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通信的一种很有前途的技术。然而，密集波分复用光通信系统必须抑制任何相邻载波之间的波长间隔在0.01 nm以内的波动。针对密集波分复用(DWDM)光通信系统中传统方法需要使用100个以上的半导体激光器(LD)，且必须对其进行精确的波长稳定控制，导致成本和技术难度较大的问题，研制并评估了一种低成本、稳定的多波长光源。它包括一个光学频率梳发生器，一个产生平顶多波长光谱的装置。其原理是通过过驱动串联光调制器来产生多个边带。该方法使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，每个通道中的载波的所有波长都稳定了。利用这种光梳产生器和稳定的种子激光器，我们成功地产生了20多个间隔为50 GHz的载波。实验还证实，我们的梳状信号发生器与种子激光器的波长无关，8个种子激光器可以覆盖大约100个C波段的信道，对于10Gbps的NRZ信号，100公里的传输实验获得了10-12的误码率，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.