Asymmetric Reflection Spectrum of Fabry-Perot Interferometer and the Application in Pressure Sensing

The performance of a fiber optic Fabry-Perot (F-P) sensor largely depends on the spectral characteristics of F-P interference, nevertheless there is little research on the spectral characteristic, such as the asymmetry shapes which are often observed in practical experiments. Here, a simple analytical formula for simulating the reflected spectrum of a F-P resonator have been provided, based on which the asymmetry spectral shape can be diversified through adjusting the refined parameters in the analytical formula. In addition, the composite film of Pt/Ge with different thickness on fiber tip has been theoretically demonstrated to change the parameters, and the F-P interferometer composed by composite film of Pt/Ge on fiber tip and gold film has been simulated to exhibit variated asymmetric reflection spectra. Meanwhile, the reflection spectrum from fiber F-P interferometer based on the composite film deposited on the end face of optical fiber has been experimentally proven to change according to the thickness variation of Ge film. Finally, a fiber based miniature extrinsic Fabry-Perot interferometer (EFPI) showing a saw tooth wave shape spectrum has been fabricated to sense static pressure through a dual-wavelength based intensity demodulation scheme, which possesses the potential to overcome the offset between sensitive and dynamic range for a traditional sensor.