Koustav Dey
Fiber optics has proven its best applications in the longdistance telecommunication and high-speed data transfer with secure features of the optical signal . Due to light weight, tiny hair like structure, compact size, high sensitivity, immune to electromagnetic interference and remote sensing features of the optical fiber bring forward its candidature became significant for the sensing applications. Evanescent-field-based fibre optic sensors in which a portion of the fibre cladding has been removed, became very attractive in chemical and biochemical applications where higher sensitivity, simplicity and the robustness are of the paramount importance . Removal of the fibre cladding layer pave the way of interaction between the evanescent field of the propagating mode (or modes) and the surrounding medium. Furthermore, thinned optical fibres and fiber Bragg gratings (FBGs) are of interest for wavelength tuning. In addition, in the last few years, several interrogation methods have been proposed.