Alcatel-Lucent’s research arm, Bell Labs, has used high-speed electronics to enable Terabit long-haul transmission using two optical carriers only.
Several vendors have already demonstrated Terabit transmission including Alcatel-Lucent, but the company is claiming an industry first in using two multiplexed carriers only.
“There is a tradeoff between the speed of electronics and the number of optical modulators and detectors you need,” said Peter Winzer, director of optical transmission systems and networks research from Bell Labs. “In general it will be much cheaper doing it with fewer carriers at higher electronics speeds than doing it at a lower speed with many more carriers.”
In the lab-based demonstration, Bell Labs sent five 1Tbps signals over an equivalent distance of 3,200km. Each signal uses dual-polarisation 16-QAM (quadrature amplitude modulation). The total bit rate is 1.28Tbps or 640Gbps per carrier.
In achieve the data rate, Bell Labs uses an 80Gbaud symbol rate, much higher than 30Gbaud at 100Gbps, and 16-QAM rather than QPSK modulation. To achieve 80Gbaud it is using state-of-the-art electronics developed at the Alcatel Thales III-V Lab. These are indium phosphide components not CMOS, and hence will not be commercially available products for several years.
The 1Tbps signal uses 200GHz of spectrum to achieve a 5.2b/s/Hz spectral efficiency, compared to 2b/s/Hz used by state-of-the-art 100Gbps systems
“Progress in photonic integration is also needed to get the cost of optoelectronics down as it [one terabit] is still going to need two-to-four sub-carriers,” said Winzer. “Without integration you are doubling up your expensive optoelectronic components which doesn’t scale.”
By Roy Rubenstein
Press release: Bell Labs lays the foundations for the future of optical communications
Gazettabyte: Alcatel-Lucent demos dual-carrier Terabit transmission