includes an input-side transmission unit for transmitting an optical signal in a predetermined mode, and an optical transmission unit for transmitting an optical signal in a higher-order mode than the predetermined mode. A first relay unit, which is connected between one end of the first relay unit and one end of the transmission unit, converts an optical signal of a predetermined mode from the input-side transmission unit into an optical signal of a higher-order mode, and A first light having an input-side mode conversion section leading to the first section and a first branch coupling section in which both end areas are arranged in parallel in both end areas of a predetermined loop-like section in the first relay section and welded to each other. A second optical fiber member having a fiber member, a waveguide portion formed of the same material as the waveguide portion of the first relay portion, and having a second relay portion for transmitting a higher-order mode optical signal; A predetermined position in a loop-shaped predetermined section of the relay unit and a position of the second relay unit The second was welded connection between the position each other
And a branch connection part.

According to a second aspect of the present invention, in the optical branching device, a higher-order mode optical signal from the first and second relay units is transmitted to the other end of the first relay unit and both ends of the second relay unit in a predetermined mode. An output-side transmission unit that transmits an optical signal in a predetermined mode is further connected via an output-side mode conversion unit that converts the signal into an optical signal.

According to a third aspect of the present invention, the input side transmission section, the first relay section, and the input side mode conversion section constituting the first optical fiber member are integrally formed of one resin optical fiber. It is characterized by being formed.

According to a fourth aspect of the present invention, there is provided an optical branching device comprising: a third optical fiber member having the same structure as the second optical fiber member; a fourth optical fiber member having the same structure as the second optical fiber member;
A third branch coupling portion in which a predetermined position in a loop-shaped predetermined section of the first optical fiber member and a predetermined position of the third optical fiber portion are welded and connected to each other; a predetermined position of the second optical fiber member and a fourth light beam; A fourth branch joint where the predetermined position of the fiber member is welded to each other, and a fifth branch joint where the predetermined position of the third optical fiber member and the predetermined position of the fourth optical fiber member are welded to each other. It is further characterized by being provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of an optical splitter according to the present invention will be described with reference to the drawings.

FIG. 1 is a view for explaining the structure of a star coupler which is an optical splitter according to the first embodiment. As shown, the star coupler 2 of the first embodiment is configured by connecting a pair of optical fiber members 3 and 4 formed in a loop.

The first optical fiber member 3 is formed by integrally forming a part of an optical fiber having a normal diameter for transmitting an optical signal in a low-order mode by heating and stretching the fiber. Input-side transmission unit 3 for transmitting an optical signal in the next mode
1, a first relay section 32 for transmitting a high-order mode optical signal having a reduced diameter, and an output-side transmission section 33 for transmitting a low-order mode optical signal with the original diameter. Input side transmission unit 31
An input-side mode converter that converts a low-order mode optical signal from the input-side transmission unit 31 into a higher-order mode optical signal and guides the signal to the first relay unit 32 is provided at a connection between the first relay unit 32 and the first relay unit 32. A certain tapered portion 34 is formed. Also, the output side transmission unit 3
An output-side mode converter that converts the higher-order mode optical signal from the first relayer 32 into a lower-order mode optical signal and guides it to the output-side transmitter 33 also at the connection between the first relay unit 32 and the third relay unit 32. Is formed.

The first relay portion 32 is welded to each other in a state where the end surface regions 32b are arranged in parallel with each other in the both end regions 32b of the loop-shaped predetermined section 32a to form an optical fiber joint portion 36. . That is,
The optical fiber joint portion 36 forms a neck portion by bending an optical fiber portion constituting the first relay portion 32 having a small diameter at a center side and bringing the optical fiber portion close to each other at an end portion side of the optical fiber portion. The optical fiber portions are connected to each other by an ultrasonic welding method.

FIG. 2 is a view for explaining the structure and function of the optical fiber joint 36. As shown in FIG. The first relay section 32 has a diameter of 1 mm
Is formed by heating and stretching the plastic optical fiber described above, and has a diameter of about 0.5 mm. This first
The relay unit 32 is located at both end regions 32b of the predetermined section 32a,
The core 32 is ultrasonically welded from 0 mm to 20 mm.
c are connected to each other. Therefore, the predetermined section 3
The optical signal guided from the outside 32d of the optical fiber 2a to the optical fiber junction 36 is reflected many times here, distributed almost uniformly with almost no loss, and is distributed in each of the predetermined sections 32d.
The light exits into the predetermined section 32a from both ends of a. That is, optical signals traveling in opposite directions propagate in the predetermined section 32a.

