In this book, the optical fiber sensor based on surface plasmon resonance with side-polished structure shows the high performance in its applications, such as biosensing, surface modification, and in-situ real-time monitor. Future works can be divided into three parts, including the basic study on SPR optical fiber, biosensing, and in-situ real-time monitor. we have successfully proposed a SPR optical fiber sensor with side-polished structure as a platform for applications in the detection field. This study is also affirmed by a number of our papers published in international journals, such as Optics Letter, Applied Optics, Sensors & Actuators A, Sensors & Actuators B, IEEE Photonics Technology Letters, Optics & Laser Technology, Chinese Optics Letters, Microwave & Optical Technology Letters, Optics Communications, Journal of Nanoscience & Nanotechnology, Journal of Microbiology, Immunology & Infection, and Sensors. I am really honored to involve this research project in my life.