Towards the design of a wideband reflective long period grating distributed sensor

Abstract

In this paper, we computationally investigate the effects of metal coating length and coating coverage on the reflected spectrum of a long period grating (LPG) over a broad bandwidth. Simulation results indicate that coating the tail end of the fiber between the LPG and the end facet of the fiber provides a reflected spectrum that mimics the LPG transmission spectrum shape over a 400 nm bandwidth. Based on single LPG simulation results, we present the design of a distributed LPG structure containing a multiple number (n) of LPGs in reflection mode for the first time. Simulation results for n = 1, 2, and 3 are presented here to demonstrate the concept of a distributed reflective LPG design. It is expected that such a sensor will open a new window for distributed sensing using reflective LPGs.

Simulation of the Transmission Spectrum of Long-Period Fiber Gratings Structures with a Propagating Acoustic Shock Front

“…In terms of sensing, it is more convenient to create a sensing head having access to a single end of the fiber. This can be attained by using a reflective surface at the end of the optical fiber with the LPFG in a self-interference Michelson configuration [39][40][41][42][43][44][45][46], and the size of the sensing head is halved in this case. An arbitrary phase shift can be introduced in the center of the grating, if a gap is added between the LPFG and the mirror.…”