System Noise Suppression And Target Signals Extraction In The Process Of Underwater Acoustic Fiber Detection

For the past few years,optical fiber underwater acoustic wave detection method has great applications due to its advantages of high security, high sensitivity and can be highly multiplexed. But, the existence of the noise in the process of underwater acoustic wave detection will reduce the detection sensitivity and precision. Therefore, we have studied the method of system noise suppression and target signals extraction in the process of underwater acoustic detection.Firstly, we analyzed the working principle of fiber acoustic sensor based on fiber-winding Mach-Zehnder interference structure. By using CMOSOL software we simulated and computed the Vibration Mode of fiber acoustic sensor with different size, and fabricated the designed sensor.Secondly, source and type of noise signal in the detection process were analyzed. According to the characteristics of system noise such as light source noise, optoelectronic devices noise and optic fiber transmission noise, we simulated the noise suppression results of the adaptive filter by using MATLAB theoretically. Meanwhile, Lab VIEW control program of the data acquisition card(DAQ card) was improved to apply this algorithm to underwater acoustic wave detection system.Finally, we analyzed the frequency characteristic of the marine environment noises, theoretically simulated the target signals extraction process based on the method of wavelet transform by using MATLAB, and improved Lab VIEW control program of DAQ card. As a result, the target signals with the frequencies of 100 Hz, 150 Hz, 200 Hz, 250 Hz and 300 Hz were extracted apart from the background noise successfully.