Improved modulation and demodulation detection method of PGC

Abstract

The invention discloses an improved modulation and demodulation detection method of a phase generated carrier (PGC). The method comprises: after an output signal of an optic fiber hydrophone is processed by mixing and low-pass filtering, mathematical calculation is carried out to obtain a proportional relation J1(C) / J2(C) between a first type of first-order Bessel function J1(C) and a second-orderBessel function J2(C) of a modulation depth C; on the basis of the proportional relation, normalization calculation is carried out on the signal after low-pass filtering of the optic fibre hydrophoneto obtain two paths of signals with the alternating-current item B and modulation depth C eliminated; the two paths of signals are processed by differential processing, cross multiplication, integration, and high-pass filtering respectively to obtain an external acoustic signal needing detection. According to the invention, the detection method has the following advantages: while hardware equipment is not changed, the detection error, caused by drifts of an output signal alternating-current item B and the modulation depth C introduced by the externally loading carrier, of an external acousticsignal is modified by a digital way; and the stability of signal detection by the optic fiber hydrophone is improved.

Description

Technical field [0001] The present invention relates to a signal detection algorithm of an optical fiber hydrophone, mainly an improved PGC modulation and demodulation detection method. Background technique [0002] As a kind of interferometric optical fiber sensor, optical fiber hydrophone has the characteristics of high sensitivity, small size, light weight, convenient large-scale multiplexing, and anti-electromagnetic interference. It is currently widely used in underwater military, petroleum exploration, confidential monitoring and other fields . [0003] The random phase decay of the interferometer will lead to random fluctuations in the signal-to-noise ratio of the output signal. Therefore, the realization of stable signal detection is one of the core technologies for the application of optical fiber hydrophones. The signal detection methods of fiber-optic hydrophones mainly include the following: active homodyne detection, closed-loop control operating point detection, phas...

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Problems solved by technology

[0022] Through the calibration method, only the state of the system parameters at the calibration moment can be determined, and the signal changes caused by the modulation depth C introduced by the external loading wave and the drift of the output signal AC term B cannot be corrected in real time, so the above-mentioned PGC modulation and demodulation detection method can be directly applied , will affect the accuracy and stability of the fiber optic hydrophone signal amplitude acquisition

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