I.M. Uzunov

Optimization of periodically dispersion compensated breathing soliton transmissions

An optimization strategy for upgrading soliton links by strong dispersion compensation is suggested. Only a definite combination of input pulse power and launch point location (or prechirping) leads to enhanced transmission distances. Propagation of a 10-Gb/s signal in a standard fiber over several thousands of kilometers is numerically demonstrated.

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.

Stability and quasi-equidistant propagation of NLS soliton trains

Abstract Using the complex Toda chain we model the asymptotic behavior of the N soliton pulse trains of the nonlinear Schrodinger equation. Stable asymptotic regimes are: (i) asymptotically free propagation of all N solitons; (ii) bound state regime where the N solitons may move quasi-equidistantly (QED); and (iii) various intermediate regimes. Our method allows one to determine analytically the set of initial soliton parameters corresponding to each regime. We list the soliton parameters, which ensure QED propagation of all N solitons since this is important for optical fiber communication.

Soliton transmission with periodic dispersion compensation: effects of radiation

We analyze the stabilization, by means of periodic dispersion compensation, of soliton transmissions operating beyond the average soliton regime. We determine optimal parameters of the dispersion compensating fibers by evaluating the fraction of generated radiation.

Adiabatic and non-adiabatic soliton interactions in nonlinear optics

Our previous results on the N-soliton interaction in the adiabatic approximation have been extended. It is shown that the complex Toda chain (CTC) model is a universal one in the sense that it describes the N-soliton train interactions for all NLEE from the NLS hierarchy. We derive the perturbed CTC system and show that the small perturbations affect only the center of mass motion and the global phase of the N-soliton train. A special reduction of CTC describes the interaction of the sine-Gordon solitons and anti-solitons. The peculiarities of the interactions in the non-adiabatic cases are outlined.

Optimization of soliton transmissions in dispersion-managed fiber links

We propose a simple optimization criterion (including the best launch point position in-between amplifiers) for the design of soliton transmission lines. The present approach is shown to minimize energy scattering from the solitons into the continuum.

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.

The N-Soliton Interactions, Complex Toda Chain and Stable Propagation of NLS Soliton Trains

One of the important problems in optical fiber soliton communication is to achieve as high of a bit rate as possible. In order to do this, one needs to be able to pack the solitons into as short of a space as possible. However, if the solitons are too close together, then their mutual interactions can cause them to collide and/or separate, thereby corrupting the signal. The current solution of this problem is simply to require each soliton to be sufficiently far apart from all others (usually 6 or so soliton widths) so that such interactions can be totally neglected. However, at the same time, it was predicted [1, 2] and experimentally confirmed [3] that for certain values of relative soliton parameters, this separation can be reduced, and at the same time, still maintain signal integrity. Our purpose is to analytically and numerically detail the soliton parameter regime, inside of which, signal integrity can be maintained. In particular, we are interested to determine how the inter-soliton interaction can be used for stabilizing a soliton train.