Integrated optic-fiber sensor based on enclosed EFPI and structural phase-shift for discriminating measurement of temperature, pressure and RI

Abstract

An optic-fiber sensor based on integration of extrinsic Fabry–Pérot interferometer (EFPI) and phase-shifted fiber Bragg grating (PS-FBG) is depicted and demonstrated. The proposed sensor structure mainly consists of an enclosed EFPI fabricated with photosensitive adhesive between two end-faces of a halved FBG. Since the periodic refractive index (RI) distribution of FBG is interrupted and resulted in a structural PS-FBG in the middle of FBG. Consequently, the enclosed EFPI is capable of measuring the variations of temperature, pressure and RI due to optical cavity length changes, whereas the notch wavelength of introduced structural phase-shift spectrum is only sensitive to temperature, and the intensity of structural phase-shift spectrum is only insensitive to pressure. Therefore, the discriminating measurement of temperature, pressure and RI can be realized, due to using the methods of wavelength modulation and intensity modulation. The relative errors of temperature, pressure and RI, between the analysis results and measurement values, are 1.4%, 4.1% and 0.1%. The proposed integrated sensor with cost-effective merit has a promising research prospect in the field of the multiple parameters distinguish measurement.