JPH02230106A - Optical fiber cable identification method and identification device - Google Patents

Abstract

PURPOSE:To easily identify a necessary cable without damaging the cable by vibrating one of many cables halfway with an ultrasonic wave and photodetecting variation in the level of output light through an analyzer. CONSTITUTION:An ultrasonic wave applying device 6 is fitted to one optional optical fiber cable 1 among many optical fiber cables halfway in the lengthwise direction to cause ultrasonic-wave vibration. The polarization state of light transmitted in the cable such as the angle of the main axis of polarization and the phase varies owing to the current polarization variation due to the vibration and the variation is passed through the analyzer of a polarization variation photodetection part 3 to photodetect the variation in the level of the output light. At this time, when a cable to be searched for is applied with a cable ultrasonic wave, the photodetection level varies, so the necessary cable can easily be identified without damaging the cable nor exerting any adverse influence upon other lines in operation.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is directed to a cable identification method for searching for a required cable from among a large number of cables installed in conduits, building ducts, etc. This relates to identification devices. (Prior art) With the development of communication networks, various cables are being installed inside pipelines, building ducts, etc. In such places, in addition to communication cables, there are many cables with similar appearances, such as power cables, and a mixture of various wires. When performing work such as branching off one of the many cables along its length, it is necessary to find the cable that will branch at that branch point. However, because cables are usually laid long, it is not possible to visually identify the input and output ends along the way. For this reason, it was difficult to connect the desired cable. Conventionally, the cable identification method in such cases was as follows:
In the case of power cables, there was a method to use a search coil. This identification method uses a coil to detect the magnetic field generated outside the power cable in use to find live wires. This method is very convenient because it allows you to find live wires without contacting them while the cable is still in operation. (Problems with the prior art) However, the above identification method (PA) is only for power cables and cannot be applied to optical fiber cables. To identify an optical fiber cable, a part of the sheath of the cable is stripped off, light is passed through the fiber inside, and the fiber is bent, etc., and the light leaks out from the part where the sheath was stripped off and detected. One possible method is local detection. However, this identification method has the problem of damaging the cable because the cable sheath must be removed, and there is also the risk that loss fluctuations may affect the line during operation. (Objective of the Invention) The object of the present invention is to realize a cable identification method and its identification device that can locate a necessary cable without damaging the optical fiber cable or adversely affecting the line in operation. There is a particular thing. (Means for solving interstitial points) The present invention applies the principle of the optical system shown in Figure 2. In the optical system shown in FIG. 2, a case where a laser beam is incident on a single mode fiber (SM fiber) 8 from an LD 7 and the light intensity is detected through an analyzer 9 on the receiving side. When the polarization state of the LD light in the SM fiber 8 changes (the angle of the principal axis of polarization, the phase, etc.), the detected output optical power changes. The level fluctuation of this output optical power differs depending on the polarization state of the output light. Incidentally, in Fig. 2, the electric field of the light at the output end of the fiber before passing through the analyzer 9 is expressed as follows. E 11 =ame”e′&E ,=a,e′″′ a) l. a,'. Amplitude δ on X axis, y axis: X axis, y
Phase difference ω at the axis: Angular frequency Here, the received power of the light that has passed through the analyzer 9 at the assumed angle between the X axis and the main axis angle θ is expressed by the following formula, P{θ) ``am'' Cog”θ+a,”sin”θ
+2am a, CO8θsinθCO+96 that is,
The received light power P is a function of the principal axis angle θ. The cable identification method and identification device of the present invention apply the above-mentioned principle of the optical system. As shown in FIG. 1, the first cable identification method of claim 1 of the present invention is to apply ultrasonic waves to any cable 1 from the outside of the cable 1 midway in the longitudinal direction of a large number of optical fiber cables. etc., and the polarization state such as the angle and phase of the main axis of polarization of the light transmitted in the cable 1 is varied by the polarization variation of the cable 1 due to this vibration,
The cable 1 is distinguished from a large number of other optical fiber cables based on the variation in the level of light emitted from the cable 1 that occurs with this variation. A second cable identification device according to the present invention, as shown in FIG.
