ABSTRACT

Fiber optic devices have been developed to sense and measure displacement, strain, flow, pressure, rotation, electrical and magnetic fields, and host of other variables. Though the basic principle of operation of many of the fiber optic devices is similar to those used in conventional measurement devices, the sensing portion could be drastically different. Fiber optic devices are grouped under two categories: extrinsic or hybrid and intrinsic or all fiber. In the former, the measurand modifies the properties outside the fiber and the fiber is used only as the carrier of information, whereas in the later, it also performs the sensing part. Proximity probes are extremely sensitive for the measurement of displacement and are used in variety of sensors like pressure transducer. It may have an input fiber and an output fiber, or an input fiber and two output fibers or vice versa or multiple input and multiple output fibers.