China Unicom’s Hainan Lingshui International Submarine Cable Landing Station in Li’an Town, Lingshui Li Autonomous County, has recently entered operation with a dual-cable setup, making it the Hainan Free Trade Port’s (FTP) only international communications hub with this configuration. Together, the two cables vastly reduce network latency for the island within the Asia-Pacific region.

On the station’s second floor, two rows of equipment cabinets in the cable room connect the submarine cables to Hainan’s provincial backbone network. The room is kept at or below 25°C to ensure the equipment operates reliably. Monitoring systems can also detect cable faults in real time and pinpoint their locations.

Zhang Zhiyong, general manager of the computing network operations group at China Unicom’s Hainan branch, said the two international submarine cables connected to the station, SEA-H2X and ALC (Asia Link Cable), provide low-latency cross-border communications. Compared with traditional routes through Guangzhou, the SEA-H2X route from Lingshui to Singapore can cut latency by about nine milliseconds.

The station connects directly to the Haikou International Communications Gateway Exchange Bureau and works with China Unicom’s data center cluster in Hainan to create an integrated network linking international submarine cables, the provincial backbone network, and regional data centers. This setup will reduce network latency between Hainan and Southeast Asia and strengthen the Hainan FTP’s international communications capabilities.

Submarine cables are essential to international communications networks. SEA-H2X spans about 5,746 kilometers and features eight fiber-pair trunk lines, with a designed capacity of more than 200 terabits per second. It links Hainan and Hong Kong, China, with the Philippines, Thailand, and Singapore. Using submarine branching units and reconfigurable optical add-drop multiplexers, the cable enhances reliability and flexibility, delivering stable, high-speed, low-latency connectivity to customers across Asia.

The ALC cable stretches about 6,100 kilometers and has a capacity of 27 terabits per second per fiber pair. Its main route, connecting Hong Kong, China, Hainan, and Singapore, is optimized for 32 milliseconds of latency, making it a key digital link between China and Southeast Asia. With its network design and technological innovations, ALC can facilitate large-scale, real-time cross-border AI computing and inference, as well as global coordination of computing resources. It also offers a high-speed, stable, and secure international channel for digital economy and AI businesses expanding overseas.

For inbound data, information sent through international submarine cable systems first reaches the Lingshui landing station, then travels along the Lingshui–Haikou trunk network to the Haikou International Communications Gateway Exchange Bureau. From there, it is routed over the secondary backbone fiber-optic network to China Unicom data centers in Haikou, Chengmai, Wenchang and other locations for storage and processing. Once processed, the data can be transmitted overseas as needed, enabling integrated submarine cable and computing services.

SEA-H2X and ALC have separate physical cables, routes, and equipment, providing mutual redundancy in case of damage or disruption. Data transmission can switch between the cables automatically or manually, helping ensure uninterrupted communication services.