Sensitivity-Tunable FBG Interrogation System Utilizing a Mechanically Induced Long Period Fiber Grating

Abstract

A mechanically induced long-period fiber grating (MLPFG) scheme and a sensitivity tunable fiber Bragg grating (FBG) interrogation system is presented. The MLPFG is made by pressing a plate with periodic grooves (which were fabricated using mechanical line processing technology) against a short length of single mode fiber. The strength of that resonant band of MLPFG is altered by applying pressure to the fiber. A FBG whose center-wavelength is localized on the slope of a resonant band of a mechanical grating is chosen. By applying a pressure with a value from 20 N to 60 N on the MLPFG, the FBG is submitted to strain values of up to 3000 μe, during which the Bragg wavelength and the respective transmitted peak power through the MLPFG are recorded. It is demonstrated that the sensitivity of this FBG interrogation system to strain variations increased from 0.802 nW/μe to 1.204 nW/μe.