Study On Optic Fiber Vector Hydrophone Integration System Based On Time Division Multiplex

Optic fiber vector hydrophone(OFVH) has characteristics such as good directivity, good sensitivity and so on. Together with optic fiber acoustic pressure hydrophone, OFVH can sense the vector signal and scalar signal at the same time. By analyzing the signal of them, we can suppress the disturbance well and improve signal to noise ratio(SNR). So OFVH has good prospect in the domain of underwater acoustic.According to the demand of underwater long-period-observation system and other applications, this thesis study on the time-division-multiplex(WDM) based OFVH system. We discuss the way to modularize the system, make the sensors of the system and we also test the basic performance of the integrate system.First,the structure of OFVH system is given and the basic theory of phase generated carrier(PGC) detecting technology is analyzed. The system uses reflection-type time division multiplex(TDM). In order to reach the purpose that there is only fiber connector between modules, we use fiber laser to supply the electric power and fiber to transmit the electric signal. The acceleration sensitivity of the hydrophone and the ability to bear water pressure are analyzed. The result shows that: when frequency is between 20 Hz and 1000 Hz, the sensitivities are 31 d B re rad/g. It also shows that: when frequency is 315 Hz the directivity index is above 35 dB and the maximum asymmetric index is less than 1dB. After analyzing and comparing different lasers we choose the right light source of the system. We analyze the theory of the semiconductor optical amplifier(SOA) being an optical switch in the system. We also test the output optical pulse of SOA.On the basis of the work above we integrate the system. The noise of the system is tested and the result is-97 dB re rad/Hz1/2 at the frequency of 1kHz. The ability of the system to sense acoustic signal is tested and the result shows that it can demodulate the signal correctly. In the experiment, the acceleration sensitivity of the first vector hydrophone is 30.1dB. The result agrees with the test before. The crosstalk between axis of the first vector hydrophone is about-32 dB, and the crosstalk between the first hydrophone and the second hydrophone is about-45 dB.