When the distance between the source and the target is long, the signal will be affected by atmospheric turbulence, weather conditions and obstacles, which cannot support the information transmission. One of the existing solutions is to use relay-assisted technology (RAT). It makes the communications between the source and the destination possible under better channel conditions by setting up relay between the source and the destination. There are few comprehensive articles about relay-assisted technology in OWC. To fill this gap, this paper introduces the RAT of indoor optical wireless communications (IOWC), outdoor optical wireless communications (OOWC) and underwater optical wireless communications (UOWC) in different application scenarios, which has a better effect than direct communication between source and destination. The relay protocols, channel models, modulation techniques under three relay modes are reviewed. Finally, challenges of RAT in OWC are put forward and potential solutions are also given.

Optical wireless communications have attracted widespread attention in the traditional power industry because of the advantages of large spectrum resources, strong confidentiality, and freedom from traditional electromagnetic interference. This paper mainly summarizes the major classification and frontier development of power industry optical wireless technologies, including the indoor and outdoor channel characteristics of power industry optical wireless communication system, modulation scheme, the performance of hybrid power line, and indoor wireless optical communications system. Furthermore, this article compares domestic and foreign experiments, analyzes parameters for instance transmission rate, and reviews different application scenarios such as power wireless optical positioning and monitoring. In addition, in view of the shortcomings of traditional power technology, optical wireless power transfer technology is proposed and combined with unmanned aerial vehicles to achieve remote communication. At last, the main challenges and possible solutions faced by power industry wireless optical technologies are proposed.

Effective information transmission between vehicles has become one of the solutions to improve road safety. Based on the huge advantages of optical wireless data transmission technology, this paper summarizes the research status of unmanned vehicles in optical wireless communication (OWC). The article not only studies the actual progress of building optical links through an unmanned vehicle, connecting air communication, ground communication, and underwater communication into a unified wireless network, and realizing the fast, stable, large-capacity data transmission system. The technical challenges of unmanned vehicle OWC are also discussed and its future development has prospected.