Key Laboratory of Optical Communication and Lightwave Technologies, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, CHN
1 Institute of Optoelectronics Science and Engineering and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, CHN
2 Telecommunication Technology Division/CESET, State University of Campinas, Limeira, SP, Brazil
Key Laboratory of Optical Communication and Lightwave Technologies, Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, CHN