WARNING DEVICE FOR PREVENTING UNDERGROUND CABLES AGAINST ACCIDENTAL EXCAVATION

Abstract

A warning device for preventing underground cables against accidental excavation comprises an optical fiber vibration sensor having a mode recognition function, a signal processing unit, a wireless communication unit and a power supply unit, wherein the signal processing unit is connected to the optical fiber vibration sensor, the wireless communication unit and the power supply unit, and the optical fiber vibration sensor is installed within a set range of a cable and is used to monitor vibration signals around the cable, so that once a behavior possibly endangering the cable occurs, an alarm is given out in time to reduce power transmission and transformation accidents. Compared with the prior art, the warning device has the advantages of low false alarm rate, rapid response and accurate localization region.

Claims

1. A warning device for preventing underground cables against accidental excavation, comprising an optical fiber vibration sensor having a mode recognition function, a signal processing unit, a wireless communication unit and a power supply unit, wherein the signal processing unit is connected to the optical fiber vibration sensor, the wireless communication unit and the power supply unit, and the optical fiber vibration sensor is installed within a set range of a cable and is used to monitor vibration signals around the cable, so that once a behavior possibly endangering the cable occurs, an alarm is given out in time to reduce power transmission and transformation accidents.

2. The warning device for preventing underground cables against accidental excavation according to claim 1, wherein the optical fiber vibration sensor having the mode recognition function is a mode-conversion optical fiber vibration sensor, and an output of the optical fiber vibration sensor varies with a vibration intensity and frequency.

3. The warning device for preventing underground cables against accidental excavation according to claim 1, wherein the optical fiber vibration sensor comprises a photoelectric transmitter LD, a photoelectric receiver PD, a mono-mode optical fiber, a multi-mode optical fiber and a reflector, the mono-mode optical fiber has an end connected to the photoelectric transmitter LD and the photoelectric receiver PD and an end connected to one end of the multi-mode optical fiber, and the multi-mode optical fiber has an end connected to the reflector.

4. The warning device for preventing underground cables against accidental excavation according to claim 3, wherein the photoelectric transmitter LD and the photoelectric receiver PD are connected to the mono-mode optical fiber via a coupler.

5. The warning device for preventing underground cables against accidental excavation according to claim 3, wherein the mono-mode optical fiber and the multi-mode optical fiber are connected by welding.

6. The warning device for preventing underground cables against accidental excavation according to claim 3, wherein a light entering the multi-mode optical fiber from the mono-mode optical fiber will be emitted in a fundamental mode; however, when the multi-mode optical fiber bends, the light turns into a high-order mode to be transmitted in the multi-mode optical fiber from the fundamental mode; when transmitted to a tail end of the multi-mode optical fiber, the light is reflected back by the reflector and is transmitted still in the high-order mode; when transmitted to the mono-mode optical fiber, the light will be no longer in the fundamental mode and will not reach the photoelectric receiver PD via the mono-mode optical fiber; in a case where multi-mode optical fiber is disturbed, the light in the high-order mode turns into the fundamental mode when transmitted to the mono-mode optical fiber, so that a light signal is detected by the photoelectric receiver PD, and the light detected by the photoelectric receiver PD varies with vibration of the multi-mode optical fiber; and when the multi-mode optical fiber stops vibrating, a straight line is output by the photoelectric receiver PD.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0013] FIG. 1 is a schematic diagram a mode-conversion optical fiber vibration sensor of the invention;

[0014] FIG. 2 is a schematic diagram of mode conversion.

DETAILED DESCRIPTION OF THE INVENTION

[0015] A clear and complete description of the technical solution of embodiments of the invention is given as follows in combination with the accompanying drawings of the embodiments. Apparently, the embodiments in the following description are only illustrative ones and are not all possible ones of the invention. All other embodiments achieved by those ordinarily skilled in this field based on these illustrative ones without creative labor should also fall within the protection scope of the invention.

[0016] A warning device for preventing underground cables against accidental excavation comprises an optical fiber vibration sensor having a mode recognition function, a signal processing unit, a wireless communication unit and a power supply unit, wherein the signal processing unit is connected to the optical fiber vibration sensor, the wireless communication unit and the power supply unit, and the optical fiber vibration sensor is installed within a set range of a cable and is used to monitor vibration signals around the cable in real time, so that once a behavior possibly endangering the cable occurs, an alarm is given out in time to reduce power transmission and transformation accidents.

[0017] The optical fiber vibration sensor having the mode recognition function is a mode-conversion optical fiber vibration sensor, and an output of the optical fiber vibration sensor varies with the vibration intensity and frequency.

[0018] As shown in FIG. 1, the optical fiber vibration sensor comprises a photoelectric transmitter LD, a photoelectric receiver PD, a mono-mode optical fiber 1, a multi-mode optical fiber 2 and a reflector 3, wherein the photoelectric transmitter LD and the photoelectric receiver PD are connected to one end of the mono-mode optical fiber 1, the other end of the mono-mode optical fiber 1 is connected to one end of the multi-mode optical fiber 2, and the other end of the multi-mode optical fiber 2 is connected to the reflector 3. The photoelectric transmitter LD and the photoelectric receiver PD are connected to the mono-mode optical fiber 1 via a coupler 4. The mono-mode optical fiber and the multi-mode optical fiber are connected by welding.

[0019] The mono-mode optical fiber can only transmit lights in a fundamental mode, and based on this characteristic of the mono-mode optical fiber, a laser output by a laser device enters the mono-mode optical fiber via the coupler. The mono-mode optical fiber also serves as a communication optical fiber. The multi-mode optical fiber is welded to a tail end of the mono-mode optical fiber to serve as a vibration sensor optical fiber. The reflector is connected to a tail end of the multi-mode optical fiber, so that the laser can return along an original path when reaching the tail end of the multi-mode optical fiber.

[0020] As the mono-mode optical fiber can only transmit lights in the fundamental mode, a light entering the multi-mode optical fiber from the mono-mode optical fibers will be emitted still in the fundamental mode; when the multi-mode optical fiber bends, the light turns into a high-order mode to be transmitted in the multi-mode optical fiber from the fundamental model; when transmitted to the tail end of the multi-mode optical fiber, the light is reflected back by the reflector (as shown in FIG. 1) and is transmitted still in the high-order mode; and when transmitted to the mono-mode optical fiber, the light will be no longer in the fundamental mode and cannot reach the photoelectric receiver PD via the mono-mode optical fiber. In the case where the multi-mode optical fiber is disturbed, the light in the high-order mode turns into the fundamental mode under the vibration of the multi-mode optical fiber when transmitted to the mono-mode optical fiber, so that a light signal is detected by the photoelectric receiver PD, and the light detected by the photoelectric receiver PD varies with the vibration of the multi-mode optical fiber. When the multi-mode optical fiber stops vibrating, a straight line is output by the photoelectric receiver PD. Thus, output signals of the photoelectric receiver PD are vibration envelopes in a certain optical relation with external vibration.

[0021] The foregoing embodiments are only specific ones of the invention, and the protection scope of the invention is not limited to these illustrative embodiments. Various equivalent modifications or substitutes easily achieved by any skilled in this field based on the technical solutions of the invention should also fall within the protection scope of the invention. Thus, the protection scope of the invention is subject to the protection scope defined by the claims.