A demodulation method of multi-channel fiber grating absolute wavelength demodulation system based on single detector

Abstract

A multi-channel fiber bragg grating absolute wavelength demodulation system based on a single detector comprises a broadband light source, a circulator, reference fiber bragg gratings, a 1*N optical switch, N-path sensing fiber bragg grating arrays, a tunable filter, a photoelectric detector and a data acquisition card. The invention simultaneously provides a demodulation method based on the system. The method is characterized in that the broadband light source generates light; the light passes through the circulator, then passes through the two reference fiber Bragg gratings and then is divided into transmission light and reflected light; the transmission light enters into the 1*N optical switch; a gating signal generated by the data acquisition card makes the light enter into a corresponding sensing fiber bragg grating channel; the reflected light enters into the tunable filter via the circulator; reflected light of a sensing fiber bragg grating also enters into the tunable filter via the circulator; frequency sweeping light is received by the photoelectric detector; a spectrum signal is converted into a time domain signal; then demodulation is performed so that a relative position of the reference fiber bragg gratings and the sensing fiber bragg grating is acquired. By using the system and the method of the invention, the system structure can be simplified and a wavelength measurement error caused by optical fiber transmission is eliminated.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a demodulation method of a multi-channel fiber grating absolute wavelength demodulation system based on a single detector. Background technique [0002] With the rapid development of optical fiber communication technology, fiber Bragg grating sensor has received more and more attention as a new sensor device for strain and temperature sensing. Compared with traditional electrical and optical strain sensors, fiber gratings have unique advantages, such as high sensitivity, no electromagnetic interference because the sensing signal is wavelength coded, easy to reuse and quasi-distributed sensing, and are currently used in civilian structures , aerospace, shipping, petrochemical and medical fields have been widely used. In order to demodulate the wavelength change of fiber gratings, many demodulation schemes have been proposed, such as: matched grating filt...

AI Technical Summary

Problems solved by technology

The separate setting of the reference optical path and the sensing optical path increases the complexity of the system, and the sensing optical path of each channel needs to be equipped with a detector, and the number of detectors is too large

In addition, when used for long-distance sensing, the sensing fiber grating is often far away from the frequency-sweeping light source, so the transmission fiber is long, so the long transmission time will be superimposed on the final demodulation result, resulting in wavelength measurement error

At the same time, when the swept light is transmitted in the long-distance optical fiber, nonlinearity and dispersion will be introduced, which will reduce the demodulation accuracy

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