Dependance of ambient refractive index sensitivity with grating period of LPFG

This study investigates the response of long period fiber grating (LPFG) to ambient index smaller than fiber cladding index at different grating periods. Here the basis of investigation is difference in resonant wavelength shifts of different ambient indices surrounding optical fiber cladding with periods. Mathematical approach using three layer geometry is implemented on standard fiber (SMF28e) to estimate cladding modes. The influence of grating periods (375 mu m, 415 mu m, 450 mu m, 500 mu m, and 550 mu m) on LPFG index sensitivity is assessed for LP03, LP04, LP05, and LP06 cladding modes. The largest shift of 127 nm for a range of ambient refractive index (1-1.455) is achieved by LP06 mode at a grating period of 550 mu m. (C) 2017 Wiley Periodicals, Inc.