| 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.
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