A fiber-optic sensing system based on broadband light source carried microwave interferometry

Fiber-optic interferometers (FOIs) are common methods in the field of sensing. However, several issues hinder the technological advancements and the expansion of the scope of applications, including the polarization fading effect, multimodal interferences, and difficulties in resolving the phase of an optical signal. Aiming at solving these problems, we theoretically and experimentally analyze an original method based on broadband light source carried microwave interferometry. Mathematical models of broadband light source interference, broadband light source modulation, and modulated signal interference are constructed and simulated. Proved that optical interference fringes visibility is small enough to be regarded as zero when using broadband ASE light source. Thus, this method will eliminate the influence of optical interference and achieve accurate OPD measurement by interrogating single frequency microwave interference pattern. Unlike an optical signal with a frequency of hundreds of THz, the phase of a microwave signal can be easily and accurately measured. Therefore, the system provides an easy, convenient, and affordable way to achieve various physical quantities sensing with a satisfactory spatial resolution. Experiment results are in good agreement with theoretical calculations, which proves the superiority of the system in practice.