Fujitsu to monitor data center heat with optical fiber

Fujitsu is looking
to optical fiber to help increase efficiency in the cooling of large data centers.
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
data center 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.

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.