Key Lab of Broadband Optical Fiber Transmission and Communication Networks of the Ministry of Education, University of Electronic Science and Technology of China, Chengdu 610054, CHN
1 State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, CHN
2 Graduate School of the Chinese Academy of Sciences, Beijing 100039, CHN
3 Department of Optoelectric Engineering, Jinan University, Guangzhou 510632, CHN