Super-long distance phase-sensitive optical time domain reflectometer (Phi-OTDR) system

Abstract

The invention discloses a super-long distance phase-sensitive optical time domain reflectometer (Phi-OTDR) system, which comprises a Phi-OTDR demodulating system and detecting optical fiber, wherein a forward amplifying unit and a backward amplifying unit are respectively arranged at the front end and the back end of the detecting optical fiber. Detecting signal light of the Phi-OTDR system is amplified in a distributed manner by utilizing a bidirectional second-order or bidirectional multi-order Raman amplifying method, so that the uniformity of the intensity and the distribution of Rayleigh scattering signals on the whole optical fiber is further improved, the problem of the prior amplifying method of the Phi-OTDR system is effectively overcome, and the sensing distance of a single segment of detecting optical fiber of the Phi-OTDR system is further prolonged; and meanwhile, by utilizing bidirectional Raman amplifying multi-segment cascade connection, the super-long distance Phi-OTDR system which requires a low cost and has high performance can be realized. The method of the super-long distance Phi-OTDR system is helpful to improvements on the whole performance and the performance price ratio of the Phi-OTDR system during the application to long-distance safety monitoring of oil and gas transmitting pipelines, large-range peripheries, large-scale civil engineering structures, and the like.

Description

technical field [0001] The invention relates to a fully distributed optical fiber sensing system, in particular to an ultra-long-distance phase-sensitive optical time-domain reflection system. Background technique [0002] The phase-sensitive optical time-domain reflectometry (Φ-OTDR) system based on the Rayleigh scattering mechanism is currently the most important fully distributed vibration measurement technology. By injecting a coherent narrow pulse at one end of the fiber, detecting the change of the interference fringe of the Rayleigh scattered light, and judging the phase change introduced by the external disturbance and its spatial distribution along the fiber. The Φ-OTDR system is based on the phase-sensitive detection mechanism with extremely high sensitivity. At the same time, it is superior to other optical fiber distributed vibration measurement systems in terms of long-distance detection and multi-point detection and positioning. The field of security monitorin...

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Problems solved by technology

[0005] The problem to be solved by the present invention is: how to overcome the deficiencies of the prior art, solve the problem of low signal-to-noise ratio in the long-distance detection of the Φ-OTDR system, further extend the sensing distance of the single-segment detection optical fiber of the Φ-OTDR system, and improve the overall The uniformity of the gain distribution of the optical fiber sensing signal realizes a low-cost and high-performance ultra-long-distance phase-sensitive optical time-domain reflectometry system

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