Photonic crystal fiber with resonant-coupling higher-order-mode suppression

Non-axially symmetric micro-structured fibers including photonic crystal fibers and leakage channel fibers have been investigated as possible means to enable mode field area scaling while retaining low-loss fundamental mode propagation. In this paper we report on the theoretical and experimental investigation of a photonic crystal fiber designed for single-polarization operation in a coiled configuration incorporating a resonant higher-order mode suppressing structure within the cladding. We performed spatially and spectrally resolved (S2) imaging of the output of a 18.6 meter length of fiber when seeded with a broadband ASE source. We observed no trace of any localized or distributed scattering to higher order modes in the spatially resolved Fourier transformed output spectra indicating robust single-transverse-mode output.