Research on noise floor of an interferometric fiber-optic hydrophone system

Abstract

For practical applications, a noise floor of an interferometric fiber-optic hydrophone system mainly originates from optical phase noise, electronic noise and demodulation algorithm noise. To assess an influence of each noise on the noise floor of the system and explain their interrelation among them, the paper demonstrates theoretically a demodulation scheme for PGC-ATAN (PGC-Arctangent) in detail, and simulates the scheme with optic phase noise and electronic noise. As a result, it proves that the noise floor of the interferometric signals after calibration, the noise floor of the demodulation signals and the PGC-ATAN principle noise floor are all basically stable when the laser intensity and a coherence length of the interferometric fringe are various. Besides, the noise floor of the interferometric signal after calibration is similarly equal to one of demodulation result. In error range, demodulation algorithm cannot raise the noise floor of the system in evidence. Finally, in the fiber-optic Michelson hydrophone system experiment, acoustic signals can successfully be detected and demodulated while the conclusion is verified. It is important significance for studying the system noise and applying for a fiber-optic hydrophone system based on a Michelson interferometer.