# Advanced Progress of Optical Wireless Technologies for Power Industry: An Overview
## 2 Classification and Progress of Power Industry Optical Wireless Communications
### Wireless Optical Sensor Monitoring of Power Lines  
High-speed communication on power industry allows for real-time monitoring of network. This allows to anticipate possible events, process those events more rapidly, and improve the quality of service to customers. Recently, communication infrastructures using broadband power lines, Wi-Fi, and optical fibers have been designed for power distribution network management services. The authors in [74] compared the speed performances of each communication. Experimental results indicated that optics fiber is the fastest communication network, and could provide a bidirectional delay of 3 ms. A significant factor to consider in the communications system is the costs of infrastructure investment. Sometimes slower solutions, for instance, PLC may be more appropriate for specific applications or when a large number of measuring devices must be installed in a distribution system. PLC is an example of a common and cost-effective means of communication for smart grid monitoring since it allows the power lines to be used for power and communication, thereby eliminating the need for special cables for transmission control and data signals. In reference [75; 76], different overhead communication PLC lines were compared for several applications of power distribution networks. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Years** & **System Types** & **Key Techniques** &
\begin{tabular}{c} **Consideration** \\ **Factors** \\ \end{tabular} & **Distance** & **Data** & **Ref** \\ \hline
2015 & \
\begin{tabular}{c} Integrated \\ PLC/IWOC \\ \end{tabular} & AF relay & Multi-path effects & 3 m &
\begin{tabular}{c} 48 Mbps \\ (Data rate) \\ \end{tabular} & [12] \\ \hline
2015 & \begin{tabular}{c} Hybrid \\ PLC/IWOC \\ \end{tabular} & OFDM modulation & \
\begin{tabular}{c} Satisfy the practical \\ application \\ \end{tabular} & 8 m &
\begin{tabular}{c} 48 Mbps \\ (Data rate) \\ \end{tabular} & [16] \\ \hline
2015 & \begin{tabular}{c} Integrated \\ PLC/IWOC \\ \end{tabular} & \
\begin{tabular}{c} DF Relay and \\ BDM \\ modulation \\ \end{tabular} & Multi-path effects and & 2.8–3 m &
\begin{tabular}{c} 0.4 bit/symbol (BDM \({}^{1}\)) \\ 0.13 bit/symbol \\ (TDM \({}^{2}\)) \\ (Data rate) \\ \end{tabular} & [18] \\ \hline
2015 & \
\begin{tabular}{c} Cascaded \\ PLC/IWOC \\ \end{tabular} & OFDM and FSK modulation & Impulsive noises & 2.8–3 m &
\begin{tabular}{c} 10\({}^{5}\) \\ (Data rate) \\ \end{tabular} & [62] \\ \hline
2016 & \
\begin{tabular}{c} PLC \\ backhauling and \\ Hybrid \\ IWOC/RF \\ \end{tabular} & OFDM & Multi-user utility function & 2.8–3 m &
\begin{tabular}{c} 10 Mbps (VLC) \\ 5 Mbps (RF) \\ (Data rate) \\ \end{tabular} & [1] \\ \hline
2016 & \begin{tabular}{c} Hybrid \\ PLC/IWOC \\ \end{tabular} & \
\begin{tabular}{c} Duplex DF \\ underlying \\ \end{tabular} & Intercell interference & Over3 m &
\begin{tabular}{c} 5–30 Mbps \\ (Data rate) \\ \end{tabular} & [14] \\ \hline
2018 & \
\begin{tabular}{c} Hybrid \\ PLC/IWOC/RF \\ \end{tabular} & OFDM modulation & Power allocation & 2.8–3 m &
\begin{tabular}{c} 18.5 Mbps \\ (Data rate) \\ \end{tabular} & [9] \\ \hline
2018 & \begin{tabular}{c} Hybrid \\ PLC/IWOC \\ \end{tabular} & AF Relay & \
\begin{tabular}{c} Relay location and \\ relay-to-destination \\ distance \\ \end{tabular} & 3.15 m &
\begin{tabular}{c} 0.04 bit/s/Hz \\ (Average capacity) \\ \end{tabular} & [36] \\ \hline
2018 & \begin{tabular}{c} Integrated \\ PLC/IWOC \\ \end{tabular} & DF Relay & \
\begin{tabular}{c} User’s location and \\ transmit power \\ \end{tabular} & 2.75 m &
\begin{tabular}{c} 0.04 bit/s/Hz \\ (Average capacity) \\ \end{tabular} & [60] \\ \hline \hline \end{tabular}  
\({}^{1}\) BDM represents for bit division multiplexing. \({}^{2}\) TDM stands for time-division multiplexing.  
\end{table} 
Table 2: Comparison of different researches between PLC and IWOC system.