Design And Implementation Of The High-speed FBG Sensing Demodulation System

The FBG (Fiber Bragg Grating) sensor technology has developed more and more rapidly and attracted more and more concerns from all over the world since Morey firstly used the FBG sensor for strain and temperature measurement in1989.With the progress of the FBG etching technologies and the reduction of the FBG production cost, the FBG sensor technology has become today’s fastest-growing and most promising sensing technology, and it has been widely used in the field of spacecraft industry, ship traffic, military industry, the oil and coal industry, civil engineering structures, power industry and chemical sensing, etc. Nowadays, the application of the demodulation products has started in domestic and foreign industry, but the existing products are incompetent to meet the actual requirements of condition monitoring for industrial structures in terms of demodulation speed and accuracy. Foreign country carried out the research earlier on design and development of high-speed demodulation products, but the price of these products are quite expensive, which make it difficult to be widely used in the engineering field.So in order to implement the high-speed and high-precision demodulation system, the difficulty of research is the optimization of the existing low-speed demodulation scheme and algorithm. This paper researches on high-speed data collecting and fast demodulation algorithm of the FBG sensor demodulation system. Firstly, this paper introduces the domestic and foreign development and research status of the FBG sensor demodulation, and then designs the high-speed FBG demodulation scheme based on tunable F-P filter.This paper focuses on the demarcation and peeks-seek algorithm of the demodulation system. The optical comb filter and optical single-peak filter are used as the reference channels in the scheme, so as to improve the demodulation accuracy by demarcation algorithm. The principle and applicability of different peak-seek algorithms are compared in this paper, and an adaptive semi-peak-seek algorithm based on state machine is proposed to implement the accurate peek-determination. The designed demodulation scheme uses high-speed AD to sample the real-time FBG spectrum wave form, and the core of the signal processing is FPGA, which is used to implement the designed demodulation algorithm and complete the corresponding function such as control and communication. At last, the feasibility of this scheme is tested by corresponding experiments.The performance of different peak-seek algorithms are proved by the experiment results, and it can be concluded that the proposed algorithm has many excellent features. The experiment results show that the demodulation speed is2KHz and the demodulation resolution is lpm. The FBG demodulator has4channels, one of which is capable to access up to64FBG sensors. By the monitoring experiment of aircraft engine using the FBG demodulator, the FBG demodulator can meet the development requirements in terms of precision, stability and practicality.