Optical biosensors based on Fiber Bragg Grating (FBG) have been widely used and studied recently due to their considerable advantages. There are many applications in which different types of optical FBG are used as biosensors depending on the different modifications. The FBG is basically a temperature or strain sensor, however, it can be used for more complex applications by modifying and controlling its main parameters such as the periods, refractive index (RI), or adding a sensitive material externally to induce a wavelength shift in the Bragg wavelength λB, phase shift, power variation which can be utilized as a parameter transducer. Therefore, the FBG can be used to measure strain, force, temperature, pressure, vibration, displacement, bio-sensor, etc. In this paper, the state of the optical biosensor based on FBGs sensors, including recent bio-sensors based on tilted FBG, Uniform FBG, Chirped FBG, Long period grating, Phase-Shifted FBG, and photonics crystal fiber (PCF) FBG, have been presented. The principles of work of each kind of FBG biosensor are concisely described.
