Analysis and modeling of an optical fiber loop resonator and an evanescent field absorption sensor for the application for chemical detection

Optical fiber loop resonator (FLR) and fiber loop ring down spectroscopy (FLRDS) are two recent techniques used for chemical and gas sensing application based on evanescent field interaction. In chemical sensing applications, a short region of the fiber core is exposed to the external environment, so that evanescent field can interact with the chemical. The evanescent field access region in single mode fiber has been developed practically by etching a small portion of the cladding and it is used as sensor element in the fiber loop cavity resonator.