NEC and NTT Conduct Groundbreaking Transoceanic Transmission Experiment

NEC Corporation and NTT Corporation have announced the completion of a transoceanic-class transmission experiment spanning 7,280 kilometers.
NEC and NTT conduct Transoceanic Transmission ExperimentThe experiment utilized a coupled 12-core multicore fiber, showcasing a groundbreaking advancement in optical network technology.

The experiment, a collaboration between NEC and NTT, marks a milestone in the development of next-generation transmission infrastructure critical for the realization of high-capacity optical networks, including future optical submarine cables.


The exponential growth of global 5G adoption and increased communication demands between data centers have led to a 30 percent annual rise in international internet traffic from 2018 to 2022. This trend necessitates enhancements in transmission capacity per optical submarine cable system.

Traditional optical submarine cables utilize single-core fiber, limiting their capacity to a single optical transmission path. In response, research and development efforts worldwide are exploring multicore fiber technology to increase transmission capacity without altering the standard outer diameter of the fiber.

NEC is involved in a project employing two-core multicore fiber for a long-haul optical submarine cable system, demonstrating a commitment to advancing transmission capabilities.

Research Results

The addition of multiple cores to an optical fiber introduces challenges such as crosstalk, where optical signals from one core interfere with signals in adjacent cores, potentially degrading communication quality. Moreover, long-distance transmission exacerbates issues related to signal delay and loss uniformity.

To address these challenges, NEC and NTT developed innovative technologies:

NEC devised an algorithm leveraging Multiple Input Multiple Output (MIMO) technology for demodulating received signals, enabling accurate separation and demodulation of high-speed signals over long distances.

NTT pioneered design technologies for coupled multicore fiber and optical input/output devices, mitigating the effects of non-uniform signal delay and loss, thus expanding the potential distance of transmission.

By combining these advancements, NEC and NTT achieved a historic feat, successfully demodulating 12-spatially multiplexed optical signals over 7,280 kilometers in a transoceanic-class transmission experiment.

Future Developments

Building upon this success, NEC and NTT will further advance these technologies with the goal of commercializing a long-haul, high-capacity optical submarine cable system and terrestrial core network system. These efforts align with the vision of the IOWN concept and the Beyond 5G/6G era anticipated in the 2030s.

The groundbreaking results will be presented as a highly regarded paper at the Technical Conference of OFC 2024, the world’s premier event on optical communications, scheduled from March 24 to March 28, 2024, at the San Diego Convention Center in California, USA. Staff Writer