Research Of Key Technologies In Distributed Feedback Fiber Laser Hydrophone

In recent years,with the development of the doped fiber Bragg grating technology and the fiber laser technology,fiber optical hydrophone which use distributed feedback fiber laser has received extensive attention.The radius of distributed feedback fiber laser as small as the radius of single-mode optical fiber and the length is only a few dozen millmeters.Compared with the fiber-optic interferometric hydrophone,fiber laser hydrophone can reduce the overall size and weight of the hydrophone system effectively,which provides a promising way for towed optical fiber hydrophone array.Fiber laser hydrophone can be used and recycled rapidly,so that greatly improve the flexibility and mobility of the towing ship,conform to the development trend of the optical fiber hydrophone.A lot of research have been done by the United States naval research laboratory(NRL),the Australian defense science and technology organization(DSTO),the France Thales underwater systems(TUS)and so on,due to the obvious technical advantages and application values of the distributed feedback fiber laser.And many sea trials have been done by DSTO,relevant results have satisfied the engineering application conditions,and the core indicators is as good as the interferometric optical fiber hydrophone.But there are still some gap between our country and the advanced level,too little principle prototype or engineering prototype has been manufactured to support deeply analysis and research which in order to solve the potential problems in real applications.The thesis is based on regional demonstration program of Marine economic innovation and development《Optical fiber hydrophone and array》,the main work of the thesis related to series of problem in the process of develop the model machine,and provide theoretical basis and data support for the prototype.The main results of this thesis are as follows:1.The sensing principle of DFB fiber laser hydrophone and PGC demodulation algorithm has been deeply understanding.And simulations have been made in order to check out the accuracy of PGC algorithm and determine the parameters of the algorithm.2.The fiber optical path and demodulation and control system was designed and manufactured,DCM-PGC algorithm was achieved by software.And the model machine was measured repeated in the pool of the laboratory.It was proven that the optical fiber hydrophone and its demodulation system were feasible and stable.3.The inherent noise in the demodulation spectrum has been studied theoretically and experimentally.The results showed that the inherent noise mainly due to the relaxation oscillation of the pump laser.The inherent noise has been reduced and detection effect has been optimized through changing the modulate frequency and suppress the relaxation oscillation noise of the pump laser.4.The output power of DFB fiber laser when wavelength division multiplexing has been analyzed.Simulation results showed that the output power of DFB fiber laser was increased caused by the external optical feedback.And the related experiments was designed and the relationship between the output power and external optical feedback has been obtained.