Optical fiber hydrophone frequency shift orthogonal demodulation system and method

Abstract

The invention relates to the technical field of optical fiber hydrophones, and provides an optical fiber hydrophone frequency shift orthogonal demodulation system and method, and the system comprises a laser pulse generation device, a frequency shift and time delay device, an optical fiber hydrophone array, and a demodulation device. A frequency shift and time delay device is adopted to generate a laser pulse pair with a fixed optical frequency difference, an optical fiber hydrophone unit is constructed based on a 2 * 3 coupler and is provided with two interference arms and a reference arm, the optical frequency difference and the path difference are utilized to form an orthogonal signal in cooperation with a specific path difference between the two interference arms of the optical fiber hydrophone unit, and the optical frequency difference and the path difference are combined to form the optical fiber hydrophone. The phase difference error of the orthogonal signals is corrected through calibration calculation; according to the invention, the hardware resource consumption is low, and phase demodulation can be realized mainly through simple mathematical multiplication and addition operation by only needing single-path photoelectric conversion and signal acquisition resources; through the proportional relation between the interference pulse and the reference pulse, demodulation errors caused by optical power fluctuation can be eliminated, and the actual use performance of the optical fiber hydrophone is effectively improved.

Description

technical field [0001] The invention relates to the technical field of optical fiber hydrophones, in particular to a frequency-shifting quadrature demodulation system and method for optical fiber hydrophones. Background technique [0002] Optical fiber hydrophone is a new generation of underwater acoustic sensor with optical fiber as the signal sensing and transmission medium. Widely used in underwater target detection, marine acoustic field environmental monitoring, oil and gas resource exploration and other fields. [0003] For fiber optic hydrophones, the target signal to be measured is included in its output phase information, which needs to be extracted by phase demodulation. Currently common phase demodulation methods mainly include: 3*3 coupler demodulation method, phase generated carrier (PGC) demodulation method, heterodyne demodulation method, each method has its own advantages and disadvantages. Among them: the advantage of the 3*3 coupler demodulation method is...

AI Technical Summary

Problems solved by technology

Among them: the advantage of the 3*3 coupler demodulation method is that the scheme is simple, no carrier modulation is required, and the dynamic range is extremely large; the disadvantage is that it needs to consume three times the photoelectric conversion and signal acquisition resources of the PGC demodulation method or heterodyne demodulation method, And the performance is affected by the angle error of the 3*3 coupler, which is sensitive to optical power fluctuations

The advantage of the PGC demodulation method is that no compensation interferometer is required, it is less affected by environmental interference and transmission line interference, and consumes less hardware resources; the disadvantage is that it is difficult to increase the carrier frequency and the dynamic range is small

The advantage of the heterodyne demodulation method is that the hardware resource consumption is small and the dynamic range is large; the disadvantage is that the scheme is more complicated, the interferometer at the transmitting end is susceptible to environmental interference, and the double pulse is inevitably affected by noise accumulation in the transmission line

Therefore, the above demodulation methods all have different defects, which have a certain degree of adverse effect on the actual performance of the fiber optic hydrophone.

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