Ildar R. Gabitov

Averaged pulse dynamics in a cascaded transmission system with passive dispersion compensation

A theory of optical pulse propagation in cascaded transmission systems that are based on the dispersioncompensatingfiber technique is developed. The existence of two scales associated with fiber dispersion and system residual dispersion leads to a simple model for the averaged pulse dynamics. In the particular case of practical importance, the averaged pulse dynamics is governed by the nonlinear Schrödinger equation. The pulse transmission stability is examined.

Optical pulse dynamics in fiber links with dispersion compensation

We examine optical pulse propagation in a transmission system with periodical pulse amplification and dispersion compensation both numerically and by a variational method. We confirm by direct numerical simulations the validity of the concept of a “breathing” soliton, which we previously proposed. We demonstrate that the sign of the residual dispersion is responsible for the stability of the pulse stream.

Optical Bistability in a Nonlinear Optical Coupler with a Negative Index Channel

We discuss a novel kind of nonlinear coupler with one channel filled with a negative index metamaterial. The opposite directionality of the phase velocity and the energy flow in the negative index metamaterial channel facilitates an effective feedback mechanism that leads to optical bistability and gap soliton formation.

Breathing solitons in optical fiber links

We introduce the concept of “breathing” solitons to describe the dynamics of optical pulses in transmission lines with passive compensation of fiber chromatic dispersion. The “breathing” pulse can be used as the information carrier. The theory presented is complimentary to the concept of the guiding-center soliton. It is shown that an average bright soliton can propagate in a system with large variations of the dispersion, including segments with high normal dispersion.

Variational approach to optical pulse propagation in dispersion compensated transmission systems

Within the area of optical pulse propagation in long-haul transmission systems various designs for dispersion compensation are investigated. On the basis of variational procedures with collective coordinates, a very effective method is presented which allows to determine quite accurately the possible operation points. We have obtained an analytical formula for the soliton power enhancement. This analytical expression is in good agreement with numerical results, in the (practical) limit when residual dispersion and nonlinearity only slightly affect the pulse dynamics over one compensation period. The procedure is suitable to analyze the proper design of dispersion compensating elements. The results allow also to describe the shape of the dispersion-managed soliton. We discuss also a qualitative physical explanation of the possibility to transmit a soliton at zero or normal average dispersion. Analytical predictions are confirmed by direct numerical simulations.

Effect of an optical negative index thin film on optical bistability

We investigate nonlinear transmission in a layered structure consisting of a slab of positive index material with Kerr-type nonlinearity and a subwavelength layer of linear negative index material (NIM) sandwiched between semi-infinite linear dielectrics. We find that a thin layer of NIM leads to significant changes in the hysteresis width when the nonlinear slab is illuminated at an angle near that of total internal reflection. Unidirectional diodelike transmission with enhanced operational range is demonstrated. These results may be useful for NIMs characterization and for designing novel NIMs-based devices.

Nonlinear optical effects in artificial materials

Abstract.We consider some nonlinear phenomena in metamaterials with negative refractive index properties. Our consideration includes a survey of previously known results as well as identification of the phenomena that are important for applications of this new field. We focus on optical behavior of thin films as well as multi-wave interactions.

Nonlinearity management in a dispersion-managed system

We propose using a nonlinear phase-shift interferometric converter (NPSIC), a new device, for lumped compensation for nonlinearity in optical fibers. The NPSIC is a nonlinear analog of the Mach-Zehnder interferometer and provides a way to control the sign of the nonlinear phase shift. We investigate a potential use of the NPSIC for compensation for nonlinearity to develop a dispersion-managed system that is closer to an ideal linear system. More importantly, the NPSIC can be used to essentially improve single-channel capacity in the nonlinear regime.

Symmetrical dispersion compensation for standard monomode-fiber-based communication systems with large amplifier spacing

Optical 10-Gbit / s return-to-zero pulse transmission in cascaded communication systems using dispersion compensation of the standard monomode fiber with large amplifier spacing is examined. It is shown that pulse distortions that are due to Kerr nonlinearity are significantly diminished by symmetrical ordering of the compensation sections when the total number of precompensation and postcompensation sections is equal. Repositioning of these sections is not critical.

Ghost-pulse reduction in 40-Gb/s systems using line coding

At high bit rates, four-wave mixing and nonlinearities in the optical channel give rise to ghost pulses. In this letter, we propose the application of modulation codes to tackle this effect.