A Recipe for Soliton Robustness in Optical Fibers

Abstract

It is often claimed in the literature that solitons in optical fibers are well-described by the nonlinear Schrodinger equation. The evidence for this claim is the remarkable series of experiments, dating from the original work of Mollenauer, et al. [1], which clearly show that single solitons in isolation act in accordance with the nonlinear Schrodinger equation in the presence of significant fiber nonidealities-physical effects not included in, the nonlinear Schrödinger equation. The most important of these are attenuation, the Raman effect, higher order dispersion, and birefringence. A clear qualitative difference in the effects of attenuation and the Raman effect on the one hand and higher order dispersion and birefringence on the other hand is visible in both experiments and numerical simulations. In the case of attenuation, a steady decrease of the soliton amplitude is observed 111 and in the case of the Raman effect, a steady decrease of the soliton central frequency is observed [2]. This steady change in the soliton parameters will ultimately destroy the soliton if it is uncompensated. In the former case, the soliton will ultimately become undetectable, while in the latter case, the soliton will be shifted into a wavelength regime where attenuation dominates, the amplitude falls, and, once again, the soliton becomes undetectable. By contrast, both higher order dispersion and birefringence change the soliton shape somewhat and shift its parameters, but lead to no steady change in these paramenters [3] - [4]. As a consequence, their effect is hard to detect experimentally unless they become quite large.