Optical Cross-Connect Reduces Loss

Daniel C. McCarthy

When your office phone rings indicating an outside call, chances are the signal passed through an electronic switch somewhere in the building -- even if the incoming signal came off an optical fiber trunk line and traveled along glass fiber to your phone.

Micromirrors enable Astarté's optical cross-connect modules to couple hundreds or even thousands of fiber ports without insertion loss. Courtesy of Astarte Fiber Networks Inc.

While optical fibers have boosted data rates to 10 Gb/s, the speed at which electronic switches convert these signals and reroute them into "high volume" local area network protocols allows operation at a fraction of that rate -- 100 Mb/s.

Low loss, many ports

Replacement of electronic switches with optical connections can regain some of that speed, but current technology limits the number of fiber ports. Generally, as the number of ports increases, so does the amount of insertion loss.

Astarte Fiber Networks Inc. has demonstrated proof-of-concept for an optical cross-connect technology enabling hundreds or even thousands of fiber ports with minimal insertion loss. The switch-actuating mechanism incorporates microelectromechanical technology from Texas Instruments Inc.'s division in Attleboro, Mass. Astarté integrated the micromirror assembly with servo-control electronics into an optical cross connect.

In tests, the prototype exceeded Astarté's expectations, according to Ed Fontenot, president and CEO of the company.

"Insertion loss is probably a good 20 to 30 percent less than we expected, and switching time to make a connection is either at, or less than, [what] we expected," he said.

The system, intended to support single-mode fibers, is transparent to optical signals between 1250 and 1650 nm. Unlike electronic switches, it does not need to be preconfigured to be compatible with specific network protocols or speeds.

Astarté's cross-connect design also allows network managers to designate connections remotely, by computer.

The next step, according to Fontenot, is to modify the prototype from a lab curiosity to a system that can be scaled up for manufacturing.

In its eventual commercial iteration, the system's 576-input-by-576-output modular design would likely target central office environments, according to David Krozier, a market development manager at Texas Instruments.

"You can install the chassis and then add cards to build up the number of fibers you can handle," he explained. Krozier added that the modular design also addresses maintenance issues in the event of a system failure.

"You can change cards without impacting everyone on the switch."