Research On FPGA-based Optical Wavelength Interrogator

In recent years, optical fiber sensor with its resistance to electromagnetic interference, distributed sensing, intrinsic insulation and the other advantages that the traditional sensors do not have, is widely used in various fields of industrial, military, architecture and petrochemical. So a variety of optical fiber sensor demodulation technique emerged as the times require followed by. The optical wavelength interrogator is widely used in analysis of the nearly infrared spectroscopy and is also the important measuring instrument of wavelength demodulation and phase demodulation type optical fiber sensor. Modern demodulation technology is more accurate and faster with the high speed development of modern integrated circuit technology. FPGA (Field Programmable Gate Array) has the characteristics of designing flexibility, high integration, high speed and so on. This paper designed a multi-channel photoelectric signal data acquisition and laser scanning control system based on FPGA controlling. The system realized the wavelength of the laser scanning and wavelength calibration. The main contents include the following:This paper made a detailed analysis to the basic principle of optical fiber sensor demodulation system based on spectral measurements. Summarizing the advantages and disadvantages of various demodulation mode. And introducing the basic principle of FPGA, describing the method and process of digital system design. Then designing a multi-channel signal acquisition system based on FPGA. This system has a series of advantages of speed transmission, large cache space, two-way controllable and so on. On this basis constituting a FPGA-based wavelength interrogator. At last doing experimental test of the FPGA-based optical wavelength interrogator. Recording and analyzing the signal-to-noise ratio of the electrical and optical signal. And using the HCN gas absorption pool and the EFPI/FBG to test the performance of wavelength interrogator. The measurement results showed that the wavelength interrogator measurement accuracy was±1.85pm,and having1.74pm resolution. In the experiments of application of optical fiber EFPI/FBG series multiplexed, the resolution of the cavity length is0.036nm and the wavelength resolution is1.94pm. The overall performance reached the best level of commercial instruments.