Research on the Rayleigh noise model of optical-fiber extrinsic Fabry-Perot sensor arrays

This study conducts theoretical modeling on the mechanism of Rayleigh scattering noise in the optical-fiber Fabry- Perot (F-P) sensing array to address the issue that it, as a key noise source, restricts the array's performance. Based on the existing theory of fiber Rayleigh scattering noise, considering the characteristics of the weak signal light of the low-finesse F-P cavity in the array and the weak coherence of the broadband light source, a unified noise model under coherent and non-coherent states is established. Specifically, based on the complex Gaussian variable property of the Rayleigh scattering coefficient and the random walk model of the light source phase noise, the model analytically describes the generation mechanism of the phase demodulation noise and qualitatively analyzes the effects of key influencing factors such as the light source linewidth. Through numerical simulation, the influence law of the light source linewidth on the power spectrum of Rayleigh scattering noise is mainly analyzed: the increase of the light source linewidth significantly reduces the noise coherence, leading to changes in the noise intensity, and becomes the dominant factor in the coherent noise state. The correctness and applicability of the model are preliminarily verified through experiments. This work provides important theoretical support for improving the noise theory system of the fiber F-P array and developing noise suppression methods, which is helpful for enhancing the stability and accuracy of the sensing system.