JPH063221A - Optical fiber coupler with abnormality alarm function and its manufacture - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an optical fiber coupler with an abnormality warning function and a manufacturing method thereof, which enables to know beforehand the disconnection of the optical fiber coupler with a high yield. An optical fiber coupler having a fusion splicing portion obtained by fusing and stretching a part of a plurality of optical fibers to each other, wherein the optical fiber 3 has a diameter 2r = 20 mm.
Use a bending loss at φ of 10 dB / m or more,
The bending loss is reduced in the fusion splicing section 4, and the bending loss is maintained as it is in the sections other than the fusion splicing section 4, and the excess of the optical fiber coupler when stress is applied to portions other than the fusion splicing section 4. An optical fiber coupler with an abnormality warning function, characterized in that an increase in loss is used as alarm information. [Effect] It is possible to prevent communication interruption by exchanging an abnormal optical fiber coupler at the time when the disconnection of the optical fiber coupler due to stress is known in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion-stretching type optical fiber coupler (hereinafter abbreviated as "optical fiber coupler") for distributing, merging or wavelength-multiplexing / wavelength-separating light. When stress is applied to the optical fiber part other than the above section, alarm information is issued in advance to warn the disconnection of the optical fiber coupler due to this stress, the above stress is detected and it is possible to prevent communication interruption due to disconnection. It is the one.

[0002]

2. Description of the Related Art As an example of a conventional method for producing an optical fiber coupler, usually, a plurality of optical fibers having a core and a clad are arranged in parallel, and a part of these is heated by a heat source such as a burner, and the vicinity of the heating section is mainly placed. The optical power propagating in the core of one of the optical fibers is coupled to the core of the other optical fiber by forming the fused and extended portion by performing the fusion and the extension. In the optical fiber coupler manufactured in this manner, the mechanical strength of the fusion splicing part is weaker than that of the optical fiber part other than the fusion splicing part. The other optical fiber parts are fixed to the reinforcing device, the holding jig, etc. with an adhesive or the like.

In the manufacturing method of such an optical fiber coupler, an optical fiber having a relatively small bending loss is used in order to reduce an excessive loss of the optical fiber coupler due to a slight bending during the manufacturing process. . For this reason, if an abnormality occurs in the adhesion part with the stiffener etc. and stress is applied to the optical fiber coupler, the excess loss of the optical fiber coupler hardly changes, so after a further period of time with stress applied There is a problem that it is difficult to know in advance the disconnection of the optical fiber coupler that may occur. In order to solve such a problem, it has been attempted to use an optical fiber exhibiting a relatively large bending loss, but in this case, there is a drawback that the excess loss of the optical fiber coupler is likely to be large and the manufacturing yield is reduced. It was

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide alarm information for warning in advance the disconnection of the optical fiber coupler due to the stress when the stress is applied to the optical fiber coupler with a high yield. An object of the present invention is to provide an optical fiber coupler with an abnormality warning function that can be emitted to detect the above stress and a manufacturing method thereof.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber coupler having a fusion spliced portion obtained by fusing and stretching a part of a plurality of optical fibers to each other. Is used, the bending loss is reduced in the fusion stretch portion, the bending loss is maintained as it is in the portions other than the fusion stretch portion, and the optical fiber when stress is applied to the portion other than the fusion stretch portion. This is solved by using the increase in excess loss of the coupler as the alarm information.

[0006]

EXAMPLES Examples of the present invention will be described below, but the gist and scope of application of the present invention are not limited to these examples. FIG. 1 is a schematic configuration diagram of an optical fiber coupler with an abnormality warning function according to an embodiment. The optical fiber coupler with an abnormality warning function of this embodiment includes a plurality of optical fibers 3 and 3 each having a core 1 and a clad 2 (2 in the figure).
Books) are arranged in parallel, and some of them are integrated at the fusion splicing part 4. In the fusion splicing / drawing section 4, the optical power propagating in the core 1 of the one optical fiber 3 is coupled into the core 1 of the other optical fiber 3.

