Multi-wavelength light source for dense wavelength division multiplexing optical communications system

密集波分复用（DWDM）光通信系统是下一代大规模光通信的重要技术。然而，DWDM光通信系统必须将任何相邻载波之间的波长间隔的波动抑制在0.01nm内。在传统的方法中，使用超过100个激光二极管（LD's），必须控制所有的精确的波长稳定，这导致了成本问题和技术困难，本研究开发和评估低成本和稳定的多波长光源的DWDM光通信系统。它包括一个光频梳发生器，产生平顶多波长光谱的设备。其原理是通过过驱动串联连接的光调制器来产生多个边带。该方法保持所有通道间隔等于梳状发生器的驱动频率。通过仅稳定种子LD的波长，稳定每个信道中的载波的所有波长。我们成功地产生了超过20个50 GHz的间隔，通过使用这种光梳发生器和稳定的种子LD的载波。实验还证实，我们的梳状发生器与种子LD的波长无关，并且可以用8个种子LD覆盖整个C波段的大约100个通道。在100 km以上的传输实验中，对于10 Gbps的NRZ信号，误码率达到10-12，这对于实际的大规模通信系统是足够的。

The dense wavelength division multiplexing (DWDM) optical communication system is a promising technology for the next generation massive communication. The DWDM optical communication system, however, has to suppress the fluctuation of the wavelength spacing between any neighboring carriers within 0.01nm. In the conventional method, more than 100 laser diodes (LD's) are used and all of them must be controlled for precise wavelength stabilization, which leads to cost problems and technical difficulties.This study developed and evaluated a low-cost and stable multi-wavelength light source for DWDM optical communication system. It consists of an optical frequency comb generator, a device producing flattop multi-wavelength spectra. The principle is generation of multiple sidebands by overdriving series-connected optical modulators. This method keeps all the channel spacing equal to the driving frequency of the comb generator. By stabilizing only the wavelength of a seed LD, all the wavelengths for the carrier in each channel are stabilized. We successfully generated more than 20 carriers with 50-GHz spacing by using this optical comb generator and a stabilized seed LD. It was also confirmed that our comb generator is independent of the wavelength of the seed LD and can cover approximately hundred channels of entire C-band with 8 seed LD's. The transmission experiments over 100 km achieved bit error rate of 10-12 for 10 Gbps NRZ signal, which is sufficient for a practical massive communication system.