Highlights

- Demonstration of spatial-division-multiplexed network based on the first field-deployed 15-mode fibers
- The world’s first successful optical switching of 15-mode multiplexed signals by spatial optical switch prototype
- A major step toward the realization of a backbone communication system that supports various information communication services after Beyond 5G

Abstract

A group of researchers from the Network Research Institute of the National Institute of Information and Communications Technology (NICT, Japan) led by Ruben Soares Luís, in collaboration with the University of L'Aquila (Italy), Heinrich-Hertz-Institute, Fraunhofer Institute for Telecommunications (HHI, Germany), Finisar Australia (Australia), Prysmian Group (Italy, Holland, France), and Nokia Bell Labs (Bell Labs, USA) achieved the first demonstration of a field deployed 15-mode optical fiber network, equivalent to 15 parallel fiber networks using a single fiber installed in the city of L’Aquila, Italy.

So far, mode-division-multiplexed fiber communication networks have been demonstrated only in a laboratory environment and the number of switching modes was limited to 10. In this demonstration, the world’s first field-deployed 15-mode fiber with standard cladding diameter, installed in the city of L’Aquila, Italy, was used to support a network node capable of switching up to six 15-mode spatial super channels, each carrying up to 5 terabit per second (Tbit/s) signals using mode-multiplexing. This was equivalent to implementing 15 parallel optical fiber networks using a single fiber and a single network node, demonstrating the potential for spatial division multiplexing (SDM) systems to greatly extend the capacity of current fiber networks in a realistic environment. The metropolitan 15-mode fiber network was a 6.1 km long and installed in an underground tunnel in the city of L’Aquila. The 15-mode network node was the first 15-mode reconfigurable optical add and drop multiplexer (ROADM), which used reprogrammed conventional wavelength selective switches (WSS). This allowed using the same switch fabric to simultaneously switch multiple modes to greatly reduce the overall cost of the system.

This demonstration shows that mode-multiplexing over multi-mode fibers with a standard cladding diameter, which are compatible with current cabling technologies and have a high spatial channel count, can be adopted in deployed networks and is a significant step toward the realization of a backbone communication systems to support various information communication services after Beyond 5G.

The results of this experiment were accepted as a post-deadline paper presentation at the 48th European Conference on Optical Communication (ECOC 2022) and presented on Thursday, September 22, 2022 local time.

Background

High-capacity SDM technologies have been under research and development, in order to cope with the ever-increasing traffic volume. Previously, NICT has successfully demonstrated high-capacity transmission and switching supported by multi-core optical fibers. However, the use of multi-mode fiber network systems, which have improved spatial density (number of channels per fiber) have been in development. Optical switching of 10 modes or less per multi-mode fiber in a laboratory environment has been demonstrated. Nevertheless, further expansion of the number of modes and verification in a real-world environment are to be expected.

Achievements

NICT and its partners have implemented a 15-mode fiber network utilizing multi-mode fibers of a field deployed testbed in the city of L’Aquila, Italy. The deployed 15-mode fibers were used to demonstrate mode-multiplexed transmissions up to 48.8 km (8 rounds). In addition, optical switching of 15-mode multiplexed signals using field-deployed fibers was achieved for the first time.

The SDM optical switch prototype was constructed using conventional wavelength selective switches (WSS) programmed to handle signals from multiple modes simultaneously. Effectively, each WSS was equivalent to 5 wavelength cross-connects (WXCs), each with a 2×2 switching capability. A total of 3 WSS were used to switch a total of 15 modes per fiber. A transmitter and the WXC node supporting 15-mode multiplexed signals were located in the facilities of the University of L’Aquila and connected to a field-deployed 6.1 km 15-mode fiber ring.

In the demonstration of optical switching, 15-mode signals with 6 wavelengths were generated. Each wavelength corresponded to a 15-mode spatial super channels with 5 Tbit/s capacity and the total data rate per fiber was 30 Tbit/s. At the network node, the path of each wavelength of the mode-multiplexed signals was directed according to the programmed configuration. Three general functions of a ROADM system were evaluated, including add/drop of all wavelengths, express pass of all wavelengths, and partial express or add/drop of individual wavelengths. For all cases, mode-multiplexed signals were appropriately received after optical switching.

Although mode multiplexing requires digital signal processing at the receiver to compensate for a mode mixing, a mode-multiplexed network utilizing multi-mode fibers with standard diameters can provide a high-density, high-capacity network at low cost. The multi-mode fibers are easy to manufacture, compatible with existing cable technology, and can provide a high-density, high-capacity network at low cost. This demonstration of optical transmission and switching of mode-multiplexed signals on the testbed is an important step toward accelerating research on mode-multiplexed communications and realizing a backbone communication system that supports the evolution of various information services through Beyond 5G.

Future Prospects

In the future, we will establish a foundation for future large-capacity optical transmission technology while working to extend the distance of large-capacity multimode optical fiber transmission, expand the scale of optical switching, and pursue the possibility of merger with multi-core technology.

The results of this experiment were published at the 48th European Conference on Optical Communications (ECOC 2022, September 2022), one of the largest international conferences related to optical fiber communications held in Basel, Switzerland. It was selected as the best hot topic paper (Post Deadline Paper) and published on September 22 (Thursday).

Responsibilities of each organization

NICT: Demonstration experiment of optical switching, prototype of 15-mode optical switch, analysis of experimental data
L'Aquila University: Construction of a 15-mode optical fiber in the testbed
HHI: Building a 15-mode transceiver
Finisar: Development of control program for wavelength selective switch for 15-mode optical switch
Prysmian: Provide 15-mode fiber cable
Bell Labs: Construction of 15-mode fiber connection

References

European Conference on Optical Communication (ECOC2022)
Title: Characterization of the First Field-Deployed 15-Mode Fiber Cable for High Density Spatial Division Multiplexing
Authors: Georg Rademacher, Ruben S. Luis, Benjamin J. Puttnam, Giammarco Di Sciullo, Robert Emmerich, Nicolas Braig-Christophersen, Andrea Marotta, Lauren Dallachiesa, Roland Ryf，Antonio Mecozzi, Colja Schubert, Pierre Sillard, Frank Achten, Giuseppe Ferri, Jun Sakaguchi, Cristian Antonelli, Hideaki Furukawa

Title: Demonstration of a Spatial Super Channel Switching SDM Network Node on a Field Deployed 15-Mode Fiber Network
Authors: Ruben S. Luis, Georg Rademacher, Benjamin J. Puttnam, Giammarco Di Sciullo, Andrea Marotta, Robert Emmerich, Nicolas Braig-Christophersen, Ralf Stolte, Fabio Graziosi, Antonio Mecozzi, Colja Schubert, Frank Achten, Pierre Sillard, Roland Ryf，Lauren Dallachiesa, Satoshi Shinada, Cristian Antonelli, Hideaki Furukawa

Previous NICT press releases

- World's First Successful Transmission of 1 Petabit per Second Using a Single-core Multimode Optical Fiber
https://www.nict.go.jp/en/press/2020/12/18-1.html
- First Demonstration of a 1 Petabit per Second Network Node
https://www.nict.go.jp/en/press/2019/10/17-1.html

 

 

 

 

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