24 February 2011

Infinera achieves 1Tb/s on integrated photonic chip

Worldwide Internet data traffic is increasing by 50% each year. Currently, more than 20 exabytes — 20 trillion trillion bytes (or 160 exabits) — have been estimated to pass through the Internet every month. Telecoms companies that handle this must be able to economically expand the capacities of their networks while also adapting to new, more efficient data-handling technologies. Over the last decade, a development team at Infinera Corp in Sunnyvale, CA, USA has pioneered the design and manufacture of indium phosphide (InP)-based photonic integrated circuits (PICs) aimed at meeting that need. This technology has enabled the team to achieve a record one trillion bits per second (1 Terabit/s) speed on a single integrated InP chip.

The findings will be presented on Monday 7 March at 3.15pm by Dr Radhakrishnan Nagarajan (Infinera research fellow and a senior member of its PIC development team) at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference (OFC/NFOEC) in Los Angeles (‘10-channel, 100Gbit/sec per channel dual-polarization coherent QPSK, monolithic InP receiver photonic integrated circuit’).

“Traditional transponder-based system architectures are inflexible and costly and time-consuming to upgrade,” says Nagarajan. “Our PIC approach enables us to make optical networks more powerful, flexible and reliable than ever before using equipment that is significantly smaller, less expensive and uses much less energy,” he adds.

PICs enable massive amounts of cost-effective bandwidth and facilitate the networks at the heart of the Internet to become more scalable and quicker to react to sudden changes in demand. “In many ways, PIC-based optical networks are starting to take on the intelligent features of routed (IP) networks, like the ability to re-route traffic in the event of a break in the fiber—but at a fraction of the cost and power consumption,” Nagarajan adds.

Infinera’s latest PIC is at the heart of a new 10-channel receiver, each channel operating at 100Gb/s data rates, making it first to achieve a capacity of 1Tb/s on a single photonic integrated chip. The chip contains more than 150 optical components — such as frequency tunable local oscillator (LO) lasers, devices for mixing the LO and incoming signals, variable optical attenuators for LO power control, a spectral demultiplexer to separate the individual wavelength channels, and 40 balanced photodetector (receiver/transmitter) pairs — all integrated onto a chip smaller than a fingernail.

The key technical advance behind 100Gb/s-per-channel technology is the ability to detect incoming data encoded using the optical industry’s most spectrally efficient modulation technique, polarization multiplexed quadrature phase-shift keying (PM-QPSK). PM-QPSK permits four times more information to be conveyed each second than was possible with the previous method, which simply switched the laser light on and off. The advance is that Infinera has, for the first time, integrated the entire the PM-QPSK modulation scheme onto a single 10x100Gb/s PIC.

“But just as important as a transmitter’s clever and efficient encoding method is a fast and reliable way for the receiver to convert the information back to its original form,” says Nagarajan. Transmitter and receiver PICs are hence typically installed at critical nodes and at each end of long-haul optical networks. “For PM-QPSK, we designed and integrated narrow-linewidth lasers that detect the phase-encoded data very efficiently.”

Infinera’s 100Gb/s PICs are widely deployed in long-haul and metro networks worldwide, while a 500Gb/s PIC should be available in 2012. The firm expects PICs with a capability of a terabit or more to be commercially available within a few years.

Tags: Infinera InP Photonic chip PICs

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