1. State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, P.R. China
2. Research Center for Optical Fiber Sensing, Zhejiang Laboratory, Hangzhou 311100, P.R. China
3. Photonics Research Center, The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P.R. China
4. Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States