Research On Fiber Bragg Grating Hydrophone System

Hydrophone underwater target is mainly used for monitoring the acoustic characteristics,since the conventional piezoelectric hydrophone anti-electromagnetic interference ability,transmission distance is short,an array of complex structure,its application has been limited.So this paper with FBG sensor was designed based on equal strength cantilever symmetrical double differential fiber Bragg grating hydrophone structure,eliminating the effects of temperature and other disturbances on the measurement results,and its performance is analyzed and tested,The main contents are as follows:(1)From the mode-coupling theory of FBG departure,deduction of its temperature and strain sensing model,the influence of the relevant parameters of the reflection spectrum;cross sensitivity for strain and temperature,temperature compensation proposed principles and methods.(2)From the fiber Bragg grating acceleration sensor theory,it analyzes the principle of FBG sensing cantilever-based strength,etc.,on the basis of equal strength cantilever design based on symmetrical double differential fiber Bragg grating hydrophone the new structure.(3)For the design of fiber grating hydrophone unit structure is encapsulated and packaged hydrophones were static experiments showed a good linear relationship between the fiber grating wavelength difference between force and pressure sensitivity coefficient is 2.4nm/N.Get its acceleration sensitivity by experimental data 24 pm/g,compared with single grating structure nearly doubled.(4)Experiments show that the designed temperature hydrophone unit effectively eliminates the temperature influence on the measurement results.(5)In the comparative analysis of various distributed FBG sensing system demodulation scheme based on the design of the wavelength scanning demodulation system based on continuous wave modulation frequency technology.The system uses a broadband light source and the optical fiber FP cavity tunable filter combination tunable narrow-band light source,not only to ensure that the system needs tuning range,and to obtain a higher signal to noise ratio.Experiments show that the design of the demodulation system demodulates speed,good stability.This article is designed based on the equal strength cantilever symmetrical double differential fiber Bragg grating hydrophone with high sensitivity and multiplexing capability,eliminate temperature influence on the measurement results,Underwater Acoustic Signal meet measurement requirements.