Will photonic integration technology power future data centres?
Dr Prince Anandarajah takes a look at the factors putting pressure on data centres and introduces a possible solution to power them into the future.
We live in a highly interconnected world, where fast and reliable exchange of information is taken for granted. We send about 100m emails, 10m instant messages, 100,000 tweets and 1m Facebook updates every 60 seconds. All this internet activity creates terabytes of new data every minute, most of which needs to be stored and processed in the cloud.
‘To accommodate growth, data centres have had to increase capacity by about a factor of 1,000 and will soon need to do the same again’
Data centres, composed of tens or hundreds of thousands of connected computer servers, currently provide us with cloud computing, online shopping, social networking and advanced video streaming services. As demand for bandwidth-hungry services increases, the networks that carry the traffic will need to be able to grow to carry thousands of times more data than they currently do.
To accommodate such growth, data centres have had to increase capacity by about a factor of 1,000 and will soon need to do the same again. This raises industry concerns about the viability of scaling present-day data centre architectures to provide the capacity that we need.
The cost of boosting network capacity
For simplicity, the data centre can be divided into two constituent parts: the server, which performs data processing and storage; and the network, which interconnects the vast number of servers.
Already, copper wire network connections of data centres are being upgraded to much faster optical fibre connections, which use lasers to transmit data efficiently.
The traditional approach was to turn a laser on and off to send the data. With this method, an increase in data transfer speed could be achieved by turning the laser on and off even more quickly – but that only gets you so much.
The alternative is to send different laser wavelengths down the same fibre. That means if you have 10 lasers, you have 10 times the capacity. 100 lasers provide 100 times the capacity. A technology called wavelength division multiplexing (WDM) does just that, but requires many laser transmitters connected to each optical fibre link, which is costly and consumes considerable energy – a growing concern for data centre operators.
Photonic integration
There are many different challenges that the next generation of data centres face. Spiralling data centre costs and power consumption are two of the limiting factors that have been well documented.
Dr Prince Anandarajah, Dublin City University
‘The requirements for a low-power, low-cost approach cannot be fulfilled by linearly scaling current optical technology within the data centres’
The requirements for a low-power, low-cost approach cannot be fulfilled by linearly scaling current optical technology within the data centres. Data centre operators will require much higher density optical interfaces that offer scalability from tens or hundreds of gigabits per second to terabits per second.
This drives a need for greater integration of the optical components using a technique called photonic integration. This is analogous to the development of microchips in the 1960s, which combined multiple electronic functions on a single silicon chip.
Along with the team at DCU School of Electronic Engineering, we have developed an ‘optical comb source’ that allows many wavelengths of light (and so, many parallel high-speed data channels) to be produced using a single laser and carried on a single optical fibre. This is a cost-effective and energy-efficient solution that is being targeted at the impending traffic bottleneck, thereby transforming data centres.
The technology has been licensed to a DCU spin-out company, Pilot Photonics, which are currently in the process of developing a photonic integration technology that it plans to apply to the data centre market.
Dr Prince Anandarajah is a lecturer at the School of Electronic Engineering in Dublin City University. He is a recipient of the Science Foundation Ireland Career Development Award, supporting early-stage researchers who are already in an independent academic position.