Long-distance optical soliton transmission with lumped amplifiers

A soliton transmission method using lumped amplifiers is presented which is named the preemphasis method. An N=1 soliton with relatively high amplitudes (1.2<A<1.4), which is used as an input soliton, plays an important role in the lumped-gain soliton transmission system. The initial soliton pulse width can be preserved after propagation over long distance despite the existence of fiber loss. It is shown that with the lumped gain, the soliton pulse can propagate over more than 9000 km when the repeater spacing is 31 km and fiber loss is 0.22 dB/km     

光纤布拉格光栅非线性孤子的特性分析

以非线性耦合模理论为基础，用数值计算的方法分析了光纤光栅非线性孤子的特性。结果表明，在较弱光脉冲输入时，脉冲被展宽幅度降低；在强光脉冲输入时，脉冲的幅度，速度和脉宽保持不变，孤子形成；当更强光脉冲输入时，脉冲被压缩同时产生随距离而变的线性啁啾。当波长位于负色散区的弱脉冲和位于正常色散区的强泵浦脉冲共同传输时，输入弱脉冲被压缩。     

应用相敏光放大器抑制光孤子互作用的研究

通过计算机系统仿真研究了应用相敏光放大器(PSA)作为在线放大器抑制光孤子传输系统中孤子间的互作用，并与相应的掺铒光纤放大器(EDFA)光孤子系统进行比较。仿真中考虑了平均孤子和动态孤子两种传输方案。结果表明，应用相敏光放大器代替掺铒光纤放大器作为在线放大器能有效地抑制孤子系统中脉冲的展宽和孤子间的互作用。对于平均孤子，在没有附加其他孤子控制措施的情况下，相敏光放大器系统中孤子间互作用得到有效的抑制，孤子对稳定传输距离得到极大的延长。对动态孤子，相敏光放大器亦表现出良好的抑制孤子间互作用的效果，但孤子脉冲的幅度经长距离传输后显著下降。     

The maximum bit rates of soliton communication systems with lumpedamplifiers and filters in different distances

The maximum bit rate of a soliton communication system with lumped amplifiers and optical filters is considered. When the dispersion of the fiber varies from one amplifier spacing to another amplifier spacing, the maximum bit rate is significantly reduced. To overcome the effect, the amplitude of the soliton is amplified so that it is still the average soliton corresponding to the fiber dispersion for an amplifier spacing. Thus, the maximum bit rate is only slightly less than that without the dispersion variations. For a given distance, the maximum bit rate limited by the stability and soliton interaction is obtained. The result is compared with that limited by the Gordon-Haus effect. For shorter transmission distance, the maximum bit rate is limited by the stability and soliton interaction. For longer transmission distance, the maximum bit rate is limited by the Gordon-Haus effect     

在线放大器为PSA的动态孤子通信系统传输性能受光纤色散参量影响的研究

通过计算机系统仿真研究光纤色散参量对以相敏光放大器(PSA)作为在线放大器的动态孤子系统传输性能的影响。研究结果表明,PSA增益的相敏特性使孤子脉冲主瓣幅度因光纤色散而下降,脉宽展宽,出现旁瓣。光纤色散值越大,经长距离传输后,孤子脉冲主瓣的下降幅度和脉宽展宽程度越显著;且旁瓣脉宽越宽。     

Dynamic optical soliton communication

Digitally coded optical solitons at 5 and 10 Gb/s have been successfully transmitted over 400 and 300 km, respectively, using erbium-doped fiber amplifiers and repeaters. The soliton pulse source is a gain-switched distributed-feedback laser diode with spectral windowing. The repeater spacing for the 10-Gb/s transmission with an input soliton of A=1.4 is 25 km, which is extended to 50 km for 5-Gb/s transmission with an input soliton of N=1.8-2.0     

Investigation of superstructured fiber Bragg grating-based OCDMA system

The bit error rate (BER) performance of a superstructured fiber Bragg grating (SSFBG)-based optical code division multiple access (OCDMA) system is investigated with different input pulse widths and grating refractive index modulation amplitudes, and the corresponding crosstalk ratio is considered at different data-rates. Simulation results show that increasing the input pulse width or grating refractive index modulation amplitude will degrade the BER performance apparently. Moreover, with fixed code length and chip-rate detection, a lower data-rate system has better tolerance to an increasing input pulse width, while a higher data-rate system has better tolerance to an increasing grating refractive index modulation amplitude.     

PSA平均光孤子系统传输性能的研究

本采用计算机系统仿真的方法，研究了应用相敏光放大器(PSA)作为在线放大器的采用平均孤子传输方案的光孤子通信系统中，泵浦光与信号光之间的相位漂移、光纤色散对光孤子通信系统传输性能的影响。仿真的结果表明：泵浦光与信号光之间的相位漂移将导致孤子幅度的下降；由于PSA增益的相敏特性，光纤色散导致孤子脉冲主瓣幅度下降，脉宽展宽，出现旁瓣。     

密集型色散管理模式中DM孤子传输特性分析

本文以经典色散管理孤子的传输特性为参照,研究了单信道40Gbit/s密集型色散管理系统内色散管理孤子的诸多传输特性,证实了密集型色散管理模式相对于经典色散管理模式的优势所在,同时给出了系统最佳传输性能与入射功率、分段数、以及脉冲初始宽度等因素的数值关系。     

Multi-thousand kilometer optical soliton data transmissionexperiments at 5 Gb/s using an electroabsorption modulator pulsegenerator

