Starting from the technical principles commonly used in high-speed large capacity optical fiber communication, this book systematically introduces the basic knowledge and principles of multidimensional modulation and coding technology, multi-band optical fiber transmission (MBT) technology, space division multiplexing (SDM) technology, and equalization and compensation algorithms. These technologies are innovatively applied to the communication system, significantly improving its performance in aspects such as capacity, rate, power, quality, and reliability. This chapter summarizes the key technologies of high-speed large capacity optical fiber communication and analyzes the future challenges.