Influence of the inter-channel frequency separation on the transmission capacity of a soliton based WDM system

We analyze the influence of the interchannel frequency separation on the transmission capacity of a soliton-based wavelength-division multiplexing (WDM) system. The input into the optical fiber is represented by a superposition of N single solitons with equal amplitudes and different frequencies. Two different cases are taken into account. In the first case, all solitons completely overlap but have different frequencies. h is found that there exists a critical frequency separation above which WDM is: feasible. Furthermore, it is shown that this critical frequency increases with the number of-transmission channels. In the second case, there is a time shift between the overlapping solitons in adjacent channels. It is demonstrated that this combination of time- and wavelength-division multiplexing yields the largest transmission capacity. In addition, it is discussed the case in which the interchannel frequency separation is smaller than the critical frequency. It is found that in this regime the soliton spectrum of the emerging optical field has a rich structure.