Returning to FIG. 1, the description will be continued. Similarly to the second optical fiber member 3, the second optical fiber member 4 is obtained by heating and stretching a part of the optical fiber, and has a reduced diameter and a second relay section 42 for transmitting an optical signal in a higher mode. It has a pair of output-side transmission units 43 and 143 for transmitting a low-order mode optical signal with the same diameter. A connection between the output-side transmission unit 43 and the second relay unit 42 includes an output that converts a higher-order mode optical signal from the second relay unit 42 into a lower-order mode optical signal and guides the converted signal to the output-side transmission unit 43. Tapered portion 4 which is a side mode conversion portion
4 are formed. Also, the output side transmission unit 143 and the second
Also at the connection with the relay unit 42, a taper processing unit 144 is formed, which converts a higher-order mode optical signal from the second relay unit 42 into a lower-order mode optical signal and guides it to the output-side transmission unit 143. .

The second relay section 42 is welded and connected to each other in a state in which both end areas are arranged in parallel with each other in both end areas 42b of the loop-shaped predetermined section 42a to form an optical fiber joint section 46. .

A predetermined section 42 in a loop shape of the second relay section 42
a and the loop-shaped predetermined section 32a of the first relay section 32,
As shown in the figure, the two sections are welded to each other at an intermediate position of each of the predetermined sections 32a and 42a by an ultrasonic welding method, and the optical fiber joint section 5 is formed here.

Although it is not clear from the drawing, the star coupler 2 shown in FIG. 1 is coated with a UV curable resin as a low refractive index protective coating material over the entire stretched portion of the optical fiber and the welded joint thereof. UV curing has been applied. Such a protective coating is applied thickly over the entire stretched portion of the optical fiber to prevent excessive propagation mode conversion.

The operation of the star coupler shown in FIGS. 1 and 2 will be described below. The low-order mode signal light from the input side transmission unit 31 is converted into a high-order mode signal light by the taper processing unit 34 and guided to the first relay unit 32. First relay unit 3
The high-order mode signal light guided to 2 is branched at the optical fiber junction 36 and guided to each of the loop-shaped predetermined sections 32a. Therefore, the higher-order mode signal light guided to the predetermined section 32a propagates in the predetermined section 32a in both directions.

The higher-order mode signal light propagating in the predetermined section 32a in both directions is split again by the optical fiber joint 5 and the optical fiber joint 36.

Among them, the higher-order mode signal light branched at the optical fiber junction 5 is guided to the second repeater 42 side. That is, the signal light of the higher order mode from the first relay section 32 passes through the optical fiber connection section 5 having the same structure as the optical fiber connection section 36 and passes through the predetermined loop-shaped section 42 a constituting the second relay section 42 in both directions. Propagate to The high-order mode signal light propagating in the second relay section 42 in both directions is further branched together by the optical fiber joint section 46 to form a loop-shaped predetermined section 42.
a, and is converted into low-order mode signal light through the tapered portions 44 and 144, and the output side transmission portion 4
3, 143.

On the other hand, the higher-order mode signal light transmitted from the predetermined section 32a and branched at the optical fiber junction 36 is
The signal is guided to the outside 32d of the loop-shaped predetermined section 32a constituting the first relay section 32, is converted into low-order mode signal light through the tapered sections 34 and 35, and is converted into the input-side transmission section 31 and the output-side transmission section 33. It is led to.

To summarize the above, the input-side transmission unit 31
Is split into three (or four if the input side is included) by the star coupler 2 in FIG. At this time, since the optical fiber joints 5, 36, 46 are formed by welding the first and second relays 32, 42 having the waveguides made of the same material, the joints at the interface of the joints are formed. The excess loss value and the insertion loss value can be reduced by reducing reflection and scattering.

The star coupler 2 shown in FIG. 1 has a structure symmetrical to the left and right, and the input-side transmission unit 31 is only defined for convenience.
3, 43, 143 can be the input side and the rest can be the output side. Therefore, the star coupler of FIG. 1 is applicable to a single-core bidirectional optical communication system in which one optical fiber is used for both transmission and reception. At this time, since each of the tapered portions 34, 35, 44, and 144 can reversibly convert the mode from a lower order to a higher order or from a higher order to a lower order, the output-side mode converter also functions as the input-side mode converter. It will also function as a conversion unit.

