**5.2 Optical fibers**

Fiber optic is an example of analytical devices that works as a transduction item, in which it generates a signal proportional to the density of chemical or biochemical elements with react of the biological element. In addition, they transfer light with silica glass or plastic fiber optic fiber based on the Total Internal Reflection (TIR) principle to the analysis site [41]. The fiber optics biosensors are categorized into two different types:


The fiber-optical sensors essential benefits can vary from their: 1) capability of hard environment to robust EMI (electromagnetic interference immunity),

chemical corrosion, high temperature, high voltage, and pressure. 2) Low power, very small size, and passive. 3) Exceptional performance such as wide bandwidth and high sensitivity. 4) Processing of long range. 5) They applied distributed or multiplexed measurements to cope with their main flaw of high cost and unfamiliarity of end-user [45].
