Research Of The Quartz F-P Cavity Pressure Sensor

Underwater shock wave is mainly generated by the air-pocket of air that bursts in water, which has been widely used in military, medical, civil and other fields, it is critical to test the parameters of underwater shock wave, at present, the sensor frequently used to test signal is piezoelectric pressure sensor, but due to the limitation of piezoelectric materials, it has some shortcomings that cannot be ignored, for example: the amplitude of output signal is small, it's difficult to survive in harsh surroundings, its stability is poor and so on. So the sensor of this type is difficult to monitor underwater electric pulse shock wave in long-term, real-time and on-line method. As optical fiber sensor has following advantages: the small size, the resistance to electromagnetic interference, the resistance to high pressure and so on. In this paper, a micro fiber F-P pressure sensor is studied which is used to test underwater explosion shock wave.My work is as follows:Firstly, simply introduce the interference principle of optical fiber Fabry-Perot pressure sensor, the method of making various kinds of sensing probe and the pressure sensitive principle of optical fiber sensing probe.Secondly, According to the characteristics of explosion shock wave which is high intensity and long duration, quartz optical fiber F-P pressure sensor is designed to test it. According to its working principle, the structure of sensing probe and demodulation method have been preliminary designed and introduced, at the same time, this paper introduces the methods of choosing the sensor's reflectivity, the thickness of the diaphragm and the effective radius based on analyzing the interference fringe contrast, sensitivity and response frequency of sensors.Thirdly, study and design the way of making various kinds of sensing probe, a method of making the optical fiber F-P sensing probe by sealing capillary quartz tube in a single mode optical fiber end face is emphasized, and in accordance with the making steps, optical fiber sensors are produced which meet our need, at the same time, using the diaphragm corrosion and grinding technology to optimize the end diaphragm of sensors to gain higher sensitivity and better frequency response.Fourthly, using piston machine oil pressure calibration to set up static testing system, which is used to do static calibration experiment, and using FM synthesis heterodyne interference principle to demodulate the signal, this paper also analyzes the differences between the test results and the theoretical value. The experimental results show that it is feasible to use optical fiber F-P sensor to test pressure signal; however, it is difficult to control the accuracy of the end diaphragm's thickness, therefore, the sensitivity of the sensor needs further improvement.