Fiber-Optic Cavities for Physical and Chemical Sensing

Fiber-optic resonators can be used as ideal mechanical probes and chemical sensors owing to their unique sensitivity to static and dynamic strain applied to the fiber as well as to optical absorption or refractive index changes in the surrounding medium when the evanescent or the internal light field is exposed. The intrinsic properties of high-finesse fiber cavities, either based on Bragg-grating structures or closed fiber rings, are discussed for quasi-static and dynamic strain sensing. Laser illumination and high precision laser frequency-locking techniques are considered for low-noise, fast and wide dynamic range active interrogation. Also, possible detection schemes for liquid sensing and spectroscopy using fiber resonators are illustrated using single-frequency tunable lasers or supercontinuum comb generators as light sources.