FBG AND LPG BASED SENSORS

Abstract

The sensors have frequent uses in all the domains of life. There are multiple types of sensors like mechanical, electrical, acoustic, optical sensors etc. out of these the optical sensors are prominent ones. The optical sensors are compact in size, cost effective, highly robust, require low maintenance. These properties of optical sensors make them popular for industrial and research applications[ 1]. The most of the optical sensors are nothing but optical waveguide. An optical waveguide is a structure which confines and guides the light [ 2]. Optical sensors, that work on the principle of the working of optical waveguide have very high accuracy and sensitivity. All these advantages over other sensors makes them potential competitor in domain of sensors. Fiber bragg grating abbreviated as FBG can be divided into two catagories. First is called ‘Short Period Grating’ and second one is called ‘Long Period Grating’. The abbrevation for the Long period grating is LPG. The criteria to decide the catagory between short period or long period depends upon the order of the wavelength of the incident electromagnetic wave and the grating period of the refractive index modulation. In simple words, if the electromagnetic wave has the wavelength of the order of 1.3µm- 1.6 µm and the grating period is of the order of 0.5 µm [3]. Then, the grating is called short period grating. On the other hand LPG has grtaing period over 100 µm.