1. [1] Cisco Systems, Inc., “Visual networking index: Forecast and trends, 2017-2022,” White paper, 2019.
2. [2] Ministry of Internal Affairs and Communications, Telecommunications Division Data Communication section, 2021. https://www.soumu.go.jp/main_content/000791761.pdf
3. [3] ITU-T Recommendation G.694.1, Spectral grids for WDM applications: DWDM frequency grids, 2021.
4. [4] R.-J. Essiambre, G. Kramer, P.-J. Winzer, G.-J. Foschini, and B. Goebel, “Capacity limits of optical fiber networks,” J. Lightwave Technol., vol..28, no.4, pp.662-701, 2010. 10.1109/jlt.2009.2039464
5. [5] R.-J. Essiambre and R.W. Tkach, “Capacity trends and limits of optical communication networks,” Proc. IEEE, vol.100, no.5, pp.1035-1055, May 2012. 10.1109/jproc.2012.2182970