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Multi-core fiber in undersea cables dramatically increases data transmission rates

In the era of wireless networks and smart devices connected to the global Internet, undersea cables are a vital artery for data transmission. More than 400 submarine cables are used to connect the world across oceans, and these cables require constant upgrades to ensure they can support the increasing bandwidth demanded of them.

Hitoshi Takeshita is part of a team of researchers developing the first uncoupled 4-core multi-core fiber in an undersea cable. It will showcase its prototype at the 2022 Optical Fiber Communication (OFC) Conference & Exhibition on Monday, March 07 which will be held at San Diego Congress Palace.

“We have demonstrated that the optical transmission performance through the 4-core uncoupled cabled multi-core fiber fully meets the requirements of modern long-distance submarine cables,” said Hitoshi TakeshitaSystem Platform Research Laboratories, NEC Corporation.

The researchers built a prototype cable using an SC520 type submarine cable, which can withstand water pressures at a depth of 8,000 meters and can contain 16 fiber pairs. The team used four multi-core and 12 single-core fiber pairs in their prototype.

More importantly, the team built their 4-core fiber design to the same dimensions as a single-core fiber, managing to significantly increase the capacity of the cable without increasing its size or reducing the number of fiber pairs.

“Multi-core fiber is now expected to further increase the number of parallel fiber optic cores without increasing the size and structure of the undersea cable, enabling the second generation of SDM (spatial division multiplexing) undersea systems,” Takeshita said. .

With the conductors being so close together and the cable experiencing additional stress due to the underwater environment, considerable effort is required to ensure minimum interference between the conductors. In their trial, testing showed inter-core crosstalk to be negligible.

It is equally important to reduce signal attenuation along the entire length of the cable. For an undersea cable that is one day expected to span hundreds or even thousands of miles, it is essential to ensure that the signal remains strong throughout the length of the cable. In particular, the team needed to ensure that the multi-core fiber would not experience additional attenuation during cabling.

“It has never been demonstrated how multi-core fiber would perform when wired inside an undersea cable, with different bending and tension, as is typically assessed in a lab experiment” , said Takeshita. “Because submarine transmission is ultra-long transport, even slight variations in cabled fiber properties have a significant impact on system performance as they accumulate over distance.”

To achieve reduced inter-core crosstalk and better signal attenuation, the team embedded a multi-core fiber amplifier into the cable, directly splicing the amplifier with the fiber. This reduced cable clutter and improved performance.

The researchers hope their multi-core fiber bundled in an undersea cable will be used to increase data transmission rates as demand increases over the next few years.

“The use of international data is expected to grow, due to factors such as the growth of 5G mobile data and the need to share ever more content between data centers distributed around the world,” Takeshita concluded. “To meet this demand, submarine networks should adopt spatial division multiplexing technology using multi-core fiber.”

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About OFC
The 2022 Optical Fiber Communication Conference and Exhibition (OFC) is the premier conference and exhibition for optical communications and networking professionals. For more than 45 years, OFC has attracted participants from all corners of the world to meet and greet, teach and learn, make connections and drive business forward.

OFC features dynamic business programming, global business exposure and high-impact, peer-reviewed research that, combined, showcases the trends shaping the entire optical networking and communications industry. OFC is co-sponsored by the IEEE Communications Society (IEEE/ComSoc) and the IEEE Photonics Society and co-sponsored and managed by Optica (formerly OSA). OFC in 2022 will be presented in a hybrid format with in-person and virtual components and will take place 06-10 March 2022 to San Diego Congress Center at San Diego, California, UNITED STATES. Follow on Twitter @OFConferencelearn more on OFC Community LinkedIn and watch highlights on OFC YouTube.

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SOURCE Optical Fiber Communication (OFC) Conference and Exhibition