Intrachannel Interactions Research Articles

The Emergence of the Noninteracting Channel in the Strongly Interacting 1D System

A strongly interacting 1D system with many channels is studied. When single‐electron interchannel backscattering processes become relevant, new fields are defined. Some fields are frozen (gapped) by these relevant perturbations, whereas others remain free. A mathematical procedure to separate gapped and conducting channels is proposed. The problem for a two‐channel system with particular relevant perturbation is then solved exactly for arbitrary intra‐ and interchannel interactions, and effective Luttinger parameter and velocity for the free field are found. The parameters of the free field are independent of the interactions between right‐ and left‐moving electrons in the same channel and between electrons moving in the same direction in different channels. Finally, if the interchannel interactions are weak, the free field becomes noninteracting (effective Luttinger parameter ) independently of how strong intrachannel interactions are.

Analysis of multichannel optical soliton collisions with asymmetric energy in strongly dispersion managed transmission networks considering higher-order effects

We study the interaction properties of optical soliton pulses propagating in a two-channel wavelength-division multiplexed strongly dispersion managed communication system. We analyze the effects of third order dispersion, Raman scattering and self-steepening using an ordinary differential equations model obtained by a variational method applied to the Generalized Nonlinear Schrodinger Equation. The validity of the model is assessed against the integration of the full nonlinear partial differential equations. The variational equations are initially solved for a single pulse in order to identify the launching parameters for each pulse in the first DM cell of the system. One pulse per wavelength is then injected in the transmission link. We then systematically study the evolution of multiplexed soliton trains and analyse the transmission system in terms of residual frequency shifts and interchannel interactions as the map strength is varied, focusing on the ratio of dissimilar peak powers in a broad range of dispersion difference values, concluding that the transmission characteristics improve by using specific values of unequal energies and considering higher-order correction terms. The work presented is an extension of previous analysis where isolated intra-channel two-pulse interactions had been addressed considering pulses with dissimilar energies.

Higher-order interaction-induced effects between strong dispersion-managed solitons with dissimilar powers

We address one of the major penalties associated with the transmission of optical solitons in fiber-optic networks: the intrachannel interactions between pulses in a single channel strong dispersion-managed transmission link. We calculate the interaction length between sets of two and three pulses as a function of the ratio of dissimilar peak powers of interacting solitons by means of a variational approach to the generalized nonlinear Schrodinger equation describing the evolution of optical soliton pulses. We find a maximum of this colliding length for specific values of pulse energies. The effect of higher-order perturbation terms, such as third-order dispersion, Raman scattering, and self-steepening, shows an enhancement of the interaction distance in a broad range of dispersion difference values. We conclude that the transmission characteristics of soliton trains may be improved by means of using specific values of unequal energies and taking into account higher-order correction terms.

Propagation properties of strongly dispersion-managed soliton trains

We analyze the intra-channel interactions of strongly dispersion-managed soliton trains. We systematically study the transmission system in terms of a coalescence distance. The impact of third-order dispersion and the positions of the amplifiers are evaluated. We also study the effect produced on the interaction patterns by the modifications in the pulse timings and relative amplitudes. Based on the results obtained, we propose a channel encoding scheme which gives a noiseless capacity very close to that of the conventional binary soliton signaling and, yet, provides a significant improvement in the interaction limitations.

Interactions between dispersion-managed solitons with unequal powers

We revisit the problem of intrachannel interactions between solitons in dispersion-managed nonlinear fiber links, which is a major limiting factor for the use of solitons in fiber-optic networks. By means of systematic simulations, we demonstrate the existence of a well-defined maximum of the interaction length, zint, as a function of the ratio of peak powers of interacting solitons, while in the case of identical solitons the interaction length always attains a minimum. An explanation to these features is proposed. Interaction effects in three-soliton sets are studied too. The results suggest that the transmission characteristics of soliton streams in the dispersion-managed system may be improved by using alternating values of the peak powers whose ratio corresponds to the maximum of zint.

Self-phase-modulation-based 2R regenerator including pulse compression and offset filtering for 426 Gbit/s RZ-33% transmission systems

We report on the experimental and theoretical study of a self-phase-modulation-based regenerator at 42.6 Gbit/s with a return-to-zero 33% format. We point out some detrimental effects such as intrachannel interactions and Brillouin scattering. An efficient solution, relying on a self-phase-modulation-based pulse compressor in combination with the regenerator, is proposed to overcome these detrimental phenomena. The experimental demonstration shows the effectiveness of a wavelength-transparent regenerator at 42.6 Gbit/s with a sensitivity-improvement of more than 5 dB and an eye-opening improvement of 2.3 dB in a back-to-back configuration, as well as a 10 times maximum transmission distance improvement for a BER of 10(-4).

Timing jitter induced by intrachannel interactions in optical fiber communication systems using CFG as dispersion compensator

In this paper, a theoretical model is proposed for the analysis of timing jitter induced by intrachannel interactions in optical fiber communication systems using chirped fiber grating (CFG) as dispersion compensator. And for the first time, the impact of group-delay ripple (GDR) on timing jitter is taken into account in detail, theoretically and numerically. Results show that the GDR may increase or decrease the timing jitter of certain pair of adjacent pulses, deciding by the ripple parameters. The maximum influence will be obtained when ripple period is about 2/5 of the input pulse width. In practical systems, the GDR enhance the timing jitter for some adjacent pulses while reduce it for some other adjacent pulses, depending on the pulse pattern and the GDR parameters. In our simulation, the GDR guarantees a 3.04 ps increase of the standard deviation of the timing jitter.

Reduction of intrachannel nonlinearity using optical phase conjugation

We study the compensation process of nonlinear intrachannel interactions in optical phase conjugation (OPC) systems using a perturbational approach. The theoretical analysis and numerical simulations reveal that the system impact of intrachannel effects can be greatly reduced by OPC combined with a symmetric fiber-link configuration.

Stabilization of solitons against timing jitter and collisions by notch filters in multichannel fiber-optic links

We report the results of a detailed numerical analysis of stabilization provided by lumped notch filters against basic degradation factors in dense-wavelength-division-multiplexed (DWDM) soliton systems, which include the noise-induced timing jitter (Gordon–Haus effect), intrachannel interactions between solitons, and cross-talk effects due to interchannel soliton–soliton collisions, in the form of temporal shifts and loss of energy to the formation of shadows in the other channel. The filtering profile is a couple of rectangular notches that bound the transmission channel in the frequency domain. For typical values of parameters relevant to the DWDM systems, we show that the stabilization is quite efficient. The version of the model with distributed notch filtering also has a different realization in terms of spatial solitons in a planar waveguide equipped with a longitudinal grating.

Fundamental properties of dispersion-managed solitons in systems with lumped frequency-sliding filters

By means of systematic numerical simulations, we investigate dynamical characteristics of dispersion-managed (DM) solitons in the system using lumped frequency-sliding (FS) filters to control transmission of the solitons. The most fundamental characteristic of the system is the soliton’s peak power as a function the DM map strength. A comprehensive set of such characteristics is produced at different values of the FS slope and path-average dispersion (PAD), which may be anomalous, zero, and normal. Simultaneously, stability borders for the solitons are identified. The borders are presented in the form of plots showing the largest DM map strength and FS slope, beyond which stable solitons are not found. The efficiency of the system is also characterized by curves showing the excess gain, which is necessary to compensate the loss incurred by the filters, vs. the DM map strength, at different values of the FS slope and PAD. Intra-channel interactions between solitons are studied too. It is concluded that the frequency-sliding does not significantly affect the corresponding collision length in comparison with the case of fixed-frequency filters.

Dispersion-managed soliton interactions in fibers with randomly varying birefringence

In this paper, a soliton transmission model in high-speed dispersion-managed systems is advanced, and the equation of intrachannel soliton interactions in randomly varying birefringent fibers is acquired. The soliton interactions with the impact of PMD in uniform dispersion systems and DMS systems are also investigated numerically. We reveal the change in the collision length with PMD and map strength, and verify the robustness of DMS to PMD in soliton interactions.

Analysis of timing and amplitude jitter due to intrachannel dispersion-managed pulse interactions

Transmission impairments due to nonlinear intrachannel crosstalk in strongly dispersion-managed systems are investigated. Analytical expressions to estimate timing and amplitude jitter due to intrachannel pulse interactions are provided. Timing jitter is found to be a dominant limiting factor for small values of map strength, whereas amplitude jitter is responsible for system performance degradation especially for large map strength. The analysis agrees with direct numerical simulations of the full system.

