By Jennifer Cline and David Hessong
Data centre optics
As befits its status as a computing giant, Microsoft’s musings about the internet’s future are poised to reshape the optical communication industry. In August 2015, following discussions with colleagues and suppliers, Brad Booth, principal engineer at Microsoft in Redmond, Washington, helped found the Consortium for On-Board Optics (COBO). The move answered a question: looking at network speeds of 400G and beyond, will networking equipment that uses faceplate pluggable optical modules continue to make sense?
When Google published an insider’s view of its data centre operations, one image showed a branded bicycle that is their employees’ preferred method for getting around the company’s warehouse-sized facilities. Google builds some of the largest data centres in the world, although it considers the precise details to be commercially sensitive. One thing is clear, however; data centres are getting bigger and bigger, and this has major implications for the way they are designed.
Multimode fibre has been the workhorse of data centre networks for many decades because it provides the lowest cost cabling system for high-speed connections between servers, switches and storage. Although the optical fibre is more expensive, the larger core size enables the use of cheaper transmitters based on vertical-cavity surface-emitting lasers (VCSELs), which reduces the overall cost of the system.
Existing 100 Gig interfaces have reaches that are either too long and costly or too short - and web companies' demands have stirred a flurry of industry activity, with four optical module initiatives announced since the year's start. Cheaper 100 Gig mid-reach interfaces also promise to benefit telecoms, with wireless being one application already identified.
Optical module designers must reconcile two contradictory trends: data centres are getting larger, inevitably lengthening the links between systems, yet optical reach gets shorter with increasing channel speed.
Cost and compatibility can make a compelling case for pushing 100Gb/s bandwidth over a single optical channel, both as individual links and supporting 400Gb/s Ethernet, finds Andy Extance
Robin Mersh takes a look at how the industry is creating next-generation optical access fit for 5G
Technological advances to aid the increasing demand for bandwidth, on the path towards the terabit network, should lead to optical signals that are flexible and adaptive, like water, argues Dr Maxim Kuschnerov and Dr Yin Wang