Transmission experiments in optical fibers supporting an enormous number of modes were restricted to small optical bandwidths. In a new study, scientists exhibited the possibility of combining exceptionally spectral efficient wideband optical transmission with an optical fiber guiding 15 fiber modes with a cladding diameter in agreement with the current industry standard of 0.125 mm.
Scientists 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 Prysmian Group (Prysmian, France) led by Pierre Sillard succeeded in the world’s first transmission exceeding one petabit per second in a single-core multimode optical fiber.
The study highlights the large potential of single-core multimode fibers for high capacity transmission using fiber manufacturing processes similar to those used to produce standard multimode fibers.
Scientists designed the experiment and conducted it using the transmission fiber. 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 transmission fiber modes. The transmission fiber was 23 km long and had a graded-index design. It was based on existing multimode fiber designs optimized for wideband operation. It 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 multimode fiber increasing the current record demonstration by 2.5.
When scientists increased the number of modes in the transmission system, the computational complexity of the required MIMO digital signal processing increases. Although, there was a small modal delay in used transmission fiber. This simplified the MIMO complexity and maintained this low modal delay over a large optical bandwidth.
Hence, scientists were able to 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.
Scientists noted, “In the future, we would like to pursue the possibility of extending the distance of large-capacity multimode transmission and integrating it with multi-core technology to establish the foundation of future optical transmission technology with large capacity.”
The paper on this experiment’s results was published at the 46th European Conference on Optical Communication (ECOC2020, December 6th—10th 2020), which is one of the largest international conferences related to optical fiber communication.