# 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
Recent updates (August 2021, September 2021) indicate that the system will include the Seychelles, the Comoros Islands, and Angola, a new landing point, to southeast Nigeria and extend to the Persian Gulf, Pakistan, and India. With its recent extension, 2 Africa is now the longest subsea cable in the world. 2 Africa will use SDM powered by ASN with up to 16 FPs and will incorporate optical switching for flexible bandwidth management. It is also the first system of its size that deploys an innovative aluminum conductor specially constructed for submarine cable systems. The project will use WSS-ROADMs (used for the first time in Africa) and is expected to go commercial in 2023-2024. The Caribbean Express (CX) will connect Florida with Balboa (Panama) and will branch to Mexico and Colombia. Future extensions include Cuba, Grand Cayman, Guatem, Jamaica, Honduras, Nicaragua, and Costa Rica. Ocean networks will provide the SDM-based system, which will deploy 18 FPs, set at a minimum of 18 Tb/s/FP. It will be the first and only cable system in the Caribbean area that will offer full fiber pairs to customers. CX is expected to be ready for service in the first quarter of 2024. The Bifrost cable system will connect Singapore, Indonesia, the Philippines, Guam, and the US West Coast. It will travel for more than 15,000 km. When fully deployed, it will be the largest-capacity high-speed transmission cable across the Pacific Ocean. Facebook, PT. Telekomunikasi Indonesia International (Telin), and Keppel Telecommunications & Transportation Limited (Keppel T&T) comprise the consortium. ASN will supply the system, which is planned to use SDM technology with 12 FPs. Bifrost is expected to go commercial in 2024. The Apricot submarine cable system will connect Japan, Taiwan, Guam, the Philippines, Indonesia, and Singapore, travelling approximately 12,000 km. It will use SDM,  
Figure 11: 2 Africa submarine cable system [3]. including 400-G transmission, multiple pairs of high-capacity optical fibers (16-20 FPs expected), and will incorporate a state-of-the-art submersible ROADM employing WSSs. The consortium comprises Facebook, Google, NTT, Chunghwa Telecom (CHT), and PLDT. NTT will operate the system and manage the three cable landing stations in Japan, Tuas, Singapore, and Indonesia. Apricot will be ready for service in late 2024. The Medusa submarine cable system will be a state-of-the-art fiber-optic system providing open cable features. It consists of 24 FPs, with 20 Tb/s/FP and a total system capacity of 480 Tb/s. The Medusa cable system will interconnect Southern European countries--Portugal, Spain, France, Italy and Greece--with North African countries--Morocco, Algeria, Tunisia and Egypt. It will travel more than 8760 km. The Medusa cable project is expected to cost \(\copyright\)326 million (US $374 million), and be partially financed by the European Investment Bank. Medusa will be ready for service in third quarter of 2024. The Hawaiki Nui submarine cable system will interconnect Southeast Asia, Australia, and North America. PT Mora Telematika Indonesia (Moratelindo) is the Indonesian strategic partner of the project. It consists of 12 FPs and has a total system capacity of 240 Tb/s. The Nui cable project is expected to be ready for service in 2025. Table 3 presents a taxonomy of SDM-based submarine cable systems; each of them deploys parallel fibers and/or novel pump-farming technology [1, 2, 3, 4, 5].