Radiation losses of the HE_11 mode of a fiber with sinusoidally perturbed core boundary

Abstract

The radiation losses of the HE₁₁ mode of a fiber with sinusoidal radius fluctuations are calculated in the weak guidance approximation. The loss formula is derived by means of the volume current method and also by using coupled mode theory. The result presented here extends earlier results to the case of radiation escaping nearly perpendicular to the fiber axis.