A tracking system for mobile FSO

Abstract

Free-space optics (FSO), or Optical Wireless, is an unlicensed line-of-sight technology that uses modulated lasers to transmit information through the atmosphere. By using light beams, FSO can transmit and receive data, voice, and video, information through the air. FSO provides data rates ranging from 100Mbps to 2.5Gbps. In most applications, FSO transceivers normally remain in a static location to ensure continuous line of sight and to maintain accurate alignment. One current challenge facing FSO technology is the desire to implement mobility. As a potential solution, this study introduces an auto-tracking system that will achieve and maintain alignment between two mobile FSO nodes. This auto-tracking system can be used in many different applications, such as reducing the time needed to achieve alignment of an FSO link, and maintaining a link between an aircraft and a stationary command post to exchange real-time video and data with high-speed laser communications. After link initiation, the auto-tracking system application will send steering commands back to the positioning gimbal. These steering commands are determined by feedback from Position Sensing Diodes (PSDs). The proposed FSO auto-tracking system provides optical beam steering and capturing mechanisms to provide tracking between two transceivers, either fixed or mobile. In this paper, we illustrate the feasibility of such a system and present experimental results for a source aligned with a PSD in a mobile environment.