Measuring and testing – Vibration – Sensing apparatus
Patent
1993-03-25
1995-10-17
Williams, Hezron E.
Measuring and testing
Vibration
Sensing apparatus
734321, 73DIG1, G01S 176, G01S 526
Patent
active
054579988
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a method of detecting a particular underground optical transmission line from the surface of the ground.
2. Prior Art
In modern telecommunication systems, optical cables are laid along the route of installation directly or housed in a duct or conduit which is lying underground.
Typical underground optical telecommunication networks comprise central stations, relay stations and terminal stations interconnected by means of a large number of optical transmission lines, which are often ramified, looped and star-connected.
There often arises cases where a particular underground optical transmission line needs to be branched, moved, tested, repaired and replaced.
Then, the particular underground optical transmission line has to be detected and dug out from the surface.
Since the routes of underground optical transmission lines are documented, it is normally not difficult to roughly trace the route of a particular transmission line from the ground surface and select a site for digging out the line. However, tremendous efforts may be required to precisely locate a particular transmission line at the work site simply because it is not visible from the surface. An old and conventional method to alleviate such efforts is to put a sign, or indicator, on the ground, telling that one or more than one optical transmission lines are buried there.
As more and more underground optical transmission lines are laid to form large networks, however, installation of such signs will become costly and, in some cases, may constitute obstacles for traffic on the ground.
Additionally, such indicators will eventually become damaged, degraded and inoperative as they are exposed to the atmosphere for a prolonged period of time.
In short, the use of signs does not provide an effective way for detecting underground optical transmission lines and is accompanied by a problem of necessity of digging the ground over a large area to take out a single transmission line. If an excavator machine is used to efficiently dig the ground over a large area, it can accidentally destroy transmission lines and/or other underground installations.
It should be noted here that an underground optical transmission line comprising an electric conductor or a metallic component can be precisely located by sending an electric signal into the conductor and detecting from the ground surface the electromagnetic wave generated by the conductor according to the electric signal.
As this technique is effective only for optical transmission lines comprising a conductor, the use of the technique will inevitably be very limited under the current circumstances where non-metallic optical transmission lines are more and more prevalent in optical telecommunication systems.
SUMMARY OF THE INVENTION
In view of the above discussed technological problems, it is therefore an object of the present invention to provide a method of accurately and efficiently detecting a underground optical transmission line regardless if it is a dielectric type or not.
According to the invention, the above object is achieved by providing a method of detecting an underground optical transmission line comprising steps of emitting acoustic vibration from vibration generating means toward an underground area where the optical transmission line is laid while moving the vibration generating means on the ground and measuring changes in the intensity of an optical signal being transmitted through the optical transmission line subjected to the vibration and the displacement of the vibration generating means to determine the location of the underground optical transmission line from the distribution of the intensity of the transmitted optical signal.
The method of detecting an optical transmission line according to the invention can be used to detect not only a particular optical transmission line contained in an optical cable but also an optical line buried underground integrally with or in parallel with another underground utility i
REFERENCES:
patent: 4405198 (1983-09-01), Taylor
patent: 4956550 (1990-09-01), Edwards et al.
patent: 5006806 (1991-04-01), Rippingale et al.
Fujisaki Akira
Nakamura Kazunori
Finley Rose M.
The Furukawa Electric Co. Ltd.
Williams Hezron E.
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