Japan Sets Optical Fiber Record With 1.02 Petabits per Second Across 1,802 Kilometers

A tiny fiber carries an extraordinary amount of data

Japanese researchers have transmitted 1.02 petabits of data per second across 1,802 kilometers, or about 1,120 miles, using an optical fiber with 19 cores inside a strand just 0.127 millimeters in diameter. The National Institute of Information and Communications Technology (NICT) announced the achievement at the 48th Optical Fiber Communication Conference in San Francisco.

The experiment combined an enormous data rate with a distance suitable for connections between faraway cities. Its reported capacity was more than 125,000 gigabytes per second, roughly 4 million times the average fixed broadband speed in the United States and more than double a record set in 2024.

NICT's achievement centers on fitting more paths for light into a fiber that remains the same diameter as most existing single optical fibers. Researchers then used amplification, repeated transmission loops and digital processing to keep those signals usable over the full experimental distance.

The result established a record for communication through fiber of this standard size, with a capacity-distance product of 1.86 exabits per second-kilometer. That measurement combines two things network builders need together: how much information a connection carries and how far it carries it.

As of July 18, 2025, the technology remained experimental and unavailable for commercial use. Its possible value reaches beyond faster downloads, toward the large connections needed by cloud computing, artificial intelligence and global communications.

How much information is 1.02 petabits?

The reported rate of 1.02 petabits per second equals 1,020,000 gigabits per second. Expressed in bytes, the units commonly used for file sizes, it exceeds 125,000 gigabytes every second. Bits and bytes measure the same information differently: eight bits make one byte.

Average fixed broadband in the United States was put at about 289 megabits per second, equivalent to roughly 36 megabytes per second. Against that figure, the Japanese result was described as about 4 million times faster. Estimates comparing it with India's lower average internet speed put the difference at 16 million times.

The download comparisons were equally striking: the entire Internet Archive in less than four minutes, the Netflix library in under a second, or the English Wikipedia 10,000 times in one second. The capacity was also described as sufficient to stream millions of movies in ultra high definition simultaneously.

Those comparisons give familiar scale to a laboratory result. The experiment's practical focus was moving huge quantities of information between network locations, while a household connection delivers a much smaller share of network capacity to an individual user.

Nineteen cores inside a standard sized strand

Traditional optical fibers transmit information as pulses of light through a single core. The Japanese team's design places 19 individual cores inside one strand, allowing each to carry its own data stream. The result packs the capacity of 19 standard fiber lines into a fiber thinner than a mechanical pencil.

The strand measures just 0.127 millimeters across, approximately the same diameter as most existing single optical fibers. Keeping that physical size matters because the researchers want greater capacity without requiring a larger strand throughout the network.

Each of the 19 cores interacts with light in the same way. Matching their optical properties helps the signals travel synchronously and reduces the loss and distortion that become harder to manage as transmission distances grow.

An unnamed expert described the design through a comparison with road traffic:

It's like replacing a single-lane road with a 19-lane superhighway, all within the same space.

The comparison captures the central idea: more information can travel along parallel paths inside the same physical space. For telecommunications operators, that combination of capacity and familiar dimensions is the main attraction.

Keeping the signals strong over 1,120 miles

Light signals weaken as they travel through fiber. Adding cores creates more paths for information, but researchers must also preserve the signals in those paths and manage interference over long distances.

NICT's team used sophisticated amplifiers and recirculating signal loops to maintain strength and clarity. The data signal passed through the transmission system 21 times, simulating the full journey of about 1,120 miles.

Special amplifiers boosted signals across all 19 cores simultaneously. Advanced amplification and error correction helped preserve the information as the signal repeatedly traveled through the experimental system.

Previous experiments had reached similar speeds over much shorter distances. This achievement extended that level of capacity beyond 1,100 miles while retaining the fiber's standard diameter. Carrying a huge amount of data becomes more useful for major communications routes when it can also travel a substantial distance.

Different wavelengths add more data channels

The researchers also used multi-band wavelength division multiplexing, known as WDM. In simple terms, the technique sends separate streams of information using different wavelengths of light, allowing several channels to share the same fiber path.

The 19 cores provided parallel physical paths, while the different wavelengths supplied additional channels within them. Using multiple wavelength bands helped increase the total amount of information moving through the system.

At the receiving end, a receiver with 19 channels and a digital processor cleaned up the signals and calculated the total data rate. The receiver and processing equipment were essential parts of the experiment, alongside the fiber and amplifiers.

The reported capacity-distance product of 1.86 exabits per second-kilometer was the highest achieved for standard sized fiber communication. A capacity-distance product multiplies transmission rate by distance, giving researchers a way to describe the combination rather than discussing speed alone.

