Multiplex your fiber to avoid upgrades, says SWDM Alliance
A new group of networking firms has formed to promote SWDM, a technology which extends the life of older fiber cables in data centers.
The SWDM Alliance says that using shortwave wavelength division multiplexing (SWDM), operators can avoid having to replace their existing multi-mode fiber (MMF) when they need to go beyond 10Gbps on their backbones. Vast numbers of data centers use pairs of multi-mode fibers (duplex MMF) for 10Gbps networking, but to go beyond this speed with current technology would require more fibers, or a move to expensive telecoms-grade single-mode fiber. The group, which includes Juniper, Huawei and Dell, says these upgrades can be avoided.
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Use existing fiber
“Data center operators have already invested in duplex MMF infrastructure for their 10Gbps deployments,” said Vladimir Kozlov, CEO of Lightcounting Market Research. “Using SWDM technology to maximize the utility of those duplex deployments is an example of how equipment providers can offer innovative, cost-effective upgrades to the higher data rates that are now required.”
Generally, 10Gbps or 25Gbps has been considered the top speed for multi-mode fiber, and data centers are now demanding faster speeds. However upgrading to single-mode fiber is a large expense. Multi-mode fibers are 50 to 100μm thick, carry various light transmission modes, and are easier to terminate, requiring cheaper electronics.
Single-mode fibers are much thinner at around 10μm, and carry a more refined light signal. In telecoms applications they can operate over vast distances, driven by lasers, but they are toio expensive for normal data center use.
Wavelength division multiplexing (WDM) uses multiple wavelengths of light to transmit more than one signal along a fiber. It’s been multiplying the capacity of single-mode fiber for some time, but now the SWDM group says a shortwave version of the technology can save data center owners from having to rip out their multi-mode fiber.
The shortwave technology is supported by cost-effective vertical-cavity surface-emitting lasers (VCSELs), which come at a price data centers can afford, and have been widely used on duplex MMF at data rates up to 10 Gb/s. To go beyond that, operators have been running four pairs of fiber in parallel, but this technique requires eight fibers instead of two, and this means recabling, with new patch cables and new fibers in the trunk.
With SWDM, four VCSELs can send light down a single fiber pair, each operating at 10Gbps or 25Gbps in a different wavelength. A single pair can then carry 40Gbps or 100Gbps.
Unlike other similar bodies, the SWDM Alliance is not a standards group - no new standards are needed, apparently. Founding members include CommScope, Corning, Dell, Finisar, H3C, Huawei, Juniper Networks, Lumentum and OFS Fitel.