## 1 Introduction  
With the rapid development of science and technology, drone technology is becoming more widely used in various fields. Light and small UAVs have gained significant attention and applications due to their portability, flexibility, and high efficiency in aerial photography, agriculture, rescue, and other fields. High-speed data transmission technology has become a key supporting technology in these applications. When performing tasks, light and small UAVs must efficiently and in real-time transmit a large amount of sensor data, images, videos, etc., to ground stations or other devices. Therefore, high-speed and stable data transmission has become essential in light and small UAV technology. Currently, the commonly used data transmission technologies are Wi-Fi, Bluetooth, Zigbee, etc. These technologies still need to fully meet the needs of light and small UAV applications regarding transmission rate, transmission distance, and stability. Traditional radio frequency (R.F.) communication is susceptible to magnetic field interference in high-voltage lines and communication base stations, making real-time and efficient communication difficult. In addition, the broadcasting characteristics of R.F. communication quickly lead to co-frequency interference and safety issues, limiting the safety performance of UAV communication. On the other hand, wireless optical communication is characterized by a high-speed rate, large bandwidth, excellent anti-interference, and good confidentiality, as well as being license-free. Combining it with UAV technology can significantly improve communication security, reduce dependence on the environment, and satisfy people's usage needs. In terms of volume, cost, ease of use, and environmental adaptability, a UAV wireless optical communication system shows significant advantages, especially in the application of small UAVs and multi-rotor UAVs. It will become increasingly important in the future in the military, agriculture, commerce, and other fields. Compared to large UAV platforms:
* Light and small UAVs are typically subject to tighter size and weight constraints, so their high-speed data transmission systems must be more compact and lightweight. * For light and small UAVs, the communication distance between them and the ground control station is closer due to the limitations of their flight altitude and speed, thus requiring more real-time performance. Large UAVs, on the other hand, usually need to communicate over longer distances. * There is a difference in the following aiming device: the following aiming stabilizing device should be added with gyroscopic stabilization to make a gyrostabilizing platform, and the following aiming device is more challenging compared to interstellar and interstellar terrestrial devices. * Large UAVs are usually used for tasks such as military reconnaissance and cargo transportation, while light and small UAVs are more often used for tasks such as aerial monitoring and terrain mapping, so there are differences in the application scenarios of their high-speed data transmission systems. Specific application scenarios for lightweight and small drones are as follows:
* In existing metropolitan area networks, to extend or connect to new networks, these links usually do not reach the end user but are used for the network's core services. The use of FSO to extend an existing metropolitan area fiber optic cable loop so that it can subsequently expand the connection of new wireless networks and the formation of a wired, wirelessly integrated optical transmission network is the best way to provide high-speed data transmission services directly to the end user. * Enterprise LAN segments are often separated by buildings or roads between buildings. The simplicity of FSO equipment installation makes it ideal for realizing the interconnection of LAN segments within an enterprise and easily solving the problem of trenching and cabling brought about by the complex terrain between buildings.