Effect of Intensity Modulator Extinction on Practical Quantum Key   Distribution System
  We study how the imperfection of intensity modulator effects on the security of a practical quantum key distribution system. The extinction ratio of the realistic intensity modulator is considered in our security analysis. We show that the secret key rate increases, under the practical assumption that the indeterminable noise introduced by the imperfect intensity modulator can not be controlled by the eavesdropper. 
Jing-Zheng Huang, Zhen-Qiang Yin, Shuang Wang, Hong-Wei Li, Wei Chen   and Zheng-Fu Han
quant-ph