Patent ID: 8369672

Claim:
A single-polarization optical fiber comprising: a core region and a cladding region surrounding the core region, a W-type refractive-index profile having a first depressed region along an unguided principal axis of the fiber; and a quasi step-index profile along a guided principal axis of the fiber, the quasi step-index profile having a second depressed region with a radial extent at least twice a radial extent of the first depressed region along the unguided axis, wherein (i) the fiber has a substantially circular output, (ii) the W-type profile of the unguided axis exhibits a finite cutoff of the fundamental mode between the core region and the cladding region, and (iii) the quasi step-index profile comprises a predominantly curved index profile extending through an annular thickness beginning at the core region or at a point radially beyond the core region.