Refractive-sensitivity of mechanical long-period fiber grating in side-hole fiber

The refractive index sensor for use of mechanically induced long-period fiber grating (MLPG) in a side-hole singlemode fiber is proposed. The principle of operation is based on using of a long-period grating that is made by pressing a plate with periodic grooves against a short length of side-hole fiber. The strength of the resonant peak is tuned by adjusting the pressure applied on the side-hole SMF. The resonance wavelengths are shifted as the two side-holes of the fiber core were filled with the different the refractive index liquids. The resonant wavelength of 1588.6 nm has a total blue shift of approximately 12.2 nm for refractive index ranging from 1.35 to 1.43. The results show that it is more sensitive than that of the conventional SMF long-period fiber gratings.