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03-13-2013, 01:13 PM #1
New distnce record for 400 Gb/s data transmisionThis shows the measured optical spectrum of the eight 100GHz-spaced 495Gb/s WDM signals at the launch into the transmission fiber. The insets are measured constellation diagrams before and after transmission. QPSK: quadrature phase shift keying; QAM: quadrature amplitude modulation; WDM: wavelength division multiplexed. Credit: AT&T Labs As network carriers debate the next Ethernet standard—and whether transmission speeds of 400 gigabit per second or 1 terabit per second should be the norm—engineers are working on new measures to squeeze next-generation performance out of current-generation systems. To that end, a team from AT&T has devised a new patent pending technique enabling tuning of the modulation spectral efficiency, which allows, for the first time, 400 Gb/s signals to be sent over today's 100 gigahertz-grid optical networks over ultra-long distances. Spectral efficiency is the information rate that can be transmitted over a given bandwidth, and measures how efficiently the available frequency spectrum is utilized.