Research On Demodulation Mechanism Of White Light EFPI Sensing System

With the improvement of coal mining technology, the quantity of gas emission and the number of high-gassy coal mines were increasing, which may result in coal mine accidents accounted for a growing proportion. Aiming at the frequent occurrence of coal mine gas accident, by researching on concentration detection based on Extrinsic Fabry-Perot Interferometer (EFPI) technology in mine and the demodulation mechanism of white light interference in spectral domain of the EFPI optical fiber sensors systematically presented a spectral domain demodulation techniques which could process high resolution sensor information on optical fiber sensing technology with high dynamic range measurements and avoid interference from light fluctuations and perturbation in transmitting fibers and other factors.The research of the demodulation mechanism of white light interference in spectral domain was mainly at principle, algorithm and new technology application. In the aspect of algorithm, applied fast Fourier transform(FFT), pattern theory, genetic algorithm, ant colony algorithm, and BP neural network algorithm as the signal demodulation algorithm and the wavelet transform, the normalization method and the Hilbert-Huang transform as the noise reduction algorithm. Meanwhile, the membrane computing was applied to multi-sensor parallel data processing. At the respect of new technology application, designed gas cell based on grin lens for gas sensor and a optical system that combine space division multiplexing with time division multiplexing technology to achieve high precision optical division multiplexing and hollow-core photonic crystal fibers, digital lock-in amplifier, distributed fiber Bragg grating sensors and other new materials and devices to avoid the influence of various interferences effectively in harsh environments and solve the problems, for instance, sensitive to changes that the effect of fluctuation of optical power and the optical fiber transmission loss in EFPI fiber sensing gas detection technology, low measurement resolution, small dynamic range, difficult to extract the effective signal, low efficiency in data processing, high system costs, susceptible to interference and other issues.The results showed that adopting of EFPI fiber sensing gas detection system with demodulation mechanism model of white light interference in spectral domain could achieve the32Road (extensible) gas online detection, precision can reach5ppm, and to eliminate all kinds of interference in the measurement of gas concentration to obtain accurate results. Through the research on the optical fiber sensing gas, obtained a new method for the realization of concentration detection in mine, which have great significance for guiding the safe production of coal mine.