Different types of photodetectors, especially the PIN photodiodes and Avalanche photodiodes, are the most useful photodetectors in microwave and fibre optic communications. Optical Fiber Connector Optical fiber communication has revolutionized data transmission by enabling high-speed, long-distance, and low-loss signal transmission. At the core of this technology are optoelectronic devices, which convert electrical signals into optical signals and vice versa. This article briefly introduces the main characteristics and selection principles of several commonly used photodetectors.