Patent ID: 7340132

Claim:
A polarization insensitive microbend-induced fiber grating formed within an optical fiber core region comprising a central core region of a selected refractive index difference (Δn c ) and a predefined radial extent (r c ), wherein the refractive index difference is measured with respect to the refractive index of silica; a trench core region surrounding the central core region, the trench core region having a selected refractive index difference (Δn t ) less than the central core region refractive index difference and a predefined radial extent; a ring area surrounding the trench core region, the ring cladding area having a selected refractive index difference greater than the trench core region refractive index difference and a predefined radial extent, the refractive indices and radii of each element configured to provide a relatively large gradient in refractive index as a function of distance from the fiber core center, sufficient to provide a resonant mode splitting between the propagating TE 0m and TM om modes with respect to the polarization insensitive odd/even HE 2m modes such that an insubstantial amount of signal is coupled into the TE and TM modes, where m defines the order of the radial mode for the wavelengths supported by the fiber; and a device for maintaining pressure along a selected section of the optical fiber core region so as to induce periodic perturbations therealong.