A Japan-led international research team has demonstrated data transmission at 1.02 petabits per second over 1,808 kilometers using a 19-core optical fiber — a record that could help advance the high-capacity backbone networks needed to carry growing volumes of digital traffic.
The achievement should not be confused with a 1.02-petabit consumer internet connection. It was an experimental optical transmission system developed by researchers led by Japan’s National Institute of Information and Communications Technology, or NICT, with Sumitomo Electric Industries and researchers from European universities.
According to the NICT research announcement, the demonstration achieved a capacity-distance product of 1.86 exabits per second-kilometer, a world record for optical fibers using the standard cladding diameter.
The experiment matters not only because of its speed, but because researchers transmitted that volume of data over a distance comparable to links between major cities while keeping the fiber’s external glass diameter consistent with established optical-fiber standards.
Why 19 Cores Matter
Conventional single-mode optical fiber typically carries light through one core.
The experimental fiber developed by Sumitomo Electric instead contains 19 coupled cores within the same 0.125-millimeter cladding diameter used by standard optical fiber.
Increasing the number of cores effectively creates additional paths for carrying information without requiring the outside diameter of the glass fiber to grow proportionally.
That is attractive because simply increasing the physical size of fiber creates practical problems for existing cabling and network infrastructure.
The researchers took a different approach. The 19 cores are placed closely enough that their optical signals can interfere with one another. Instead of trying to eliminate that interaction physically, the transmission system uses multiple-input multiple-output, or MIMO, digital signal processing at the receiver to separate the signals.
The principle is related to MIMO techniques used in wireless communications, where signal processing distinguishes multiple overlapping transmission paths.
How the 1.02-Petabit Experiment Worked
The researchers did not lay a new 1,808-kilometer cable between two Japanese cities.
Their experimental system used an 86.1-kilometer section of 19-core fiber in a recirculating configuration. Signals passed through the system repeatedly to achieve an effective transmission distance of 1,808 kilometers.
The transmitter generated 180 wavelengths across the C and L optical bands. Those wavelengths carried polarization-multiplexed 16QAM signals across the fiber’s 19 cores.
Long-distance transmission presented another challenge: signal loss.
NICT and its research partners developed an amplification system capable of supporting all 19 cores. Optical amplifiers compensated for losses as the signals traveled through the experimental system.
After transmission, a 19-channel receiver collected signals from all of the cores simultaneously, while MIMO digital processing removed interference between them.
The resulting total data rate reached 1.02 petabits per second.
Sumitomo Electric’s technical announcement says the researchers achieved a capacity-distance product of 1.86 exabits per second-kilometer.
Why the Distance Is as Important as the Speed
Petabit-scale transmission itself was not new.
NICT and its partners had previously demonstrated transmission above 1 petabit per second using advanced optical fibers, including an earlier generation of 19-core fiber that reached 1.7 petabits per second over 63.5 kilometers.
The challenge was maintaining extremely high capacity across much longer distances.
The newer demonstration traded some peak capacity for dramatically greater reach: 1.02 petabits per second across 1,808 kilometers.
That distance is approximately equivalent to traveling from Sapporo to Fukuoka, according to NICT, making the experiment relevant to the type of distances encountered in networks connecting major cities.
This combination of capacity and distance is why researchers emphasize the capacity-distance product rather than transmission speed alone.
Why the Standard Fiber Diameter Matters
One of the most commercially relevant aspects of the experiment is easy to overlook.
The 19-core fiber has a standard 0.125-mm cladding diameter.
Existing telecommunications infrastructure has been developed around standardized fiber dimensions, so next-generation fibers that require substantially different physical handling can face additional deployment barriers.
Keeping multiple cores inside a familiar fiber diameter could make future integration easier than technologies requiring much larger fibers.
That does not mean today’s telecommunications providers can simply replace conventional fiber with this 19-core design.
The experimental system also depends on specialized multiplexing, amplification, receiving equipment and substantial MIMO signal processing. NICT says further improvements to optical amplification and faster MIMO processing are among the areas requiring additional research.
This Is Not a 1.02-Petabit Optical Fiber Home Internet Connection
Calling the achievement an “internet speed record” can create the wrong impression.
The 1.02-Petabit figure describes the aggregate transmission capacity achieved across many wavelengths and 19 fiber cores in a research system. It is not the download speed available to a single computer, household or smartphone.
NICT itself offered a more useful comparison: 1.02 petabits per second is approximately 26 times the total download traffic generated by all subscribers to Japan’s fixed broadband services as measured in November 2024.
The research is therefore primarily relevant to future network backbones rather than individual broadband plans.
Backbone capacity is becoming increasingly important as cloud computing, streaming services and large-scale computing infrastructure generate more network traffic. The growth of AI infrastructure adds another source of demand; Gignomist has separately examined how data center expansion is putting pressure on infrastructure and communities.
High-performance computing also depends on advances across processors, memory and networking. That broader infrastructure buildout is visible in the rising demand for components used in AI servers and data centers.
What Happened After the Record
The 1.02-petabit result was presented at the Optical Fiber Communication Conference in San Francisco on April 3, 2025 and later detailed publicly by NICT and Sumitomo Electric.
Optical-network research has continued since then.
NICT subsequently reported additional transmission records using different types of fiber and network configurations, reinforcing an important point about these experiments: there is no single universal “internet speed record.”
Researchers can optimize for different combinations of transmission capacity, distance, fiber type, wavelength range and compatibility with deployed infrastructure.
The significance of the 19-core experiment is its particular combination of attributes — petabit-class capacity, 1,808-kilometer reach and a fiber that retains the standard cladding diameter.
The next challenge is turning advances like these into systems that telecommunications operators can deploy economically and reliably.
For now, 1.02-petabit home broadband remains a misleading interpretation. What researchers demonstrated is potentially more important for the underlying internet: a way to dramatically increase the amount of information future long-distance fiber networks may be able to carry.
