Fiber F-P sensor cavity length wavelet phase extraction demodulation method

Abstract

The invention provides a fiber F-P sensor cavity length wavelet phase extraction demodulation method. At first, the interference spectrum is calculated by means of a fast fourier transform algorithm to obtain a cavity length value to be a cavity length rough measuring value; the searching scope of a scale factor is determined by taking the 2-3 times of the precision of the fast fourier transform algorithm as the radius, and the phase information corresponding to each point in the interference spectrum is solved by continuous complex wavelet transform; and the cavity length value of the fiber F-P sensor is calculated by the linear gradient obtained by the linear fitting phase and wavenumber to be the final cavity length value. The absolute measurement of the F-P sensor cavity length can be achieved, so that the high-precision and high-resolution measurement of physical quantity can be achieved.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a method for extracting and demodulating the phase of an optical fiber F-P sensor cavity with long wavelets. Background technique [0002] According to the modulation type of its parameters, fiber optic sensors can be divided into intensity modulation type, polarization state modulation type, phase modulation type and wavelength modulation type. Intensity-modulated optical fiber sensors are widely used in general engineering because of their simple structure and fast response. Polarization modulation and phase modulation optical fiber sensors are widely used in the detection of physical quantities such as strain, temperature, pressure and magnetic field because of their high measurement accuracy. The most common wavelength modulation sensor is the Fiber Bragg Grating (FBG) sensor. This type of sensor is widely used in various occasions due to its simple...

AI Technical Summary

Problems solved by technology

Among them, the intensity demodulation method obtains the corresponding sensor cavity length value according to the change of light intensity. Although this demodulation method has a fast demodulation speed and is simple to implement, the demodulation result is easily affected by the fluctuation of the light source.

The phase demodulation method obtains the cavity length value of the F-P sensor through the phase information in the interference spectrum of the F-P sensor. The demodulation speed of this method cannot reach the level of the intensity demodulation method, but its demodulation accuracy is higher than that of the intensity demodulation method. It is suitable for For the measurement of quasi-static physical quantities (temperature, pressure, etc.)

Although the existing phase demodulation methods such as the single-peak method have high demodulation accuracy and resolution, they can only perform relative measurements, and the measurement dynamic range is limited, only within λ / 4

Although the multi-peak method has a large dynamic range and can realize the demodulation of the absolute cavity length, the measurement accuracy is limited

The Fourier transform demodulation algorithm also has the problem of low measurement accuracy and resolution

The discrete cavity length (DGT) demodulation method proposed by S.M.Musa of Virginia Institute of Technology improves the demodulation accuracy by reducing the cavity length search step size, but the spectral peak width is large, which will cause errors in peak finding, and the algorithm The amount of calculation is huge, not suitable for practical engineering applications

Other algorithms such as cross-correlation demodulation algorithm, curve fitting demodulation algorithm, minimum root mean square demodulation algorithm, etc. can achieve absolute cavity length demodulation with higher precision and resolution, but there is also a problem of huge amount of calculation

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