Higher Order Mode Convertors for “Ribbon” Fibre

Higher order mode convertors for ribbon fibres with rectangular cores were made by postprocessing a photonic crystal fibre and introducing an enlarged parasitic core beside the input single-mode core. These two cores were merged to form the output rectangular core. By focusing light into the input core, third- to sixth-order modes could be excited at the output. The devices were low loss (<;0.2 dB) and broadband (1250-1650 nm).