Fibre-optic cables are well known as a medium for data transmission, but they have another use that is not as widely appreciated: as multi-purpose sensors.
The refraction of light within a cable is subject to external factors, including the temperature, pressure and strain on the cable.
Analysing the precise patterns of photons that reach one end of the cable can therefore reveal statistics about the environment the cable runs through.
This technique is already used in a handful of niche applications. The utilities industry, for example, uses fibre-optic cables to measure tiny differences in pressure and temperature along a pipeline. This allows them to spot faults or leaks as soon as they arise.
Now, a Cambridge-based start-up called Alquist is applying the technology in the data centre.
The company’s product, Celsius, gives data centre operators a real-time “heat map” of their facilities by analysing refraction in fibre-optic cables.
A network of lasers and fibre-optic cables is installed around the facility. Each meter-long stretch of cable acts as an individual sensor. Once active, the network generates thousands of readings every minute, which can be fed into a number of data centre management and industrial control software packages.
According to Alquist founder Toby Burton, having real-time data from every corner of the server farm allows operators to spot anomalies as soon they as occur, and address issues before they get out of hand.
“Processing occurs at different points across a data centre floor, especially with virtualised systems,” says Burton. “This means equipment can get hot quickly, potentially invalidating warrantees and causing problems with other equipment nearby, or even starting fires.
“That can cause downtime, which is the dread of any data centre manager.”
Having that detailed view will also allow data centre operators to reduce their expenditure on cooling, Burton says.
Most data centres run cooler than necessary in case there is an unexpected spike in temperature. If they could spot those spikes immediately, data centre operators would not need to maintain that expensive temperature buffer.
Celsius, Burton claims, offers superior heat monitoring to the products available today.
“The only competitive products offering anything like the same level of information are wireless systems which are very costly, complex to install, difficult to manage and require constant maintenance including battery management for hundreds of end devices.
“There are also thermal cameras, but they’re very costly and fiddly to get into awkward places,” he says.
For smaller data centres, Burton says, the cost of the lazer equipment may be prohibitive.
But based on prelimnary tests, Alquists estimates that mid-size data centre could achieve 10% to 30% reduction in electricity bills, paying for itself in about nine months and reducing carbon emissions by up to 2,000 tonnes per annum.
Burton admits, though, the output of the system depends heavily on how efficiently a data centre is already run and what kind of airflow management they have in place.
Once installed, the company claims, the system needs no maintenance and is guaranteed for around 30 years.
In August, a consortium of suppliers led by Alquist won a grant of just under £1 million from the Technology Strategy Board to pilot the Celsius equipment in two large-scale data warehouses.
The pilot project will see Celsius installed at two data-centres by engineering firm Schneider Electric. Alquist will use the results of that pilot to create a “savings calculator” for operators to work out exactly what benefits are possible.
“Our current research and development focuses on extending the areas where the system can be installed,” says Burton. “For example, how it can be used to monitor new parts of existing centres and how it can be built in to individual components and building routines for new centres.”
“But the simplicity and resilience of the Celsius system means it could be specified as a standard monitoring system for all new build data centres,” he adds.