In this paper, we propose and experimentally demonstrate an auto-bias control scheme for stabilizing a lithium niobate (LN) Mach-Zehnder modulator (MZM) at any operating point along the power transmission curve. It is based on that the bias drift would change the operating point and result in varying the output optical average power of the Mach-Zehnder modulator and its first and second derivatives. The ratio of the first to the second derivative of the output optical average power is used in the proposed scheme as the key parameter. The experimental results show that the output optical average power of the LN MZM hardly changes at the desired operating point, and the maximum deviation of output optical average power is less than ±4%.

A novel scheme employing low-density parity-check (LDPC) codes in atmospheric optical communication system is proposed. We deploy coherent detection at the receiving side in the proposed scheme. To reduce bit error rate (BER) and enhance the system performance, LDPC codes are exploited and coherent receiver is used to improve the receiving sensitivity. Experiments are implemented to evaluate the performance of the transmission system. The atmospheric channel attenuations are set to 20-30 dB/km. The coherent detection with LDPC codes can reduce the received power requirement by ~4 dBm at the BER of 10^-9.

文章对动态可重构光分插复用器(ROADM)进行了介绍；对实现ROADM的多种方案进行了归纳整理和简要分析；对其中解复用/开关矩阵/复用(DSM)、DSM波段、广播与选择(B&S)3种典型的ROADM结构进行了较详细的说明。文章作者设计并实现了广播与选择型ROADM，并对实验系统的上/下路功能和信道功率均衡功能进行了验证。