The Study On The Fiber Bragg Grating Demodulation Technique Based On The Edge Filter

Acoustic detection technology is an exclusive way through which people can get to know the underwater circumstances effectively. High-qualified sonar equipments hold a very significant position in defending state coastal areas & territorial seas and in helping people to exploit ocean easily. In order to satisfy the increasing needs of economy and military, the exploration of new types sonar equipments become much more important.As part of a state 973 task, we have systematically researched the feasibility of using fiber Bragg grating to detect acoustic signals underwater and its basic principle. It is a very exciting study filled with challenges.The following are some of my study:First, based on the mechanism of underwater acoustic energy exchanger and the sensor theory of fiber Bragg grating, working principle and design method of fiber Bragg grating hydrophone are proposed.Second, through the research of underwater acoustic with slender scope; 'this paper put forward a demodulation method of FBG (Fiber Bragg Grating) sensors based on the edge filter. We developed a reflected wavelength demodulation system based on the voltage drive Fabry-Perot (F-P) cavity, in which we have signals operated to control the drive voltage of F-P in feedback. A novel automatic trace method is creatively proposed. By using the operation circuit, the drive voltage of F-P in feedback can automatic trace the reflected FBG wavelength which induced by static acoustic pressure and underwater circumstances; The system have an extraordinary wide demodulation range of frequency achieved in the high accuracy. The demodulation designed from this method can meet the need of acoustic detecting system.Third, in experiment, the system based on the edge filter has been analyzed; we have tested static response and dynamic frequency response of the system respectively. The findings indicate that the demodulation system eliminates the effective of static acoustic pressure and environments, and the response to the strain of FBG has high sensitivity. On account of its low cost while high performance and easy to use, this novel demodulation system is conceivable to be used in acoustic sensing field far and wide.Relative theories and analysis of the subject show that the novel demodulation system can be widely applied in areas, such as the measurement of hydro-acoustics, acoustic/vibration signal, and the measurement of pressure and so on.