[0024]

[Table 1]

Table 1 above shows specific examples of the characteristics of the star coupler 2 shown in FIG. In the evaluation of the optical characteristics, a stabilized light source having a divergence angle of 0.3, an output of 34 microwatts, and a wavelength of 660 nm was used. Then, the input light from the stabilized light source is input from the end (input channel) of the input side transmission unit 31 of the star coupler 2 after the shape is stabilized. As a result, the output side transmission units 33, 43, and 143 were sequentially set as the first to third output channels (1 to 3 channels), and outputs as shown in Table 1 were obtained from each channel. Note that the excess loss slightly increased to 2.8 dB because the input light having been divided into four returned to the input channel. These data are equivalent to an optical star coupler in which an ordinary optical fiber having an NA of about 0.5 is joined. That is, the plastic optical fiber of the above embodiment has an NA of 0.3.
Although it is about 3 and it is harder to distribute the signal light than usual, the configuration according to the present embodiment can achieve the same distribution efficiency as a normal optical fiber having an NA of about 0.5.

FIG. 3 is a view for explaining the structure of a star coupler which is an optical splitter according to the second embodiment. The star coupler 20 of the second embodiment is a modified example of the star coupler 2 of FIG. Therefore, the same portions are denoted by the same reference numerals, and redundant description will be omitted.

As is clear from the drawing, the star coupler 20 of the present embodiment has a first star coupler portion 20a having the same structure as the star coupler 2 of FIG. 1 and a pair of first star coupler portions 20a formed in a loop. And a second star coupler portion 20b that is folded at the upper ends of the second relay portions 32 and 42. However, due to the difference in function and role, a portion corresponding to the input-side transmission unit 31 is expressed as an output-side transmission unit 243, and portions corresponding to the output-side transmission units 33, 43, and 143 are output-side transmission units 343, respectively. , 443, 543.

The first relay section 32 forming the first star coupler section 20a and the first relay section 32 forming the second star coupler section 20b are mutually ultrasonically welded in their respective loop sections. Is welded by
Here, the optical fiber joint 7 is formed. Furthermore, the first
The second relay portion 42 forming the star coupler portion 20a and the second relay portion 42 forming the second star coupler portion 20b are welded and connected to each other in each loop-shaped section by an ultrasonic welding method. Here, the optical fiber joint 8
Is formed. As a result, the first star coupler portion 20a
The higher-order mode signal light propagating through the first relay unit 32 on the side of
The light is branched at the optical fiber joining section 7 and guided to the first relay section 32 on the second star coupler section 20b side. The higher-order mode signal light propagating through the second relay section 42 on the first star coupler section 20a side is branched at the optical fiber junction section 8 and guided to the second relay section 42 on the second star coupler section 20b side. I will

As is clear from the above description, in the star coupler 20 of the second embodiment, the signal light introduced into the input side transmission unit 31 is divided into seven (or eight if the input side is also included), and each signal is divided into eight. Output side transmission units 33, 43, 143, 24
3, 343, 443, and 543, respectively.
As described above, the star coupler 20 of the second embodiment is also formed by welding the optical fibers made of the same material as in the case of the star coupler 2 of the first embodiment. Scattering can be reduced to reduce excess loss values and insertion loss values.

[0030]

[Table 2]

Table 2 above shows specific examples of the characteristics of the star coupler 20 shown in FIG. The conditions for evaluating the optical characteristics were the same as those in Table 1. Each output side transmission unit 33, 43, 143,
243, 343, 443, and 543 were sequentially set as first to seventh output channels (1 to 7 channels), and the outputs as shown in Table 2 were obtained from each channel. The excess loss was 2.67 dB.

[0032]

According to the optical splitter of the first aspect, the input-side mode converter converts an optical signal of a predetermined mode from the input-side transmitter into an optical signal of a higher-order mode and guides the signal to the first repeater. At the same time, since both end regions are arranged in parallel at both end regions of the predetermined loop-shaped section in the first relay portion to form a first branch joint portion which is welded and connected to each other, the first branch connection portion is formed in the predetermined section of the first relay portion. The optical signal of the higher-order mode distributed by the first branch / coupling unit propagates in both directions. Further, since a second branch connecting portion in which a predetermined position in a predetermined section of the first relay portion and a predetermined position of the second relay portion are welded and connected to each other, the first branch connecting portion is provided.
A higher-order mode optical signal that propagates bidirectionally in a predetermined section of the relay unit is propagated and distributed to the second relay unit, and emitted from both ends of the second relay unit. Therefore, the optical signal transmitted through the input-side transmission unit is emitted from both ends of the second relay unit, and is also emitted from both ends of the first relay unit. That is, the optical signal propagating through the input side transmission unit is divided into four.
At this time, the first having a waveguide portion made of the same material
Since the first and second branch joints are formed by welding and joining the second junctions, reflection and scattering at the interface of the joints can be reduced, and the excess loss value and the insertion loss value can be reduced.

