NICT and NTT announce world records for ultra-large-capacity optical fiber transmission: Results accepted as an 'outstanding paper' at ECOC 2023

During the 49th European Conference on Optical Communications (ECOC 2023) held in Glasgow, UK, a paper authored by an international collaborative research team led by the Photonic Network Laboratory at the National Institute of Information and Communications Technology (NICT) garnered significant recognition. The paper reported the achievement of the world's largest transmission capacity, reaching 22.9 petabits per second using a single optical fiber. This paper was selected as the post-deadline paper.

During the same conference, a paper submitted by NTT, reporting the successful implementation of a 1.6 Terabit optical transmission experiment using a multi-core fiber cable in a field environment, was accepted as the top-scoring paper. These outstanding papers, presenting world record-breaking results, were presented during the conference on October 5.

NICT has successfully integrated multi-band wavelength division multiplexing and spatial multiplexing over a multi-core multi-mode fiber. This was accomplished by adapting the MIMO receiver within the 38-core 3-mode optical fiber transmission system, which demonstrated a 10.66 petabits per second data-rate in 2020, for multi-band transmission. The institute announced the successful demonstration of an ultra-data-rate optical communications system, achieving a total of 22.9 petabits per second.

A total of 750 wavelengths were employed in this optical communication system, with 293 wavelengths allocated to the S-band and 457 to the C- and L-bands. These wavelengths utilized a frequency bandwidth of 18.8 THz.

A polarization-multiplexed 256-QAM signaling, carrying a substantial volume of information, was used for the modulation. The number of optical paths was increased by a factor of 28.5 compared to the experiment conducted with a 4-core fiber having approximately same frequency bandwidth. A transmission capacity ranging from approximately 0.3 to 0.7 petabits per second per core was achieved, resulting in a total transmission capacity of 22.9 petabits per second across all 38 cores. This is equivalent to approximately 1,000 times the transmission capacity of existing commercial optical communication systems, representing more than a two-fold increase in transmission capacity compared to the record NICT set three years ago.

Currently, the practical implementation of 4-core fiber is actively underway. However, further improvement of the telecommunication infrastructure will be needed in the future, where the data traffic demand is expected to increase by 3 orders of magnitude (x1,000 times).

The present result by NICT showed the first successful combination of multi-band WDM and SDM employing a multicore multimode fiber, which is key to the realization of future ultra-large-capacity optical fiber communication networks.

Meanwhile, NTT has demonstrated transmission and reception of IM-DD optical signals exceeding 400 gigabits per second per lane in the Ethernet standard 1.3-micrometer wavelength band (O-band). Furthermore, NTT announced that it was the first company in the world to successfully transmit ultra-high-speed IM-DD signals at a data-rate of 1.6 terabits per second per fiber across a 10-kilometer field environment.

This achievement was realized through the advanced integration of NTT's proprietary ultra-wideband baseband amplifier IC module, ultra-high-precision digital signal processing technology, and spatial multiplexing transmission technology employing multi-core fiber.

One notable component is the ultra-wideband baseband amplifier IC module developed by NTT. This module features an ultra-wideband baseband amplifier IC with the world's most extensive bandwidth and is housed within a package equipped with a 1 mm coaxial connector, capable of accommodating frequencies up to 110 gigahertz.

The amplifier IC is the result of applying NTT's proprietary high-precision circuit design technology and new circuit architecture technology, enabling the attainment of wide bandwidth capabilities through the utilization of InP-HBT technology.

The multicore fiber employed in the experiment was a 4-core fiber cable laid in an underground facility at NTT Laboratories. This setting was chosen to simulate real-world cable installation conditions. This 4-core fiber has an identical cladding outer diameter of 125 micrometers as existing fibers, and each core maintains a simple step-index refractive index structure, consistent with conventional fiber designs. This feature makes it highly suitable for mass production.

This achievement demonstrates the potential for substantial enhancements in the scalability of large-scale data center networks. It demonstrates a capacity that is four times greater than the conventional practical standard, positioning it as a core technology for the forthcoming era of next-generation Ethernet.