JPS61228405A - Method for connecting single mode fiber - Google Patents

Abstract

PURPOSE:To increase a clad mode light leak output by compressing and deforming a buffer layer or primary coat nearby a connection part where the other single mode fiber is connected and then scattering light propagated in the buffer layer or primary coat out of a jacket. CONSTITUTION:A compressing jig 30 is installed between a sensor 8 and the end surface of an SM fiber 2 which is at the distance of a gap G from the core end surface of an SM fiber 1 and pressure is applied without rupturing any fiber. Then, the light 10 propagated in the primary coat 25 leaks out of the jacket 27 and is detected by the sensor together with clad mode leak light 9 before the compressive deformation. Consequently, the output of the clad leak light is much larger than before and a long-distance connection which is impossible before is made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for splicing single mode fibers while detecting cladding mode leakage light.

[Prior art] Single mode fiber (hereinafter abbreviated as 3M fiber) is attracting attention for its ability to transmit large amounts of information, but it has a very small core diameter of 5 to 10 μm, and requires advanced technology for connection. is required.

Examples of the 3M fiber connection method include a single optical power monitor method and a cladding mode leakage light detection method. The former type of optical power monitor is aligned so that light (λ = 0.85 μm or 1.3 μm) is input from one 3M fiber end and output from the other 3M fiber end to maximize the leading wave mode output. However, it is necessary to guide the optical output emitted from the other 3M fiber back to the connection point using a multimode fiber, which is not only extremely troublesome when the fiber length is 1- or more.
Securing that line was economically disadvantageous.

For this reason, the latter cladding mode leakage light detection method has recently begun to be adopted.

FIG. 2 is an explanatory diagram showing the principle of the cladding mode leakage light detection method. 1.2 is 3M fiber, 13.23
is a core, 14.24 is a cladding, 15.25 is a primary coat of silicone resin or the like, 16.26 is a buffer layer of silicone resin or the like, and 17.27 is a jacket made of nylon or Teflon.

Light is input into the 3M fiber 1 from a light source such as a semiconductor laser, and the light is emitted from the end face of the core 13, and is directed to the core 2 of the 3M fiber 2, which is separated by the distance of the gap G.
3 and the end faces of the cladding 24 in a radial manner.

At this time, if the cores 13 and 23 are axially misaligned, cladding mode leakage light 9 leaks out of the jackets 1 to 27 according to the amount of axial misalignment, and the sensor 8 can detect the output. In addition, 3M fiber 1 and 3M fiber 2
Since they are separated by the gap G, cladding mode leakage light can be detected as shown in FIG. 3 even when there is no axis deviation.

Therefore, as shown in FIG. 3, the cladding mode leakage light 9
If you connect it when the output of
There is no axis misalignment.

[Problems to be Solved by the Invention] However, most of the light emitted from the core 13 is transmitted through the core 23, the cladding 24, and the primary frames 1 to 25.
The output of the cladding mode leakage light 9 is small because it propagates to a long distance while being confined inside, and the output becomes further smaller as the connection point becomes farther from the light source. That is, if the lower detection limit of the sensor 8 is a in FIG. 3, there is no problem in the curve A, but in the curve B, it becomes impossible to detect the cladding mode leakage light in the vicinity of zero axis deviation. Therefore, the distance between the conventional connection point and the light source is 20KII &
is the limit, and in order to lower the detection limit a, a sensitive and expensive sensor is required.

Furthermore, due to variations in the materials of the primary coat and jacket, as well as variations in manufacturing conditions, the amount of leaked light for each fiber varies significantly, resulting in the problem of requiring a long time for connection work.

[Object of the Invention] In view of the problems of the prior art described above, the object of the present invention is to provide a method for easily and quickly connecting single mode fibers, and to significantly improve the connectable distance. The purpose of this invention is to provide a method for connecting single mode fibers that can be used.

[Summary of the Invention] The gist of the present invention is to make the end faces of two single mode fibers face each other so that the cladding mode leaked light is incident on one single mode fiber and leaks out of the jacket of the other single mode fiber. In the method of connecting while detecting -C, by compressively deforming the vicinity of the connection part of the other single mode fiber and scattering the light propagating inside the buffer layer or the primary coat to the outside. The aim is to increase the cladding mode leakage light output.

[Example] Embodiments of the present invention will be described below with reference to FIG.

The arrangement of the 3M fibers 1 and 2 is similar to that shown in FIG. 2, and their core end faces are separated by a gap G. When a compression jig 30 is installed between the SM fiber 7 and the sensor 8 and pressure is applied to an extent that does not break the fiber, the light 10 propagating inside the primary coat 25 is transferred to the jacket 1. .

Therefore, the output of the cladding mode leakage light is significantly increased compared to the conventional method, and it becomes possible to perform long-distance connections that were not possible in the conventional method.

Example 1 A compression jig was grounded at a position approximately 100 degrees from the core end surface of the 3M fiber 2, and a sensor was installed at a position approximately 3# behind it.

The 3M fiber has a buffer layer diameter of 0.5% and a Teflon jacket diameter of 0.88. When this 3M fiber was deformed by 50% using a compression jig, the transmitted power was approximately 3
The 5db lower cladding mode leakage light was reduced to 1q.

Light source output is 112 dbm, minimum detection sensitivity of sensor is 16 dbm
Since the fiber loss is 5 db, it was confirmed that if the fiber loss is 0.6 db/candy, connection with a connection interval of 30 KIn is possible.

In addition, in the conventional method that does not deform the fiber, only Talarad mode leakage light that is about 50 db lower than the transmitted power can be obtained, and the connectable length is greatly limited.

In addition, in Example 1, there is only one compressive deformation part, but by providing another compression jig at a position about 10 s closer to the connection part, the scattering of the Tararad mode is further promoted, and the leakage light output is reduced. It was confirmed that there was a significant improvement.

As described above, as a result of conducting experiments on connecting 3M fibers using the method of the present invention, the number of connection points was 100, and the average connection loss was 0.07 dB for 1q, which is equivalent to the optical power monitor system currently in practical use. A connection was made. Further, since the amount of axis deviation can be detected near the connection part, the work is easy and connection can be made in a short time.

Note that the shape of the compression jig 30 is preferably such that it does not damage the fiber, and one side may be used as a fixed plate and compression may be performed from the other side.

[Effects of the Invention] As explained in detail above, the present invention provides the following remarkable effects.

(1) Since the amount of axis misalignment can be detected near the connection part, it is economical because it does not require a fiber-back circuit like a one-sided optical power monitor. (2) It is easy to work and can be connected in a short time. It is possible.

(3) By compressing and deforming the vicinity of the connection part, it is possible to significantly increase the Talarado mode leakage light output, and it is possible to connect a relay section of 30 KIn or more.

(4-) Since the sensor and compression jig are small and can be integrated, they can be easily attached to a conventional fusion splicer.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a conventional example, and FIG. 3 is an explanatory diagram showing the relationship between the amount of axis deviation and Talarado mode leakage light. 1.2...3M fiber, 8...Sensor, 9...Tararad mode leakage light, 10...Light, 13.23...Core, 14.24...Clad, 15.25...・Primary court, 16.26...
- Buffer layer, 17.27... Jacket, 30... Compression jig. Agent: Patent Attorney Sa Ni Fujiyomi 112]

Claims (1)

[Claims] (1) In a method in which the end faces of two single-mode fibers are made to face each other, light is input into one single-mode fiber, and the cladding mode leakage light leaking out of the jacket of the other single-mode fiber is detected while being connected. . A method for connecting single mode fibers, characterized in that the vicinity of the connecting portion of the other single mode fiber is compressively deformed.