The company is demonstrating a 400 Gbit/s photonic integrated circuit (PIC) here at OFC/NFOEC, and has outlined a roadmap that will see the capacity of its equipment double every three years. Based on this scaling, Infinera expects to produce a 4 Tbit/s PIC within the next ten years.
The company’s DTN optical system currently delivers 100 Gbit/s over ten 10 Gbit/s wavelengths. The new PIC will quadruple system capacity by employing differential quadrature phase-shift keying (DQPSK) modulation at 40 Gbit/s on each of ten wavelengths.
Infinera’s chief marketing and strategy officer David Welch says the 400 Gbit/s PIC will be “system ready” in 2009, although he isn’t prepared to give a date for availability of the system.
Welch says that increasing capacity per chip is the only way to address the multiple challenges facing systems vendors, namely that while boosting data rates, they must also reduce cost, space, and power consumption. Cost is tightly tied in with integration. “The cost of a chip is the cost of a chip,” he says.
So how does Infinera plan to scale its technology? “To get beyond where we are today you need a combination of better spectral efficiency, and spectral width to give you access to more of the fibre bandwidth,” says Welch.
The use of DPQSK modulation addresses the first point because it delivers higher data rates using the same DWDM channel spacings. Using more of the fibre bandwidth will require the elimination of erbium-doped fibre amplifiers (EDFAs) from the network. “At the moment only 10% of the low loss region of the fibre is being used,” says Welch. That 10% is constrained by the operating window of the EDFA.
All of a sudden the various announcements Infinera made in the past week start to make sense. At the OFC exhibition, which starts today, Infinera will be demonstrating transmission over 320 km of Corning’s SMF-28 ULL fibre using Raman amplification instead of in-amplifiers. The company will also show transmission of data over 320 km using a 100 Gbit/s chip containing on-chip semiconductor optical amplifiers (SOAs) operating in the S-band (1940-1512 nm). Both of these techniques provide alternatives to the use of EDFAs in the network.
There’s no doubt that Infinera will face significant challenges as it follows its roadmap, not least of which will be the need to keep yields up as the PIC becomes increasingly complex. Infinera’s current 100 Gbit/s chip integrates around 60 optical components, while the 400 Gbit/s chip contains the equivalent of 150-200 photonic components and 300-400 fibre couplings, depending on how you define an individual component.
'Slower than Moore's Law'
Infinera has a lot of fans, but technology visionary George Gilder doesn’t appear to be one of them. Speaking at the 2008 Executive Forum yesterday, he said: “I’m very impressed with what Infinera has achieved, but it’s completely contrary to the paradigm I’ve been expounding, and it's completely contrary to the optical paradigm. It’s essentially a digital technology used to process data at every node.” Infinera’s roadmap, which anticipates that capacity doubles every three years, is “a lot slower than Moore’s Law, and a lot slower than the rate of advance we had before.”