The optical fiber cable 1 is characterized in that an identification section 5 located midway in the longitudinal direction of the optical fiber cable 1 is provided with an ultrasonic application device 6 that applies ultrasonic vibrations to the cable 1 from the outside of the cable 1. (Function) In the optical fiber cable identification method and leg separation device of the present invention, when any cable l among a large number of optical fiber cables is located midway in the longitudinal direction (for example, at a branch point λ), the same cable l is Since vibrations such as ultrasonic waves are applied to the cable, the polarization state such as the angle and phase of the main axis of polarization transmitted through the single mode fiber of the same cable l changes, and the output emitted from the cable l changes. The level of optical power fluctuates. In this case, if vibrations such as ultrasonic waves are applied to the optical fiber cable that you want to find, the power of the light emitted from the cable through the analyzer will change, making it difficult to identify the same cable from among a large number of optical fiber cables. can. (Example) Figure 2 is an explanatory diagram of the optical fiber cable identification device of the present invention. In the figure, 2 is a light source that generates coherence light, etc.;
. is a polarization variation light receiving section that receives light transmitted by the optical fiber cable l, and these are provided in the transmitting/receiving station 4. The optical fiber cable l used is a single mode optical fiber. 6 is an ultrasonic applying device, and the optical fiber cable l
This is for applying ultrasonic waves to the cable l from the outside of the cable l at the identification part 5 located midway in the longitudinal direction.
This ultrasonic wave applying device 6 is configured to be able to perform intensity modulation and phase modulation by changing the intensity and period of ultrasonic vibration using a controller 10. In this case, current optical communication systems use intensity modulation/direct detection, so even if polarization fluctuations occur in the line in use, there is no effect. In other words, applying ultrasonic vibration to another optical cable in use will not have any negative effect on that line. Reference numeral 11 in FIG. 1 is a return station, in which the input optical cable l2 and the output optical cable l3 are connected to loop II.
Connected by 14. According to experiments conducted by the inventors, the optical fiber strand l5 with an outer diameter of 0.4 mm in FIG.
In an experimental system using the same optical fiber element! When ultrasonic vibration was applied to the isotropic wire 15 midway in the longitudinal direction of 15,
The fluctuations in the received power of the light received from the optical fiber 15 through the analyzer 9 are as shown in Figure 4. (Effects of the Invention) The optical fiber cable identification method and identification device of the present invention have the following effects. ■． Since vibrations such as ultrasonic waves are applied to the cable 1 from the outside of the optical fiber cable, there is no need to peel off a part of the cable 1 to leak light to the outside, and therefore the cable 1 is not damaged. ．． ■Identification work becomes easier because there is no need to strip off part of the cable l. ■． There will be no negative impact on the lines in operation. ii
! ! You can perform separate work without disrupting the lines in use.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram showing an embodiment of the identification device of the present invention, Fig. 2 is an explanatory diagram of polarization plane fluctuation in the optical system, and Fig. 3 is an experiment of the identification device of the present invention. An explanatory diagram of the system, Figure 4 is an explanatory diagram showing the fluctuation of the output optical power when ultrasonic vibration is applied to the experimental system of Figure 3. ■The optical fiber cable 3 is the polarization variation light receiving section 4, the transmitting/receiving station 5 is the identification section 6, and the ultrasonic wave applying device.

Claims (2)

[Claims] (1) Vibrations such as ultrasonic waves are applied to any cable 1 from the outside of the cable 1 in the longitudinal direction of the cable 1 among a large number of optical fiber cables, and the polarization of the cable 1 changes due to this vibration. The polarization state, such as the angle and phase of the main axis of polarization of the light transmitted through the cable 1, is changed by changing the polarization state, such as the angle and phase of the main axis of polarization of the light transmitted through the cable 1, and the level change of the output light from the cable 1 that passes through the analyzer, which occurs due to this change, can be used to determine the same. A method for identifying an optical fiber cable, characterized in that a cable 1 is identified from a large number of other optical fiber cables. (2) A transmitting/receiving station 4 equipped with a light source 2 and a polarization variation light receiving section 3 that receives light transmitted by the optical fiber cable 1, and an identification section 5 located midway in the longitudinal direction of the optical fiber cable 1.
A cable identification device comprising: an ultrasonic wave applying device 6 that applies vibrations such as ultrasonic waves to the cable 1 from the outside of the cable 1.