“Photonic lantern” spectral filters in multi-core fibre

Abstract
Fibre Bragg gratings are written across all 120 single-mode cores of a multi-core optical fibre. The fibre is interfaced to multimode ports by tapering it within a depressed-index glass jacket. The result is a compact multimode “photonic lantern” filter with astrophotonic applications. The tapered structure is also an effective mode scrambler.