Phi-OTDR quantitative measurement method based on integral least square fitting

Abstract

The invention provides a Phi-OTDR quantitative measurement method based on integral least square fitting, and relates to the technical field of optical fiber sensing. In a phase optical time domain reflectometer based on a digital coherent detection mode, optical phases for measuring dynamic events on the optical fiber are continuously accumulated in the length direction of the optical fiber, dueto the nonuniformity of refractive index distribution of the optical fiber, the accumulated phases have the characteristic of random distribution in the length direction of the optical fiber, and thefrequency drift of laser also affects a measurement result. In order to obtain accurate quantitative demodulation results, through a series of data acquisition and processing processes such as data acquisition, coordinate regulation, position judgment, original phase resolution, new origin setting, phase subtraction and mean value removal, a relatively smooth phase change value is obtained in thelength direction of the optical fiber, and in order to further achieve accurate solution, a solution result is obtained after the processes of data fitting and applicable judgment. According to the method, the influence of laser frequency drift is reduced as much as possible, and meanwhile, the influence of noise such as polarization fading is reduced, so that the measurement result has high reliability and accuracy.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a method for quantitative measurement of Φ-OTDR based on overall least squares fitting. Background technique [0002] Distributed optical fiber sensing technology is an important branch of optical fiber sensing technology. It uses the signal carried by the backscattered light in the optical fiber to locate, identify, and measure events along the optical fiber. In the backscattered light, according to the different physical mechanism and parameter characteristics, it can be divided into Rayleigh scattered light, Brillouin scattered light and Raman scattered light. Among them, the Rayleigh scattered light is based on the elastic effect, and the light intensity is relatively large among the three kinds of backscattered light, and relatively speaking, it is the easiest to detect. [0003] Based on Rayleigh backscattered light, people invented OTDR (optical time domain ...

AI Technical Summary

Problems solved by technology

To make matters worse, since the light source used by the phase optical time domain reflectometer is a highly coherent light source, there will be fading zeros in the detection curve generated by the Rayleigh backscattered light, which will cause the phase to be unable to be demodulated

Therefore, it is very difficult to achieve reliable, accurate and repeatable quantitative measurement in phase optical time domain reflectometer.

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