The Interference Signal Processing Of EFPI Optical Fiber Sensor Based On FPGA

With the development of aerospace and all walks of life,people urgently need a kind of sensor which can work in bad conditions.In this case,optical fiber sensor came into being.Optical fiber sensor is especially outstanding in anti strong electromagnetic interference because it does not use electronic devices,and its other advantages are simple structure,low cost,high resolution,wide dynamic range,strong reusability and so on.FPGA(field programmable gate array)is a kind of semi customized hardware circuit with high speed and flexible composition.It can integrate peripheral control,decoding and interface circuits,and can process data in parallel.Applying FPGA to optical fiber sensing system can greatly improve the response and processing time of the system to signals.In the optical fiber sensor,the Fabry Perot optical fiber sensor has been applied to various industries for its advantages of simple structure,small volume,low cost,high sensitivity and large dynamic range,among which the extrinsic Fabry Perot interference is the most important Fiber optic sensor(EFPI)is widely used in every part of our life because of its flexible composition and the ability to measure various physical quantities.Starting from the sensing principle of EFPI optical fiber sensor,this paper briefly introduces the interference principle of EFPI optical fiber sensor,and then introduces two structures of EFPI optical fiber sensor,capillary type and diaphragm type EFPI optical fiber sensor,as well as their interference mechanism for the external environment pressure and temperature sensor.Finally,the demodulation principle of EFPI fiber optic sensor is introduced in detail.In this paper,the demodulation principle of EFPI optical fiber sensor is used to design the interference signal processing module based on FPGA.The specific design principle of the interference signal processing module is introduced in detail,and the design of the whole FPGA system is described.Finally,the FPGA interference signal processing module is tested.In this paper,the real interference spectrum of the sensor is used as the input.The interference spectrum of two sensors is mainly used,one is the interference spectrum with the cavity length of 128?m,the other is the interference spectrum with the cavity length of 441?m,and then compared with the results of the PC platform software processing,the phase demodulation junction of the interference signal processing module is found The result is consistent with that of the PC platform software.Combined with the interference signal processing module in FPGA,a complete white light interference demodulation system is built.A semiconductor laser MG-Y tunable laser with small volume,low price,simple structure and wide wavelength tuning range is selected as the light source of the system.In this paper,the 5-way parallel control laser with ADN8810 chip is used to output a single wavelength of cyclic scanning ranging from 1527 nm to 1567 nm,with a total of 1250 wavelength points and a wavelength interval of 32 pm.Finally,the selected data acquisition chip AD9226 and the USB 2.0 chip CY68013 A completed the construction of the entire system.The system can realize real-time demodulation of the cavity length of 200 HZ with demodulation accuracy of 1nm.In this paper,the preparation of the two silicon thin film of EFPI optical fiber sensor diaphragm type,using the white light interference demodulation system of these two sensors for pressure demodulation experiment,the experiment results show that the sensor in the 0 to 40 KPa pressure range,sensitivity of 20 nm/KPa,through repeatedly of sensor measurement,linear fitting of the sensor has remained at 99.82%,the stability of the white light interference demodulation system is further validated.