Sensitive strain measurements with a fiber Bragg-grating ring resonator

We describe a novel strain sensor based on a fiber Bragg grating (FBG) ring resonator. The spectrum of this resonator consists of equally-spaced resonances, exhibiting a frequency splitting proportional to the reflectivity of the intracavity FBG. A strain applied to the FBG causes a shift of the bragg wavelength, and thus a variation of the resonance splitting. The splitting is insensitive to the thermal/strain noise affecting the fiber in the region outside the FBG. The sensitivity and resolution of the sensor are analyzed in detail, showing that a subpicostrain resolution can be easily achieved with an optimized setup. © 2014 SPIE.