Research On The Performance Of Remotely Fiber Optical Hydrophone System Based On PMDI

The PMDI fiber sensor is simple in structure and flexible in demodulation scheme.In this paper,the PMDI is combined with the remote transmission system,the comprehensive performance of this system is effectively improved through the optical structure improvement and parameter optimization.The main work and innovations of the thesis are as follows:1.The advantages and disadvantages of the PMDI sensor in large-scale array remote transmission are analyzed.A scheme of combining unbalanced PMDI sensor array with remote transmission system is proposed.A scheme of combining non-balanced matched interferometer sensor array with remote transmission system is proposed.The fiber disturbance noise is effectively suppressed throughe the PGC modulation and the PM modulation.The phase noise of the 50km-long system is basically equivalent to that of the short-range system,about-102db@1khz.2.The influence of the interference structure and arm difference on optical road sound pick noise was studied.When the PMDI and TDM are placed next to each other,the differential action of this structure greatly reduces the noise and makes the system have the function of self-suppression.The experimental results show that,compared with the separated PMDI sensor structure,the pick-up noise of the adjacent structure can be suppressed up to 29.5 d B@2khz,which is basically consistent with the theoretical simulation results.3.The pulse distortion and line-spectrum noise characteristics introduced by the saturation gain of the EDFA-BA in the PMDI fiber hydrophone remote transmission system were studied,and the optical power and noise limitations caused by MI were tested when high power was injected into the remote system.The system has a better performance while using EDFA/FRA hybrid amplification,the transmission distance can be increased by about 10 km.4.The remote transmission system combined with unbalanced PMDI sensor array is designed.The system comprehensive performance is tested and evaluated.The results show that the demodulated parameters of the PMDI-PGC system are good,the background noise of each channel is around-100 d B,and the demodulated signal stability is better than ± 0.5d B.The system crosstalk mainly consists of AOM finite extinction ratio crosstalk and differential crosstalk,and the average TDM crosstalk of each channel is better than-45 d B.