JP2721251B2 - Optical fiber identification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention includes, for example, a required optical fiber (including an optical fiber core and a tape core) from a large number of optical fibers in a laid optical cable. ) To identify an optical fiber.

(Prior Art) With the development of communication networks, various multi-core optical cables are being laid in pipes, building ducts and the like. Many optical fibers are accommodated in such an optical cable.

When any one of these optical fibers is taken out of the many optical fibers and construction such as post-branching is performed in the longitudinal direction, it is necessary to find an optical fiber that branches at the branch point. Normally, optical fibers are distinguished by color or the like, and can be identified to some extent by the color. However, since the connections may be crossed on the way, identification becomes difficult when the number is large. In addition, when laying or repairing an optical cable, it is necessary to distinguish an optical fiber used at a construction site from an unused optical fiber.

Conventionally, as an optical fiber identification method in such a case, there has been a method of bending an optical fiber to leak light from the optical fiber and detecting the leaked light. This identification method is for identifying an operating optical fiber without cutting it, and is very convenient because the optical fiber can be identified in the operating state.

(Problems of the prior art) However, in the above identification method, since the optical fiber is bent,
If the operating optical fiber is bent by mistake, the operating line may be adversely affected such as loss fluctuation, and in the worst case, a bit error may occur.

(Object of the Invention) An object of the present invention is to realize an optical fiber identification method that does not adversely affect a line in operation and can easily find a necessary optical fiber.

(Means for Solving the Problems) The present invention is an application of the principle of the optical system shown in FIG.

In the optical system shown in FIG. 2, when a laser beam enters the single mode optical fiber (SM fiber) 8 from the LD 7 and the light intensity is detected through the analyzer 9 on the light receiving side, the polarization state of the LD light in the SM fiber 8 is detected. When the (polarization main axis angle, phase, etc.) fluctuates, the detected output light power fluctuates. The level fluctuation of the output light power differs depending on the polarization state of the output light.

Incidentally, in FIG. 2, the electric field of light at the fiber output end before passing through the analyzer 9 is expressed as follows.

^{_{E x = a x e j e}} j E y = a y e j a x, a y: x -axis, the amplitude of the y-axis [delta]: x-axis, the phase difference of the y-axis omega: angular frequency, where it is assumed The light receiving power of the light passing through the analyzer 9 at the angle of the main axis angle θ with the x axis is represented by the following equation.

P (θ) = a _x ² cos ² θ + a _y ² sin ² θ + 2a _x a _y cos θ sin θ cos δ That is, the received light power P is a function of the principal axis angle θ. An optical fiber identification method and an optical fiber identification device according to the present invention apply the above principle of the optical system.

In the optical fiber identification method of the present invention, as shown in FIG. 1, polarized light is transmitted to an arbitrary optical fiber 1 among a large number of optical fibers, and an ultrasonic wave or the like is transmitted from the outside of the optical fiber 1 to the optical fiber 1. By vibrating, the polarization in the optical fiber 1 is changed from the polarization state, and the optical fiber 1 is distinguished from other optical fibers from the level change of the light emitted from the optical fiber 1 caused by the change. It is characterized by doing so.

(Operation) In the optical fiber identification method of the present invention, vibration such as ultrasonic waves is applied to the optical fiber 1 from outside at an arbitrary midpoint in the longitudinal direction (for example, a branch point) of the arbitrary optical fiber 1 among many optical fibers. At this time, the polarization state such as the angle and phase of the polarization main axis of the polarized light transmitted through the optical fiber 1 fluctuates, and the level of the output light power emitted from the optical fiber 1 fluctuates. In this case, if an ultrasonic fiber or the like is applied to the optical fiber to be searched for, the power of light emitted through the analyzer of the optical fiber fluctuates. Therefore, a desired optical fiber is selected from among a large number of optical fibers in the optical cable. 1 can be identified.

(Embodiment) FIG. 1 is an explanatory diagram of an optical fiber identification method of the present invention.

In FIG. 1, reference numeral 2 denotes a light source that generates linearly polarized light (if the light source is not linearly polarized light, a polarizer is inserted to obtain linearly polarized light). Reference numeral 3 denotes a polarization fluctuation light receiving unit that receives light transmitted by the optical fiber 1. These are provided in the transmitting / receiving station 4. As the optical fiber 1, a single mode optical fiber is used. Reference numeral 6 denotes an ultrasonic wave applying device for applying ultrasonic waves to the optical fiber 1 from outside the optical fiber 1 in the identification section 5 in the longitudinal direction of the optical fiber 1. The ultrasonic wave applying device 6 is configured so that the intensity can be modulated by changing the intensity and period of the ultrasonic vibration by the controller 10.

In this case, since the current optical communication system uses the intensity modulation / direct detection method, even if polarization fluctuation occurs in the line being used, there is no influence. In other words, applying ultrasonic vibration to the other optical fiber in use has no adverse effect on the line.

In FIG. 1, reference numeral 11 denotes a return station, in which an input optical fiber 12 and an output optical fiber 13 are connected by a loop line 14.

According to an experiment performed by the inventors, in the experimental system shown in FIG. 3, an optical fiber 15 having an outer diameter of 0.4 mm was used and ultrasonic vibration was applied to the same optical fiber 15 in the longitudinal direction of the optical fiber 15. As a result, the fluctuation of the light receiving power of the light received from the optical fiber 15 through the analyzer 9 is as shown in FIG.

(The invention's effect) . The optical fiber identification method according to the present invention includes:
Since the ultrasonic vibration is applied from the outside, there is no need to cut or bend the optical fiber 1. For this reason, even if the identification work is erroneously performed on the operating line, the optical fiber line is not adversely affected.

. Since the light emitted from the optical fiber 1 is received through the analyzer 9, only the modulation signal can be reliably detected, and highly accurate optical fiber identification becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an example of the identification method of the present invention, FIG. 2 is an explanatory view of a polarization plane variation in an optical system, FIG. 3 is an explanatory view of an experimental system of the identification method of the present invention, and FIG. FIG. 4 is an explanatory diagram showing a change in output light power when ultrasonic vibration is applied to the experimental system in FIG. 3. 1 is an optical fiber 2 is a light source 3 is a polarization fluctuation receiving unit 4 is a transmitting and receiving station 5 is an identification unit 6 is an ultrasonic wave applying device

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Haruki Ogoshi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Mitsuo Miyazaki 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo TEPCO (72) Inventor Morinobu Mizutani 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company

Claims (1)

(57) [Claims] A light is transmitted to an arbitrary optical fiber 1 among a large number of optical fibers, and vibrations such as ultrasonic waves are applied to the optical fiber 1 from the outside of the optical fiber 1 so that the optical fiber 1 has an optical fiber. , The light emitted from the optical fiber 1 is received through the analyzer 9, and the optical fiber 1 is distinguished from other optical fibers based on the level change of the light emitted from the optical fiber 1. An optical fiber identification method comprising: