Soliton Pulse Generation Research Articles

Analysis of soliton pulse propagation in an optical fiber using the finite‐element method

AbstractSoliton is one of the key concepts that will support future optical communications with a capability for large‐capacity, longdistance transmission systems. In general, the propagation of soliton pulses in an optical fiber is described by the perturbed nonlinear Schrödinger equation (PNLSE). Without any perturbation, this equation is reduced to the canonical nonlinear Schrödinger equation (NLSE) and can be solved analytically. However, in an attempt to take into account a variety of perturbations such as higher‐order dispersion, nonlinear dispersion, shock effect, induced Raman scattering, dissipation, etc., it is no longer solvable in an analytical fashion.This paper proposes a useful method based on the finite‐element method to carry out systematically the evolutional analysis that includes these perturbations. This method can easily deal with cases with realistic perturbations. To confirm the validity of this approach, it is applied to solving unperturbed cases, and it is shown that the same results as those using other solution methods are obtained.

Analysis of soliton pulse propagation in a birefringent optical fiber using the finite‐element method

AbstractSince the problem of waveform distortion in optical communications can be overcome by optical soliton, very wide band transmission becomes possible. It is foreseen that soliton propagation is the candidate for future optical systems. The soliton behavior can be expressed by the coupled nonlinear Schrödinger equations.In this equation, taking the nonlinear oscillatory or loss terms due to the mutual parametric effects of each polarization component into account, the analysis will become very complicated. Concerning this point, in most analytical procedures, such oscillatory terms are neglected. However, the contribution of these terms are large in optical fibers of low birefringence and, therefore, they cannot be neglected.In order to establish a unified and effective approach, taking these perturbation and oscillatory terms into account, an analytical procedure based on the finite element method is proposed. Ultrashort pulse transmission in various fibers and the effects of the birefringence upon soliton pulses are investigated. The correctness of the present method is verified and several new results are obtained. Finally, in case of subpicosecond pulse transmission in optical fibers of low birefringence, it is shown that the contribution of the above mentioned terms is quite remarkable.

Experimental observation of adiabatic compression and expansion of soliton pulses over long fiber paths

In a recirculating 42-km fiber loop with round-trip loss compensated by Raman gain, we have used excess gain to study the influence of adiabatic energy changes on the propagation of soliton pulses over fiber paths of hundreds to thousands of kilometers. Both the measured pulse shapes and the corresponding optical spectra vary in agreement with simple scaling laws and maintain the expected time-bandwidth product.

Theoretical description of transient stimulated Raman scattering in optical fibers

The authors derive a single-wave equation which describes transient stimulated Raman scattering in optical fibers. The equation is valid for forward traveling waves whose bandwidths are less than approximately=1/3 the carrier frequency. It correctly conserves a classical photon number and not the total optical energy as is appropriate for Raman scattering problems. From this equation, the authors derive a formula for the small-signal gain spectrum which includes the effects of Raman scattering, four-wave mixing, and modulational instabilities. Examples of numerical integrations are given which show the generation of short soliton pulses from the nonlinear evolution of a noise band around a continuous wave pump. >

Generation and stabilization of short soliton pulses in the amplified nonlinear Schrödinger equation

The nonlinear Schrodinger equation (NLS), with its modified forms, is the central equation for the description of nonlinear pulse propagation in optical fibers. There are a number of different physical situations in which coupling between waves leads to energy transfer. In such systems, ultrashort pulses have been observed to form during propagation. In this paper we show that much of this behavior can be understood by considering the effects of gain in the NLS. We also show that perturbations of the NLS do not destroy these results, provided that the modified equation possesses solitary-wave solutions.

Multistable self-trapping of light and multistable soliton pulse propagation

It is demonstrated that a nonlinear Schrodinger equation with certain nonlinearities allows for an existence of multistate single solitons (i.e., single solitons with the same carried power but different propagation parameters). In nonlinear optics, these solitons may exist either in the form of short bistable pulses, or bistable self-trapping (both two- and three-dimensional).