We have demonstrated the transmission of data-coded optical soliton pulse at the bit-rate of 5 Gb/s over a few thousand kilometers. Ultra-short optical pulses generated with a sinusoidally driven electroabsorption modulator and a DFB-LD that were approximately hyperbolic-secant squared shape were transmitted through the fiber. Both recirculating loop transmission lines and straight transmission lines were used for the experiments. The pulse width was maintained well over 6,000 km transmission in the recirculating loop experiment. Three-thousand-km stable transmission was achieved using a straight-line setup at the bit-rate of 5 Gb/s, although the average fiber chromatic dispersion deviated slightly from the optimum value. The results indicate the possibility of the soliton transmission system for multi-thousand-km optical communication systems     

Comparison of nonlinear pulse interactions in 160-Gb/s quasi-linear and dispersion managed soliton systems

The understanding and development of 160-Gb/s transmission systems requires the study of the impact of different dispersion compensation schemes on pulse propagation in nonlinear fiber. In this paper, we present an investigation of 160-Gb/s optical transmission systems, focusing on optimal propagation regimes, and in particular, we analyze different transmission limitations and dominant nonlinear effects by comparing quasi-linear and dispersion managed soliton systems. Two quasi-linear systems, one using nonzero dispersion-shifted fiber (NZDSF) and the other single-mode fiber (SMF), and one short-period (1 km) dispersion managed soliton (DMS) system are studied, both for single-channel and wavelength-division-multiplexed (WDM) transmission. First, the performance of the two quasi-linear systems in single-channel transmission are compared and it is shown that the NZDSF and SMF systems allow similar error-free transmission distances with only small differences in the intrachannel four-wave mixing (IFWM) induced amplitude jitter. The effect of pulsewidth on transmission performance in this regime was investigated and the use of shorter pulses was found to result in lower amplitude jitter. We analyzed the behavior of the DMS system and showed that the reduced pulse broadening during transmission allowed a significantly longer single-channel transmission distance with a smaller impact of nonlinearities compared to quasi-linear propagation. The sensitivity of the DMS system performance to statistical fluctuations in the fiber dispersion was studied and the results show the level of accuracy in the dispersion management map which must be ensured in these systems. Finally, the performance of the DMS in WDM transmission was investigated and it was found that it was subject to very large penalties increasing the minimum channel spacing possible because of the strong impact of interchannel cross-phase modulation (XPM).     

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．     

4 Gb/s soliton data transmission over 136 km using erbium dopedfiber amplifiers

The use of semiconductor-laser-pumped erbium-doped fiber amplifiers and an externally modulated mode-locked external-cavity semiconductor laser to obtain soliton data transmission at 4 Gb/s over 136 km of nondispersion shifted fiber is described. After 136 km of transmission and at low pulse powers, the ~80 ps fiber input pulse width was broadened to ~150 ps. At high pulse powers the output pulse width was maintained at 80 ps, as expected for N=1 solitons. N =3 solitons were also observed at lower data rates     

注入幅度失配平均孤子自稳定传输

分析平均孤子传输系统中光源注入脉冲幅度失配对光脉冲传输稳定性产生的影响,提出利用工作在饱和区的光纤放器实现系统中脉冲自稳定传输的方案,并验证了这一措施的可行性。     

光纤孤子激光器及用其作源的光孤子传输实验

介绍了一个１．５５μｍ光纤孤子激光器及利用它作源的光孤子脉冲传输实验。其中采用了掺铒光纤放大器锁模技术．实测孤子激光器输出脉冲宽度为３０ｐｓ．谱宽为０．１６ｎｍ；经过５０ｋｍ色散位移光纤传输后，其脉宽与谱宽基本维持不变．     

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     

光纤级联系统中准孤子传输的数值模拟

本文基于一种光纤级联系统模型,用数值模拟方法考察准孤子在这种中的传输情况,得到了传输１００００ｋｍ的最佳方案并给出了当输入光脉冲的峰值功率、初始宽及啁啾变化时,系统的传输特性     

亮孤子在升余弦变迹光纤布拉格光栅中传输特性的数值分析

在耦合模理论的基础上,运用有限差分法数值模拟了布拉格孤子在升余弦变迹光纤光栅中的传输以及孤子之间的相互作用.模拟结果表明,合适选择输入功率和初始脉宽等初始条件,可以实现升余弦变迹光纤光栅中孤子的稳定传输.输入两个孤子时,发现两个孤子之间的相互作用对它们的相对相位和相对振幅参数敏感.初始间隔较近的孤子对,随着它们之间的相对相位差和相对振幅参数的不同而发生相互吸引、相互排斥、交换能量等现象.     

New phase modulation technique based on spatial soliton switching

A phase modulation technique able to increase the transmission capacity of an optical channel is presented. It is based on spatial soliton switching properties. The modulator device accepts as inputs two streams of amplitude modulated pulses and generates an output stream of phase modulated pulses whose phase values depends on the different input combinations, coding properly the input streams and increasing the transmission capacity of the optical channel that carries this information. The modulator device can be properly cascaded, generating a unique stream of pulses capable of carrying the information of a certain number of input channels. A proper demodulator device is also presented. It is capable of accepting as input a phase modulated stream of pulses, generating as outputs the original amplitude modulated pulse streams     

光孤子通信系统的仿真

光孤子通信技术充分利用了光纤中色散参数和非线性效应的相互作用,可以使光脉冲在光纤中无畸变的进行传输,不受外界条件的影响,从而可以实现脉冲的超长距离传输。利用OptiSystem提供的强大的工具箱,模拟了光孤子通信系统的模型。并在给定的参数下,实现了系统的仿真,证实了仿真模型的可行性和正确性,为将来在此基础上实现改进的光孤子通信系统提供了有力的实验依据。