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NEC brings AI to submarine cable networks

NEC Corporation announced that successful transmission tests that took place over a commercial subsea cable measuring more than 10,000 kilometers using artificial intelligence (AI) and probabilistic shaping at a modulation of 64QAM.

NEC, in a joint research publication with Google, has demonstrated for the first time that the faster open subsea cable can be upgraded to a spectral efficiency of 6 bits per second per hertz (b/s/Hz) in an 11,000km segment. 

This represents a capacity of more than 26 terabits per second (Tb/s) in the C-band, which is over 2 1/2 times the capacity originally planned for the cable, for no additional wet plant capital expenditure. 

In doing so, the authors set a spectral efficiency-distance product record of 66,102 b/s/Hz in a field trial performed together with live traffic through neighbouring channels.

The team achieved this result using near-Shannon probabilistic-shaping at a modulation of 64QAM, and for the first time on a live cable, artificial intelligence (AI) was used to analyze data for the purpose of nonlinearity compensation (NLC). 

NEC developed an NLC algorithm based on data-driven deep neural networks (DNN) to accurately and efficiently estimate the signal nonlinearity.

These field trial results were recently presented at the post-deadline session of the Optical Fiber Communication Conference and Exhibition (OFC) 2018 in San Diego, California. 

The experimental demonstration of NLC achieved a generalized mutual-information (GMI) capacity gain of -0.15 b/s/2-pol, which is equivalent to a capacity increase of 15 gigabits per second (Gb/s) in every 100GHz of fiber bandwidth. 

NEC announced plans to continue this AI-based research, with the dual aims of increasing system capacity while reducing the complexity of implementation.

NEC has more than 40 years of experience in the submarine cable business and is recognized as one of the world's top submarine system vendors. 

NEC has laid a total of more than 250,000 kilometers of submarine cable, the equivalent of six trips around the earth. 

As a total system integrator, NEC produces optical submarine cable, optical submarine repeaters and equipment for connecting optical transmissions to land, in addition to carrying out ocean surveys, route design, laying optical submarine cable and training personnel for the handover of these systems.