M. Gölles

On the description of N-soliton interaction in optical fibers

We show that the interaction of a finite number of solitons propagating in an optical fiber may be reasonably described by a generalized quasiparticle approach. The results for the positions of the pulses agree well with the numerical findings, at least up to the point of the smallest separation, even for pulses with slightly different amplitudes. It turns out that for trains with a large number of out-of-phase pulses the positions may be reasonably described by the Toda lattice equation although their derivation is mathematically not consistent.

Break up of N-soliton bound states due to intrapulse Raman scattering and third-order dispersion — an eigenvalue analysis

Abstract By using a numerical Zakharov-Shabat eigenvalue analysis we study the effect of third-order dispersion (TOD) and intrapulse Raman scattering (IRS) on Satsuma-Yajima N -soliton bound states (NSBS). Two stages of bound state break up can be identified. Moreover, we show that even a weak TOD considerably reduces the self-frequency shift caused by IRS.

Optimization of signal transmission by an in-line semiconductor optical amplifier-saturable absorber module

A module consisting of a semiconductor optical amplifier and a saturable absorber is investigated with respect to gain, pulse and noise dynamics and their dependence on device parameters. Based on the analytical and numerical results optimization strategies were found regarding high-bit-rate signal transmission. The results are compared with recently reported experimental data.

Effect of nonlinear gain and filtering on soliton interaction

We show that suppression of soliton interactions in the presence of bandwidth limited amplification and nonlinear gain may be achieved through the formation of chirped solitons. We reveal that equal in-phase pulses are unstable with respect to small changes of their relative amplitude, and evolve into noninteracting π phase shifted solitons.

Robust solitary waves in fiber transmission lines with semiconductor optical amplifiers

A two-parameter family of single- and multiple-hump solitary waves in a fiber transmission line with periodically aligned semiconductor optical amplifiers and fixed in-line filters can be identified, provided that the dispersion length considerably exceeds the spacing period and that the average-soliton concept can be adopted. These solitary waves are robust against fluctuations of the input amplitude. We show that the finite gain recovery time of the amplifier leads to the formation of topological solitons. Multiple-hump solutions decay into pulses with equal amplitudes if the dispersion length is comparable with the amplifier spacing.

Stabilization of soliton trains in optical fibers in the presence of third-order dispersion

We analyze the propagation of soliton trains with small initial separation in the presence of third-order dispersion. We show that both the amplitudes and the positions can be stabilized, provided that phase modulation is applied and adjacent pulses are initially out of phase.

The effect of bandwidth limited amplification on soliton interaction

Abstract A detailed investigation of the effect of bandwidth limited amplification on the propagation of a single soliton as well as on the interaction process in soliton trains is performed both numerically and in the framework of a perturbation approach. Two major effects of the bandwidth limited amplification may be identified, namely the creation and amplification of low-frequency radiation and the shift of the frequencies of the pulses towards the centre of the filter curve. It is shown that the initial separation and the strength of bandwidth limited amplification determine which effect prevails. Furthermore, we show that the perturbation approach describes reasonably the latter effect whereas the amplification of the low frequency components may lead to soliton instability invalidating perturbation arguments. Eventually, it turns out that the results obtained for two-soliton interaction cannot be extended straightforwardly towards N -soliton interaction.

Enhanced sideband instability in soliton transmissions with semiconductor optical amplifiers.

We show that the gain saturation of semiconductor optical amplifiers can lead to enhanced sideband instability in soliton transmissions, provided that the amplifier spacing is comparable with the dispersion length. With sliding filters the pulse can be stabilized and the radiation created is partially absorbed.

Modulational instability in a transmission system with semiconductor optical amplifiers and in-line filters

Modulational instability of continuous waves in transmission systems with semiconductor optical amplifiers and in-line filters was theoretically and experimentally analyzed. Stable and unstable domains were identified. Even in the normal-dispersion region, modulationally unstable domains can exist for an appropriate filter detuning.