# Toward SDM-Based Submarine Optical Networks: A Review of Their Evolution and Upcoming Trends
## 3 Recently Announced Submarine Cable Systems
### A Detailed Overview of SDM-Based Technology Cable Systems
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Submarine Cable** & **RFS** & **Cable Length** & **Capacity (Tb/s)** & **Technology** & **Fiber Pairs** & **SDM** \\
**System** & **2021** & 6400 & 250 & SDM\({}^{\dagger}\)ASN & 12 & Pump Sharing Repeater/(12 FPs) \\
**Malbec** & **2021** & 2600 & 108 & SDM & 8 & Fiber Count \(\geq\) * SFPs (8 FPs) \\
**Hainan to Hong** & **2021** & 675 & 307 & SDM \({}^{\ddagger}\)HMN & 16 & High Fiber Count (16 FPs) \\
**Kong Express** & **2022** & 15,000 & 90 & SDM \({}^{\ddagger}\)ASN & \({}^{\ddagger}\)16 & SDM Repeater/(16 FPs) \\
**Equiano** & **2022** & 12,000 & 200 & SDM & 12 & Fiber Count \(\geq\) * SFPs (12 FPS) \\
**Grace Hopper** & **2022** & 7191 & 352 & SDM & 16 & High Fiber Count (16 FPs) \\
**Amitie** & **2022** & 6792 & 320 & SDM & 16 & High Fiber Count (16 FPs) \\
**2 Africa** & **2023** & 45,000 & 180 & SDM \({}^{\ddagger}\)ASN & 16 & Fiber Count \(\geq\) * SFPs/(12 FPs) \\
**ECHO** & **2023** & 17,184 & 144 & SDM & 12 & Fiber Count \(\geq\) * SFPs (12 FPs) \\
**IAX** & **2023** & 5791 & 200 & SDM & 12 & Fiber Count \(\geq\) * SFPs (12 FPs) \\
**Confluence-1** & **2023** & 2571 & \(\geq\)500 \({}^{\ddagger}\) & SDM & 24 & Ultrahigh Fiber Count (24 FPs) \\
**Firmina** & **2023** & 2500 & N.A & SDM & 12 & Fiber Count \(\geq\) * SFPs (12 FPs) \\
**Bifrost** & **2024** & 15,000 & 180 & SDM\({}^{\ddagger}\)ASN & 12 & Fiber Count \(\geq\) * SFPs (12 FPs) \\
**Apricot** & **2024** & 12,000 & 190 & SDM & \({}^{\ddagger}\)16–20 & Fiber Count \(\geq\) (12 FPs), \({}^{\ddagger}\)16–20 FPs) \\
**IEX** & **2024** & 9775 & 200 & SDM & \({}^{\ddagger}\)16 & High Fiber Count (16 FPs) \\
**Medusa** & **2024** & 8760 & 480 & SDM & 24 & Ultrahigh Fiber Count (24 FPs) \\
**Blue Raman** & **2024** & 7500 & 400 \({}^{\ddagger}\) & SDM & 16 & High Fiber Count (16 FPs) \\
**Caribbean Express** & **2024** & 3472 & 280 & SDM & 18 & Very High Fiber Count (18 FPs) \\
**CNO** & **2025** & 22,000 & 240 & SDM & 12 & Fiber Count \(\geq\) * SFPs (12 FPs) \\
**Faavik Nui** & **2025** & 19,200 & 126 & SDM & 10 & Fiber Count \(\geq\) * SFPs (10 FPs) \\ \hline \end{tabular} \({}^{\star}\) 8 FPs is the limit of previous technologies cable systems, \({}^{\dagger}\) expected/predicted.  
\end{table} 
Table 3: A taxonomy of SDM-based submarine cable systems [1, 2, 3, 4, 5]. RFS: Ready for Service year, SDM \({}^{\ddagger}\): First Generation of SDM-based system introduced by (ASN/HMN) supplier. 19.2 Tb/s per fiber and delivering a capacity of 307.2 Tb/s to its users. The H2 HE cable system is invested and owned by China Mobile, supplied by HMN Tech, and has been in service since September 2021. The Malbec cable system is a new investment owned by Facebook and Globenet. It consists of a cable 2600 km in length and connects the cities of Rio de Janeiro, Sao Paulo, and Buenos Aires, with a future connection to Porto Alegre. It uses the latest SDM technology with low latency and 400 Gb/s optical channels. The initial available capacity of the Malbec system is 108 Tb/s, approximately 18\({}^{+}\) Tb/s/FP, and has been in service since 10 June 2021. The Grace Hopper cable system (another Google investment like Curie, Dunant, and Equiano) connects the US with the UK and Spain. It travels for approximately 6250 km from New York to Bude (UK), and another 6300 km from New York to Bilbao (Spain). It is a private subsea cable and the first-ever route to Spain. It incorporates 16 FPs and it transports 22 Tb/s/FP, thus delivering a total of 352 Tb/s, which is higher than the capacity of current internet infrastructure from the US to Europe. SumCommand and Tekius are the supplier and Spanish landing partner, respectively. Grace Hopper is expected to be ready for service in 2022. The Amitie submarine cable system will interconnect Massachusetts (US), Le Porge (France), and Bude (UK). The signal will travel for 6600 km through the Atlantic Ocean. Facebook, Microsoft, Aqua Comms, and Vodafone (through Cable & Wireless Americas Systems, Inc.) are the consortium partners.