On January 13, 2026, three major Japanese corporations announced a landmark joint venture to strengthen digital connectivity across Asia. NTT Limited Japan (a subsidiary of NTT Data Group), Sumitomo Corporation, and JA Mitsui Leasing have established Intra-Asia Marine Networks Co., Ltd. (I-AM NW) to build and operate a large-scale submarine communication cable system connecting Japan with Southeast Asia.

The project, named the Intra-Asia Marine Cable (I-AM Cable), represents a total investment of approximately $1 billion (150 billion yen), positioning it among the most significant digital infrastructure projects in the Asia-Pacific region. Commercial operations are scheduled to begin in early fiscal year 2029.

Technical Specifications and Scale

The I-AM Cable is designed as a state-of-the-art high-capacity communication infrastructure leveraging the latest fiber optic technologies.

Key Specifications

  • Total Length: Approximately 8,100 km
  • Design Capacity: Approximately 320 terabits per second (Tbps)
  • Technology: SDM (Space Division Multiplexing) technology
  • Fiber Capacity: Up to 16 fiber pairs (32 cores) per cable
  • Landing Points: Japan (Chiba, Mie, and Fukuoka Prefectures), Malaysia, and Singapore
  • Future Connections: South Korea, Philippines, Taiwan

The system incorporates Wavelength Selective Switch (WSS) functionality, enabling remote adjustment of wavelength bandwidth allocation across different routes. This allows operators to flexibly respond to changing business needs and traffic demands without physical intervention.

The Strategic Importance of Submarine Cables

The Backbone of the Digital Economy

Approximately 99% of international data communications travel through submarine cables. From video streaming and social media to cloud services and financial transactions, these undersea networks form the critical foundation of the modern digital economy.

The explosive growth of AI and machine learning applications, combined with surging data center interconnection demands, has driven sharp growth in international communication traffic across the Asia-Pacific region.

Japan's Geopolitical Advantage

Japan occupies a strategic position between Asian countries and the United States, serving as a crucial data hub for the Asia-Pacific region. However, in recent years, several cable projects have bypassed Japan, routing through Taiwan and the Philippines to Singapore instead, a trend industry observers have called "Japan Passing."

The I-AM Cable represents a strategic investment to maintain and strengthen Japan's position as Asia's data hub, ensuring the country remains central to regional connectivity architecture.

Disaster Resilience and Redundancy

The cable system features landing points in three Japanese prefectures (Chiba, Mie, and Fukuoka) to ensure high resilience against natural disasters affecting Japan's coastal waters. This distributed approach reflects lessons learned from the 2011 Great East Japan Earthquake, when multiple submarine cables along the Pacific coast were damaged, requiring several months for full restoration.

Fukuoka is being developed as a Western Japan international telecommunications hub, coordinating with newly planned data center clusters, a development that also supports regional economic revitalization efforts.

Economic Security Considerations

Submarine cables have evolved from simple communication infrastructure to critical national security assets.

Since 2024, submarine cable damage incidents have occurred near Taiwan and in the Baltic Sea, with some observers pointing to potential involvement by China and Russia. The Japanese government has responded by promoting cable route diversification under its "Digital Garden City Nation Infrastructure Development Plan" and strengthening support for related companies.

The DX and Innovation Acceleration Plan 2030, published by Japan's Ministry of Internal Affairs and Communications on May 23, 2025, sets a target of raising Japanese companies' global submarine cable market share from roughly 20% to 35% by 2030, backed by subsidies for cable-laying vessels and manufacturing capacity. A government expert panel on submarine cable protection was convened in November 2025.

The Three Partners and Their Roles

NTT Limited Japan

As NTT Data Group's global ICT services provider, NTT brings decades of experience in building, selling, and operating major submarine cable systems including JUPITER, JUNO, MIST, and ASE. The company provides technical expertise and operational know-how.

Sumitomo Corporation

With 125 offices across 63 countries and regions, this global trading company brings extensive customer networks and business development capabilities. Sumitomo participates through an intermediate holding company established jointly with SMFL Mirai Partners, leveraging the combined customer bases and networks of both organizations.

JA Mitsui Leasing

Built on the foundations of the JA Group and Mitsui Group, this comprehensive leasing company brings financial structuring expertise. The firm has investment experience in information and communications infrastructure including mobile base stations, optical networks, and cloud/data center platforms. In 2022, JA Mitsui Leasing entered the submarine cable sector through its investment in JUNO, a cable connecting Japan and the U.S. West Coast.

Position in Japan's Digital Infrastructure Strategy

The I-AM Cable aligns closely with the Japanese government's digital infrastructure resilience policies.

Through the "Digital Infrastructure Development Fund," Japan's Ministry of Internal Affairs and Communications supports regional distribution of data centers, development of domestic submarine cables (particularly on the Sea of Japan side), and installation of international submarine cable branch lines. Diversifying landing stations beyond their current concentration on the Boso and Shima peninsulas is a key priority, making the Fukuoka landing strategically significant.

Cable manufacturing is a three-firm oligopoly: NEC, SubCom, and Alcatel Submarine Networks together hold roughly 90% of the market. NEC, through subsidiary OCC among others, keeps an end-to-end production line inside Japan, which is where the economic security argument gets its force.

Looking Ahead

I-AM NW will run the entire value chain, from cable planning through selling circuits to global technology firms and regional telecom operators.

Service is due to start in early fiscal 2029. How far AI-driven data centre traffic actually grows is not knowable now, but an 8,100km cable is a piece of equipment that stays in the water for two decades or more. Three Japanese companies have put 150 billion yen on that timeframe.

Japan is steadily advancing its digital infrastructure capabilities, but what about your country? How are submarine cables and international communication infrastructure being developed where you live? Share your thoughts in the comments!

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