1. Key Laboratory of Optical Fibre Sensing and Communications (Education Ministry of China) University of Electronic Science and Technology of China Chengdu 611731 China
2. State Key Laboratory of Electronic Thin Film and Integrated Devices University of Electronic Science and Technology of China Chengdu 611731 China
3. School of Engineering University of Glasgow Glasgow G12 8QQ UK
4. Institute of Solid State Physics Friedrich Schiller University Jena 07743 Jena Germany
5. Abbe Center of Photonics Friedrich Schiller University Jena 07745 Jena Germany
6. Research Centre for Optical Fiber Sensing Zhejiang Laboratory Hangzhou 310000 China