1. School of Information and Communication Engineering, Beijing University of Posts and Telecommunications,State Key Laboratory of Information Photonics and Optical Communications,Beijing,China,100876
2. Institute of Semiconductors, Chinese Academy of Sciences,State Key Laboratory on Integrated Optoelectronics,Beijing,China,100083
3. Research Institute of China United Network Communications Co., Ltd,Beijing,China,100048
4. The University of Aizu,Division of Computer Engineering,Fukushima,Japan,965-8580