Study On Pulse Signal Generating Technology Of Distributed Optical Fiber Sensing Based On FPGA

Distributed optical fiber sensing technology has became a highly favored sensing and measuring method depending on its particular advantages both at home and abroad, such as high accuracy, remote, full range and real-time online monitoring, high sensitivity, superior spatial resolution, etc. The measurement accuracy and spacial resolution of the fiber sensing system will be directly affected by the key parameters such as the pulse width, waveform and repetition frequency of the pulsed pump light in distributed optical fiber sensing system based on optical time-domain technology. So, to generate the narrow pulsed pump light with high precision, high stability and adjustable pulse width is of paramount importance to this kind of sensing system mentioned above.The sensing principles of the distributed optical fiber sensing technology based on Rayleigh Scattering, Brillouin Scattering and Raman Scattering were introduced briefly first in this paper, progresses people have made in the field of pulse signal sources’ development and the research trends about the applications of narrow pulse light signal in distributed optical fiber sensing system were illustrated, meanwhile, the design scheme and implementation process of the system for generating pulsed laser signal based on Electro-optic intensity modulation was elaborated in this paper.This paper made detailed research on the design proposals of electrical pulse signal sources based on DDS technology and frequency multiplication and division technology of clock signal by using FPGA device named EP4CE15F17C8 N as the hardware platform. The design ideas and the implementation of these two design plans were expounded in the article, besides, the practicability of these two design schemes and their advantages and disadvantages also were compared and analyzed by function simulation and circuit experiment, in the meantime, the bias voltage control circuit of EOM was designed based on FPGA; and the feasibility of the pulsed laser generation system designed in this paper was proved by experimental test.Additionally, for obtaining the narrow pulse modulating signal with high precision and high stability, the design plans of one-level shaping circuit and two secondary link shaping circuit of electrical pulse modulating signal were proposed, and their proof tests have been completed, meanwhile, the experimental results of pulse shaping were analyzed and discussed.Finally, the electrical pulse signal source designed in this paper was applied to the system for generating pulsed light, and then the pulsed pump light was applied to the distributed optical fiber sensing system in the experiment. The experimental results show that the pump light obtained in this paper is completely suitable for the distributed optical fiber sensing system.