The Study On Fiber-optic Micro-vibration Sensor Based On Nano-thick Silver Film And Its Application

The key technologies of a micro-vibration optical-fiber sensor based on thick diaphragm are a high-sensitivity sensing diaphragm and the fabrication of a sensing head. In this article, we fabricated a high-sensitivity micro-vibration sensor based on the nano-thick silver film, which is prepared by use the electroless plating method, we set up an advanced micro-vibration optical fiber demodulation system based on the Phase Generated Carrier (PGC) method. The experimental results fully prove that such sensors possesses simple structure, compact size, and highly-sensitive response to acoustic pressure and photon radiation pressure, which make it an attractive tools for acoustic sensing and gas detection based on photo-acoustic spectroscopy. The acoustic pressure sensitivity of such a sensor is up to160nm/Pa and the noise-limited detectable pressure level of14.5μPa/Hz1/2. In addition, the radiation pressure sensitivity is5.1nm/mW at4kHz modulation frequency for such sensors, which is higher than that of the sensor reported in literatures.The content of the paper is as follows:Chapter Ⅰ, the introduction on research development of fiber optic sensor based on sensing diaphragm. Then, we put forward the research significance and purposes in this paper.Chapter Ⅱ, we introduced the principle of fiber-optic interferometric sensor based on Mach-Zehnder interferometer and the Phase Generated Carrier (PGC) method, which can be used in optical-fiber interferometric demodulation system. These are the theoretical basis of our experiments in this paper.Chapter Ⅲ, we proposed and demonstrated the fabrication of the sensing diaphragm, i.e. nano-thick silver film, and the configuration of the sensing head.Chapter Ⅳ, We measure the acoustic pressure and the radiation pressure by use micro-vibration fiber-optic test system based on the nano-thick silver film, and study the pressure response performance of this sensing diaphragm. From the experimental results, such sensors show the dynamic pressure sensitivity of160nm/Pa, which is approximately two-orders of magnitude higher than that of the sensor based on the graphite diaphragm, and the sensor exhibits a noise limited detectable pressure level of14.5μPa/Hz1/2. We also test its response of photon-induced radiation pressure. Such sensor shows a radiation pressure sensitivity of5.1nm/mW at4kHz modulation frequency. In addition, we evaluate its performance of multi parameter sensing using frequency multiplexing.Chapter V, we summarize the experimental results in this paper. And make some suggestions on the further research works in the future.