JPS6257003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an optical distributor/combiner that can be used in an optical communication network.

[Prior art and its problems]

Conventionally, an optical communication network using an optical splitter and an optical combiner has a configuration as shown in FIG.

This optical communication network includes four terminal pairs of optical distribution/combiners 1 to 3, optical transmitters 5 to 12, and optical receivers 15 to 2.
2 and a trunk line, and each station consists of a pair of optical transceivers.

Further, these optical distribution/combiners 1 to 3, optical transmitters 5 to 12, and optical receivers 15 to 22 are respectively coupled by optical fibers, so that optical communication can be performed between each station. . In this case, each optical distributor/combiner 1 to 3 is connected in cascade, but each optical distributor/combiner 1 to 3 is connected to the station that has emitted the optical signal in order to prevent collision detection with optical signals from other stations. It is desirable to have a configuration in which this optical signal does not return to the outside.

In order to realize the functions of the light distribution/combiners 1 to 3, as shown in FIG. .

By the way, the optical splitter/combiners 1 to 3 having such functions are designed to reduce the loss of the optical communication network and reduce the demands on the dynamic range of the optical receiver. It is necessary to control the distribution ratio and the combination ratio of the light combiner 32 to predetermined values.

Conventionally, there is a third method for controlling the distribution ratio of the light splitter 31 and the combination ratio of the light combiner 32.
A light splitter or light combiner as shown in the figure was devised.

For example, the one-to-three optical splitter shown in FIG. 3 is composed of optical fibers 41 to 44, optical lenses 51 to 54, and half mirrors 61 and 62.

First, the light emitted from the optical fiber 41 is converted into substantially parallel light by the optical lens 51, and then enters the half mirror 61. A part of the light incident on this half mirror 61
After being reflected by the optical lens 52, it is focused by the optical fiber 42, and the other part of the light is reflected by the half mirror 61.
After passing through, the light enters the next half mirror 62. In this half mirror 62, a part of the reflected light passes through the optical lens 53 and enters the optical fiber 43, as in the case described above, and the transmitted light passes through the optical lens 54 and enters the optical fiber 44.

Such a light distributor can have a predetermined distribution ratio by changing the light reflectance or light transmittance of the half mirrors 61 and 62.

In addition, in the above case, it was used as an optical distributor, but
It is clear that if the optical fibers 42 to 44 are used as input ports and the optical fiber 41 is used as an output port, a 3:1 optical combiner can be easily obtained.

That is, a 1:N light combiner can be used as an N:1 light splitter, and vice versa.

1:3 optical splitter and 3:1 optical splitter as shown above
When two optical combiners are connected and used in an optical distribution/combiner as shown in Figure 2, the loss caused by connecting the optical distributor and optical combiner is the sum of the loss of the optical distributor and the loss of the optical combiner, respectively. It becomes something. For example, if an optical splitter with an equal distribution ratio and a distribution loss of 6 dB is connected to an optical combiner with a similar structure and used for optical communication, the loss due to this part will be 6 dB in the optical splitter. This results in a loss of 6 dB in the optical combiner, resulting in a loss of 12 dB.

Therefore, when using the conventional optical combiner and optical splitter as described above for optical communication, there is a drawback that the loss becomes large.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned problems, and it is an object of the present invention to provide an optical distributor/combiner with extremely low loss of optical power during optical communication.

[Summary of the invention]

The present invention is an optical distribution/combiner constructed using N+1 each of 1:N optical distributors and N:1 optical combiners.
In the optical combiner, a bundle of N optical fibers is processed into a tapered shape, and the end of the tapered shape is connected to one optical fiber.

The distribution ratio of the 1:N optical splitter and the combination ratio of the N:1 optical combiner are determined by the shape of the tapered end or the optical axis between the tapered end and one optical fiber. This is to control the amount of deviation and butt each other to obtain a connected optical distributor/combiner.

