Phase delay extraction and compensation method for PGC phase demodulation

Abstract

The invention discloses a phase delay extraction and compensation method for PGC phase demodulation. A sinusoidal phase modulation interferometric signal is converted into a digital interferometric signal through an analog-to-digital converter after amplifying and filtering, first-order, second-order and fourth-order harmonics of the digital interferometric signal are subjected to orthogonal downmixing simultaneously, and three pairs of orthogonal harmonic amplitude signals are obtained. Phase delays are extracted from the three pairs of orthogonal harmonic amplitude signals, and corresponding phase delay correction coefficients are calculated out by using the phase delays. The phase delay correction coefficients are multiplied by the absolute harmonic amplitude signal equal to the sum ofthe absolute values of the orthogonal harmonic amplitude signals to obtain new harmonic amplitude signals which are not affected by the phase delays, and then a to-be-measured phase is obtained through antitangent operation. The problems are solved that in the PGC phase demodulation technology, phase delay is difficult to measure and non-linear errors caused by the phase delay are difficult to compensate for in real time, the phase measurement accuracy is improved, and the method is widely applied to the technical field of sinusoidal modulation interference.

Description

technical field [0001] The invention belongs to the technical field of laser interferometry, in particular to a phase delay extraction and compensation method in a PGC phase demodulation method. Background technique [0002] Phase-generated carrier (PGC) modulation and demodulation technology is widely used in interferometric fiber optic sensors and sinusoidal phase modulation interferometers due to its advantages of high phase detection sensitivity and large dynamic range. PGC modulation and demodulation technology includes differential cross multiplication algorithm (PGC-DCM) and arctangent algorithm (PGC-Arctan). The PGC-DCM method obtains the phase to be measured by performing differential cross multiplication and integral operations on the quadrature components. This method is easily affected by laser light intensity, carrier phase delay, and phase modulation depth. The PGC-Arctan method divides the quadrature component and performs an arctangent operation to directly ...

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Problems solved by technology

[0003] In order to solve the problems existing in the background technology, the present invention discloses a phase delay extraction and compensation method in the PGC phase demodulation method, and the present invention solves the difficulty in accurately measuring the phase delay in the sinusoidal modulation interferometer and the nonlinear error caused by the phase delay Difficult to suppress problems in real time

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