Why it matters: A technological leap in fiber optics has shattered previous limitations, achieving what experts once considered impossible: transmitting data at 1.02 petabits per second – enough to download every movie on Netflix 30 times over – across 1,808 kilometers using a single fiber no thicker than a human hair.

At the heart of this breakthrough – driven by Japan’s National Institute of Information and Communications Technology (NICT) and Sumitomo Electric Industries – is a 19-core optical fiber with a standard 0.125 mm cladding diameter, designed to fit seamlessly into existing infrastructure and eliminate the need for costly upgrades.

Each core acts as an independent data channel, collectively forming a “19-lane highway” within the same space as traditional single-core fibers.

Unlike earlier multi-core designs limited to short distances or specialized wavelength bands, this fiber operates efficiently across the C and L bands (commercial standards used globally) thanks to a refined core arrangement that slashes signal loss by 40% compared to prior models.

The experiment’s success relied on a complex recirculating loop system. Signals traveled through an 86.1-kilometer fiber segment 21 times, simulating a cross-continental journey equivalent to linking Berlin to Naples or Sapporo to Fukuoka.

To maintain integrity over this distance, researchers deployed a dual-band optical amplification system, comprising separate devices that boosted signals in the C and L bands. This enabled 180 distinct wavelengths to carry data simultaneously using 16QAM modulation, a method that packs more information into each pulse.

At the receiving end, a 19-channel detector, paired with advanced MIMO (multiple-input multiple-output) processing, dissected interference between cores, much like untangling 19 overlapping conversations in a crowded room.

Schematic diagram of the transmission system

This digital signal processor, leveraging algorithms developed over a decade of multi-core research, extracted usable data at unprecedented rates while correcting for distortions accumulated over 1,808 km.

The achievement caps years of incremental progress. In 2023, the same team achieved 1.7 petabits per second, but only across 63.5 km. Earlier efforts using 4-core fibers reached 0.138 petabits over 12,345 km by tapping the less practical S-band, while 15-mode fibers struggled with signal distortion beyond 1,001 km due to mismatched propagation characteristics.

The new 19-core fiber’s uniform core design sidesteps these issues, achieving a capacity-distance product of 1.86 exabits per second per kilometer – 14 times higher than previous records for standard fibers.

Image diagram of 19-core optical fiber.

Presented as the top-rated post-deadline paper at OFC 2025 in San Francisco, this work arrives as global data traffic is projected to triple by 2030.

While challenges remain, such as optimizing amplifier efficiency and scaling MIMO processing for real-world use, the technology offers a viable path to petabit-scale networks. Researchers aim to refine production techniques for mass deployment, potentially enabling transoceanic cables that move entire data centers’ worth of information hourly.

Researchers aim to refine production techniques for mass deployment, potentially enabling transoceanic cables that move entire data centers’ worth of information hourly.

Sumitomo Electric’s engineers, who designed the fiber’s coupled-core architecture, note that existing manufacturing lines can adapt to produce the 19-core design with minimal retooling.

Meanwhile, NICT’s team is exploring AI-driven signal processing to further boost speeds. As 6G and quantum computing loom, this breakthrough positions fiber optics not just as a backbone for tomorrow’s internet, but as the central nervous system of a hyperconnected planetary infrastructure.

What just happened? The Trump administration has announced a significant shift in the $42.45 billion Broadband Equity, Access, and Deployment (BEAD) program, eliminating the preference for fiber Internet infrastructure. This change is expected to redirect substantial funding towards non-fiber technologies, such as Elon Musk’s Starlink satellite service, potentially allocating between $10 billion and $20 billion to such providers.

This move marks a departure from the Biden administration’s approach, which emphasized fiber-optic networks as the most future-proof and reliable option for broadband deployment.

The BEAD program was authorized by Congress in November 2021, with the National Telecommunications and Information Administration (NTIA) developing rules under the Biden administration. These rules prioritized end-to-end fiber-optic architecture due to its ability to be easily upgraded by replacing equipment at the ends of fiber-optic facilities.

This approach also supports the deployment of 5G and other advanced wireless services, which rely heavily on fiber for backhaul. However, the Trump administration has criticized these rules as overly restrictive and ineffective.

Secretary of Commerce Howard Lutnick has been vocal about the need for change, stating that the program has not connected anyone to the Internet due to “woke mandates, favoritism towards certain technologies, and burdensome regulations.”

The Trump administration is adopting a “tech-neutral” approach to provide Internet access at the lowest cost to taxpayers. This shift includes exploring ways to cut government red tape that slows down infrastructure construction to deliver high-speed Internet access efficiently and effectively.

The decision to end the fiber preference has been criticized by Democrats and advocacy groups. House Commerce Committee Ranking Member Frank Pallone, Jr., accused Republicans of undermining efforts to deploy reliable and affordable broadband, labeling Elon Musk as a “grifter.”

The Benton Institute for Broadband & Society expressed concerns that the shift could leave millions with slower and less reliable Internet, as fiber broadband offers faster speeds, higher bandwidth, and symmetrical upload and download speeds, making it ideal for demanding applications like telehealth and gaming.

Despite these concerns, the Trump administration is moving forward with changes, aiming to reduce bureaucratic hurdles and expedite infrastructure construction. Republicans are also proposing legislative changes to eliminate what they see as burdensome conditions imposed by the Biden administration.

Meanwhile, Starlink could benefit significantly from these changes, potentially gaining access to substantial funding through both the BEAD program and other federal initiatives. The Federal Communications Commission could also direct more money to Starlink through universal service programs, although the FCC is not directly involved in the BEAD program.

The shift in policy has also raised questions about conflicts of interest, particularly given Elon Musk’s role in the Trump administration. Recent reports suggest that Starlink could take over a $2 billion contract with the Federal Aviation Administration, although SpaceX has denied seeking to replace existing contracts. The FCC’s newly appointed chairman, Brendan Carr, has expressed support for Starlink, potentially paving the way for future grant awards.