100G Duplex LC in core networks

When migrating your core network to 40G or 100G using LC Duplex, there are two non-standard solutions available: BiDi and Short Wavelength Division Multiplexing. Both are based on proprietary solutions, not supported by IEEE. They are popular in data centres because they are heavily supported by Cisco and Arista, and Cisco still has the majority of the switching calls into a data center. Typically one-supplier solutions, these can lock the customer into a proprietary environment, but both are fully supported by Nexans.

swdm Short Wavelength Division Multiplexing offers a new LC-based migration concept. The technology multiplexes 4 optical carrier signals onto a single optical fibre by using 4 different wavelengths of laser light. Nexans’ OM5 fibre is optimised for short division multiplexing and allows multiple short wavelengths in the 850-950nm range. Unlike OM3 and OM4 fibres, which are only optimised at 850nm, OM5 fibres can carry at least four wavelengths, thereby quadrupling capacity.

swdm4

OM5 is targeted at upcoming high speed applications for 40G and 100G that will use Short Wavelength Division Multiplexing. The result is a cable infrastructure based on LC connectivity rather than the existing protocols that require parallel optics with MTP connectivity.
OM5 fibre is designed to provide backwards compatibility with OM4, with a similar modal bandwidth of 4700MHz at 850nm. Its 50µm core offers a user-friendly solution for installation in data centres and enterprise with regard to connectivity, maintenance and cleaning.

Should you consider using single mode?

If you compare cabling technology and transceivers, you’ll see that when comparing multimode to single mode the cost of a single mode transceiver will be high. So we’ll see a lot of multimode cabling and transceivers in data centres over the next few years and probably in the new technologies, because it is just one step from 10 Gigabit to 100 Gigabit.

As the market for 10G matures, the prices of transceivers for both MM and SM have gone down. The difference between SM and MM has been reduced from 4x to a 2x difference.  
For 100 Gigabit, only parallel optics for multimode and an SM mode version with a reach up to 10km have been standardised and are widely available. For typical enterprise installations with a reach of 50m the difference between MM and SM is huge.

Because of reach requirements, single mode is currently being used in hyperscale data centres, and is being promoted as the only viable future solution by businesses such as Microsoft and Google. In typical enterprise data centres the reach requirement is not as demanding and the cheaper multimode solution is preferred.