## 4 Empirical Study  
### Overview of 5G Optical Networks  
Before the researchers performed the technology network analysis, they first analyzed the patent search results to obtain a preliminary understanding of the status of technology development. A complete CPC code consists of five levels, namely the Section, Class, Subclass, Main group, and Subgroup (e.g., H04Q 11/00). Table 2 lists the top 10 level-4 CPC codes of 5G optical networks with regards to their frequency of appearance.  
In terms of CPC distribution, the results encompassed a total of 104 CPC technologies. Table 2 indicates that the focus of 5G optical network technologies is mostly on H04B10, H04W88, H04B7, H04L5, and H04J14; Appendix A displays the definition of each CPC code. According to the CPC definition, H04B10 belongs to transmission systems employing electromagnetic waves other than radio waves, such as infrared, visible, or ultraviolet light, or those employing corpuscular radiation, such as quantum communication; H04W88 belongs to devices specially adapted for wireless communication networks, such as terminals, base stations, or access point devices; H04B7 belongs to radio transmission systems, such as those using radiation fields; H04L5 belongs to arrangements affording multiple uses of the transmission path, as well as the presentation of data, record carriers, and handling record carrier; and lastly, H04J14 belongs to optical multiplex systems.  
The analysis results indicated that the focuses of 5G optical networks lie in the following domains: radio transmission systems employing electromagnetic waves other than radio waves; wireless communication network facilities; the transmission of digital information; and optical multiplex systems. Additionally, the researchers conducted analysis of the top 10 patentees (Table 3). The results  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Indicator** & **Formula** \\ \hline Closeness centrality & \(\text{C}_{c}(i)=\left[\sum\limits_{j=1}^{n}d(i,j)\right]^{-1}\) \\  & \(d(i,j)\) represents the distance from node \(i\) to node \(j\). \\ \hline Betweenness centrality & \(\text{C}_{b}(i)=\frac{n}{i\
eq j\
eq k}\ d_{jk}(i)/d_{jk}\) \\  & \(d_{jk}\) represents the number of shortest paths from node \(j\) to node \(k\); \(d_{jk}(i)\) represents the number of shortest paths that must pass through node \(i\) to get from node \(j\) to node \(k\). \\ \hline Fragmentation centrality & \(\text{C}_{f}(i)=1-\frac{2\sum_{i,j}\frac{d(i,j)}{n(i-1)}}{n(i-1)}\) \\  & \(d(i,j)\) represents the distance from node \(i\) to node \(j\). \\  & \(n\) represents the total number of nodes. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Methods used for measuring the centrality of the technology network.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ranking** & **CPC Code** & **Frequency of Appearance** & **Percentage** \\ \hline
1 & H04B10 & 146 & 10.38\% \\
2 & H04W88 & 92 & 6.54\% \\
3 & H04B7 & 76 & 5.40\% \\
4 & H04L5 & 75 & 5.33\% \\
5 & H04J14 & 68 & 4.83\% \\
6 & H04Q11 & 66 & 4.69\% \\
7 & H04W72 & 66 & 4.69\% \\
8 & H04L27 & 63 & 4.48\% \\
9 & H04W84 & 62 & 4.41\% \\
10 & H04L25 & 43 & 3.06\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: Frequency distribution of the top 10 level-4 CPC (Cooperative Patent Classification) codes.  
revealed the patentee with the highest number of approved patents in recent years to be Huawei Technologies Co., Ltd., followed by Smart Mobile, Inc., and Telefonaktiebolaget LM Ericsson (publ). Among the top patentees, Telefonaktiebolaget LM Ericsson (publ) has been actively promoting the development of 5G. The company published a report titled 5G Business Potential to uncover the unexplored potential business opportunities for telecommunication operators under the current trend of industry digitization, prompting these operators to deliberate over their company values and business model as a network developer, service facilitator, and service creator to gain a head start in the industry.