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Chiaro router employs optical phased array switching

Posted: 22 Nov 2002 ?? ?Print Version ?Bookmark and Share

Keywords:chiaro network? California institute for Telecommunications and Information Technology? optical-networking? photonic switch?

Chiaro Networks Inc. has emerged from stealth mode after signing a contract with the California Institute for Telecommunications and Information Technology for an optical-networking grid program. Meanwhile, the optical-router startup, which has raised more than $200 million since its founding in 2000, will be coming to market in early 2003 with a router that has two distinct claims to fame.

On the physical-component layer, the company hopes to show some breakthroughs in photonic switches by demonstrating GaAs waveguide structures that implement what the company calls an optical phased array switching. Like phased-array radar, the OPA components select wavelength paths across a 64-by-64 crosspoint switch via a photonic constructive and destructive interference mechanism that operates by changing the waveguides' refractive indices.

Chiaro also is working on TCP/IP recovery concepts that will handle many of the problems of the Border Gateway Protocol, without the change in transport protocol promoted by Packet Design Inc. If Chiaro pulls it off, the result may revolutionize the way core routers are developed.

'Fast' not the focus

The company, which has recruited specialists in photonics, Layer 3 routing, and supercomputing - including Steve Wallach, co-founder of Convex Computer Corp. - explicitly avoids the focus on fastest forwarding and fastest packet analysis that is common among core router vendors, such as Caspian Networks, Hyperchip, and Procket.

Wallach, who is VP of Chiaro's office of technology, believes the understanding of core photonics at most router vendors remains superficial, limiting the usefulness of what these companies will offer.

Chiaro's first contract involves the OptIPuter at the University of San Diego, but Wallach stressed that "our main target is not grid computing, though this (architecture) represents an ideal platform for grid computing. The contract only indicates the extent to which the LAN, WAN, and SAN are melding, but our primary target continues to be the service providers."

The Chiaro router due next year, dubbed Enstara (for stateful assured routing), is deliberately called a "platform" because the physical and logical router may not reside in the same rack. One of the tricks of the TCP failover is the designation of a primary and backup master control processor, which may or may not reside in the same box. In fact, vice president of marketing Carey Parker said that in many cases it may be preferable to put the two processors in separate racks for better reliability and link them via optical interconnect.

The center of expertise for Chiaro's optical-component technology is outside of Jerusalem, where Chiaro employs some 80 photonic specialists; another 140 routing and processor specialists work at company headquarters in Richardson, Texas. The optical-switching devices are based on a 64-by-64 switch, which is implemented as a non-blocking 1-by-64 switch replicated 64 times. This core switch can be scaled to 128-by-128, and then 256-by-256, based on current technologies, the company said.

Laser-like control

Some 128 GaAs waveguides are combined to form a beam deflector, and 18 beam deflectors are combined per die to create an optical device. Flip-chip bonding was required to connect to each of the 128 discrete waveguides within each beam deflector, the company said. A DAC is flip-chip bonded to the top of the device, and the optical switch then can be controlled electronically so that wavelength port assignment decisions can be made in the same way as a phased-array radar performs beam forming. Although the 64-by-64 switch has a sub-nanosecond switching speed, bringing in electronic controls takes the practical switching speed to 30ns.

Chiaro combines the switch device with a global arbitration ASIC and four off-the-shelf network processing units per line card. Since each NPU is rated at 1.6 billion fixed-point operations per second, the entire line card has a performance of 6.4 billion operations per second.

"This optical fabric can easily scale to a petabit, though we are not emphasizing that theoretical speed because it is not relevant for most carriers these days," said CEO Ken Lewis.

The stateful TCP/IP protection scheme may be as vital as optical switching, said Parker. Chiaro's software allows TCP state resynchronization without requiring long route table reconvergence times.

- Loring Wirbel

EE Times

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