High precision and low noise demodulation scheme using adaptive fast fourier transform for fiber-optic interferometric sensors

This paper presents an adaptive fast Fourier transform (adaptive FFT) demodulation scheme, aimed at enhancing the precision and noise suppression capability of signal processing in fiber-optic interferometric sensors. By adaptively optimizing the length of the acquired spectrum and dynamically adjusting the frequency domain resolution, the proposed scheme can precisely calculate the eigenfrequency of the reflected spectrum. Therefore, the adaptive FFT demodulation scheme can effectively enhance the extraction ability of phase quadrature demodulation signal. In comparison to traditional FFT demodulation scheme, the proposed scheme demonstrates nearly a tenfold improvement in eigenfrequency calculation accuracy. The experimental results indicate a significant improvement in the stability of the adaptive FFT demodulation scheme. The fluctuations are reduced to approximately 0.03 dB. This value is roughly equivalent to 25% of the fluctuations typically observed in traditional FFT demodulation schemes. Additionally, the adaptive FFT scheme demonstrates superior adaptability to sensors with varying optical path differences (OPDs). It maintains noise levels below -100 dB@1 kHz across sensors with different OPDs, and substantially reduces noise fluctuations compared to traditional FFT scheme. Furthermore, the proposed scheme exhibits notable advantages in crosstalk suppression for multiplexed signal demodulation. The fundamental frequency crosstalk (FFC) is reduced to below -50 dB, which is approximately 10 dB lower than that achieved by traditional FFT methods. The adaptive FFT demodulation scheme shows promising potential for applications in low noise, high precision, and dynamic signal detection within fiber-optic interferometer sensors and multiplexing arrays.