How the result compares with earlier milestones

Home broadband in the early 2000s was measured in kilobits or low megabits per second. Optical transmission research later advanced to records measured in hundreds of terabits per second, before reaching the petabit scale described in the Japanese experiment.

The previous record cited for 2024 was 50,250 gigabytes per second. Compared with that figure, the new result of more than 125,000 gigabytes per second represented an increase of more than twofold.

Other milestones included 402 terabits per second over 63 kilometers by Aston University in the United Kingdom, and 402 terabits per second over 50 kilometers using advanced amplification and spectrum shaping technologies by NICT in 2024. The Japanese result combined a much longer distance with a higher transmission rate in a standard sized fiber.

• Early 2000s: Home broadband speeds were commonly measured in kilobits or low megabits per second.
• 2024: A previous fiber transmission record reached 50,250 gigabytes per second. NICT also achieved 402 terabits per second over 50 kilometers.
• By July 18, 2025: NICT had announced transmission at 1.02 petabits per second across 1,802 kilometers at the 48th Optical Fiber Communication Conference in San Francisco.

The distance is a central part of the advance. The earlier achievements cited here had not combined this speed with such a long transmission distance inside a fiber of standard dimensions.

Why growing data demand matters

Streaming services, cloud computing, artificial intelligence, smart cities and billions of connected devices are increasing the amount of information that networks must carry. Industry estimates cited alongside the achievement put annual data growth at about 50 percent.

Current networks are already under pressure to keep up with that growth. When demand approaches the capacity of a connection, the connection can become a bottleneck, limiting how much information moves between the places it serves.

NICT's experiment addresses that problem by increasing capacity within a familiar fiber diameter. The design could make deployment easier and more economical by allowing new fibers to fit existing cable infrastructure.

The potential benefit concerns shared communications capacity as much as individual download speed. Cloud platforms serving billions of users and AI systems processing information from millions of sources require large amounts of data to move between locations.

The same demand extends to the Internet of Things, the term for connected objects such as traffic lights and refrigerators. Smart cities bring many such devices together, adding to the information networks must handle.

Possible uses beyond movie downloads

NICT's team identified telecommunications applications that could benefit as networks develop beyond 5G. These include autonomous vehicles sharing data across cities and countries, virtual reality operating in real time, global AI systems and large cloud computing platforms.

Autonomous vehicle networks would use communications links to share information quickly across many locations. Global AI systems would move and process information from millions of sources, while cloud platforms would serve large numbers of users at once.

Smart cities would connect services and devices across urban areas. The proposed fiber technology could provide part of the underlying network that carries their combined traffic.

Dr. Ren Resch, identified as a technology analyst, described the result in terms of both its speed and the communications infrastructure it could support:

At this new record-breaking speed, you could download the entire Netflix library in under a second. It's not just about speed—it's about future-proofing our global communications infrastructure.

Public reaction on social media mixed amazement with humor. Some users joked that such capacity would mainly go toward watching HD videos, while others focused on the technical work needed to reach the reported result.

What must happen before commercial use

The record had not yet been independently verified, and further testing was needed to assess reliability and cost effectiveness under real operating conditions. No date for commercial availability was given.

The fiber's dimensions offer a practical advantage because it can fit existing cable infrastructure. Deployment would still involve the wider network: routers, switches and other equipment would need upgrades to handle such large data flows, requiring substantial investment.

NICT's team was exploring practical telecommunications uses and working with industry partners to develop commercial solutions. That work would move the research toward systems capable of operating beyond the experimental setup.

Japan's result also forms part of international competition to build faster, more reliable communications infrastructure. The connections needed for AI, autonomous vehicles and future mobile networks make transmission capacity a concrete concern for countries developing those industries.

The immediate achievement is a laboratory demonstration of enormous capacity over a long distance within a standard fiber diameter. Its future usefulness will depend on the testing, equipment and investment needed to turn that combination into a working telecommunications service.

Key Points

• NICT announced transmission at 1.02 petabits per second across 1,802 kilometers, or about 1,120 miles.
• The experiment used 19 cores inside an optical fiber measuring 0.127 millimeters in diameter.
• Amplification, wavelength division multiplexing, 21 passes through a transmission system and digital processing supported the result.
• The reported capacity exceeded 125,000 gigabytes per second, more than twice the cited 2024 record of 50,250 gigabytes per second.
• The capacity-distance product reached a reported record of 1.86 exabits per second-kilometer for standard sized fiber communication.
• Potential applications include cloud computing, AI, autonomous vehicle networks and connected city services.
• As of July 18, 2025, independent verification, further testing and network equipment upgrades remained necessary before commercial deployment.