JPH03136008A - Manufacture of fiber type coupler - Google Patents

Abstract

PURPOSE:To connect a light source and a photodetector to an optical fiber efficiently by making a specific quantity of light incident on one end side of the optical fiber and detecting the light when the light passes through a coupler formation part and is reflected on the other end side to pass through the coupler formation part again. CONSTITUTION:A specific quantity of light 3 is made incident on one end side of at least one optical fiber and this light is detected on one end side of the one optional optical fiber when the light is reflected on the other end side to pass through the coupler formation part 5 again. Then the stop of drawing is controlled according to the ratio of the detected quantity of light and the quantity of incident light. Thus, the light is incident on one end side of the optical fiber and detected only one the incidence end side without detecting the light on the other end side, so that the light can be made incident and detected only one end side of the optical fiber. Consequently, the connecting operation between the light source and photodetector, and optical fiber in the manufacturing process of the coupler 2 can be facilitated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fiber-type coupler manufactured by the so-called fusion-stretching method, in which a portion of a plurality of optical fibers is stretched while being heated and fused to form a coupler. Relating to a manufacturing method.

[Conventional technology]

A fiber coupler is a device that splits and couples light between multiple optical fibers, and melt-drawing is currently considered the most suitable method for manufacturing single-mode fiber couplers.

This fusion-stretching method generally involves preparing a plurality of short optical fibers whose coatings have been partially removed to form exposed portions, and then bringing the exposed portions into close contact with each other while heating and fusing them with a burner or the like. Stretch and form. At that time, a light source (
A semiconductor laser) and a photodetector (light receiving element) are connected, and the light from the light source entering from one end is detected by the photodetector at the other end, and while monitoring this, a predetermined branching ratio is obtained. At this point, the stretching and heating of the exposed portion is stopped to form a coupler (Japanese Unexamined Patent Publication No. 175812/1983).

[Problem to be solved by the invention]

In this way, in the conventional manufacturing method of fiber-type couplers, it is necessary to connect a light source and/or a photodetector to the target optical fiber each time a coupler is formed. , I spent a considerable amount of time making this connection.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a fiber coupler that simplifies the work of connecting a light source or a photodetector to an optical fiber in the coupler manufacturing process.

[Means to solve the problem]

In order to achieve the above object, the invention of claim 1 detects light passing through the coupler forming part when forming a coupler by stretching the coupler forming part of a plurality of optical fibers while fusing them,
A method for manufacturing a fiber coupler in which the stop of stretching is controlled based on this includes a first step of injecting a predetermined amount of light from at least one end side of the one optical fiber, and a step in which the light is transmitted to a coupler forming part. a second step of detecting this light at one end of an arbitrary optical fiber when the light passes through the optical fiber, is reflected at the other end of the optical fiber, and passes through the coupler forming section again; The method is characterized by comprising a third step of controlling the stop of stretching based on the ratio between the detected light amount and the incident light amount.

Further, the invention of claim 2 detects light passing through the coupler forming portions of a plurality of optical fibers when the coupler forming portions are stretched while being fused to form a coupler. A method for manufacturing a fiber coupler that controls the stop of stretching includes a first step of injecting a predetermined amount of light from one end of the optical fiber, and this light passing through a coupler forming section. A second step of detecting this light at one end of two or more optical fibers when the light is reflected at the other end of the optical fiber and passes through the coupler formation part again, and the amount of the detected light is detected. and a third step of controlling the stop of stretching based on the ratio between the two.

In these cases, it is preferable to use a long optical fiber, provide a light source and a photodetector at one end, and provide a coupler forming section at the other end.

[Effect]

According to claims 1 and 2, light is incident from one end of the optical fiber, and reflected light that passes through the coupler forming part and is reflected from the other end of the optical fiber is reflected from the other end. By detecting the light, it is possible to detect the light entering and detecting it only at one end of the optical fiber, instead of entering the optical fiber from one end and detecting it at the other end as in the conventional method. and can be done.

In this case, if a long optical fiber is used, a light source and a photodetector are provided at one end, and a coupler forming section is provided at the other end, the first coupler can be formed. Sometimes, by providing a light source and a photodetector at one end of an optical fiber, it is possible to avoid connecting the light source and photodetector to the optical fiber each time during the manufacturing process of the second coupler. , the couplers can be manufactured one after another on the other end side.

