Infrared lasers may replace wires in data centres

Scientists, including those of Indian origin, have developed a system of infrared lasers and receivers that can eliminate the need for cables and wires at data centres, an advance that may lead to faster wireless communication.
Data centres are the central point of many, if not most, information systems today, but the masses of wires interconnecting the servers and piled high on racks begins to resemble tangled Christmas-tree lights.
Scientists, including Sami R Das and Himanshu Gupta from Stony Brook University in the US, have proposed a way to eliminate most of the wires and substitute infrared free-space optics for communications.

"We and others tried radio frequency signaling, but the beams become wide over short distances," said Mohsen Kavehrad, Professor at Pennsylvania State University in the US.
"The buildings could be a mile long and every rack should be able to communicate," said Kavehrad.
In an experiment, researchers, including Vyas Sekar from Carnegie Mellon University in the US, found that radio-frequency signalling resulted in high interference, limited active links and limited throughput - the amount of data that can go through a system.

"We use a free space optical link. It uses a very inexpensive lens, we get a very narrow infrared beam with zero interference and no limit to the number of connections with high throughput," said Kavehrad.

The Free-space optical Inter-Rack nEtwork with high FLexibilitY (Firefly) would use infrared lasers and receivers mounted on top of data center racks to transmit information.
The laser modules are rapidly reconfigurable to acquire a target on any rack. 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.
According to Kavehrad, data centres may house 400,000 servers on racks filling a mile-long room. Data centres typically build for peak traffic, which means that most of the time about 30 percent of servers are offline.

However, because they are still on, they continue to create heat and need cooling.
When hundreds of cables merge into a few, data transfer bottlenecks form that reduce the speed at which the data center can deliver information.
A flexible, configurable system can reduce bottlenecks and even the number of servers needed.
The receiver captures the infrared signal and directs it to the fibre-optic cable which sends the information to its final destination.
The researchers have created a simple, proof-of-concept system to show that their infrared laser can carry the signal and target the receiver.
They are transmitting wavelength division multiplexed - multiple signals sent by different coloured lights - bi-directional data streams each carrying data at a transmission rate of 10 Gigabits per second from a Bit Error Rate (BER) test set.