Two-mode operation in highly birefringent photonic Crystal fiber

A photonic crystal fiber with different air-hole diameters along the orthogonal axes is found to support only the first two modes over a very broad wavelength range (>650 nm). The second-order mode is approximately linearly polarized and has stable-intensity lope positions that do not change in response to environmental disturbances. Strain sensitivity as a function of operating wavelength of a two-mode interferometric sensor made from such a fiber is also investigated.