Variable-step-size rapid high-precision signal demodulation method for optical fiber F-P sensor

Abstract

The invention relates to a variable-step-size rapid high-precision signal demodulation method for an optical fiber F-P sensor. The method comprises the following steps: preprocessing a spectral signalreceived by an optical fiber F-P sensor to obtain a normalized spectrum sequence in a discrete form; carrying out demodulating by using a fast Fourier transform method to obtain a cavity length roughvalue; constructing a series of virtual cavity lengths and corresponding interference spectrums thereof in a virtual cavity length simulation range with a relatively large step size; calculating meansquare errors between the virtual spectrums with different cavity size values and real spectrums; acquiring a virtual cavity length value corresponding to the minimum mean square error, then reducingthe virtual cavity length simulation range and step size, calculating the mean square error of the virtual cavity length and the actual spectrum to find out the cavity length value corresponding to the minimum mean square error, and repeating the steps in sequence until the demodulation precision requirement is met to obtain a final cavity length value. According to the method, absolute measurement of the cavity length of the optical fiber F-P sensor can be realized, the demodulation speed is high, and the cavity length resolution is high.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a fast and high-precision signal demodulation method of an optical fiber F-P sensor with variable step size. Background technique [0002] For fiber optic F-P sensors, the quality of the signal demodulation method directly affects the response speed and detection accuracy of the sensing system. At present, signal demodulation methods can be roughly divided into two types: intensity demodulation method and phase demodulation method. In the intensity demodulation method, the system often uses a narrow linewidth light source or a monochromatic laser light source to ensure a constant light wavelength. The change of light intensity and cavity length in the working area is linear for demodulation, and the demodulation speed is fast, which is suitable for measuring dynamic signals such as vibration and sound wave frequency. The phase demodulation method is to obtain the r...

AI Technical Summary

Problems solved by technology

The Fourier transform demodulation method uses Fast Fourier transform (FFT) to solve the frequency spectrum of the output signal. The demodulation speed is fast, but the demodulation accuracy is poor.

The discrete cavity length demodulation algorithm constructs a series of virtual cavity length values ​​at a certain step interval within a cavity length range, and compares the spectral signals of different virtual cavity lengths with the actual spectral signals. When the accuracy is high, this method exists The problem of huge amount of calculation is not suitable for practical application

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