1. Key Laboratory of In-fiber Integrated Optics of the Ministry of Education, College of Physics and Optoelectronic Engineering , Harbin Engineering University , Harbin 150001 , China
2. Key Laboratory of Optoelectronic Devices and Systems of the Ministry of Education and Guangdong Province, College of Optoelectronic Engineering , Shenzhen University , Shenzhen 518060 , China
3. Optical Fiber Sensors Research Centre (OFSRC), Department of Electronic and Computer Engineering , University of Limerick , Limerick V94 T9PX , Ireland