Study On Demodulation Of Interferometric Optical-fiber Vibration Measurement

A variety of optical sensors have been paid a lot of attention by people in photoelectron technology, especially interferometer optic-fiber sensor with higher sensitivity and precision has been developed greatly, and hundreds of kinds of optical fiber sensors had been developed successfully. The research direction is novel demodulation methods of optical fiber interferometer sensors, and more convenient demodulation steps make vibration measurement have higher signal to noise ratio (SNR). In this paper, some of the work carried out with the new style of the interferometer optical-fiber sensors and the demodulation methods.The first chapter introduces the development of optical fiber sensors from abroad, describes optical fiber sensors with phase modulation, intensity modulation and wavelength modulation, at last several optical fiber sensors of phase modulation such as Mechelson, Mach-Zehnder have been introduced.The second chapter introduces the fiber optic sensor demodulation system used several methods, vibration measurement systems were used for phase detection techniques highlighted, focusing on the PGC method. And then arctangent method which was not affected by the light source and carrier, was compared to the PGC demodulation.The third chapter describes the noise of the optical fiber vibration sensor system, mainly from the laser source noise and circuit noise. And discuss ways to reduce laser source noise, and fundamentally improve the system SNR; proceed through the dual detection of the light path system to reduce the impact of the external environment noise to improve SNR; in circuit analysis to understand the root causes of noise by optimizing the circuit can also improve system SNR and stability.Chapter IV introduces a structure which was based on the Michelson interferometer, we use the circulator to realize the dual-path detection of the vibration signal, which reduce the intensity noise caused by laser source. The fiber waveguide modulator was used in the system instead of PZT. Then the arctangent algorithm was used instead of PGC algorithm to demodulate the signals, which could greatly simplify the algorithm. The output of the signals were demodulated by arctangent algorithm compiled by Labview, the vibration signal can be detected at the same time. And then presents a optical fiber interferometer based on laser of two wavelengh, simulation experiments show that this method can eliminate the environmental impact of interference on the demodulation result, reducing the disturbance of the environment.