Design Of Embedded Software For Acquisition And Control Of Optical Fiber Brillouin Sensor

With the development of human society,people's demand for the detection of external environmental physical quantities is higher and higher,and various sensing technologies emerge as the times require.Optical fiber sensing technology with anti-electromagnetic interference,environmental adaptability,small size,simple structure,high signal-to-noise ratio,long distance and other advantages,has become a research hotspot.Compared with other sensing technologies,optical fiber sensing technology based on stimulated Brillouin effect(BOTDA)has become a popular solution with the advantages of sensing distance and signal-to-noise ratio.Based on the optical fiber Brillouin sensing system,the software of the control board and the receiving board in the system is designed,and the key parts of the hardware are tested.Optical fiber Brillouin sensing system is composed of host computer,control board,receiving board,pulse board,frequency sweep board and so on.The control board is used for data exchange between the upper computer and other sub boards;the pulse board and the frequency sweep board are used for generating pulse light and continuous detection light.The receiving board collects and detects Brillouin scattering light and completes photoelectric conversion.The main control chip of the receiving board and the control board adopts the cortex-m4 architecture embedded microcontroller combined with the real-time operating system(RTOS)to organize each task module and realize each function on the board.The control board realizes the serial communication between PC and sensor equipment,realizes the data verification and forwarding,data frame analysis,escape and anti escape,and communicates with other daughter boards through I2C.On the receiving board,MCU is used as the core to maintain and control the working state of each device on the board.Based on the software design of the peripheral circuit,the bias control of avalanche photodiode(APD)and the DC regulation of electrical signal are realized;the temperature control accuracy of 0.002? is realized by using high-precision temperature control chip and semiconductor refrigeration chip,and the parameters are automatically obtained through the open-loop step response.At the end of the paper,a method to detect the frequency stability of distributed feedback laser(DFB)based on the Bragg grating(FBG)is proposed.According to the rising edge of the grating reflection spectrum,the power change of the laser is detected and then converted into its frequency drift.The central wavelength of the grating is stabilized by the temperature control strategy,and the accurate and fast detection of the frequency stability of the laser is realized.