摘要
利用孤子位相进行信息传输的相移键控(PSK)系统，需要用放大器来补偿光纤损耗，但放大器自发辐射噪声导致了孤子参数的波动，从而引起了孤子的位相抖动，限制了PSK系统的传输性能。本文着眼于这一点，采用滑频滤波控制方案来抑制孤子位相抖动，取得了非常好的效果，使得利用PSK系统进行信息传输成为可能。
文中第一部分利用微扰理论发现在无任何控制措施的情况下，孤子位相抖动与传输距离成立方关系，显示了使用滤波器控制位相抖动的必要性；第二部分同样用微扰理论来研究滤波器的作用，导出了频域滤波孤子传输系统的脉冲演化方程；在第三部分中，采用固定滤波器方案来抑制孤子位相抖动，结果显示位相抖动现仅随传输距离成线性增长，但同时发现滤波器中心频率附近的色散波呈指数增长，导致了系统的不稳定。第四部分在传输系统中我们采用滤波器中心频率随传输链路按恒定速率滑动的方案，发现此方案不仅可使孤子位相抖动随传输距离成线性增长，而且还抑制了滤波器中心频率附近色散波的增长。当考虑滤波器三阶项时，出现了上下滑频的区别，并且上滑频方案要优于下滑频，但在不考虑滤波器三阶项时这些都是不存在的现象。第五部分总结了本文，给出结论。
Phase shift keying (PSK) soliton system that transmits information via the phase of the soliton attracted much attention because of its superior transmission performance. However, phase noise caused by amplified spontaneous emission (ASE) poses new limitations on PSK systems. In this letter one way of overcoming the problem, which was used to reduce soliton interaction and timing jitter, is to slide the filters center frequency linearly with propagation distance. We have found it efficient on reducing soliton phase jitter and making PSK possible at long-distance soliton transmission.
Firstly, in this paper, we use perturbation theory and find that the soliton phase jitter increases as the propagation distance cube in the absence of control. The results show it essential to use the filters and reduce the phase jitter.
Secondly, we have studied the effect of filters by the use of perturbation theory and derived the evolution equation of the soliton pulse in the presence of sliding frequency.
Thirdly, to reduce the soliton phase jitter, an optical filter of fixed center frequency is inserted after every optical amplifier. Now we find the soliton phase jitter increases only linearly with the propagation distance, but we also find the dispersive wave existing around the center frequency of the filters increases exponentially depending on the propagation distance at the same time.
In the fourth section, through sliding the filters center frequency linearly with propagation distance, the soliton phase jitter is found that increases also linearly with the distance. Furthermore, the dispersive wave existing around the center frequency of the filters is reduced. We find that the third-order guiding filter term causes a significant difference between the regimes of up- and down-sliding of filter frequency. But there is no difference between up-sliding and down-sliding when we ignore this term. Consequently, it is more preferable to use up-sliding.
The last section is the conclusion.
引文
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