Low-loss single polarization fibers

Abstract

Low-loss single polarization fibers that maintain a state of linear polarization well are proposed. This fiber is composed of four regions: the concentric circular GeO₂- and/or P₂O₅-doped core and pure silica clad regions for constructing the low-loss waveguide, and the B₂O₃-doped elliptical-jacket and the silica outer support regions for introducing the large nonsymmetric stress in the core. Theoretical and experimental studies on the coupling length of the two fundamental modes of orthogonal polarization and transmission loss have been carried out. An extinction ratio of less than −33 dB at 1-km fiber length and a loss of μm were achieved.