Japan sets new world record for internet speed: 4 million times faster than the US average

A team in Japan set a new world record in fiber optics, reaching a data speed of 1.02 petabits per second over roughly 1,123 miles with a new kind of optical fiber. The achievement yielded a capacity–distance product of 1.86 exabits per second per mile.

That rate is about four million times higher than the U.S. median fixed broadband download speed of about 285 Mbps.

Lead researcher Hideaki Furukawa of the National Institute of Information and Communications Technology (NICT) in Japan guided the transmission experiments and system work.

A paper presented at the Optical Fiber Communication Conference and Exhibition (OFC) 2025 reported these results.

Inside the redesigned optical fiber

The cable fits 19 light paths inside a cladding that measures about 0.005 inches, the same size used by most existing lines. This design allows it to slot into current routes without changing the outside diameter.

The cores share a single glass cladding and are engineered to behave the same way, so the light follows a uniform path through each core.

This uniform behavior reduces power swings and lowers loss in both the C band and L band – the primary wavelength ranges for long-distance links.

The design also avoids the spacing penalties of uncoupled multicore layouts, where engineers minimize crosstalk by spacing cores farther apart.

In a coupled layout, the system allows mixing between cores and later corrects it using digital processing at the receiver.

Low fiber loss across wide wavelengths, combined with predictable coupling, made long range and high rate possible at the same time.

Earlier projects achieved fast signals over much shorter spans, but this approach pushes capacity and reach together.

Breaking down the jargon

A petabit equals one million gigabits, a unit that marks a leap beyond the gigabit tier common to residential plans.

The capacity–distance product multiplies data rate by distance to compare systems that go fast, far, or both.

A multicore fiber places several cores inside one cladding so that many signals travel in parallel. MIMO is a digital filter that separates mixed signals from different cores or modes, allowing the original data streams to emerge cleanly.

Long-haul optical links use the C band and L band as their main wavelength windows because standard amplifiers operate efficiently in those ranges.

The 16-state Quadrature Amplitude Modulation (16QAM) method stores more information per symbol than simpler formats, raising data rates when noise and distortion are controlled.

Fiber speed experiment

The team built 19 synchronized recirculating loops, each fed by one core of a 53.5-mile spool that included splitters, combiners, amplifiers, and a control switch.

A switch sent the signal around the loop 21 times before it reached a bank of receivers, producing the full end-to-end distance.

They lit 180 wavelengths across the C and L bands and modulated each with 16QAM, a higher-order format that increases bits per symbol when conditions are clean enough.

Multiple wavelengths across two bands gave the system a wide runway for total throughput.

At the end, a coherent 19 channel receiver separated spatial channels while a MIMO engine untangled the mixed signals introduced by the coupled cores.

Error correction code finished the job and produced the net payload figure used to report the result.

How distance impacts fiber speed

Short bursts in a lab are one thing; dependable hauls between cities are another. Long spans expose loss, amplifier noise, nonlinear effects, and chromatic dispersion that often remain hidden on short test beds.

Engineers track progress in optical fiber systems with the capacity-distance product, which multiplies rate by distance to summarize both speed and reach in a single number.

A higher product means a system can carry more bits for longer without running out of margin.

This demonstration shows that dense spatial channels inside a standard-sized fiber, combined with broad wavelength use and shared amplification, can lift that product.

It achieves this without changing the outside fiber size – a practical way to scale, since networks care about what fits in ducts, trays, and connectors.

What it could mean for networks

A key choice was keeping the cladding diameter at about 0.005 inches, which matches the size used by most installed fiber and the tools built around it. 

“For fiber fabrication and deployment, it is highly beneficial to use fibers with a standard cladding diameter,” said Menno van den Hout from the National Institute of Information and Communications Technology.

Keeping dimensions and interfaces familiar lowers the barrier to field trials and later deployment if costs align.

It also enables step-by-step rollouts, where multicore spans boost capacity on tough segments while other spans remain single-core.

The idea of space-division multiplexing has been studied for more than a decade, and its value has been demonstrated across many experiments.

“This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibers to expand the data carrying capacity of optical communications,” said Benjamin Puttnam of the National Institute of Information and Communications Technology.

The study is published in the OFC 2025 postdeadline proceedings.

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