Fujitsu to monitor datacenter heat with optical fiber

Prototype monitoring system uses a single optical fiber to measure temperatures in a datacenter in up to 10,000 points

Fujitsu is looking to optical fiber to help increase efficiency in the cooling of large datacenters. The company has developed a prototype monitoring system that can measure the temperature in up to 10,000 points using a single optical fiber connected to a measuring device.

It works by sending pulses of light down the fiber, which is laid around the datacenter and through the server racks, and measuring the minute amount of light that is sent back down the line due to Raman scattering, said Fumio Takei, a research fellow at Fujitsu who has been working in the system.

The intensity of the light varies depending on the temperature so this can be used to estimate the temperature along the fiber while the time it takes to come back can be used to measure the distance from the start of the fiber. Combining the two together means that the temperature can be estimated at numerous points along the fiber.

[ Learn more about the issue of energy efficiency in datacenters in 'Datacenters heading for cash crunch.' ]

The basic idea isn't new and fiber optic cables have been used for some time to monitor the temperature of things like tunnels, but the resolution of the system has never been precise enough to be useful in a data center, said Ei Yano, president of Fujitsu's device and materials laboratory.

The Fujitsu system is accurate to within half a degree Celsius and one meter. The temperature range that can be measured is between -10 degrees and 300 degrees Celsius.

In a demonstration at the company's research and development laboratory here near Tokyo a fiber was strung around a small server room and displays showed temperature read-outs for each rack starting at 32.4 degrees at the bottom of the rack and rising steadily -- 33.9, 34.1, 34.4 and 35.9 -- to 37.8 degrees at the top.

Fujitsu said the system can be used with fiber optic cables up to 10 kilometers long and at one-meter resolution that means approximately 10,000 points can be measured.

The company hopes to commercialize the system sometime in 2009. There is no word on price but Yano said such a system isn't likely to be cheap but comparably good value for a 10,000-point measurement system.

As computers get more powerful the amount of heat generated by them is increasing making datacenter cooling an increasingly difficult job. The new technology should be able to help better employ cooling systems so hot areas are more efficiently cooled and less power wasted.

An added benefit is that the system relies solely on light and not electrical measurements so stringing the cable close to servers won't cause interference.

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