Phi-OTDR threshold adaptive device and method

Abstract

The invention discloses a phi-OTDR threshold adaptive device and method. The device comprises a laser 1, a laser 2, an optical switch (2*1), an acoustic optical modulator (AOM), an erbium-doped optical fibre amplifier 1 (EDFA1), an optical circulator, a Raman amplifier (RA), a wavelength division multiplexer (WDM), an erbium-doped optical fibre amplifier 2 (EDFA2), a photoelectric detector, a dataacquisition module and a processing server. According to the phi-OTDR threshold adaptive device and method in the invention, a phi-OTDR technology is realized through conduction of the laser 1 and the optical switch; when a sensing optical cable receives external vibration, a system can rapidly detect vibration and vibration source positions, screen and judge in time, upload, and give an alarm; the optical switch is switched to the laser 2 every a certain period; line loss of the sensing optical cable is scanned and calculated for one time; alarm threshold adaptivity of a phi-OTDR system is realized in a software and hardware combination manner; the efficiency is high; the adaptivity is high; maintenance is easy; the reliability and the stability of the system can be greatly improved while a small amount of cost is increased; and the practical value is very high.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensors, in particular to a threshold adaptive device and method for a Φ-OTDR alarm system. Background technique [0002] The distributed optical fiber sensing system has a series of advantages such as small size, passive, anti-electromagnetic interference, and anti-corrosion. The coherent optical time-domain reflectometry technology (φ-OTDR, positioning type vibrating optical fiber system) based on Rayleigh scattering also has long-distance transmission. , high sensitivity, and precise positioning advantages, vibrating optical fibers, especially φ-OTDR systems, are increasingly being used in petroleum, military and security fields. [0003] However, due to its coherent characteristics, the φ-OTDR system can measure the result of Rayleigh scattered light coherence. It cannot quantify the fiber loss, but can only observe it qualitatively. In the actual implementation and maintenance process, ...

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Problems solved by technology

However, this method responds slowly, and the threshold value cannot be corrected in time; the threshold value needs to be corrected point by point, and the workload is heavy; especially for long perimeters, the change of line loss is a high probability event, which consumes a lot of manpower. The other is software algorithm optimization, mainly There are dynamic threshold method (calculate the threshold of the current time according to the previous certain time) and normalized threshold algorithm (relative value comparison), but the signal-to-noise ratio of the φ-OTDR system has a great relationship with the optical power (the optical power is attenuated by 3dB, the signal Noise ratio reduction > 3dB), pure software compensation is difficult to restore the threshold to an appropriate value, obviously the above two processing methods still have a high rate of false alarms and false negatives, the current processing method cannot meet the actual needs Therefore, a set of effective threshold adaptive methods is very important and urgent

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