〔Effect of the invention〕

According to the present invention, the distribution ratio of the optical splitter of 1:N and the combining ratio of the optical combiner of N: By controlling the amount of optical axis misalignment with the fiber to a predetermined value, the optical distribution/combiner can reduce the loss of optical power during optical communication, and further improve the overall performance of the optical communication network. Optical power loss can be significantly reduced.

[Embodiments of the invention]

An embodiment of the invention will be described with reference to FIGS. 4 to 10.

First, a 1:3 optical splitter (hereinafter referred to as 1x3 optical splitter) and a 3:1 optical combiner (hereinafter referred to as 3x1 optical combiner) using tapered fibers are constructed as shown in Figure 4a. We will explain the case when it is connected. First, in the optical splitter, one end of one optical fiber 63 is
One end of each of the optical fibers 64 to 66 of the book is fused into a bundle and connected by butt to the tapered end. That is, the one optical fiber 63 serves as a light introducing section, and the tapered portions of the three optical fibers 64 to 66 serve as optical branching sections to constitute a light distributor. Next, in the light synthesizer, one end of each of the three optical fibers 67 and 68 and the other end of the optical fiber 65 are fused together to form a bundle and processed into a tapered shape. The optical fiber 69 is connected to one end of the optical fiber 69 by butting. That is, the three optical fibers 67, 68,
The tapered portion 65 serves as a light introducing portion, and the single optical fiber 69 serves as a light combining portion to constitute a photosynthesizer. In this embodiment, as is clear from the figure, one of the three optical fibers constituting the optical splitter and one of the three optical fibers constituting the optical combiner are the same optical fiber 65. Although this is intended to prevent a decrease in transmission efficiency and simplify the configuration, it is also possible to create them separately and connect them.

Here, it is assumed that the optical fiber 63 is uniformly excited with optical power P having mode numbers O to M, for example, as shown in FIG. 4b.

A 1×3 optical splitter using this tapered fiber has a function of converting an input mode to a lower order mode. That is, assuming that the 1×3 optical splitter and the 3×1 optical combiner have the same distribution ratio and combining ratio, the mode volume is almost conserved within each of the optical fibers 64 to 66, and the fourth As shown in FIG. c, mode numbers from O to M/3 are excited with optical power P.

Furthermore, since the next 3×1 light combiner has a function of converting to a higher order mode, the optical fiber 69 has a fourth mode.
As shown in Figure d, 1/3 of the modes from O to M are excited discretely with optical power P.

Therefore, in the first 1×3 optical splitter, the optical power is 1/
However, it can be seen that no loss occurs in the next 3×1 photosynthesizer.

If you connect a light splitter and light combiner as shown in Figure 3 using conventional lenses, half mirrors, etc., the optical power will theoretically be reduced to 1/9; Connecting a splitter and optical combiner reduces optical power by only 1/3, reducing loss.

In addition, in actual optical splitters and optical combiners using tapered fibers, the mode volume is not completely conserved, resulting in some loss of optical power, but the amount of loss is greater than that with conventionally devised lenses, half mirrors, etc. It is much smaller than the constructed photolysis synthesizer.

Next, a light splitter or light combiner in which the distribution ratio or combination ratio is controlled using the above-mentioned tapered fiber will be explained with reference to FIGS. 5 to 8.

First, in FIG. 5a, the cross-sectional shape of the tapered end is thicker than the core 71 of one optical fiber 70, as shown in FIG. 5b, and the core 71 of this one optical fiber 70 is This shows the cores 72 and 73 at both ends of the tapered fiber slightly overlapping each other.

In this case, the light incident on the optical fiber 70 is transferred to each optical fiber 74, 75,
76 at different distribution ratios of -7, -3, and -7 dB, respectively.

6a has a tapered tip shape that is almost the same as that in FIG. 5a, but as shown in FIG. 6b, the core 81 of one optical fiber 80 is
It overlaps the cores 84 and 85 of 2 and 83, and the other 1
The core 87 of the optical fiber 86 is connected by controlling the amount of optical axis deviation between the tapered tip and one optical fiber 80 so that they hardly overlap. In this case, the light incident on one optical fiber 80 is transferred to each optical fiber 82, 83,
86 at distribution ratios of -4, -4, and -10 dB, respectively.

