Temperature-Compensated Long Period Grating Chemical Sensor

Long Period Gratings (LPGs) in a single-mode fiber, whose period is on the order of hundreds of microns, couples light from the forward-propagating mode into several forward-propagating cladding modes. The resulting transmission spectrum shows characteristic loss peaks. Since any variation on the core/cladding guiding properties modifies the transmission spectrum characteristics, LPGs have been used as strain sensors, temperature sensors, and refractive-index sensors.