Research Initiation: Multi-Channel Wavelength-Division- Multiplexed Technique in a Soliton-Based Optical Fiber Communication System

自从低损耗光纤发明以来，提高光纤信道的通信能力一直是许多科学努力的目标。在传统的光纤信道中，无论是单模还是多模，比特率通常被限制在50兆赫以下，经常使用电子中继器。近年来，在光纤信道中发展了相干检测技术。这一发展可以将比特率提高到几GHz。然而，在相干通信系统中，色散效应对通信能力的限制仍然存在。孤子传播的发现创造了一种新的可能性，可以在不使用电子中继器的情况下，将长光纤长度（高达1000公里）的比特率提高到100千兆赫以上。主要问题是从传播的角度研究多通道波分复用技术应用于基于孤子的光纤通信系统的可能性。在这个问题中，有两个重要的考虑因素需要研究。第一个问题是不同通道脉冲序列之间的相互作用。这些相互作用至少包括交叉相位调制和拉曼转换。在这种多通道光纤中，脉冲的形状和传播速度将被改变。第二个问题是这种多通道系统中线性损耗的拉曼补偿。通过考虑不同通道之间的拉曼转换，可以实现对多通道的最优补偿。

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.