As the optical fiber 3, the core 1 of the optical fiber 3 is used.
There is a residual strain in the tensile direction in the longitudinal direction and the diameter is 2
A bending loss of 10 dB / m or more at r = 20 mmφ is preferably used, and the bending loss is reduced in the portion in which the residual strain is restored in the core 1, and the bending loss remains in the portion in which the residual strain is not restored. It is a configuration that is maintained. The residual strain in the core 1 of the optical fiber 3 can be recovered by annealing and is about 3 to 10%. The degree of bending loss when the diameter 2r of the optical fiber 3 is 20 mmφ is about 10 to 50 dB / m within a range that does not interfere with ordinary fiber handling. As the degree of bending loss after recovery of residual strain in the core 1,
It is desired to be sufficiently small, and it is set to about 0.01 to 1 dB / m. As a specific example of such an optical fiber 3, a fluorine-doped clad fiber, a high silica core fiber, a pure silica core fiber, etc. spun at a high tension of about 60 to 100 g are used.

In the optical fiber coupler with an abnormality warning function of the embodiment using the optical fiber 3 as described above, the bending loss is reduced at the fusion splicing portion 4, and the bending loss is caused at the optical fiber portion other than the fusion splicing portion. Has been maintained as is. This is annealed by the heat received when the optical fibers 3 and 3 in the fusion-stretching portion 4 are fusion-stretched, the residual strain in the core 1 is recovered, and the bending loss is reduced compared to before heating. Because. On the other hand, since the optical fiber portion other than the fusion splicing portion 4 is not annealed by heating, the bending loss is maintained as it is while the residual strain remains in the core 1. Here, the bending loss when the diameter of the fusion-bonded stretched portion 4 is 2r = 20 mmφ is 0.01
It is set to about 1 dB / m. The bending loss at the diameter 2r = 20 mmφ of the optical fiber portion other than the fusion drawing portion 4 is about 10 to 50 dB / m.

The optical fiber coupler with a warning function of this embodiment is housed in a reinforcing device or the like in order to prevent mechanical damage to the fusion spliced portion 4. FIG. 2 is a view in which the optical fiber coupler with the disconnection warning function of the embodiment is housed in the reinforcing device 5. When the optical fiber coupler with the wire break warning function of the embodiment is housed in the reinforcing device 5, the optical fiber portion other than the fusion extending portion 4 is fixed to the reinforcing device 5 with an adhesive or the like. At this time, the fusion-bonding extension part 4
When stress is applied to the other optical fiber portions, the diameters of the optical fiber portions other than the fusion extending portion 4 are 2r = 20 m.
Since the bending loss at mφ is 10 dB / m or more, the excess loss of the optical fiber coupler increases. On the contrary, unless stress is applied to the optical fiber portion other than the fusion splicing portion 4, the excess loss of the optical fiber coupler does not increase. Therefore, the increase in the excess loss of the optical fiber coupler can be used as the alarm information of the disconnection of the optical fiber coupler.

In order to detect such an increase in excess loss of the optical fiber coupler, for example, as shown in FIG. 3, either one of the two optical fibers 3 is used.
Of the optical fiber 3 into which the monitor light is incident, the first optical power meter 7 that measures the intensity of the emitted light emitted from the other end of the optical fiber 3 into which the monitor light is incident, and the other optical fiber 3 A second optical power meter 8 for measuring the intensity of the emitted light, the light source 6 and the first and second optical power meters 7, 8 connected to each other, and a measured value of the intensity of the incident light from the light source 6. A computer 9 for calculating an excess loss from the measured values of the emitted light intensities of the first and second optical power meters 7 and 8 and for calculating an increase in the excess loss, and a computer 9 connected to the computer 9 There is prepared an abnormality warning system including a warning device 10 which sounds an alarm when the increase of the excess loss of the optical fiber coupler is larger than a predetermined value based on the signal sent from 9.

Then, the computer 9 stores the excess loss of the optical fiber coupler having no abnormality, and one end of one of the two optical fibers 3 and 3 of the optical fiber coupler to be measured. When the monitor light is incident from, the monitor light is emitted from the other end of the optical fiber 3 on which the monitor light is incident and the optical fiber 3 on which the monitor light is not incident. At this time, the incident intensity of the monitor light and the emitted light intensity of the monitor light measured by the first and second optical power meters 7 and 8 are sent to the computer 9, and the computer 9 calculates the excess loss. , This value is compared with the excess loss of the optical fiber coupler which is stored in advance and has no abnormality, and when the increase of the excess loss is larger than the predetermined value, the alarm of the warning device 10 sounds,
It is possible to detect an excessive loss increase of the optical fiber coupler.

