Application Of Electro-optical Phase Modulator In Interferometric Optical Fiber Sensor

Interferometric fiber sensors have become one of the most popular research subjects due to high sensitivities and wide dynamic ranges. In order to get sensing information in the interferometric signals, we need valid interferometric signal counter modulating methods to attain how outside parameters change with phase information. PGC demodulating technique is widely used as an efficient interferometric signal demodulating technique in interferometric fiber sensing fields. Generating phase carrier is a key factor of PGC modulating technique. Electro-optical phase modulator takes advantage of photoelectric effect to modulate optical signals. This method has a character of a wide modulating bandwidth, low transmission loss, a small chirp and low noises. Electro-optical phase modulators applying in fiber sensing PGC technique have the advantages of stretching dynamic modulating frequency and lowering detective signals noises.This paper reveals how to apply electro-optical phase modulators in providing phase carrier in Michelson interferometric fiber sensing systems. Firstly, we state the basic principles of the interferometric fiber sensors, which are focusing on analyzing the methods of signal modulations and carriers generated by phase. Secondly, we tested the system’s performances by designing and building Michelson interferometry and the non-contact electro-optical phase modulation interferometer measurement system. We also discussed the origins of systematic polarization reductions and the methods of improving stabilities and reducing polarization reductions. Thirdly, we adapted Faraday rotating mirrors to the arms of Michelson interferometry respectively, so that we can inhibit polarization fading, enhance the contrast of the interference signal, and improve system stability. We also make use of ARCTAN PGC counter modulating program to counter modulate signals. At last, experimental results demonstrate that the system has excellent sensitivities and wide responsive ranges when the sampling frequency, available frequency ranges and voltage amplitude is200KHz,1000Hz, and12.59rad respectively.