Robust Wide-Angle Optical Wireless Communication System: From Design to Prototype

Optical wireless communication (OWC) systems rely on precise alignment between transmitter and receiver, often requiring tracking equipment in practical applications. However, the complexity and cost associated with such tracking equipment hinder the advancement of OWC technology. To promote its wider adoption, wide-angle OWC systems have emerged, eliminating the need for tracking equipment. Based on the channel model of OWC, the reason why it is difficult to realize wide-angle OWC system is quantitatively analyzed in this paper. These systems feature large half-power full angle (HPFA) for light sources, leading to significant geometric attenuation. For example, comparing a system with HPFA of 120 degrees to one with HPFA of 1 mrad shows a channel attenuation difference of 64.443 dB. Additionally, wide-angle OWC systems must reduce the size of the optical receiving antenna to achieve a broader field of view (FOV). For instance, a system with an antenna diameter of 2.54 cm compared to one with an antenna diameter of 20 cm results in a channel attenuation difference of 17.924 dB. According to the characteristics of the wide-angle OWC system, in this paper, the appropriate light source and detector were selected, and the wide-angle OWC systems based on infrared/blue light were designed. Among them, the infrared light-based system utilizes an average optical power of 0.765 W with an HPFA exceeding 60 degrees and an FOV of approximately 5 degrees. It achieves a maximum communication distance of 2.61 km at a rate of 115.2 kbps. The blue light-based system operates at an average optical power of 0.334 W. It features an HPFA of about 120 degrees and an FOV of around 40 degrees, enabling communication up to 2 km at the same rate. In this paper, two novel methods for measuring and calculating the pulse peak optical power of light source are proposed. One method is designed specifically for Lambert light sources, while the other is tailored for non-Lambert light sources. In addition, a more reasonable evaluation index with practical physical significance is proposed in this paper, named energy communication efficiency. This index standardizes comparisons between different OWC systems by neutralizing variations in HPFA. The wide-angle OWC system designed in this paper enhances robustness without requiring tracking equipment. This advancement is expected to accelerate the advancement of OWC technology in applications such as the Internet of Things, the Internet of Vehicles, indoor positioning, and underwater communication.