〔Example〕

First, a fiber coupler manufacturing apparatus that implements the manufacturing method of the present invention will be explained based on FIG.

In this manufacturing apparatus, two long single-mode optical fibers 1 are prepared, and a large number of fiber-shaped couplers 2 with a branching ratio of 1:1 are formed.

One end of the optical fiber 1 includes a semiconductor laser 3 as a light source, a first detector 4a connected to the first optical fiber 1a, and a second detector 4b connected to the second optical fiber 1b. A coupler forming section 5 is formed on the other end side by removing a part of the coating of both optical fibers la and lb.

The semiconductor laser 3 is connected to both optical fibers la and 1b via a light source optical switch 6, and switching operation of the light source optical switch 6 selectively switches between the first optical fiber 1a and the second optical fiber 1b. The detection light can be incident on the sensor.

The first photodetector 4a includes a first branch coupler 7a provided between one end of the first optical fiber 1a and the light source optical switch 6, a first optical switch 8a connected to this, and a first branch coupler 7a.
The second photodetector 4b includes a power meter 9a, and a second photodetector 4b.
It consists of a second branch coupler 7b provided between one end of the second optical fiber 1b and the light source optical switch 6, and a second optical switch 8b and a second power meter 9b connected to this. . Then, the incident light from the semiconductor laser 3 and the reflected light from the other ends of the optical fibers la and lb are branched by the double-branching coupler 7as7b, and guided to the power meters 9as9b composed of light-receiving elements to measure the amount of reflected light. It is now detectable.

Each branching coupler 7a s 7b is composed of a fiber type with a branching ratio of 1:1, and both optical switches 8a,
By selectively switching 8b, both optical fibers la
, the incident light and the reflected light to the respective power meters 9
8% I am trying to lead to 9b.

The detection signals from both power meters 98% 9b are input to the stretching control device 10 to calculate the branching ratio, and based on this value, the heating source 11 of the coupler 2 and the stretching table 12.
2 operations can be controlled.

To explain this principle in detail, as shown in Fig. 2, the incident power (unit: mW) of light entering one end of the optical fiber from the semiconductor laser 3 is Po, and the Fresnel reflection from the other end of the optical fiber causes Let Pr be the reflected power of the reflected light, let P be the incident power of the light branched by the branching coupler 7 and guided to the power meter 9, and let P be the reflected power of the light branched by the branching coupler 7 and guided to the power meter 9. , then measure P and P t
.

Therefore, the total optical loss including Fresnel reflection is α −P /P −P /P.

rof , and from the relationship with Po4, the amount of reflected light, which serves as a reference value when monitoring the stretching state of the branch coupler, is determined.

Next, the power meter 9a is used when making the coupler 2 while monitoring the reflected light based on FIG.

Let us consider the change in the display of 9b. Here, the incident power on the first optical fiber la side before the coupler forming section 5 is P
and the output power on the first optical fiber la side is P ′
If the output power on the second optical fiber lb side is P', and the attenuation ratio of the power by the coupler forming part 5 is α1 between the same fibers and α2 between different types of fibers, α - P'/P.

1 α −P’/P 22.

becomes.

Therefore, the reflected powers from the other ends of both optical fibers a s 1 b are αfl and αr2, respectively, and the reflected powers PMl and 2M2 separated by both branching couplers 7a and 7b and guided to both power meters 9a and 9b, respectively, are PMl- f'0 [(0,5Xαl×αr1×αlxO
,5)+(0,5Xα2Xαr2x a 2 ×0
, 5)] P −P [(0,5Xα ×αf2×α1M2
0 2X0.5)+ (0
, 5Xαl×αr1×α2 X O−5)]. Expressing this in dB, P −-1
0# oglo [(0,5Xαl×l αrl×α1x O, 5) + (0,5Xa2xa(
,,xa2xO,5)] P = -ICN! oglo [(0,5Xα2×2 αr2×αlX0.5)+ (0,5xαl×αrl×
α2 X O-5) ].

Next, it is assumed that α and a2 are expressed by the following equation corresponding to the amount of physical stretching, and the calculation results are shown in FIG. In addition, αrt−αr2”10−14/”−0,
03981.

α - cos2 (x) a ml-cos2 (x) As shown in Fig. 4, when manufacturing coupler 2 with a branching ratio of 1:1, when the insertion loss of coupler 2 reaches 3 dB, PM
The value of l reaches from -20 dB to -236 dB, and the value of 2M2 reaches from 100 dB to -23 dB. At this time, if heating and stretching are stopped, the coupler becomes 3 dB, that is, the branching ratio is 1:1.
coupler 2 can be obtained.

