1Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Jinan University, Guangzhou 510632, China
2Department of Optoelectronic Engineering, Jinan University, Guangzhou 510632, China
3e-mail: zhuwg88@163.com
4Key Laboratory of Optoelectronic Information and Sensing Technologies of Guangdong Higher Education Institutes, Jinan University, Guangzhou 510632, China