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The data transmission system uses 4-core optical fiber and sets a distance record | Technological impulse | October 2021

A research team led by Benjamin J. Puttnam of the National Institute of Information and Communication Technologies (NTIC) reported that it transmitted data over a distance of more than 3000 km (1860 miles) to a throughput of 319 Tbit/s and a transmission bandwidth of more than 120 nm, on the S, C and L bands.

The team used a 4-core optical fiber with an outer diameter of 0.125mm to transmit the data, setting a record for data transmission over an optical fiber with a standard clad diameter. The signal bandwidth of the long distance transmission included 552 wavelength division multiplexing (WDM) channels.

The system uses WDM and a combination of optical amplification technologies to enable long distance transmission of 552 WDM channels ranging from 1487.8 to 1608.33 nm. The team constructed a transmission loop combining erbium and thulium doped fiber amplifiers with distributed Raman amplification along the fiber itself to allow recirculation of wideband signal transmission.

By combining various amplification technologies, the researchers built a transmission system that capitalized on the strengths of WDM technology.

The Raman amplification part of the transmission system. Courtesy of the National Institute of Information and Communication Technologies.

The system measured the transmission rate achievable with each channel with PDM-16QAM modulation at distances up to 3001 km, where the data rate of 319 Tbit/s was achieved.

In addition to the C and L bands typically used for high-speed long-distance transmission, the researchers included the S-band in their transmission. Until now, NICT had only built transmission systems that used C- and L-band WDM, along with state-of-the-art modulation technology, to explore high-speed transmission in optical fibers.

Although S-band transmission has led to several new transmission capacity records in optical fibers, the transmission distance in S-band has so far been limited to only a few tens of kilometers.

The NICT team hopes its achievement will pave the way for systems capable of supporting optical communications at the data rates needed for 5G and beyond. The reported transmission demonstrates the potential of space division multiplexing (SDM) fibers to support near-term high-speed SDM fiber systems, provided they are compatible with existing cabling technologies. The standard cladding diameter 4-core fiber used for the demonstration is compatible with conventional cable infrastructure, and the researchers estimate that its mechanical reliability is comparable to that of single-mode fibers.

Graphic illustrating transmission demonstrations using 125 µm diameter fibers.  Courtesy of the National Institute of Information and Communication Technologies.

A graph illustrating transmission demonstrations using 125 μm diameter fibers. Courtesy of the National Institute of Information and Communication Technologies.

NICT said it plans to work to extend its transmission range to transoceanic distances, as well as continue to develop broadband and long-distance data transmission systems to increase the transmission capacity of low-core-count multicores. and other new SDM fibers.

The research was presented at the International Conference on Optical Fiber Communications (OFC), held June 6-11.