According to the optical splitter of the second aspect, the first
At each of the other end of the relay unit and both ends of the second relay unit, an output-side mode conversion unit that converts the higher-order mode optical signal from the first and second relay units into the original predetermined mode optical signal is provided. Since the output-side transmission unit that transmits the optical signal in the predetermined mode via the signal line is further connected, the signal light after division can be in the original predetermined mode.

According to the optical splitter of the third aspect, the input-side transmission unit, the first relay unit, and the input-side mode conversion unit are integrally formed from one resin optical fiber. Therefore, the insertion loss due to the provision of the input-side mode converter can be reduced.

According to the optical splitter of the fourth aspect, the second
A third optical fiber member having the same structure as the optical fiber member, a fourth optical fiber member having the same structure as the second optical fiber member, and a third position in a loop-shaped predetermined section of the first optical fiber member; A third branch joint where the predetermined position of the optical fiber portion is welded to each other; a fourth branch joint portion where the predetermined position of the second optical fiber member and the predetermined position of the fourth optical fiber member are welded to each other; And a fifth branch coupling portion in which the predetermined position of the third optical fiber member and the predetermined position of the fourth optical fiber member are welded to each other.
The optical signal transmitted to one end of the first optical fiber member is
The light is emitted from both ends of the first optical fiber member, and
To the fourth optical fiber member. That is, the optical signal propagating through the input side transmission unit is:
It will be divided into eight.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure of a star coupler according to a first embodiment.

FIG. 2 is an enlarged view illustrating a part of the star coupler of FIG. 1;

FIG. 3 is a diagram illustrating a structure of a star coupler according to a second embodiment.

[Explanation of symbols]

 2, 20 star coupler 3 first optical fiber member 31 input side transmission part 32 first relay part 34, 35 taper processing part 36 optical fiber joint part 4 second optical fiber member 33, 43, 143 output side transmission part 42 second Relay part 44,144 Tapered part

Claims (4)

(57) [Claims] 1. An input-side transmission unit that transmits an optical signal in a predetermined mode, a first relay unit that transmits an optical signal in a higher-order mode than the predetermined mode, and one end of the first relay unit and the transmission unit. An input-side mode converter connected between the input-side transmission unit and the input-side transmission unit, the input-side mode conversion unit converting the optical signal of the predetermined mode from the input-side transmission unit into the optical signal of the higher-order mode and guiding the optical signal to the first relay unit; A first optical fiber member having, at both end regions of a loop-shaped predetermined section in the relay portion, a first branch coupling portion in which both end regions are arranged in parallel and welded to each other; A second optical fiber member having a waveguide portion formed of the same material as the portion and having a second relay portion for transmitting the higher-order mode optical signal; and the loop-shaped predetermined section in the first relay portion. And a predetermined position of the second relay portion. Optical splitter, characterized in that it comprises a second branch coupling portion that mutually welded connection, a. 2. The optical signal of the higher mode from the side of the first and second relay units is supplied to the other end of the first relay unit and both ends of the second relay unit, respectively. The optical splitter according to claim 1, further comprising an output-side transmission unit that transmits the optical signal in the predetermined mode via an output-side mode conversion unit that converts the optical signal into an optical signal. 3. The input-side transmission section, the first relay section, and the input-side mode conversion section constituting the first optical fiber member are integrally formed from one resin optical fiber. 3. The method according to claim 1, wherein
The optical splitter according to any one of the above. 4. A third optical fiber member having the same structure as the second optical fiber member, a fourth optical fiber member having the same structure as the second optical fiber member, and the loop in the first optical fiber member. A third branch coupling portion in which a predetermined position in a predetermined section of the shape and a predetermined position of the third optical fiber portion are welded to each other, a predetermined position of the second optical fiber member, and a predetermined position of the fourth optical fiber member. A fourth branch connecting portion that is welded and connected to each other; and a fifth branch connecting portion that welds and connects a predetermined position of the third optical fiber member and a predetermined position of the fourth optical fiber member to each other. The optical splitter according to claim 1, wherein: