Maximum transmission capacity of a soliton communication system with lumped amplifiers

For a soliton transmission system which uses lumped optical amplifiers with a fixed amplifier spacing and a fixed bit rate, the optimum input pulse width and input amplitude are presented to maximise the soliton transmission distance. In a 10 Gbit/s soliton system with a repeater spacing of 40 approximately 50 km, a pulse width of 20 ps, and an amplitude of 1.4 approximately 1.8, the limitation owing to mutual soliton interaction is negligible compared with that resulting from the interaction between amplifier noise and the soliton pulse, and the soliton pulse can propagate up to the Gordon-Haus limit.<>     

Constraints on the design of single-channel, high-capacity (>10Gb/s) soliton systems

We have examined the design constraints of single-channel soliton systems operating at high data rates (>10 Gb/s). While Gordon-Haus timing jitter is the most important effect for 10 Gb/s transoceanic systems, it is fiber perturbations arising from discrete in-line amplification that severely limit the transmission distance and amplifier spacing at higher data rates. Dispersion-decreasing fiber or distributed optical amplification, both of which locally balance dispersion and fiber nonlinearities, could eliminate this constraint and extend the regime of stable soliton transmission     

Dispersion-managed solitons for 160-Gb/s data transmission

The use of dispersion-managed (DM) solitons for 160-Gb/s data transmission in fiber lines where the period of dispersion management is much shorter than the amplifier spacing is investigated through numerical simulations. It is shown that DM solitons outperform both standard solitons and “quasi-linear” return-to-zero (RZ) pulses. The dispersion tolerance is limited by pulse-to-pulse interactions and Gordon-Haus jitter and decreases with increasing transmission distance     

The Effect of System and Amplifier Parameters on the Performance of Average Soliton Transmission System Using PSA as In-Line Amplifier

In this paper,the effect of system and amplifier parameters on the performance of soliton transmission systemusing Phase Sensitive Amplifier(PSA)as in-line amplifier has been researched theoretically by computer simulation.Since in PSA soliton system the performance of average soliton regime is much better than that of dynamic soliton regime,in our simulation we only considered average soliton regime.Our simulation results show that although using PSA as in-line amplifiers in soliton system can not only overcome Gordon-Haus restriction but also suppress solitons interaction,lengthen soliton stable transmission distance significantly,the system and amplifier parameters have to be chosen carefullyin order to get a better system perorformance.     

Suppression of Gordon-haus effect and interaction of dark soliton by optical phase conjugation

The optical phase conjugation is put forward for the first time to suppress the Gordon-Haus effect caused by amplifier spontaneous emission noise, and soliton interaction in the dark soliton transmission system. The simulation results show : If the conjugator is sited at proper situation, it can suppress the Gordon-Haus effect or the dark soliton interaction effectively.     

Optical soliton transmission experiment in a comb-like dispersion profiled fiber loop

We discuss the properties of comb-like dispersion profiled fiber (CDPF) for an optical soliton transmission. It is found that the CDPF in which the standard single-mode fiber is placed both at the first and at the end of each section is more suitable to reduce dispersive waves if chirp-free transform limited optical pulse is used as a light source. A 10-ps optical soliton transmission experiment is performed in such a CDPF over 1000 km with the amplifier spacing of 80 km that corresponds to 3.1 times the dispersion distance.     

Equalization in coherent lightwave systems using microwavewaveguides

The maximum bit rate/ distance product in recent single-frequency laser direct-detection lightwave system experiments has been limited by dispersion. An equalization technique, appropriate for coherent lightwave systems, that uses a microwave waveguide for overcoming the delay dispersion problem is considered. Results show that small low-loss waveguides can be used to greatly reduce dispersion. For example an 8 GHz bandwidth signal transmitted over 68 km of fiber can be equalized by a waveguide with a cross section of 6 mm×3 mm and a length of only 17 cm. With the waveguide equalizer, the dispersion-limited maximum bit rate/distance product for a standard fiber system can be increased to that of a dispersion-shifted fiber system at 1.55 μm, e.g., a 16-fold increase in maximum bit rate for 100 km transmission     

级联PSA非零色散位移光纤通信系统传输性能的研究

本文通过计算机系统仿真研究了以相敏光放大器（PSA）作为中继光放大器的非零色散位移光纤通信系统的传输性能,分析了PSA系统的码间干扰（ISI）限制距离与信号速率、光纤色散、放大器间距和放大器平均输出信号功率的关系,以及PSA中泵浦光和信号光之间的相位漂移和信号脉冲波形对级联PSA光传输系统传输性能的影响。     

Signal transmission by optical solitons in monomode fiber

A transmission rate of ≃1 Tbits/sec (≃0.1 Tbits/s) per 30 km can be achieved using envelope solitons with peak power of ≃10 W (≃10 mW) in a monomode optical fiber, respectively. Unlike the linear pulse in which the bit rate is limited by the group dispersion, the bit rate of soliton transmission is limited by the fiber loss and the input power. Conditions for achieving optimum transmission rate using solitons are theoretically obtained including the effects of fiber loss and second order group dispersion.     

10 Gbit/s optical soliton transmission over 7200 km by using amonolithically integrated MQW-DFB-LD/MQW-EA modulator light source

The authors demonstrate 10 Gbit/s optical soliton transmission in a recirculating loop through the use of a monolithically integrated MQW-DFB-LD/MQW-EA modulator light source. The timing jitter due to the Gordon-Haus effect is successfully reduced by the optical bandpass filters conventionally used in the cascaded EDFAs to avoid the accumulation of amplified spontaneous emission. The transmission distance of 7200 km is achieved at a bit error rate of 10^-9     

应用相敏光放大克服光孤子传输系统中Gordon-Haus限制的研究

通过计算机系统仿真研究了应用相敏光放大器(PSA)作为在线放大器的光孤子传输系统，并与相应的掺铒光纤放大器(EDFA)光孤子系统作了比较。仿真了平均孤子和动态孤子两种传输方案．研究结果表明，由于PSA不存在ASE噪声，应用PSA作为在线放大器可以克服光孤子系统中的Gordon-Haus限制．对平均孤子，在没有附加其它的孤子控制技术的情况下，PSA系统孤子的稳定传输距离得到极大的延长．对动态孤子，PSA亦表现出良好的抑制脉冲展宽效果，但脉冲的幅度经长距离传输后显著下降．     

Jitter in fibre- based soliton transmission systems

High bit rate long-haul transmission systems on optical fibres are mainly limited by the Kerr effect. Solitons, that balance exactly the Kerr effect by the chromatic dispersion are thus the optimal pulses for fibre transmission. However, the chromatic dispersion associated to the amplifier noise is responsible for a large jitter at receiver end. A calculation of the jitter variance and statistics is presented in this paper. Soliton control techniques can reduce efficiently the jitter variance but they are shown to strongly affect the statistics. It is finally demonstrated that the whole jitter statistics is needed to correctly characterize the soliton transmission system performance.     

光孤子在分布式光纤放大器中传输特性的研究

光纤放大器用于补偿光信号在光纤中的传输损耗,是全光通信网中的核心器件。建立了光孤子在分布式光纤放大器中传输的物理模型,采用分步傅里叶变换法数值模拟了光孤子的传输放大特性,讨论了增益色散对光孤子形状和频谱的影响。结果表明：在放大器的反常色散区,随着光孤子的放大,会不断地产生啁啾孤子,孤子频谱会加宽并且产生振荡结构。放大介质的增益色散将会使光孤子幅度下降,宽度展宽,频谱窄化。因此,光纤放大器的色散、非线性效应和增益色散均会对光孤子的传输特性产生影响。     

A filtering approach for reducing timing jitter due to the acousticeffect

We introduce a signal processing approach to compensate for the timing jitter produced by the acoustic effect in soliton communications. The other main sources of timing jitter, the Gordon-Haus effect and the polarization effect, are inherently stochastic. By contrast, the acoustic effect is deterministic and becomes the dominant source of bit error rates in standard soliton systems when the bit rates are more than 10 Gb/s and the transmission distance is more than several thousand kilometers. We exploit the deterministic nature of the acoustic effect to introduce a scheme that predicts the amount of timing jitter as a function of the previous transmitted bits and uses the information to adjust the sampling period of the received soliton pulses. We demonstrate successful application of the scheme by simulations and discuss implementation issues     

Comparison between NRZ and RZ signal formats for in-line amplifiertransmission in the zero-dispersion regime

Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal formats are experimentally and numerically compared for single-channel long-distance transmission in an in-line amplifier system with dispersion management providing average zero dispersion and local nonzero dispersion at an interval equal to the in-line amplifier spacing. Among a 20-ps RZ signal, a 40-ps RZ signal, and an NRZ signal transmitted in 10 Gb/s straight-line experiments, the last signal achieves the longest transmission distance of 6000 km while the others are limited to 4400 km. Numerical simulations explain these results well and show that, along with linear amplified spontaneous emission (ASE) accumulation, signal waveform distortion due to the combined effect of higher order group-velocity dispersion (GVD) and self-phase modulation (SPM) dominates the performance. Nonlinear optical noise enhancement is not obvious because of the fiber dispersion arrangement. Signals with large pulse widths are less affected by the combined effect, while small-width signals yield superior initial signal-to-noise ratio (SNR) as determined by optical noise. A detailed simulation indicates that a pulse width of about 60 ps is optimum for long distance transmission under the fiber dispersion arranged in this paper     

Numerical study of moderate distance high bit-ratealternating-amplitude soliton systems

We present a numerical investigation of alternating-amplitude soliton systems. We propagate 100 Gb/s, pseudorandom bit sequences of 2 ⁵-1 to 2⁷-1 solitons through fibers of different lengths and calculate the corresponding eye opening penalty at the receiver. The influence of different amplitude ratios, amplifier spacings, pulse widths, and dispersion slopes as well as of the soliton self-frequency shift are studied. We also study the effect of compression of the alternative-amplitude solitons with the larger amplitudes to preserve their soliton character and the impact of the relative initial phase between the alternating-amplitude solitons. When the amplifier spacing is 10 km the system length can be at least 400 km with alternating-amplitude solitons compared to only 200 km in the case of equal amplitude solitons with similar penalties. Our simulations show-that third-order dispersion and the soliton self-frequency shift limit the maximum allowable amplitude ratio     

An alternative derivation of the Gordon-Haus effect

One of the limitations on the achievable data rate of soliton lightwave systems at fixed distance, or on the achievable distance at a fixed data rate, is a timing jitter that is caused by the interaction of the soliton pulses with spontaneous emission noise. An elementary derivation of the Gordon-Haus effect that does not require prior knowledge of any of the more advanced concepts used in the original derivation is presented     

Long-haul soliton transmission at 1.3 μm using distributed Ramanamplification

10 Gb/s single channel soliton transmission over more than 10000 km in a standard communication fiber with distributed Raman amplification has been demonstrated in a recirculating fiber loop setup. It has been found that the Gordon-Haus timing jitter becomes the main limiting factor, provided that the generation of dispersive waves due to polarization mode dispersion has been minimized by adjusting the polarization state of the signal     

The Transmission Performance of Non-zero Dispersion Shifted Fiber Communication Systems Using In-line Phase-sensitive Amplifiers

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A multilevel soliton communication system

A multilevel soliton communication system is proposed and assessed. In this system, at the transmitter end each channel transmits its data via fundamental solitons with a pre-specified amplitude (i.e., soliton width). At the receiver end we take advantage of the sensitive relationship between the amount or fundamental soliton self-wavelength shift and the width of the soliton in the subpicosecond region. We first compress the incoming soliton noises to the subpicosecond level and pass them through a short length of fiber at the end of which the pulses have become separated in the wavelength domain since each soliton, corresponding to a data channel, has experienced a different Raman self-wavelength shift. The channels are then easily separated by optical filters. We have derived the design constraint relations for such a system. We have then heuristically designed a 40 Gbs (four channels) system for a 1000 km propagation distance (total data-rate distance product of 40 Tb/km). Numerical simulations and noise analyses have verified the feasibility and practicality of the proposed system with very good design margins. The wavelength jitter is found to be much smaller than the desired filter spacing, and thus its contribution to the bit error rate is negligible. We also argue that the system is more tolerant to Gordon-Haus timing jitter than conventional TDM soliton systems. The system is all fiber and is, therefore very cost effective as it does not require sophisticated electro-optic and microwave circuits for demultiplexing. The system can potentially operate at much higher speeds than those achievable in conventional soliton systems and it can be used in parallel with WDM soliton system