The optical fiber coupler with an abnormality warning function of the embodiment uses an optical fiber having a bending loss of 10 dB / m or more at a diameter 2r = 20 mmφ. This bending loss is maintained as it is in parts other than the splicing / stretching part 4, and since the increase in excess loss of the optical fiber coupler when stress is applied to parts other than the fusion splicing part is used as alarm information, the stress is detected. It is possible to know in advance the disconnection of the optical fiber coupler due to this stress.
Therefore, it is possible to prevent interruption of communication by replacing the abnormal optical fiber coupler at this point. Further, in the optical fiber coupler with an abnormality warning function of the embodiment, the bending loss is reduced in the fusion splicing section 4, so the excess loss of the optical fiber coupler is usually small, and it is difficult to be defective.

Next, an example of a method of manufacturing the optical fiber coupler with the abnormality warning function of the embodiment will be described with reference to FIG. First, an optical fiber preform having a higher softening point temperature in the core portion than in the clad portion is melt-spun with a high tension of about 60 to 100 g and remains in the core 1 in the longitudinal tension direction. An optical fiber 3 having a bending loss of 10 dB / m or more at a strain of 2r = 20 mmφ is manufactured.

Next, a plurality (two in the figure) of the optical fibers 3 are prepared, and a part of these is heated by a heat source such as a burner, and the optical fibers 3 are fused to each other around the heating portion.
Stretching is performed to form the fusion stretch portion 4. At this time, the fusion-stretching part 4 is annealed by the heating at the time of fusion-stretching,
The residual strain in the core 1 of the fusion-stretched portion 4 is recovered, and the bending loss is reduced before heating. On the other hand, since the optical fiber portion other than the fusion drawing portion 4 is not annealed by heating,
The bending strain is maintained as it is, with residual strain still existing in the core 1 of the optical fiber portion other than the fusion extending portion 4.

In the manufacturing method of the optical fiber coupler with the abnormality warning function as described above, the residual strain is recovered in the core 1 of the fusion extending portion 4 so that the bending loss is reduced, and thus the excessive loss of the optical fiber coupler is suppressed to a small value. It is possible to obtain a high yield. Further, the bending loss is maintained as it is with residual strain existing in the core 1 of the optical fiber portion other than the fusion splicing portion 4, and the excessive loss is increased even with respect to a minute bending that occurs during manufacturing of the optical fiber coupler. As a result, it is possible to manufacture an optical fiber coupler with an abnormality warning function that enables the disconnection of the optical fiber coupler to be known in advance.

(Example) First, the relative refractive index difference is 0.40.
%, And a core / clad ratio of 14.7 times was prepared as a base material for pure quartz / fluorine-doped clad fiber. Then, this was spun at a linear velocity of 100 m / min and a tension of 80 g to obtain an optical fiber 3 having a core 1 and a clad 2 for producing an optical fiber coupler. The optical fiber 3 had a cutoff wavelength of 1.25 μm, a mode field diameter of 10.1 μm, and a bending loss of 14 dB / m (diameter 2r = 20 mmφ, uniform bending). Then, two of these optical fibers 3 were prepared, arranged in parallel, and a part of them were fused and stretched to form a fused stretched portion 4 to produce a 3 dB optical fiber coupler for 1.55 μm. Excess loss is 0.15 dB
Met. Then, an adhesive having a large thermal strain was applied and fixed between the reinforcing device 5 and the optical fiber portion other than the fusion splicing portion 4 of the optical fiber coupler. Then, a low temperature test of −40 ° C. was performed, and stress was intentionally applied to the optical fiber portion other than the fusion drawing portion 4, and the excess loss was 0.3 d.
It was possible to detect that the stress increased to B and stress was applied to the optical fiber coupler.

Comparative Example First, the relative refractive index difference is 0.40.
%, And a core / clad ratio of 14.7 times was prepared as a base material for pure quartz / fluorine-doped clad fiber. Then, this was spun at a linear velocity of 100 m / min and a tension of 25 g to obtain an optical fiber 3 having a core 1 and a clad 2 for producing an optical fiber coupler. The optical fiber 3 had a cutoff wavelength of 1.35 μm, a mode field diameter of 9.6 μm, and a bending loss of 1.1 dB / m (diameter 2r = 20 mmφ, uniform bending). Then, two of these optical fibers 3 were prepared, arranged in parallel, and a part of them were fused and stretched to form a fused stretched portion 4 to produce a 3 dB optical fiber coupler for 1.55 μm. Excess loss is 0.15 dB
Met. Then, an adhesive having a large thermal strain was applied and fixed between the reinforcing device 5 and the optical fiber portion other than the fusion splicing portion 4 of the optical fiber coupler. Then, a low temperature test of -40 ° C was performed, and stress was intentionally applied to the optical fiber portion other than the fusion spliced portion 4 of the optical fiber coupler. However, since the bending loss was sufficiently small, the excess loss did not increase, The stress applied to the fiber coupler could not be detected.

