Topics cover a wide range, including the principles of operation, different types of fiber amplifiers like Erbium-Doped Fiber Amplifiers (EDFAs) and Raman amplifiers, as well as advancements in technology that enhance their efficiency and output power. This paper summarizes the development of fiber amplifier in recent years, and explains the basic principles of fiber amplifier, so that other scholars to find the data of fiber amplifier, convenient for other scholars to study. As the demand for high-speed data transmission and long-distance communication continues to surge, the role of optical amplifiers. The simulation and design software RP Fiber Power of RP Photonics is an excellent tool for such purposes and has been extensively used for this tutorial. Here, we focus on active fibers, containing some laser-active dopant (s). For the basics of fibers, please look at our tutorial on passive fiber. Whether browsing the Internet, streaming high-definition video, or conducting real-time international meetings, all of these activities rely on optical signals traveling across thousands of kilometers of glass fibers beneath oceans and cities. It leverages a process called stimulated emission, where a fiber doped with rare earth elements (such as erbium, thulium, or ytterbium) is energized by a pump.