Resonant intrachannel pulse interactions in dispersion-managed transmission systems

Nonlinear intrachannel interactions in a transmission system with strong periodic dispersion management are investigated. An analytical model that describes the fluctuation of the temporal position and amplitude of the main signal and ghost pulse generation at zero bits due to intrachannel crosstalk is developed. Intrachannel nonlinear effects are found to be a resonant process which is induced by periodic forcing due to lumped amplification assisted by temporal phase matching. Explicit formulae to estimate transmission impairments such as timing and amplitude jitter are provided based on the analytical model. The role of distributed amplification to suppress intrachannel nonlinear effects is also discussed. A more fundamental analytical framework which enables one to evaluate intrachannel crosstalk over a wide regime of system configurations is also presented.

Bisoliton propagating in dispersion-managed system and its application to high-speed and long-haul optical transmission

We show that, in addition to a stable single soliton, a dispersion-managed (DM) system can also support stable bisolitons. The system parameters in which the bisolitons can exist are also studied. In addition, we propose novel error preventable line-coding schemes in which binary data are assigned to bisolitons and single DM solitons. By using the schemes, impairments arising from intrachannel interactions can be drastically reduced compared with the conventional scheme for the same bit rate. The compatibility of bisoliton to wavelength-division-multiplexed system is also discussed.

Distributed-Raman-amplification effect on pulse interactions and collisions in long-haul dispersion-managed soliton transmissions

We study the effect of distributed Raman amplification on strongly dispersion-managed soliton interactions and collisions in N×20 Gbit/s wavelength-division-multiplexed long-haul transmissions. The measured reduction of noise accumulation with Raman amplification permits determination of the allowable reduction of signal power, when compared with the case of lumped erbium-doped fiber amplifiers. Hence we analytically estimate the reduction of intrachannel interactions and interchannel collisions induced by distributed Raman amplification and evaluate the corresponding decrease of timing jitter.

Suppression of intrachannel dispersion-managed pulse interactions by distributed amplification

Nonlinear intrachannel interactions in a transmission system with strong periodic dispersion management and distributed amplification are studied. When average dispersion is negligible, distributed amplification provides significant suppression of timing shift and energy transfer caused by the intrachannel pulse interactions, as compared with lumped amplification for the same value of path average signal power.

Suppression of nonlinear intrachannel interactions between return-to-zero pulses in dispersion-managed optical transmission systems

Strong dispersion management, in which an optical pulse is highly dispersed and the pulse width is extremely broadened, can suppress nonlinear interactions such as cross-phase modulation between neighboring pulses in optical time-division-multiplexed systems, but it causes intrachannel four-wave mixing, which is an obstacle to achieving high performance in the system. We study the physical mechanism of intrachannel four-wave mixing. The dependence of the effect on the initial pulse width, the initial phase difference, and the dispersion map is also discussed, and we conclude that a narrower initial pulse, a larger accumulated dispersion, or both are effective in suppressing the effect of four-wave mixing.

Intrachannel pulse interactions in dispersion-managed transmission systems: energy transfer

Energy transfer between adjacent pulses as a result of nonlinear intrachannel interactions in a transmission system with strong periodic dispersion management is analyzed. With small average dispersion, the energy change between nonzero bits grows linearly with respect to distance in the presence of loss and lumped amplification, whereas in a lossless system the energy change is found to be significantly suppressed. The analytical results compare favorably with the results of direct numerical simulation of the full system.

Intrachannel pulse interactions in dispersion-managed transmission systems: timing shifts

Nonlinear intrachannel interactions responsible for timing shifts in a transmission system with strong periodic dispersion management are investigated. Formulas describing the evolution of the timing shift are obtained for general bit patterns. When average dispersion is negligible, the timing shift is shown to grow linearly in distance in a system with loss and lumped amplification, whereas in a lossless system the timing shift is sufficiently small at every chirp-free point. The analysis agrees with direct numerical simulations.

Timing jitter owing to intrachannel pulse interactions in dispersion-managed transmission systems

We study interaction-induced timing jitter in single-channel dispersion-managed return-to-zero ttransmission systems operating at high map strengths. An equation for the frequency and timing shifts of two interacting pulses is derived by a variational approach. The interaction can be of either an attractive or a repulsive character, and we show that the resultant timing jitter can be reduced by proper design of the dispersion map.