DESIGN AND ANALYSIS OF DUAL SHAPE CORE FIBER BASED REFRACTIVE INDEX SENSOR 

Abstract

A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. A sensor is a device which receives and responds to a signal when touched. A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. The resolution of a sensor is the smallest change it can detect in the quantity that it is measuring. Different chemical substances as well as several physical and biological parameters can be detected through measurements of the refractive index (RI). For this reason, RI sensors have gained considerable attention by the sensor community. Fiber-based refractometric devices are attractive; owing to the inherent advantages over their counterparts based on other techniques i.e. they can be multiplexed on a single fiber network and are suitable for in situ and remote RI measurements. Moreover, they are compact and lightweight. The resolution of fiber-based RI sensors can be as high as 10-5. So far, different alternatives have been proposed to design RI sensors with conventional optical fibers. These include core-exposed or tapered fibers, fiber Bragg gratings (FBGs), long period gratings (LPGs), interferometers made with FBGs or LPGs, refractive index sensors based on core diameter mismatch etc. Technological progress allows more and more sensors to be manufactured on a microscopic scale as micro sensors using dual shape core fiber based refractive index properties.