The Design And Implementation Of Distributed Fiber Optic Sensing System Base On FPGA

In the optical distributed optical fiber sensing system,the data sampling rate will affect the spatial resolution of the system,and the high spatial resolution is the pursuit of the system,while the sensor signal is very weak,the signal to noise ratio is very low,the sensor signal usual submerged in the noise and can't be directly identified,so that need for some data processing.Therefore,it is very important to design a system that not only can freely set the pulse width of the detected pulse light,also can carry out high-speed data acquisition to ensure system spatial resolution,and capable of large-capacity cache,but also can real-time data processing to improve the signal to noise ratio.In this paper,based on the principle of Rayleigh scattering distributed optical fiber sensing technology,combined with system performance requirements,Select the Altera corporation model EP4CE15F17C8 N of FPGA chip as the main controller,responsible for system time series?logic control and signal conditioning,designed a distributed optical fiber sensing system based on FPGA.The system uses modular design,and it can divided into five key functional modules;For respectively : one pulsed light generating module,one data acquisition module,one data buffer module,one data processing module and one data transmission module.And described each module of the main functions and the device of choice:Pulse light generation module can achieve the minimum pulse width of 5ns and maximum frequency of 100 MHz pulse light generation;The data acquisition module using high-speed AD6645 chip as sensor signal A / D converter;FPGA control AD6645 to convert data and acquisition convert data,ADC conversion rate up to 80Mbs;the cache module using ping-pong operation uses two SDRAM to storage data;the data processing module is mainly for the sensor signal is extremely weak and time-varying characteristics,first use the sliding cumulative averaging algorithm to process the data to improve the signal to noise ratio of the system;and then to improve the signal to noise ratio of the data after the wavelet transform processing to extract the details of the signal part;finally through the USB transfer module to achieve data transmission between the FPGA and the host computer.This paper describes the system each function module design of the key techniques and implementation method in detail,analyzed the influence factors related of the spatial resolution and signal-to-noise ratio of the system and put forward the corresponding improvement measures,at the same time,verify the design of each of the functional modules.Finally,combination all of the functional modules to achieve the entire system functions,and that verification testing of the entire system,successful test of the fiber connection point and the fiber at the end of the Fresnel reflection signal,the test results show that the distributed optical fiber sensing system based on FPGA is excellent in this paper,the design scheme are feasible and effective,the distributed optical fiber sensor signal acquisition and processing effect is obvious.