Characteristic research on mechanically induced long-period fiber gratings

A full experimental characterization of mechanically induced long-period fiber gratings (MLPFGs) fabri-cated by pressing a plate with periodic grooves against a short length of fiber is presented. This technique enables a good control over the gratings' isolation loss peaks and has high repeatability. The spectra characteristics of MLPFGs are studied with the change of the parameters including pressure, period, and temperature. The produced MLPFGs have low insertion loss (<0.2 dB) and the loss peaks can be higher than 20 dB. A large tunability of the resonant wavelength (> 14 nm) is achieved through adjusting pres-sure grooves' period. The center wavelength temperature sensitivities of 0.057, 0.086 nm/℃, and resonant peak temperature sensitivities of 0.230, 0.312 dB/℃, are achieved for jacketed and unjacketed fibers, re-spectively. These MLPFGs, which are simple and inexpensive, also offer the unique advantages of being tunable, erasable, and reconfigurable.