Method for measuring optical fiber distributed Brillouin vibration sensor based on phase-BOTDR

Abstract

The invention provides a method for measuring an optical fiber distributed Brillouin vibration sensor based on phase-BOTDR (Brillouin Optical Time-Domain Reflectometry) The method comprises the following steps: modulating continuous lights emitted by a light source into pulse lights by a pulse modulator; amplifying the pulse lights by an erbium-doped optical fiber amplifier, the amplified pulse lights entering a single-mode sensing optical fiber through an optical circulator, and then backward Brillouin scattered lights at a position of vibration change entering an optical fiber Bragg gratingthrough the optical circulator to filter out noises; and performing interfering on the Brillouin scattered lights by a non-equilibrium Mach-Zehnder interferometer, and receiving the outputted three-way lights by a photoelectric detector and processing the outputted three-way lights by a data acquisition processing system; using a non-equilibrium Mach-Zehnder interferometer structure to convert a backward-scattered Brillouin frequency shift change amount into a change of an interference light output phase; using a phase demodulation method and a reverse trigonometric function method to demodulate the phase to obtain a Brillouin frequency shift change Therefore, measurement of optical fiber dynamic strain, and phase accuracy is higher than that obtained by a differential cross multiplying method.

Description

technical field [0001] The invention relates to the technical field of distributed optical fiber sensing, in particular to a distributed vibration sensing measurement based on a phase-BOTDR Brillouin fiber. Background technique [0002] Optical fiber distributed measurement is widely used in bridges, railway monitoring, rocket propulsion systems and oil well detection in urban construction. It mainly adopts the light scattering theory in optical fibers, including Rayleigh scattering, Raman scattering and Brillouin scattering. In the current domestic and foreign optical fiber sensing systems, distributed optical fiber sensing technology based on Rayleigh scattering is often used for qualitative detection of fiber breakpoints and attenuation characteristics. BelalM,Newson T P.A distributed optical fibre dynamic strain sensor based on phase-OTDR[J].Measurement Science&Technology,2013,24(8):085204.); Raman scattering is mainly used for temperature sensing measurement; Brillouin ...

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Problems solved by technology

[0003] To achieve long-distance, high spatial resolution, and high-sensitivity optical fiber sensing, the main limiting factors include: the nonlinear effect caused by excessive pulse power; the incompatibility between dynamic range and resolution caused by pulse width changes; weak scattering Signal detection and dynamic signal processing, etc.

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