Since the invention of low-loss optical fiber, to increase the communication capability in a fiber channel has been the goal of much scientific effort. In a conventional fiber channel, either single- mode or multiple-mode, the bit-rate is usually limited to below 50 MHz with frequent use of electronic repeators. Recently, the coherent detection was developed in a fiber channel. This development can raise the bit-rate up to several GHz. However, in a coherent communication system, the limitation on communication capability due to dispersion effects still exists. The discovery of soliton propagation creates a new possiblity for increasing the bit-rate to over 100 GHz with a long fiber length (up to 1000 km) without using an electronic repeator. The major problem is to investigate from the propagation viewpoint the possibility of applying the multi-channel wavelength-division- mutiplexed technique to a soliton-based fiber communication system. In this problem, two important considerations are to be studied. The first issue is the mutual interaction among the pulse trains of different channels. These interactions include at least the cross-phase moduation and Raman conversion. The shapes and propagation speeds of the pulses insuch a multiple-channel fiber will be changed. The second issue is the Raman compensation for linear loss in such a multiple-channel system. It is likely to achieve an optimal compensation for multiple channels by including the Raman conversions among different channels.
