Pressure and Temperature Sensor Based on Fiber-Optic Fabry-Perot Interferometer by Phase Demodulation

A phase demodulation of dual-cavity fiber-optic Fabry-Perot interferometer based on open-cavity and silica-cavity was proposed and experimentally demonstrated for pressure and temperature sensing. In contrast to the commonly used wavelength demodulation, the phase demodulation for dual-cavity fiber-optic Fabry-Perot interferometer used in this paper has the advantages of simplicity, rapidity and high precision. By the phase demodulation in the spatial frequency domain, pressure sensitivity of -2.07 rad/Mpa and temperature sensitivity of -5.48 x 10 ^-4 rad/°C are obtained for the open-cavity, and pressure and temperature sensitivity are respectively -0.16 rad/Mpa and -1.5 x 10 ^-2 rad/°C for the silica-cavity. Thus, this structure can achieve concurrent the pressure and temperature sensing as a result of that pressure and temperature sensing characteristics of the open-cavity are different from silica-cavity.