1. Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan
2. Department of Electronics and Computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan
3. Department of Photonics, Feng Chia University, Taichung 40724, Taiwan
4. Department of Computer Science and Network, Kyushu Institute of Technology, Fukuoka 804-0015, Japan