ABSTRACT
This chapter reviews the many ways in which optical fibers may be used, in conjunction with optoelectronic instrumentation, to sense physical or chemical parameters. Optical fibers are widely used in long distance trunk telecommunications systems and their use in shorter distance applications is growing rapidly. It starts with intrinsic sensors and discusses extrinsic types. Microbend sensors are intrinsic sensors, which take advantage of the loss in optical fibers when they are bent. Intrinsic fiber sensors rely on deliberately configuring the optical system to be sensitive to external influences on the fiber or cable. An extrinsic fiber sensor usually uses a conventional optical fiber, which is only employed as a convenient light-guiding medium to transport light to and from more conventional optical sensors at the end of, or at specific points on, the cable. The chapter describes the very simplest form of intensity-based sensors, where only the transmitted or reflected light level is measured.
