## 5 Conclusions  
### Discussion and Implications  
This study used network analysis to explore critical SOA technologies. The empirical results indicate that the critical technologies are mainly used in basic electric elements, optical elements, and communication technique. Critical technologies do not centralize in specific fields, which indicates that SOA-related research is an interdisciplinary field. In addition, the analysis of major patentees indicates Lucent Technologies Inc., Finisar Corporation, and Alcatel-Lucent Enterprise have long history in SOA technology development. These enterprises started developing SOA-related technologies and patents earlier than other companies did; however, they do not have the highest number of patents. Lucent Technologies Inc. and Alcatel-Lucent Enterprise are businesses that provide telecommunication software and hardware equipment, and Finisar Corporation is a manufacturer of optical communication components. The aforementioned businesses are private businesses. In addition, the top 10 patentees all belong to private businesses, indicating that the private sector plays an important role in the technology development of SOAs. In the future, the government can assist industry by gathering software and hardware manufacturers in the country to collaborate in developing complete solutions toward the development trend of SOAs. In doing so, a consensus can be established, and research resources can be integrated. In addition, the top 10 patentees are all private businesses, which indicates that the public sector and academia are weaker in the early development phase and following technology development. However, with the rapid development of mobile communication and optical communication technologies, governments of different countries can consider investing additional R&D funds and resources in the public sector and academia to help technology development in the aforementioned fields. With regard to the technology tendencies, this study discovered that the critical technologies of SOA mainly centralize under the H0155 category (the centrality indexes of H0155 include closeness centrality, eigenvector centrality, betweenness centrality, and reinforced structural holes at 67.75, 0.341, 830.995, and 0.867, respectively), which comprises the technologies related to semiconductor lasers and not the more mature technologies of light guides, transmission systems, or devices or arrangements for the control of light arriving from an independent light source. Although these technologies are also critical for developing SOAs and are indispensable, semiconductor lasers have been prioritized after 2000. Semiconductor lasers have the characteristics of small volume, high efficiency, small attrition power, and long lives [36]. These characteristics allow semiconductor lasers to be extensively applied in data processing, optical fiber communication, and precision measurement. Consequently, for the light industry, semiconductor lasers are one of the key elements. Most prior studies related to SOAs have mainly focused on technical discussions [6; 7; 8] and market research [5; 9]. However, they have failed to indicate the major technology field focuses, technology development tendencies, and network distribution between technology fields. This study filled this research gap, adopted new viewpoints, and focused on technology fields. With regard to policy recommendation, this study provides valuable information to countries, research universities, or businesses and proposes the technology map of SOAs. In the technology network, the SOA technology development focus, R&D resource allocation, and information regarding novel technology promotion were analyzed to determine the important critical SOA technologies. This study discovered that the critical SOA technology is semiconductor lasers and not light guides, transmission systems, or light control equipment or techniques.