# Advanced Progress of Optical Wireless Technologies for Power Industry: An Overview
## 1 Introduction  
Optical wireless communications (OWC), have many advantages such as large spectrum resources, strong confidentiality, and freedom from traditional electromagnetic interference. Therefore, it has been widely concerned by the habitual industry represented by the electric power field. The further deepening of the integration of various emerging information technologies and the power grid, various optical wireless technology solutions that rely on and serve smart power have been proposed successively and formed a preliminary scale. Optical wireless technologies are mainly classified into two categories: outdoor wireless optical communication, which is often called free space optical (FSO) technology, and indoor wireless optical communications (IWOC), which is regarded as visible light communications (VLC) because of using visible light as the emitter light [1; 2; 3; 4; 5; 6]. Specifically, Table 1 provides specific parameter indicators to help better understand the differences between the two types of technologies [7; 8; 9; 10]. It can be seen from Table 1 that the most obvious disadvantage of IWOC is that it is not suitable for outdoor applications because of its short communication distance [7], while outdoor OWC is suitable for long-distance transmission due to its transmission distance up to tens of thousands of kilometers despite environmental interference [7]. Optical wireless technologies with the traditional power of the intersection of information technology can be traced back to 2003. Researchers at Japan's Keio university took into account the characteristics of white light-emitting diode (LED): high brightness, low power consumption, and long service life etc., and based on the superior properties, first proposed the white LED IWOC and traditional power line communications (PLC) integrated system solutions [1]. This scheme has the inherent advantage that IWOC is free from the traditional radio frequency (RF) electromagnetic interference and the LED light source has high radiation power. Furthermore, the scheme can reduce the construction cost to a greater extent by reusing existing power line infrastructure and avoiding the introduction of new communications cables. At the same time, the above team also presented the prototype system implementation of the proposed scheme, which uses a desk lamp equipped with 120 LED as the IWOC light source and adopts sub-carrier binary shift keying (SC-BPSK). In addition, in the system of compact design, the team could apply to existing ball steep light screw is given and at the same time meet the requirements of the proposed scheme of bulb type IWOC transmitter components. This groundbreaking work has aroused the enthusiasm of many domestic and international research teams. So far, researchers from the University of Johannesburg in South Africa, the University of Texas in the United States, the University of Southampton in the United Kingdom, the University of British Columbia in Canada, Tsinghua University and the Information Engineering University of the People's Liberation Army have participated in the research work in this interdisciplinary field, and the research results have begun to take shape [10; 11; 12; 13; 14; 15; 16; 17]. At present, the research directions in this field mainly include integrated channel characteristics and transmission scheme of PLC and IWOC, modulation schemes, the performances of hybrid PLC and IWOC system, and optical wireless monitoring of high-voltage lines and inspection. This paper will sort out the development of optical wireless technologies for power industry in recent years about the above directions, and demonstrate the frontier progress in this field by combining with a number of experimental prototypes. The main challenges and possible solutions for power industry OWC are summarized to provide useful guidance for the further development of the technology. With the development of science and technology, power industry optical wireless technologies are widely used in positioning, monitoring, and people's daily life.