Robust solitary waves in fiber transmission lines with semiconductor optical amplifiers

Abstract

Owing to their robustness solitons are attractive as basic units of information in long- and medium-haul optical transmission lines. This robustness prevents the soliton from being destroyed by various perturbations occurring in practical fiber networks. The European network is peculiar because it consists almost entirely of standard fibers with a high dispersion at the preferred communication wavelength of 1550 nm. Thus the large peak power required and the short dispersion length do not permit an increase of the bit rate beyond 2.5 Gbit/s. Recently two options for upgrading the network are in the focus of interest, viz. dispersion management in the soliton regime and the operation of the network near the zero dispersion point at λ≈1300 nm. With regard to signal transmission at λ≈1300 nm semiconductor optical amplifiers (SOA) are mostly used for periodic signal amplification. In contrast to erbium-doped fiber amplifiers SOAs introduce an own nonlinear dynamics into the line. Thus, even in the case where attenuation is neglected the resulting evolution equation does not admit soliton solutions. However it is worthwhile to look for solitary wave solutions because they may represent some stable attractors in parameter space. Thus it might be expected that one can save, at least to some extend, the robustness familiar from solitons. The aim of this contribution is to identify such solitary waves in a fiber line with losses and bandwidth-limited saturated amplification.