Feasibility study for high bit rate pulse position modulation in fibre communications

With the rapid progress of optical communication systems, capacity limitation becomes important in high bit rate links. Overcoming this limitation may involve using different modulation and multiplexing methods, including RZ modulation with on-off keying or pulse position modulation. In soliton links, the capacity limitation at high bit rates is likely to be caused, not by the widely studied Gordon Haus Jitter, but by soliton interaction. In this project, a semi-analytical model for the soliton interaction effect on the maximum length of a solitonic link is developed. Soliton interaction is shown to decrease the transmission distance substantially for links using either on-off keying or pulse position modulation; on-off keying maintains superior performance under all conditions studied. The prospects of pulse-position modulation for linear (non-solitonic) RZ links are also assessed briefly, and some methods of practical implementation of PPM at high bit rates suggested.