Parallel Optics Boosts Bandwidth

A couple of startups are about to ship prototype transmitter and receiver modules that could have a big influence on tomorrow’s giant routers and switches.

The startups -- TeraConnect Inc. and Blaze Network Products Inc. -- claim their developments will deliver a fourfold boost to the bandwidth that can be carried over the ribbon connectors used to link together multiple chassis in distributed architecture equipment.

Vendors that might benefit from these developments include Avici Systems Inc. (Nasdaq: AVCI; Frankfurt: BVC7), Charlotte’s Networks Ltd., Hyperchip Inc., and Pluris Inc., all of which have distributed architecture core routers. The high-capacity connectors might also be good news for BrightLink Networks Inc., which has a distributed architecture optical switch.

Right now, these vendors typically link together boxes using ribbon connectors comprising arrays of transmitter-receivers at either end of a bunch of parallel fibers. Pluris, for example, uses 10-Gbit/s optical modules based on 1x12 arrays of transmitters and receivers, according to Russ Tuck, a systems architect with the company (see Pluris Is Back). Pluris uses multiple ribbons to support whatever bandwidths are needed between its boxes.

Those bandwidths are increasing rapidly as higher-speed line cards are introduced. "It's critical that the bandwidth between chassis grows to support the data coming in,” says Tuck. “If you have 160 Gbit/s arriving on the front face, then the bandwidth across the backplane should be at least that much." Higher-capacity optics, like the ones from TeraConnect and Blaze, would reduce the amount of board space and connectors required, he adds.

Several vendors are readying 1x12 parallel interconnects that move 30 Gbit/s of data around, by putting 2.5 Gbit/s on each channel. TeraConnect and Blaze extend this idea further by providing 48 channels, each capable of pushing 2.5 Gbit/s of data, resulting in aggregate capacities in excess of 100 Gbit/s. However, the two vendors do this in very different ways.

TeraConnect's T-48, announced yesterday, incorporates a 4x12 VCSEL (vertical cavity surface emitting laser) array operating at around the 850 nanometer wavelength. The light from each laser is output to a separate fiber, and those fibers interface to two standard 24-element MT connectors (see TeraConnect Launches Products)

Bill Lindsay, TeraConnect's director of sales and marketing, says the startup's "secret advantage" is its integration technology. It claims to have a proprietary method of integrating electronic chips, lasers, detectors, and fibers that enables "a significant reduction in the cost of packaging and alignment."

One of the tricks up TeraConnect's sleeve may be a so-called "pitch transition device" that collects light from the laser and feeds it to the fiber ribbon. That way, lasers in the array can be closely spaced to maximize yield, instead of having to match the 250-micron spacing of the fibers in the fiber ribbon (see Startup Gets Flexible). Lindsay declined to comment.

Blaze demonstrated its development in this field, a transmitter-receiver pair called the Inferno-CGSX, at the Supercomm trade show earlier this month (see Blaze to Demo 100-Gig CWDM Gear ). It plans to announce it formally next Monday (June 25).

As noted, the startup is taking a totally different tack from TeraConnect's with its device. It’s combining four CWDM (coarse wavelength-division multiplexed) channels on each fiber in a twelve-fiber ribbon. This means its transmitter-receiver pair can move 120 Gbit/s of data using one fiber ribbon instead of four. "Fiber ribbon assemblies aren't cheap", says Kirk Bovill, Blaze's director of product marketing.

Pluris's Tuck points out a potential drawback to Blaze's product: It won't be as easy to build into existing equipment. It's only compatible with other products that use CWDM. If the product on the other end of the link doesn't employ CWDM, then only one of the four channels on the Blaze module could be utilized. In contrast, one of TeraConnect's 48 channel transmitters (or receivers) could interface with four existing 12-channel modules.

— Pauline Rigby, Senior Editor, Light Reading
http://www.lightreading.com

(9)  |