| With the advantages of samll size,high sensitivity,and anti-electromagnetic interference,fiber Bragg grating sensors have been widely used in various fields including the large-scale construction engineering,aerospace,nuclear industry and so on.The process of detecting the variation of reflected light signal from the sensing FBG is called demodulation.The performance of the demodulation unit is very important to the whole sensing detection system.Therefore,it is very significative to develop a demodulation system with low cost,fast demodulation speed and high precision.A time division multiplexing demodulation system for identical weak fiber Bragg gratings based on a semiconductor optical amplifier(SOA)is proposed in this paper.By the control of the FPGA part,the SOA can be used as a high-speed optical switch for its threshold characteristic to control the generation of gated optical pulses.Thus realizing the separation of cascaded FBG reflected light in time domain.The main contents of the paper are as follows:Firstly,by consulting a large number of related literatures,the development status of FBG demodulation technology at home and abroad is summarized.The existing problems of the demodulation technology with weak FBGs are discussed.Secondly,according to the practical requirements of cascaded weak identical FBG sensors in engineering applications,a time division multiplexing demodulation system based on SOA is proposed.And the overall scheme of the system is designed according to the parameters of each component of the demodulation system.Thirdly,the high-speed optical switch driver unit and data acquisition unit based on FPGA system are designed,and the related hardware and software systems have been completed.Finally,the time division multiplexing demodulation system with 4 weak identical FBGs are constructed.Through a lot of experimental studies,the speed and accuracy of the demodulation system are analyzed in detail.The time division multiplexing demodulation system designed in this paper has the advantages of low cost,fast speed and hign precision.And the demodulation result can be monitored with PC in real time.In summary,the research findings has important reference value for high-speed sensor system. |
