Transport optical network company Infinera (Sunnyvale, CA) and communications carrier services company BICS (Brussels, Belgium) successfully completed an extended laboratory trial of quadrature phase shift keying (QPSK), 8 quadrature amplitude modulation (QAM), and 16QAM transmission over OFS (Norcross, GA) Terawave [trade mark] large area/low loss (LA/LL) fiber that is optimized for terrestrial cables. The trial included a range of advanced FlexCoherent modulation features that will continue to drive capacity and reach for the Intelligent Transport Network using the FlexCoherent Processor combined with photonic integrated circuit (PIC) technology.
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This trial shows the dramatic improvement in optical reach and capacity that can be expected as these new fibers are deployed in the next generation of terrestrial and submarine fiber links. LA/LL fibers are being deployed in a handful of submarine cables now and will likely be the technology of choice for future submarine cable builds. The deployment of new LA/LL fiber in terrestrial applications could be delayed because of the large base of existing fiber, but there are early examples of such deployments. Existing fiber types typically have a much lower optical performance compared to LA/LL fiber.
High order modulations, such as 16QAM, promise to deliver double the capacity of QPSK – the de facto 100Gb/s modulation – at the expense of 80 percent reduction in reach, using existing fiber types. This makes 8QAM a promising option over existing fibers for both submarine and terrestrial applications. In a recent submarine trial performed on existing fiber, 8QAM delivered a reach of over 2,200 km while increasing capacity by 50 percent. When the same test was performed on the new LA/LL fiber, 8QAM demonstrated an optical reach up to 7,400km with a 50 percent increase in fiber capacity.
Steve Grubb, Infinera Fellow, and the architect behind the trial summarized the findings. "With the optical reach we achieved using this new type of LA/LL fiber we could envisage a future in which PM-QPSK could be used to close trans-Pacific links, PM-8QAM could cross the Atlantic, and PM-16QAM could span a European backbone. This would enable between 50 percent and 100 percent increase in new submarine or terrestrial cable capacity."
"This trial was extremely useful for our future network planning process," said Eric Loos, Senior Product Manager Capacity & IP at BICS. "It's clear to us that many of the trials of 16QAM in the market today are performed on these new fiber types – because they dramatically improve the optical reach. When it comes to existing fiber types in the terrestrial applications, like SMF or LEAF®, it's clear that 16QAM can be useful at the shorter reach end of the scale, especially where no optical protection will be used. In contrast PM-8QAM seems to offer a sweet spot for longer metro, regional and even long haul distances, and could give us enough reach to include optical protection. 8QAM delivers a 50 percent capacity boost compared to QPSK, and that's going to be extremely useful for service providers facing the unprecedented demand increase from Cloud-based services."
SOURCE: Infinera; http://www.infinera.com/j7/servlet/NewsItem?newsItemID=445