A World Record Transmission in an Optical Fiber

Experimental setup of the record transmission of 1 petabit per second in a multimode optical fiber. (Source: NICT)

A group of researchers from the Network System Research Institute of the National Institute of Infor­mation and Communi­cations Technology (NICT, Japan) led by Georg Rademacher, Nokia Bell Labs (Bell Labs, USA) led by Nicolas K. Fontaine and Prysimian Group (Prysimian, France) led by Pierre Sillard succeeded in the world’s first trans­mission exceeding 1 petabit per second in a single-core multi-mode optical fiber. This increases the current record trans­mission in a multi-mode fiber by a factor of 2.5.

To date, trans­mission experiments in optical fibers supporting large number of modes was limited to small optical bandwidths. In this study, the researchers demonstrated the possi­bility of combining highly spectral efficient wideband optical trans­mission with an optical fiber guiding 15 fiber modes that had a cladding diameter in agreement with the current industry standard of 0.125 mm. This was enabled by mode multi­plexers and an optical fiber that supported wideband trans­mission of more than 80 nm over a distance of 23 kilometers.

The study highlights the large potential of single-core multi-mode fibers for high capacity trans­mission using fiber manu­facturing processes similar to those used in the production of standard multi-mode fibers. Over the past decade, intensive research was carried out worldwide to increase the data rates in optical transmission systems using space-division multi­plexing in order to accom­modate the expo­nentially increasing data trans­mission requirements. Compared to multi-core optical fibers, multi-mode fibers can support a higher spatial-signal-density and are easier to manufacture. However, using multi-mode fibers for high capacity space-division multiplexed transmission requires the use of computa­tionally intensive digital signal processing. These requirements increase with the number of trans­mission modes and realizing transmission systems supporting large number of fiber modes is an active field of research.

At NICT, a transmission experiment was designed and carried out that utilized the transmission fiber made by Prysmian and mode multi­plexers developed by Bell Labs. A wideband transceiver subsystem was developed to transmit and receive several hundred highly spectral efficient WDM channels of high signal quality. The novel mode multiplexers were based on a multi-plane light conversion process where the light of 15 input fibers was reflected multiple times on a phase plate to match the modes of the transmission fiber. The trans­mission fiber was 23 km long and had a graded-index design. It was based on existing multi-mode fiber designs that were optimized for wideband operation and had a cladding diameter of 0.125 mm and a coating diameter of 0.245 mm, both adhering to the current industry standard. The transmission system demonstrated the first transmission exceeding 1 petabit per second in a multi-mode fiber increasing the current record demons­tration by a factor of 2.5.

When increasing the number of modes in a multi-mode fiber transmission system, the computational complexity of the required MIMO digital signal processing increases. However, the used transmission fiber had a small modal delay, simplifying the MIMO com­plexity and maintained this low modal delay over a large optical bandwidth. As a result, we could demons­trate the transmission of 382 wavelength channels, each modulated with 64-QAM signals. The success of large-capacity transmission using a single-core multimode optical fiber, which has a high spatial signal density and easy manu­facturing technology, is expected to advance high-capacity multimode trans­mission technology for future high capacity optical transmission systems.

In the future, the researchers would like to pursue the possi­bility of extending the distance of large-capacity multi-mode trans­mission and integrating it with multi-core technology to establish the foundation of future optical trans­mission techno­logy with large capacity. (Source: NICT)

Reference: G. Rademacher et al.: 1.01 Peta-bit/s C+L-band transmission over a 15-mode fiber, Post Deadline Paper, International Conference: European Conference on Optical Communication ECOC2020, Bruxelles, Belgium

Link: Photonic Network System Laboratory, National Institute of Information and Communications Technology, Tokyo, Japan

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