Fast and accurate full-spectrum interrogation for fiber Fabry–Perot interferometric sensor consisting of Bragg gratings in polarization maintaining fiber

A measurement method for many sharp transmittance peaks of a fiber Fabry–Perot interferometer (FPI) with high resolution in a short time is proposed. Using the proposed method, temperature and strain dependences of an FPI constructed using polarization maintaining type fiber Bragg grating (PM-FBG-FPI) are evaluated. By detecting wavelength shift occurring in many peaks of a PM-FBG-FPI with high resolution, it is possible to quantitatively evaluate a slight shift coefficient difference due to the difference in resonance order of each peak. Simultaneous measurement resolution of temperature and strain by the PM-FBG-FPI sensor is also improved by using the average value of the wavelength shift detected at many peaks. The resulting high-resolution measurements are demonstrated experimentally.