Fiber laser hydrophone signal demodulating system

Abstract

The invention relates to a fiber laser hydrophone signal demodulating system. The laser output by a fiber laser hydrophone is transmitted to the terminal b of a 3x3 fiber coupler (3) through a single mode fiber (2) from an input terminal (1), the laser is output in three ways through the 3x3 coupler, wherein the terminal e is vacant, the laser is divided into two ways by the terminal d and the terminal f, the laser signal after interference of the two lasers is output by the terminal a and the terminal c of the 3x3 coupler, the laser signals of the terminal a and the terminal c are received by a photoelectric detector (8), and V1(t) signal and V2(t) signal output by two photoelectric detectors are transmitted to a demodulation operation processing system (10) by a signal transmission wire (9) to obtain sound pressure size. The fiber laser hydrophone demodulating system of the invention demodulates a sound pressure signal in high resolution and high stability based on a Michelson nonequilibrium fiber interferometer and eliminates influence of polarization random change on an interference demodulating signal in a common single mode fiber interferometer.

Description

technical field [0001] The invention belongs to signal modulation and demodulation system, more specifically it is a fiber laser hydrophone signal demodulation system. It is mainly used for fiber laser hydrophone signal demodulation based on unbalanced fiber interferometer. Background technique [0002] Fiber laser hydrophone is a recently developed underwater acoustic sensing technology, and it is receiving extensive attention due to its advantages of small size, high sensitivity and anti-electromagnetic interference. The sensing element of the fiber laser hydrophone is a fiber laser. When it is affected by the sound pressure in water, the output wavelength of the laser will move proportional to the external sound pressure. As long as the displacement of the wavelength is detected, the change of the external sound pressure can be obtained. Therefore, the wavelength demodulation technology directly limits the detection accuracy of the entire system, and it is very important...

AI Technical Summary

Problems solved by technology

[0005] However, due to the microbending, twisting of the fiber and the change of the ambient temperature, the polarization state of the two light beams participating in the interference may change, so that the output signal is in a random blanking state, especially when the polarization states of the light waves in the two arms of the interferometer are orthogonal When , the output visibility of the interferometer is zero, and the information of the external parameters will be completely lost

And the splitting ratio of the 3×3 coupler cannot maintain strict symmetry, and the asymmetrical three-way signal will cause the external environment change to have a nonlinear impact on the demodulated output signal

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