1. Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing Guilin University of Electronic Technology Guilin 541004 P. R. China
2. Key Lab of In-fiber Integrated Optics Ministry Education of China College of Physics and Optoelectronic Engineering Harbin Engineering University Harbin 150001 P. R. China
3. Academy of Marine Information Technology Guilin University of Electronic Technology Beihai 536000 P. R. China