Method and device for sensing and demodulating Bragg fiber grating

Abstract

The invention relates to a method and device for sensing and demodulating Bragg fiber grating. The method in the invention uses the principle that chatter fiber grating has different reflective wavelengths at different positions to convert the change of sensed fiber grating wavelength into the change of system optical path difference, and then the optical path difference is measured by low coherent demodulating method, thereby being capable of accurately obtaining wavelength change of sensed fiber grating so as to obtain sensing amount. The device realizing the method comprises a broadband light source at the optical communication band of center wavelength, a fiber optic isolator, a four-port 3-dB optical fiber coupler, a polarization controller, a tunable fiber delay line, a three-port 3-dB optical fiber coupler, a sensing fiber grating, a linear chatter fiber grating, a photodetector and an oscillograph. The invention has higher measurement precision of wavelength resolution, has the advantages of strong anti-interference, simple structure, low cost, and the like, and can obtain different resolutions and parameter ranges, thereby being much applied to practical application.

Description

technical field [0001] The invention belongs to the field of sensing technology, and relates to a method for realizing high-precision fiber grating sensing and demodulation by using a linearly chirped fiber grating as a reference combined with a low-coherence demodulation technology, and equipment for realizing the method. Background technique [0002] Fiber Bragg grating (FBG) has become an important device for optical fiber sensing due to its unique advantages of optical fiber internal sensitivity, wavelength coding, and easy networking, and has been widely used, such as: health monitoring of railways, bridges, dams, etc. Temperature monitoring along main transmission lines, etc. Traditional fiber grating demodulation methods often use optical filter demodulation methods, such as tunable F-P filter method, matched grating method and so on. These methods either have higher requirements on the performance of optical filters and higher cost; or require more optical filters, ...

AI Technical Summary

Problems solved by technology

However, the existing fiber grating sensing coherent demodulation schemes are all based on the intensity demodulation of the amplitude of the detection interference signal, and the intensity of the interference signal is affected by the stability of the light source, fiber loss and other environmental uncertainties, so the intensity demodulation The measurement accuracy of the scheme is limited

In addition, the existing coherent demodulation scheme can only measure the change of grating wavelength, but cannot measure whether it changes in the direction of long-wave or short-wave

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