Single mode operation of elliptical gain guided and index antiguided fibers

Elliptical gain guiding fibers in which gain guiding effects are dominant compared to conventional index guiding fiber is analyzed by solving Mathieu equations with complex-valued fiber parameters. The properties of mode propagation and single mode operation are evaluated in this elliptical gain guiding fiber with the assumption of a uniform gain distribution in the active core medium. Threshold for lossless mode propagation increases exponentially with the eccentricity of the elliptical cross section. Further, the difference in threshold between the lowest two order modes is constant for arbitrary eccentricity.