The Free Vibration Characteristics of Bar-type Fiber Optic Hydrophone UnitZHANG Xi-ping,XIE Guan-mo,JIN Shan,WANG Chao,ZHOU An(School of Sciences,Wuhan University of Technology,Wuhan 430070,China)Fiber optic hydrophone unit was the basis of fiber optic hydrophone system.The free vibration characteristics of bar-type fiber optic hydrophone unit were investigated in this paper.By means of Rayleigh's method its fundamental frequency was derived,the influence of some parameters on which was analyzed comprehensively.In addition,ANSYS was employed to simulate the natural frequencies and modes of the fiber optic hydrophone unit,numerical results were found to agree well with analytical results.fiber optic hydrophone unit;free vibration;Rayleigh's method;ANSYS simulation