Note that 13 in the figure is a power source for the semiconductor laser 3, etc., and 14 is a power source for the semiconductor laser 3, etc.
indicates an isolator. This isolator 14 is provided to prevent the semiconductor laser 3 from becoming unstable due to light returning due to Fresnel reflection. Further, each optical switch 6.88% 8b is controlled by a switch control device 15.

The manufacturing process using this manufacturing apparatus will be explained in detail with reference to FIGS. 1 and 5.

First, the semiconductor laser 3 is turned on (step 501). Next, the light source switch 6 is connected to the side connected to the first optical fiber 1a (0→1) (step 502), and the first
The optical switch 8a is connected to the incident light guiding side (0→2) to guide the branched light of the incident light from the first branching coupler 7a to the first power meter 9a (step 503). Then, this branched light is detected by the first power meter 9a (step 504).
. Next, in order to capture the reflected light reflected from the other end of the first optical fiber 1a, the first optical switch 8a is switched to the side that guides the reflected light (0→1), and the reflected light is branched from the first branching coupler 7a. Guide the light to the first power meter 9a (step 5
05). Then, this branched light is detected by the first power meter 9a (step 506). Through the above operations, the amount of reflected light from the first optical fiber 1a is measured in the stretching control device 10.

Next, the light source switch 6 is switched from the first optical fiber 1a side to the second optical fiber lb side (0→2) (step 5
07), the second optical switch 8b is set to the side that guides the incident light (
0→2) to guide the branched light of the incident light from the second branching coupler 7b to the second power meter 9b (step 508).
. Then, this branched light is detected by the second power meter 9b (step 509). Next, in order to catch the reflected light reflected from the other end of the second optical fiber 1b, the second optical switch 8b is switched to the side that guides the reflected light (0→1), and the reflected light is branched from the second branching coupler 7b. the light to the second power meter 9b
(step 510).

Then, this branched light is detected by the second power meter 9b (
Step 511). Through the above operations, the amount of reflected light from the second optical fiber 1b is measured in the stretching control device 10.

At this stage, the drawing control device 11 calculates αr1 and αf2 from the amount of light reflected from the first optical fiber 1a and the amount of light reflected from the second optical fiber 1b, respectively (step 512).

After the reference value is calculated in this way, the process moves to the welding and stretching process of the coupler forming part 5. First, a part of the coating of the optical fiber is removed to form the coupler forming part 5 (step 51).
3). This coupler forming section 5 is connected to a pair of stretching tables 12 on both sides.
12 (step 514). Next, switch the light source optical switch 6 to the first optical fiber side 1a (0→1)
(Step 515). In this state, the coupler forming part 5 is heated by the heating device 11 to fuse this part.Step 5
16), further stretching (step 517).

During this stretching, PM and 2M2 are calculated (step 518), and a coupler 2 with a branching ratio of 1:1 should be formed.
1-2M2 (step 519), the stretching and heating are stopped (step 520). The coupler 2 thus formed is finally molded or bonded to a protective member (not shown) such as a quartz case (step 521).

By repeating the above steps as needed, a large number of couplers 2 are formed from the two long optical fibers la and lb. In this case, the semiconductor laser 3 and the first and second photodetectors 4as
4b means that if the first and second optical fibers 1 a s 1 b are connected to each other when manufacturing the first coupler 2, the connection work can be done from the manufacturing of the second and subsequent couplers 2. Can be omitted.

In addition, several basic variations including this embodiment can be considered as a method for detecting reflected light and the like to control the stop of stretching. This will be explained based on FIGS. 6(a) and (b).

As shown in FIG. 6(a), if the incident light of two optical fibers 1°1 is ■, and the reflected lights are ■ and ■, then at least ■ and ■
, ■ and ■, and ■ and ■, a predetermined branching ratio can be determined.

As shown in Figure 6(b), three optical fibers 1°1.1
When the incident light is ■, and the reflected light is ■, ■, and ■, at least ■ and ■, ■ and ■, ■ and ■, ■ and ■, ■ and ■, and ■ and ■
By detecting this, a predetermined branching ratio can be determined. Of course, it goes without saying that it is preferable to detect and compare ■, ■, and ■. In addition, in the case of using more than this number, the above may be followed.

