Double-pulse phase-sensitive optical time-domain reflectometer and its method combined with weak reflection grating

Abstract

The invention discloses a double-pulse phase sensitive OTDR (optical time-domain reflectometer) integrated with a weak reflection grating, and the OTDR comprises a narrow-pulse laser, a light modulator, a circulator, a data collection device, an avalanche detector, a weak reflection grating array, a sensing optical fiber, and a pulse signal generator. The invention also discloses a vibration measurement method for the OTDR. The OTDR employs a mode of integrating with the weak reflection grating, and improves the signal to noise ratio of a system. Through employing a double-pulse detection method, the OTDR solves a problem that most of grating sensing is just sensitive to the position event of a grating, and is enabled to be sensitive to all events of the sensing fiber along a line. Because the signal to noise ratio of the system is very high, the OTDR can measure the high-frequency vibration of limit frequency under the limiting of the length of the sensing fiber, and also can measure the low-frequency vibration (less than 10 hertz).

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a double-pulse phase-sensitive optical time-domain reflectometer combined with a weak reflection grating and a method thereof. Background technique [0002] Phase-sensitive optical time-domain reflectometry (Φ-OTDR) realizes the detection of external disturbances by detecting the change of the interference signal of back Rayleigh scattered light in the sensing fiber. It has high sensitivity, distributed measurement, and long sensing distance. The advantages. Φ-OTDR was first proposed by H.F.Taylor (Taylor H F, Lee C E. Apparatus and method for fiberptic intrusion sensing[P].1993-.http: / / www.google.co.uk / patents / US5194847) in 1993 Yes, its basic structure is similar to that of OTDR, the only difference is that a narrow linewidth laser is used as the light source, so that the scattered light of the superimposed scattering centers interferes with each other to form a jittering ...

AI Technical Summary

Problems solved by technology

Although the use of weak reflection grating arrays can solve the problem of small back Rayleigh scattered optical power to a certain extent, most of the current sensing methods using weak reflection grating arrays are only sensitive to light that occurs at places where weak reflection gratings are placed. event, which greatly reduces the spatially detectable range of the sensing system

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