Brillouin scattering signal processing method and distributed fiber sensing system thereof

Abstract

The invention relates to the technical field of intelligent sensing and particularly discloses a Brillouin scattering signal processing method and a distributed fiber sensing system thereof. The system comprises a sensing fiber, a laser signal source, an annular device, a detection pulse optical path modulation module, a frequency shift reference optical path modulation module, a coherent detection unit and a data acquisition processing module, so relative variation quantity of Brillouin frequency shifts can be precisely acquired, backward Brillouin scattering spectrums are acquired and the complete Brillouin scattering spectrum is obtained. The method comprises steps of firstly, establishing a detected Brillouin scattering signal spectrum model; and using a fast iteration algorithm based on numerical optimization to carry out characteristic extraction on the Brillouin scattering spectrum. In the method, scattering signal frequency spectrums obtained through frequency scanning of each time are fit, so sensing information of temperature or stress distributed along the fiber is precisely acquired. A solving method has strong global searching ability, so algorithm action time is shortened and measurement precision and timeliness of the system are effectively improved.

Description

technical field [0001] The invention belongs to the technical field of intelligent sensing, and in particular relates to a signal processing method and system for Brillouin scattering signal spectrum fitting. Background technique [0002] The distributed optical fiber sensing technology based on Brillouin scattering has the characteristics of high measurement accuracy, high spatial resolution, real-time online measurement of temperature and strain information, etc. It can be applied to aircraft health status monitoring and can effectively evaluate the health status of aircraft , thereby improving the safety and reliability of aircraft operation. In this kind of distributed optical fiber sensing system, the Brillouin scattered optical signal has random polarization states at different positions along the optical fiber, and the scattered signal is affected by nonlinear effects in the optical fiber, so that the optical signal is doped with a lot of noise. Therefore, the photoc...

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Problems solved by technology

Among them, the superposition average algorithm uses the time correlation of the signal and the non-correlation characteristics of the noise to continuously sample and accumulate the measured signal and take the average value. Finally, the periodic signal is strengthened, and the noise tends to However, the signal extraction performance of this algorithm depends on the number of superimposed averages. The more times, the better the signal-to-noise ratio, and the algorithm has poor real-time performance; the low-pass filter denoising method can Using software to design a virtual filter, although the high-frequency noise other than the Brillouin gain spectrum width can be filtered out, but the comparison between the denoised signal and the original signal shows that after low-pass filtering, the Brillouin scattering signal intensity is also the same. The wavelet-based envelope demodulation algorithm can achieve signal denoising and feature extraction, but the processing effect is related to the choice of wavelet function, and Can not take into account the high resolution of frequency domain and time domain

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