Patent ID: 7865051

Claim:
An optical fiber comprising: a hollow core region having a longitudinal axis, said core region configured to support and guide the propagation of signal light in a transverse core mode characterized by either a first polarization state, or a second orthogonal polarization state, or both, said core mode propagating in said core region in essentially the direction of said axis, and a cladding region including a localized hollow waveguide region configured to support and guide the propagation of light in a transverse waveguide mode, said waveguide mode propagating in said waveguide region in a direction essentially parallel to said axis, said core and waveguide regions being further configured so that (i) at least one of said core mode and said waveguide mode is birefringent, and (ii) at least one of said core mode polarization states is resonantly coupled to said waveguide mode, wherein said core region includes a multiplicity of micro-defects disposed at or near the periphery thereof, said core region micro-defects being positioned in a non-rotationally symmetric pattern within the cross-section of said core region so that signal mode energy therein is distributed therein more along a first transverse axis than along a second orthogonal axis, and wherein said waveguide region includes a multiplicity of micro-defects disposed at or near the periphery thereof, said waveguide region micro-defects being positioned in a non-rotationally symmetric pattern within the cross-section of said waveguide region so that mode energy therein is distributed therein more along said second orthogonal transverse axis than along said first transverse axis.