Dual-cavity interferometric wavelength-shift detection for in-fiber Bragg grating sensors

A dual-cavity interrogation method used to enhance the unambiguous measurement range of in-fiber Bragg grating sensors with high-resolution interferometric wavelength-shift detection is described. This novel technique is based on the use of two sets of fringes obtained with a stepped interferometric wavelength scanner with dual cavity lengths. We demonstrate the concept by interrogating an in-fiber grating temperature sensor with a stepped Michelson wavelength scanner.