Further, FIG. 7a shows a case where the shape of the taper tip is thicker than that shown in FIGS. 5a and 6a, and the distribution ratio of light to the taper fiber is particularly increased.

As shown in FIG. 7b, the core 92 of one optical fiber hardly overlaps the cores 90, 91 at both ends of the tapered fiber.

In this case, the light incident on one optical fiber 93 is transferred to each optical fiber 94 constituting the tapered fiber.
95 and 96 at distribution ratios of -10, -1.5, and -10 dB, respectively.

Furthermore, as shown in FIG. 8a, the distribution ratios of the three optical fibers 100, 101, and 102 constituting the tapered fiber are approximately equal, and the tip of the tapered fiber is connected to one optical fiber as shown in FIG. 8b. The diameter of the fiber 103 is approximately equal to that of the core 104, and the tip of the tapered fiber has a circular cross section.
In this case, the light incident on one optical fiber 103 is transferred to each optical fiber 10 constituting the tapered fiber.
−6, −4, and − at 0, 101, and 102, respectively.
It can be distributed with a distribution ratio of about 6dB.

In general, the distribution ratio becomes more uniform as the tip of the tapered fiber becomes thinner and the cross-sectional shape of the tip becomes more circular.

Above, we have described an optical splitter that can control the distribution ratio. In this case, the combination ratio can be controlled by reversing the input/output relationship between one optical fiber and the three optical fibers that make up the taper fiber. A photosynthesizer capable of this can be easily obtained.

Therefore, by controlling the shape of the tip of the tapered fiber or the amount of optical axis deviation between the tip of the tapered fiber and one optical fiber, it is possible to obtain a light splitter or light combiner having a predetermined distribution ratio or combination ratio. can.

Hereinafter, an optical distribution/combiner according to the present invention using the above-mentioned optical distributor and optical combiner will be explained.
This light distribution/combiner is constructed by combining a light splitter and a light combiner with different distribution ratios and combination ratios, respectively.

For example, the optical distribution combiners 1 and 2 in FIG.
3 will be explained.

That is, in consideration of reducing the loss of the optical communication network and the dynamic range of the optical receiver, the central optical distribution/combiner 2 has a It is desirable that the losses be extremely low.

Therefore, in an optical distribution/combiner as shown in FIG. 9 used in the center of an optical communication network, each pair of terminals 110, 111 and 112, 113 of the main line of the optical communication network
The optical splitters 114 and 115 connected to the central optical fibers 122 and 123 are determined so that the distribution ratio to the central optical fibers 122 and 123 is larger than the distribution ratio to the other two optical fibers 124 and 125 and 126 and 127. good.

In addition, the light combiners 116 and 117 are also connected to the optical fiber 12.
Preferably, the combining ratio from the optical fibers 2,123 is greater than the combining ratio from the other two optical fibers 128,129 and 130,131.

In other words, by using an optical splitter or optical combiner as shown in FIGS. 7a and 7b, the overall loss of the optical communication network can be significantly reduced.

Furthermore, in the optical distributor/combiner shown in FIG. 9 used at the center of an optical communication network, optical distributors 118, 119 and optical combiner 120 are connected to the optical transmitter T and optical receiver (R) constituting the station. ,121
Similarly, it is preferable to determine the distribution ratio toward the main line or the synthesis ratio from the main line side to be larger than the other ratios.

That is, by using an optical splitter or an optical combiner as shown in FIGS. 6a and 6b, the overall loss of the optical communication network can be reduced.

Next, it is preferable that the optical distributor/combiner 1, 3 used at both ends of the optical communication network as shown in FIG. 1 have a different distribution ratio and combination ratio from the optical distributor/combiner 2 used at the center.

