Fiber-Optic Sensing Interrogation System for Simultaneous Measurement of Temperature and Transversal Loading Based on a Single-Passband RF Filter

In this paper, a fiber-optic sensing interrogation system for simultaneous measurement of temperature and transversal loading based on a single-passband RF filter has been proposed and experimentally demonstrated. This sensing interrogation system consists of a fiber Mach-Zehnder interferometer (FMZI) as the sensing device and a dispersive medium. The FMZI also acts as the spectrum slicer to induce continuous sampling, which results in the single-passband frequency response together with the dispersive medium. Two arms of the FMZI are used to measure the temperature and transversal loading respectively. The temperature change on one arm introduces the variation of fiber refractive index, which will change the central frequency of the RF filter's passband, while the transversal loading induces the change of polarization state of the light, and thus, the amplitude of the RF filter's passband will be changed accordingly. By tracking the central frequency and amplitude changes of the passband, temperature, and transversal loading can be monitored simultaneously. With the proposed fiber-optic sensing interrogation system, the temperature and transversal loading variation-induced optical spectra changes can be converted to the variation of frequency and amplitude of the RF filter's passband in electronic domain, which greatly facilitates the measurement.