Standard Multi-Core Fiber Transmits 40.5 Petabits per Second

Optical Data Transmission Standard Multi-Core Fiber Transmits 40.5 Petabits per Second

2026-09-22 By Dipl.-Ing. (FH) Hendrik Härter | Translated by AI 2 min Reading Time

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Japanese researchers have succeeded in increasing the data rate in optical fibers to over 40 petabits per second. The standard cladding diameter of 125 µm (0.0049 inches) plays a key role in this. This is the only way to ensure compatibility with existing manufacturing processes and connection technologies.

More and more data must be modulated onto light waves and transmitted through the global fiber-optic network. Japanese researchers are now pushing the limits of the physics of this transmission even further.(Image: freely licensed / Pixabay) — More and more data must be modulated onto light waves and transmitted through the global fiber-optic network. Japanese researchers are now pushing the limits of the physics of this transmission even further.
(Image: freely licensed / Pixabay)

The National Institute of Information and Communications Technology (NICT) in Japan has once again raised the bar for spectral efficiency in optical data transmission. A team of researchers succeeded in transmitting 40.5 Pbit/s over a distance of 50 km (31.1 miles).

The key technical aspect of this record lies not only in the absolute data rate, but in the combination of extreme spectral efficiency and an industry-compatible fiber geometry. The researchers used a multicore fiber (MCF) with four cores but retained the standard cladding diameter of 125 µm.

Massive Spectral Expansion and Modulation

Basic architecture of the transmission system. The diagram illustrates the multiplexing of the S-, C-, and L-band signals onto the four cores of the MCF, as well as the required broadband amplification and subsequent MIMO DSP processing in the receiver.(Image: NICT) — Basic architecture of the transmission system. The diagram illustrates the multiplexing of the S-, C-, and L-band signals onto the four cores of the MCF, as well as the required broadband amplification and subsequent MIMO DSP processing in the receiver.
(Image: NICT)

To achieve this capacity in a standard-diameter fiber, the engineers had to expand the optical spectrum used far beyond the usual C- and L-bands. Transmission took place over a combined bandwidth of approximately 20 THz, distributed across the S, C, and L bands.

The most technically challenging aspect here is the varying attenuation and dispersion characteristics of the bands. To achieve the necessary spectral efficiency, NICT relied on sophisticated modulation schemes. Signals with high-order probabilistic constellation shaping (PCS)—typically ranging from 64 QAM to 256 QAM—were used, adapted to the respective signal-to-noise ratio (SNR) of the different spectral bands.

Photonic Circuits

Maintaining the 125-µm standard for four cores increases crosstalk between the cores. Compensating for this crosstalk requires complex MIMO (Multiple-Input Multiple-Output) algorithms in the digital signal processor (DSP) on the receiver side.

For hardware developers in the field of optical communications, the results point to two trends: First, the increased use of broadband optical amplifiers (e.g., doped fiber amplifiers for the S-band in addition to EDFAs) that extend beyond the C+L window commonly used today.

Second, the growing demand for high-performance DSPs capable of handling both chromatic dispersion over a bandwidth of 20 THz and inter-core crosstalk in real time. The experiment demonstrates that it is possible to scale fiber capacity without having to fundamentally change the established infrastructure for splicing and connection technology.

In contrast to WLAN and other wireless technologies, Li-Fi Grathus uses light signals. This has a decisive advantage: the transmission is insensitive to electromagnetic interference (EMC). The picture shows two modules of the evaluation kit. (Image:Fraunhofer IPMS)

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