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A method to find discrete solitons in nonlinear lattices is introduced. Using nonlinear optical waveguide arrays as a prototype application, both stationary and traveling-wave solitons are investigated. In the limit of small wave velocity, a fully discrete perturbative analysis yields formulas for the mode shapes and velocity.

Applying variational methods, we derive a reduced system of equations from the nonlocal equation that governs the average dynamics in dispersion-managed systems. These equations, which apply for any type of return-to-zero pulse, describe the stroboscopic evolution of the pulse parameters and bypass the fast variations inside each dispersion map. In the limit of large map strength we integrate the equations to obtain explicitly formulas for the parameters of a chirped return-to-zero pulse as well as the amount of post-transmission compensation needed to restore the initial pulse width.

We derive the asymptotic equations governing the evolution of a quasi-monochromatic optical pulse in a nonresonant quadratic material starting from Maxwell equations. Under rather general assumptions, equations of nonlinear Schrödinger (NLS) type with coupling to mean fields result (here called NLSM). In particular, if the incident pulse is polarized along one of the principal axes of the material, scalar NLSM equations are obtained. For a generic input, however, coupled vector NLSM systems result. Special reductions of these equations include the usual scalar and vector NLS equations. Based on results known for similar systems which arise in other physical contexts, we expect the behavior of the solutions to be characterized by a rather large variety of phenomena. In particular, we show that the presence of the coupling to the dc fields can have a dramatic effect on the dynamics of the optical pulse, and stable localized multidimensional pulses can arise through interaction with boundary terms associated to the mean fields.

A unified analytical description of the evolution of quasi-linear optical pulses and solitons in strongly dispersion-managed transmission systems is developed. Asymptotic analysis of the nonlocal equation that describes the averaged dynamics of a dispersion-managed system shows that the nonlinearity decreases for large map strength s , as O(log s/s) . The spectral intensity is found to be an invariant of the propagation, which allows the phase shift to be computed. These findings provide a clear description of pulse propagation in the quasi-linear regime, which is characterized by much lower energies than those required for stable dispersion-managed soliton transmission with the same dispersion map.

This article serves as an introduction to the focus issue on optical solitons. After a short review of the history of solitons and the field of integrable systems, a brief overview of the development of nonlinear optics and optical solitons is provided. Next, the various contributions to this focus issue are presented, and a few separate remarks are devoted to optical communications, where solitons promise to play a decisive role in the next generation of commercial systems. (c) 2000 American Institute of Physics.

The evolution of an optical pulse in a strongly dispersion-managed fiber-optic communication system is studied. The pulse is decomposed into a fast phase and a slowly evolving amplitude. The fast phase is calculated exactly, and a nonlocal equation for the evolution of the amplitude is derived. In the limit of weak dispersion management the equation reduces to the nonlinear Schrödinger equation. A class of stationary solutions of this equation is obtained; they represent pulses with a Gaussian-like core and exponentially decaying oscillatory tails, and they agree with direct numerical solutions of the full system.