Research On Underwater Shock Wave Detection System Based On Optical Fiber F-P Sensor

The shock wave generated by plasma expansion based on the technology of underwater pulse electric discharge has widely broad application prospects, but the measurement and evaluation of shock wave slow down its practical process. At present, the sensors mainly used for detecting shock wave are piezoelectric ceramic and piezoelectric polymer based on the electrical principle. As strong radiation will be produced in the process of underwater pulse electric discharge, and extreme situation where it works, the traditional electrical sensor is no longer applicable.Based on the above reasons, we choose the optical fiber sensor which has the following characteristics: the small size, the fast response, the resistance to electromagnetic interference, the large dynamic range, especially it can stand high pressure and get signal far away, this paper does the research on the underwater shock wave detection system based on optical fiber Fabry-Perot(F-P) sensor. Detect outside pressure signal by optical fiber F-P sensor in real time, getting the pressure signal by data acquisition and analysis, and then we can modify the performance parameters that produce shock wave, which will well satisfy the specific requirements. My specific work is as follows:Firstly, this paper analyzes the characteristics of underwater shock wave and the performance of optical fiber F-P sensor; underwater shock wave detection system based on optical fiber F-P sensor is studied.Secondly, analyze the basic working principle of optical fiber F-P sensor, and a small batch of polymer film optical fiber F-P sensor with low precision has been made, adopt passive homodyne phase algorithm with three-wavelength light source excitation and the known initial phase interval, using the double beam interference sinusoidal output mathematical model to demodulate the phase.Thirdly, the hardware and software aspects have been considered to design and implement the whole system. The hardware includes the automatic temperature control circuit, photoelectric detection and light transmission channel; the software includes the data acquisition and data processing program based on LabVIEW, the whole preliminary system has been set up.Fourthly, the reflected light interference phase difference is large between them, the power and wavelength of the light source is stable, which is easy to demodulate signal accurately. The static characteristics and dynamic characteristics of the F-P sensor we have made meet the demand of experiment. Such a mature system can apply to the underwater shock wave measurement in practice.Finally, the whole system is used in the actual project. It can obtain complete shock waveform, peak pressure and the pulse width of the shock wave generated by water switch, and the peak pressure of vacuum insulation heap where can be detected continuously.This paper involves making polymer film optical fiber F-P, and installing it in water switch and vacuum insulation heap of PTS, respectively, designing data acquisition system based on LabVIEW, by analyzing the data, the whole system can preliminary measure the peak pressure and the pulse width of shock wave, which is helpful to adjust the parameter of the PTS device which produces shock wave.