In an optical distribution/combiner as shown in FIG. 10, one optical fiber 122, each of the optical distributor 114 or the optical combiner 116, which will be connected to the terminal pair 110, 111 of the trunk line of the optical communication network, 12
This is because the loss of optical power must be relatively small compared to the other two optical fibers.

In this case, the optical splitters 132 to 134 and the optical combiners 135 to 137 connected to the optical transmitter T and the optical receiver R constituting the three stations have a distribution ratio toward the main line or a combination from the main line side. The ratio may be determined to be larger than the others.

Therefore, the optical distributor 132 and the optical combiner 13 used in the optical distributor/combiner at the end of such an optical communication network
By using the optical divider or optical combiner shown in FIG. 5 a, b or FIG. 8 a, b as 3, the loss of the optical communication network can be reduced.

As described above, according to the configuration of the optical communication network, the distribution ratio or combination ratio of each optical splitter or optical combiner can be adjusted depending on the shape of the tapered end or the axis of this end with one optical fiber. By controlling the amount of deviation, it is possible to obtain an optical distribution/combiner that can significantly reduce loss in an optical communication network.

In the above embodiment, a light distribution/combiner using a 1:3 light splitter and a 3:1 light combiner was explained, but this generally refers to a 1:N light splitter and an N:1 light combiner. It is clear that it can be applied as a light splitting/combining device using

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of an optical communication network using an optical distributor/combiner, Figure 2 is a configuration diagram of the optical distributor/combiner shown in Figure 1, and Figure 3 is a configuration diagram of a conventional optical distributor/combiner. , FIG. 4 is a diagram showing a connection of a 1:3 optical splitter and a 3:1 optical combiner, and FIGS. 5 to 8 show embodiments of the optical divider or optical combiner according to the present invention. 9 and 10 are diagrams showing embodiments of the optical distributor/combiner of the present invention. 63, 69, 70, 80, 93, 103... one optical fiber, 64 to 68, 74 to 76,
82,83,86,94 to 96,100 to 1
02, 122 to 131...Each optical fiber constituting the taper fiber, 71, 81, 92, 104
...One optical fiber core, 72, 73, 8
4, 85, 90, 91...Core of optical fiber forming tapered fiber, 110 to 113... Trunk line of optical communication network, 114, 115, 118, 11
9,135 to 137... Optical distributor, 116,1
17, 120, 121, 132 to 134...Photosynthesizer.

Claims (1)

[Scope of Claims] 1. An optical distributor/combiner having N+1 1:N optical distributors and N:1 optical combiners, each of which does not return the optical signal to the station from which the optical signal is transmitted, At least one of the light distributor or the light combiner has a tapered part in which one end of each of the N optical fibers is fused to each other and the fused part is formed in a tapered shape;
1 connected to the end of this tapered part by butt
a main optical fiber, and by controlling the shape of the end of the tapered part or the amount of optical axis deviation at the abutting part, the light distribution ratio or the photosynthesis ratio can be varied. A light distribution combiner. 2. One of the N optical fibers constituting the optical combiner and one of the N optical fibers constituting the optical distributor are the same optical fiber. A light distributor/combiner according to scope 1. 3. Each of the one optical fiber of at least one optical combiner of the optical combiner and the at least one optical distributor of the optical distributor constitutes a main line of an optical communication network, and the station has an optical transmitter and an optical receiver. An optical distribution/combiner according to claim 1, characterized in that it has: 4. A patent claim characterized in that, in the optical splitter, a distribution ratio of the one optical fiber to an optical combiner constituting a main line of an optical communication network is set to be larger than a distribution ratio to the receiver side. The light distribution/combiner according to item 3. 5 The optical combiner in which the one optical fiber constitutes the trunk line of an optical communication network has a combining ratio from the optical splitter in which the one optical fiber constitutes the trunk line of the optical communication network is the same as the combining ratio from the transmitter side. 4. The light distribution/combiner according to claim 3, wherein the ratio is set to be larger than the ratio.