Intentionally, the fusion extending portion 4 of the optical fiber coupler.
As is apparent from the result of applying stress to the other optical fiber parts, the optical fiber coupler of the comparative example cannot detect the stress and cannot know the disconnection of the optical fiber coupler in advance. On the other hand, in the optical fiber coupler of the embodiment, it is possible to detect stress because the excess loss of the optical fiber increases, and it is possible to know the disconnection of the optical fiber coupler in advance.

[0019]

As described above, the optical fiber coupler with an abnormality warning function of the present invention uses an optical fiber having a large bending loss, and the bending loss is reduced in the fusion drawing portion, and the fusion drawing is performed. The bending loss is maintained as it is in the parts other than the parts, and since the increase in the excess loss of the optical fiber coupler when stress is applied to the parts other than the fusion stretched part is used as the alarm information, the stress can be detected. The disconnection of the optical fiber coupler due to the stress can be known in advance. Therefore, it is possible to prevent interruption of communication by replacing the abnormal optical fiber coupler at this point. Further, since the bending loss is reduced at the fusion splicing portion, the excess loss of the optical fiber coupler is usually small, and it is difficult for the optical fiber coupler to be a defective product.

The manufacturing method of the optical fiber coupler with the abnormality warning function of the present invention is such that the optical fiber preform having a softening point temperature of the core portion higher than that of the cladding portion is melt-spun with high tension to cause bending loss. To obtain a large optical fiber, and then prepare a plurality of this optical fiber, part of these are fused with each other, and stretched to form a fused stretched part to produce an optical fiber coupler, so fusion splicing Since the bending loss is reduced in the section, the excess loss of the optical fiber coupler can be suppressed to a small value, resulting in a high yield. In addition, since the bending loss is maintained as it is in the optical fiber part other than the fusion splicing part, excess loss increases even for minute bending that occurs during manufacturing of the optical fiber coupler, and it is necessary to know the disconnection of the optical fiber coupler in advance. It is possible to manufacture an optical fiber coupler with an abnormality warning function.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical fiber coupler with an abnormality warning function according to an embodiment.

FIG. 2 is a diagram in which the optical fiber coupler with an abnormality warning function of the embodiment is housed in a reinforcing device.

FIG. 3 is a schematic configuration diagram showing an example of an abnormality warning system for detecting an increase in excess loss of the optical fiber coupler with an abnormality warning function of the embodiment.

[Explanation of symbols]

1 ... Core, 2 ... Clad, 3 ... Optical fiber, 4 ... Fusion extension part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Noboru Kawakami 1440 Rokuzaki, Sakura City, Chiba Prefecture, Sakura Factory, Fujikura Cable Co., Ltd. (72) Ryozo Yamauchi 1440, Rokuzaki, Sakura City, Chiba, Fujikura Cable Company, Ltd.

Claims (3)

[Claims] 1. An optical fiber coupler having a fusion spliced portion obtained by fusing and stretching a part of a plurality of optical fibers to each other, wherein the optical fiber has a large bending loss,
The bending loss is reduced in the fusion stretch portion, and the bending loss is maintained as it is in the portions other than the fusion stretch portion,
An optical fiber coupler with an abnormality warning function, characterized in that an increase in excess loss of the optical fiber coupler when stress is applied to a portion other than the fusion stretched portion is used as alarm information. 2. The bending loss at a diameter of 20 mmφ is 10
The optical fiber coupler with an abnormality warning function according to claim 1, wherein an optical fiber having a dB / m or more is used. 3. An optical fiber preform having a higher softening point temperature in the core portion than in the clad portion is melt-spun with high tension to obtain an optical fiber having a large bending loss. A method for manufacturing an optical fiber coupler with an abnormality warning function, characterized in that a plurality of the optical fiber couplers are prepared, and a part of these is fused and stretched to form a fused stretched portion to manufacture an optical fiber coupler.