Mode recoupling between core and cladding modes of cascaded-LPFGs fabricated with heat-shrinkable tube employing a thin confinement layer

Abstract

Cascaded long period fiber gratings (LPFGs) fabricated with heat-shrinkable tube, screw, and single-mode fiber are proposed herein that employ a thin confinement layer on the bare fiber. The transmittance of a proposed cascaded-LPFG is theoretically and experimentally investigated regarding the cladding mode loss. By employing the confinement layer on the cladding of the proposed LPFGs, mode recoupling between core and cladding modes is successfully induced. Our cascaded-LPFG has potential application for the simple and low-cost optical filters and for the optical sensors monitoring vibration, refractive index, or temperature.