Granary Temperature Measurement Network Based on Chirped FBG
LIU Zhi-chao1, YANG Jin-hua1, ZHANG Liu2*, WANG Gao3
1. School of Optoelectronic Information, Changchun University of Science and Technology, Changchun 130000, China 2. Jilin University, Instrumentation and Electrical Engineering, Changchun 130000, China 3. National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan 030051, China
Abstract：In conventional optical fiber grating temperature measuring system, it can be loaded into a small number of fibers grating probe. At the same time, the intensity of back waves is relatively weak, and its multiplexing capability is poor. In order to solve these problems, temperature measurement system was designed based on chirped Fiber Bragg Grating. Its purpose is to obtain large-scale, multi-point temperature measurement data. The bandwidth of back waves was improved by chirp modulation techniques, so that available processing power of signal was increased, and the number of the chirped FBG probe in one fiber was greatly increased. Grating period expression was derived in chirp modulation, and modulation method and the wavelength range was provided. In the experiment, LPT-102 broadband light source and the FP optical fiber demodulator were used, and the modulation bandwidth of the system was from 1 535.0 to 1 555.0 nm. It used the WR-201 type temperature sensor as calibrated detector. Experimental results show that when the temperature changed by 1 ℃ from 20~60 ℃, the test temperature error would be closed with traditional Fiber Bragg Grating probe and chirped Fiber Bragg Grating probe, and they both meet the design requirements. In contrast, the wavelength shift data of chirped FBG was more monotone linear than the characteristic FBG, so its data was more stable. Meanwhile, in one fiber, the number of probes in the chirped FBG system was greatly more than the Uniform FBG system. In the original FBG system, without increasing the number of optical fiber or reduced the temperature measurement accuracy, design requirements for increase with the number of probe points in the system was achieved.
