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SDM: Spatial dividing mentality?

By David Nugent

“Attention, everyone. Would those in favour of SDM please form an orderly line on the left. Those in favour of MDM please disperse throughout the room whilst choreographing yourself into patterns of uniquely identifiable shape.”

I honestly don’t know how Anping Liu, Corning, will canvass the OFC/NFOEC community on its preference for spatial division multiplexing (SDM) versus mode division multiplexing (MDM). What I do know is that the SDM Workshop he chairs (Sunday, March 4, 4:30PM – 7:30PM), and the rump session (Tuesday, March 6, 7:30PM to 9:30OM), will stimulate debate on the pros and cons of SDM for fulfilling future network requirements.

It’s easy to see why the community is undecided. For the past 30 years fiber capacity has followed an evolutionary trajectory encompassing wavelength division multiplexing and more recently higher-order modulation. With laboratory trials within reaching distance of the theoretical limit around (my best estimate is 150 Tb/s on an EDFA network), practical options appear to be running out. Will OFC/NFOEC 2012 be the first time we must hold our hands up and concede the inevitable? Are we the Dunno Generation?

Those against SDM point out the requirement to design and install new optical amplifiers and ROADMs, not to mention the complexity of fiber splicing and device integration.

Call me an optimist but these challenges appear minor compared to the benefits of a successful resolution. Already the literature is brimming with great ideas for multi-core design and amplification. For my part I reckon spatial light modulators (SLMs) used so effectively in wavelength selective switches (WSSs) could be used to guide light into and out of a multi-core fiber. Moreover they could provide by-pass routing option via inter-core switching.

Considering the importance of SDM and associated MIMO encoding in the wireless domain, it seems certain to me that spatial muxing will be adopted. The real question is whether we also need MDM and if so when?

SDM or not SDM? My glass will definitely be half full. See you in the bar!

Dr David Nugent is Founder and CEO of Elucidare Limited, a boutique technology development and investment advisory business.


Posted: 21 February 2012 by David Nugent | with 0 comments

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