As an important part of fiber-optic communication, an optical module is a photoelectric converter which converts electrical signals into optical signals and vice versa. An optical module works at the physical layer of the OSI model and is one of the core components in the fiber communication. There is provided a photoelectric conversion module in which an optical device and an optical waveguide are arrayed in a horizontal direction, thereby improving the optical coupling efficiency and therefore, reducing light loss. It is composed of optoelectronic devices, functional circuits and optical interfaces, etc. Today we will learn and explore the working principle of the optical transceiver. It has four high-speed differential signal channels, each with a transmission speed of 25Gbps.