Study On Key Techniques Of Fiber Optic Vector Hydrophone For High Resolution Seafloor Strata Detection

With the commencement of the new energy and resources development strategyand the increasing emphasis on the territorial rights of our country, the development ofadvanced seafloor strata detection technology is extremely urgent. The high resolutionapplication requirements are ever-increasing demands on the seafloor strata detectionsystem. The development of fiber optic vector hydrophone provides a new technicalway. At present, survey with large-scale vector array has become the forefront of thedevelopment of seafloor strata detection technology.This thesis studied the key technologies of the fiber optic vector hydrophone arrayfor the seafloor strata detection application based on the requirement in dynamic range,noise floor, sensitivity, working frequency band and other aspects of the fiber opticvector hydrophone system, which are analyzed according to the characteristics of theseafloor strata detection. To satisfy the design requirements to the sensitivity andworking band, a theoretical model of the cylindrical thin-shell fiber optic accelerometeris established, and a co-vibrating three-component fiber optic vector hydrophone isproduced based on this model. A partial gravity structure supporting skeleton isdesigned to solve the attitude control problem of the towed array. To reach therequirement to the dynamic range and the noise floor, a PGC scheme with highmodulation frequency on the light is put out, and a real-time PGC modulation anddemodulation system is developed. To offer a variety of options to the development ofadvanced fiber optic accelerometer, a dual-coupler fiber ring resonater sensor, which hasthe feature of multi-beam interferernce, is designed, and its response characteristics areanalyzed and tested, and the PGC scheme for this type sensor is also put forward. Vectorseismic signal processing method is investigated, vector signal fusion method isproposed to improve the quality of the seismic data from the fiber optic vectorhydrophone, optimization fitting method is put out to correct the seismic data phase axisjitter, good result has been achieved with actual data. Lake trial is conducted to examinethe effect of the submarine strata detection using the towed fiber optic vectorhydrophone array we developed.The main research results and innovations are as follows:1. The detection scheme using the co-vibrating fiber optic vector hydrophonetowed on the sea surface is proposed, which provides a new technical way to sovle theproblems of depth contral and the anti surface reflection superimposed fading of thetowed array.2. A theoretical model of the cylindrical thin-shell fiber optic accelerometer isestablished, and the effect of the materials and structural parameters are analyzed. Thismodel provides a theoretical basis for the development of new type fiber optic vector hydrophone for seabed strata detection.3. To improve the detection performance of the fiber optic vector hydrophone, theoptical detection scheme using fiber ring cavity based on the multi-beam interference isproposed, and the response characteristics of the fiber ring cavity are analyzed, and itsmoudlaiton and demodulation algorithm are also put forward with some experiments toveritfy the feasibility.4. Signal modulation and demodulation scheme of the fiber optic vectorhydrophone system which is suitable for the underwater stratum detection is put out,and a real-time demodulation hardware and software systems is developed, which canmeet the demand of dynamic range and noise levels from the high resolution seafloorstrata detection.5. Square mosaic vector signal fusion method is proposed, which can improve thequality of seismic data, and the optimization fitting method put out to correct theseismic data phase axis jitter and good results are achieved in the actual data processing.6. A co-vibrating three-component fiber optic vector hydrophone with the outerdiamter of56mm is developed, partial gravity structure supporting skeleton is designedfor attitude contral, and a towed fiber optic vector hydrophone array with the diameterof68mm is assembled. The static and lake dynamic towed test carry out, the resultsverify correctness and technical feasibilityof the surface towed detection using fiberoptic vector hydrophone.