en.Wedoany.com Reported - The Southeast Asia-Hainan-Hong Kong Express Submarine Fiber Optic Cable System (SEA‑H2X) has entered commercial operation, achieving a design capacity of over 200 Tbps on the Hong Kong-Singapore trunk route. The system was jointly funded by China Mobile, China Unicom, Converge ICT Solutions, and several regional partners.
HMN Tech provided 39.5nm ultra-wideband titanium alloy repeaters for the project. By expanding the usable optical spectrum, this technology enables the system to meet the rapidly growing demands of artificial intelligence, cloud computing, and data center interconnection scenarios. The SEA‑H2X trunk route is equipped with eight fiber pairs, with landing points covering the Hong Kong Special Administrative Region, Hainan, the Philippines, Thailand, and Singapore, ensuring geographic route diversity.
The system adopts an open cable architecture, separating the submarine wet-end equipment from the terminal transmission equipment. This allows operators to select SLTE equipment from vendors such as Ciena, Infinera, or Nokia, avoiding dependence on a single supplier. HMN Tech, as an end-to-end turnkey provider, was responsible for design, manufacturing, marine installation, and system integration.
The 39.5nm bandwidth covers the standard C-band and extended C-band (approximately 1528nm to 1567.5nm), adding about 4.5nm of spectral space beyond the conventional 35nm C-band. For regional links exceeding 3,000 kilometers, SEA‑H2X employs a 75 GHz (approximately 0.6nm) channel spacing and 400G PM‑16QAM modulation, supporting 64 active wavelength channels per fiber pair with a capacity of 25.6 Tbps. The eight fiber pairs collectively provide a system capacity of 204.8 Tbps, surpassing the design target of 200 Tbps. The engineering team selected the 75 GHz grid and 64-channel configuration to balance spectral efficiency, transmission distance, and operational reliability.
SEA‑H2X also deploys HMN Tech's advanced branching units with 18 kV hot-switching capability, enabling connection of the trunk route to secondary landing points or future expansions without interrupting main path services. The high-voltage switching capability facilitates safe power supply configuration during maintenance or after faults.
The industry is transitioning from C-band-only to C+L-band and even Super C+Super L architectures. However, expanding the L-band in submarine environments faces challenges due to relatively immature amplification technology. HMN Tech's focus on the extended C-band offers a practical solution, achieving capacity gains without introducing the complexity of dual-band amplification. Currently, C+L-band architectures are widely deployed in terrestrial fiber backbone networks, but among submarine cable systems, only the Pacific Light Cable Network (PLCN) employs similar technology.
SEA‑H2X is now carrying commercial traffic. Combining 39.5nm ultra-wideband repeaters, 75 GHz channel spacing, and 64×400G PM‑16QAM modulation, the system achieves an engineering baseline of 25.6 Tbps per fiber pair and a total capacity of 204.8 Tbps, while prioritizing reliable 400G performance over long distances.
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