Infrared lasers must replace data center wiring, say engineers

Using infrared lasers instead of fiber optics or radio signaling improves data center communications, and it can help data centers reduce power costs

Infrared must replace data center wiring, say engineers
Patrick Mansell / Penn State

Eliminating a “tangled Christmas tree lights” wiring scenario in data centers is imperative and can be achieved with infrared, reckons an academic network engineering team.

Infrared lasers should be installed on the top of data center racks and be used to transmit information. It would be far superior and cheaper than fiber optic, and it would be better than attempted, but lacking, radio signaling.

Radio doesn’t work, says Mohsen Kavehrad, the W. L. Weiss Chair Professor of Electrical Engineering at Penn State and one of the developers, in an article on the school’s website.

Radio, in millimeter spectrum, an alternative to fiber-optic wires, has an issue in that the signals get unmanageable quickly. “The beams become wide over short distances,” Kavehrad says. That results in inadequate throughput, he says.

Infrared laser helps simplify communications in data centers

The way to handle increasing complexity in data centers is to simplify the communications. And you do that with flexible infrared “free-space” laser, Kavehrad says. Buildings should be able to be a mile long, yet allow each rack to individually communicate with another.

Kavehrad’s and his collaborators’ developing system is called Free-space optical Inter-Rack nEtwork with high FLexibilitY, or Firefly. Kavehrad says it works in proof of concept, using a cheap lens to obtain a narrow beam.

That beam is not susceptible to interference like radio; there aren’t any limits to the number of servers and racks that can be connected. And it has high, uninterruptable throughput—the laser won’t be interrupted by humans walking around because it's placed on the top of the cabinets.

“Human interference is minimal because the racks are more than 6.5 feet high, so most workers can walk between the rows of racks without breaking the laser beams,” the Penn State article says.

The existing standard—fiber—is a hindrance to flexible data centers, the team says. It’s too cumbersome. The group includes members from Carnegie Mellon University and Stony Brook University.

The researchers say fiber-optic cable not only begins to resemble jumbled, stored Christmas lights over time, but it causes bottlenecks. Those choke points slow the whole system down.

In addition, the team points out that large numbers of servers are offline in many data centers at any one time because the operation is built for peak traffic. Those on-hold racks and servers are still powered, though. That costs money, not only in electricity consumption, but also in cooling. Easier provisioning negates the need to power the servers all the time.

Rising power costs make cutting data center power usage critical

Some say power costs are going to skyrocket. In fact, a University of Michigan study found climate change will increase American power costs during the next century billions of dollars more than economists previously predicted. Current estimates don’t take into account peak usage during hot weather properly, the study claims.

That’s why cutting electricity costs for data centers may become crucial. Pulling unused, idling servers out of a data center’s mix can be achieved by more efficient provisioning of rack communications, such as that conceivably provided by laser. It could reduce power consumption. Kavehrad estimates that typically 30 percent of data center servers are powered but offline.

Different colored lights are behind Firefly, the bi-directional infrared system. The researchers say it will achieve transmission rates of 10 Gbps. They say that their architecture, which uses multiplexed signals carried by the different colors, also implements miniscule, almost undetectably moving mirrors. Those are used for the “rapid targeting and reconfiguring.”

Ultimately, “we would like to get rid of the fiber optics altogether,” Kavehrad says.

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