Abstract

In order to prevent the appearance of nonlinear effects in optical fibers supporting high optical power, new structures with Large Mode Area (LMA) are actively studied. Bragg fibers are good candidates for the realization of such single-mode and flexible fibers because the use of the appropriate Half Wave Stack (HWS) condition applied to low index ring helps to reject Higher Order Modes (HOM) and make the fiber single-mode for the end user [1, 2]. Moreover, they can operate as true photonic bandgap fibers when pixelization of the high index rings is operated – we talk about “Pixelated Bragg Fiber” (PiBF) [3] – and specific properties such as spectral filtering can then be accessible in fibers easy to splice (all-solid) that can be doped with rare-earth ions. In the proposed structure, cladding is designed so as to generate two HWS conditions for the three first HOM, namely LP₁₁ and LP₀₂-LP₂₁. Moreover, high-index rings were hetero-structured by replacing some high-index rods by pure silica rods to enhance HOM leakage. By combining these two different concepts, we show that pixelated Bragg fiber can be designed to obtain single-mode guidance with core diameter larger than 45 μm.

© 2015 IEEE