By the way, among this series of devices, the semiconductor laser 3 and the first
The section from the second photodetectors 4a, 4b to the optical fiber 1 in front of the coupler forming section 5 is integrally constructed as a measuring device 16, as shown in FIG.

This measuring device 16 has a slip ring 18 and two bobbins 19 on both sides of a main body 17, and inside the main body 17 is a semiconductor laser 3 and both power meters 9a.

9b and various switches 6.8a, 3b, etc. are accommodated in the slip ring 18, a power cord 20, an optical switch signal cord 21, and both power meters 9a.

The signal cord 22 from 9b is wound. Further, a first optical fiber 1a and a second optical fiber 1b are wound around the bobbin 19, respectively.

As described above, ten couplers 2 with a branching ratio of 1:1 were manufactured using the specifically configured fiber coupler manufacturing apparatus, and variations in the branching ratio were measured. In this case, a 1.3 μm single mode optical fiber for band communication was used as the optical fiber 1, and a prism type optical switch with a reproducibility of ±0.02 dB or less was used as the optical switch 6.8 a s 8 b. .

The following measurement results were obtained.

According to this measurement result, the standard deviation of the variation in branching ratio was 2.31%, and although the variation was slightly larger than that in the conventional manufacturing method, it did not pose a practical problem. Furthermore, the manufacturing time was reduced by 15 minutes per piece compared to the conventional method (approximately 40 minutes per piece).

In addition, in the present invention, 3 dB is applied to the optical branching of incident light and reflected light.
Although a coupler is used, it is not limited to this as long as it can perform optical branching.

〔Effect of the invention〕

As described above, according to the invention of claim 1, since the detection light can be incident and detected only on one end side of the optical fiber, the light source and the photodetector are installed on one side of the optical fiber. By providing this, the stretching state of the coupler can be monitored, and the combination of a light source and a photodetector can be connected to one end of the optical fiber, making the connection work more efficient. can.

Further, according to the invention of claim 1, in the manufacturing process of the second coupler and thereafter, there is no need to connect the light source and the photodetector to the optical fiber each time, and the couplers are manufactured one after another on the other end side. This has the effect that connection work can be omitted and manufacturing time can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an outline of a fiber coupler manufacturing apparatus embodying the present invention, Figs. 2 and 3 are explanatory diagrams explaining the principle of the manufacturing method of the present invention, and Fig. 4 is a detection using a power meter. Figure 5 is a flow diagram showing the manufacturing process of the fiber type coupler, Figure 6 is a diagram explaining variations in the detection method, and Figure 7 is the manufacturing process of this example. FIG. 2 is a side view of a measuring device forming part of the device. 1... Optical fiber, 1a... First optical fiber, 1b
...Second optical fiber, 2...Coupler, 3...Semiconductor laser, 4a...First detector, 4b...Second detector, 5...Coupler forming part, 7a... - First branch coupler, 7b... second branch coupler.

Claims (1)

[Claims] 1. When forming a coupler by stretching the coupler forming portions of a plurality of optical fibers while fusing them, detecting the light passing through the coupler forming portions and drawing based on this. A method for manufacturing a fiber-type coupler that controls stopping of a fiber coupler includes a first step of injecting a predetermined amount of light from at least one end of the one optical fiber, the light passing through the coupler forming part, A second optical fiber that detects this light at one end of an arbitrary optical fiber when it is reflected at the other end of the optical fiber and passes through the coupler forming section again.
A method for manufacturing a fiber coupler, comprising the steps of: and a third step of controlling the stop of stretching based on the ratio between the detected light amount and the incident light amount. 2. A fiber that detects the light passing through the coupler forming part when the coupler forming part of a plurality of optical fibers is stretched while being fused to form a coupler, and controls the stop of drawing based on this. A method for manufacturing a shaped coupler includes a first step of injecting a predetermined amount of light from at least one end of the first optical fiber, and this light passes through the coupler forming section and the other end of the optical fiber. a second step of detecting the light at one end of the two or more optical fibers when the light is reflected at the end and passes through the coupler forming section again; and a ratio between the amounts of the detected light. and a third step of controlling the stop of stretching based on. 3. Claim 1 or 2, wherein the optical fiber is a long one, and a light source and a photodetector are provided at one end thereof, and a coupler forming portion is provided at the other end. A method of manufacturing the described fiber coupler.