NTT has completed a field trial of 400 Gbps optical signals on its existing network without affecting existing 100G channels as it added and removed 400G channels in a 100G WDM system.
During the trial, the service provider leveraged installed dispersion shifted fiber (DSF) cable with polarization mode dispersion (PMD).
In addition, NTT applied advanced 400G digital coherent optical transmission techniques with novel waveform distortion compensation techniques, and confirmed the high performance in 400G optical transmission compared to its conventional digital signal processing techniques.
The service provider said the additional 400 Gbps channels and the existing 100 Gbps channels did not cause mutual degradation from the viewpoint of the transmission characteristics.
Two of the experimental configurations it applied during the trial were 16 Quadrature Amplitude Modulation (16QAM) and Sub-Carrier Wavelength Multiplexing, which superimposed 200 Gbps information on the amplitude and phase of the light per sub-carrier, and integrated two sub-carrier wavelengths to compose a single 400 Gbps channel. NTT said these "technologies enable us to expand the optical communication capacity of the installed 100-Gbps systems up to four fold."
NTT also said it confirmed "that the addition and removal of the 400-G channels in the existing 100-G-based WDM system did not affect the communication performance of the other channels, although the communication performance was anticipated to degrade."
Based on the trial results, NTT Corporation and NTT Communications plan to establish optical transport systems, including optical fiber cables, and apply them commercially for a number of uses. Some of these uses may be for 400 Gbps technology and other flexible optical network technology and Ethernet technologies, including 400 GigE to compose 400 Gbps optical signals.
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