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19 April 2012
Huawei has demonstrated a prototype optical switch that can scale to 10 petabits per second or 10 million Gbps. Dubbed the Petabit Packet Cross Connect (PPXC), the switching platform is aimed at metro and the data centre markets. 
Huawei says the system, first shown at the OFC/NFOEC exhibition held in March, is a technology demonstrator and is unlikely to become a product before 2017. 
Current platforms have switching capacities of several terabits. Yet Huawei believes a one thousand-fold increase in switching capacity will be needed in the coming years. Fibre capacity is moving towards 16Tbps with the advent of higher-order modulation schemes, and traffic from multiple fibres will need to be switched at busy network exchanges. "This can add up to about a petabit at a site," said Reg Wilcox, vice president of network marketing and product management at Huawei.
The PPXC uses optical burst transmission to implement the switching. Ultra-fast switching lasers are set to a particular wavelength in nanoseconds, with each wavelength assigned to a destination port. As packets arrive, they are assigned a "colour" before being sent on the required wavelength to their destination. 
The Huawei demonstration linked two Huawei OSN8800 32-slot platforms, each with an OTN switching capacity of 2.56Tbps, to the core optical switch, to implement what is known as a three-stage Clos switching matrix. 
The optical switch effectively implements an 80x80 matrix with its 80 wavelengths, each at 25Gbps. To scale to 10 petabits, multiple such matrix units would be used. The PPXC can groom traffic starting at 1Gbps rates, and switch 100Gbps and even higher incoming wavelengths.
The demonstration highlighted the PPXC switching OTN traffic, but Wilcox stresses that the architecture is cell based and can support all packet types. Accordingly the design is also suited to large data centres to switch traffic between servers and for linking aggregation routers.
Oclaro provided Huawei with the ultra-fast lasers. "We have seen quite some interest recently in this area [of optical burst transmission]," said Robert Blum, director of product marketing for Oclaro's photonic components. "I wouldn't be surprised if other companies make announcements in this space."
By Roy Rubenstein