Selecting the appropriate fiber cabling for a Data Center (DC) is both a financial and a strategic decision. DCs have a choice between multi-mode fiber (MMF) and single-mode fiber (SMF). The shorter distances and slower data rates (i.e., below 25 Gbps) of earlier DC architectures, made it financially feasible to use multi-mode fiber. Also in the past, the comparatively high cost of pluggable optics discouraged DCs from using SMF over MMF.
|Picture credit: www.chinacablesbuy.com|
Currently, three changes are favoring single-mode fiber:
- Data rates are increasing from 10 Gbps to 40 Gbps, 100 Gbps and beyond
- DCs that deployed OM1 and OM2 fibers have had to upgrade to OM3 and OM4 multi-mode fibers to support higher rates
- As data rates grow greater than 100 Gbps, OM3 and OM4 will also have to be upgraded
- Intra-DC distances are increasing
- With DCs getting larger, intra-DC distances are increasing; as such, the distance limitations of OM3 and OM4 will constrain growth
- Silicon photonics is reducing the cost of serial optics
- The silicon photonics manufacturing process is driving down the cost of serial optics. The industry is nearing cost parity when the price of fiber is factored into cost estimates.
- Intel® recently announced that it is launching silicon photonics for datacenter traffic management (see http://www.zdnet.com/article/intel-launches-silicon-photonics/).
Facebook has worked with the industry to develop a single-mode, fiber-optic cabling solution that operates over greater distances, at a much lower cost, than the longer-haul, single‑mode fiber which has historically been available for 100 Gbps links.
|Graph source: http://www.nextplatform.com/2016/03/18/datacenters-get-high-fiber-bandwidth-diet/ “Datacenters to Get A High Fiber Bandwidth Diet,” March 18, 2016, Timothy Prickett Morgan, The Next Platform|
DCs have to look at cabling costs versus not being able to scale and offer newer services. With intra-DC distances getting longer and capacities expanding to 40 Gbps and higher, a DC equipped with multi-mode fiber is analogous to a competitive runner using ill-fitting shoes—it’s questionable whether he’ll finish the race and if he does, he won’t be competitive. To compete successfully, DCs will have to transition to a fiber plant that will support scale, longer distances and higher capacities. At present, SMF is the best means for achieving this goal.