Interesting Article on Modulation Schemes

Fri Jul 8 22:15:15 UTC 2016

I don't see wide spread deployment. The most recently built TransAtlantic cable is Aquacomms It is QPSK and 130 100 gig waves per pair. Does one really need more? C-Lion, the new Finland/Germany cable is 18 terabits per fiber pair. I think that is 8 QAM. Is that a representative sample?  I don't know. It is certainly a small sample and hence could be highly contained by random error. Since so many ISPs dropped their Layer 2 networks in favor of buying cheap transit, the market for 100 gig waves is limited to Tier 1 ISPs, a few huge hosting companies, and the public Web giants in shopping, social media. I have been told that the video streaming guys like Netflix are more similar to Akamai than Telia. Dense local footprints.

Bottom line. I don't think the demand is sufficient or the interface costs on the customer side sufficiently low. Could be wrong about both.

Regards,

Roderick.

________________________________
From: Eric Kuhnke <eric.kuhnke at gmail.com>
Sent: Friday, July 8, 2016 11:45 PM
To: Rod Beck
Cc: nanog at nanog.org
Subject: Re: Interesting Article on Modulation Schemes

Not just "talking about" 16QAM is in active use for subsea high capacity channels...  Both Xtera and Infinera are shipping DWDM terminals for installation at cable landing stations that use 16QAM for 100/200/400 Gbps superchannels.

http://www.xtera.com/home/technology/100g-and-400g/
100G and 400G Coherent | Xtera<http://www.xtera.com/home/technology/100g-and-400g/>
www.xtera.com
Xtera's coherent technology support 100G, 400G and beyond optical channel rates for high-capacity backbone networks.

http://www.xtera.com/home/products/nu-wave-optima/

Unless I'm grossly mistaken, Alcatel-Lucent and Huawei as well.

On Fri, Jul 8, 2016 at 2:24 PM, Rod Beck <rod.beck at unitedcablecompany.com<mailto:rod.beck at unitedcablecompany.com>> wrote:

Apparently 40 gigs is the limit of simple laser flash equals 1, no flash equals 0. Above that threshold the signal becomes larger than an ITU 50 gigahertz channel. Most new undersea cables are using QPSK or 8 QAM and talking about 16 QAM.

This companion piece explains it: http://digital.lightwaveonline.com/lightwave/20130708/?pm=1&u1=friend&pg=19#pg19.

- Roderick.

________________________________
From: Eric Kuhnke <eric.kuhnke at gmail.com<mailto:eric.kuhnke at gmail.com>>
Sent: Friday, July 8, 2016 10:40 PM
To: Rod Beck
Cc: nanog at nanog.org<mailto:nanog at nanog.org>
Subject: Re: Interesting Article on Modulation Schemes

Essentially the transceiver optics are applying the same modulation and coding that have been used in point-to-point microwave for a long time...   Starting from OOK, up to BPSK and then on to QPSK, 16QAM and possibly 64QAM with varying levels of FEC.

A singlemode fiber is just an extremely narrow diameter waveguide. Big difference in frequency between a 71-86 GHz FDD radio pair and optical at 191 to 196 THz.

On Fri, Jul 8, 2016 at 1:50 AM, Rod Beck <rod.beck at unitedcablecompany.com<mailto:rod.beck at unitedcablecompany.com>> wrote:
The new undersea cable systems are now capable of 18 terabits per fiber pair. It is interesting how combinations of bits are being represented by combinations of optical features.

http://www.lightwaveonline.com/articles/print/volume-30/issue-5/features/which-optical-modulation-scheme-best-fits-my-application.html

Roderick Beck

Director of Global Sales

United Cable Company

www.unitedcablecompany.com<http://www.unitedcablecompany.com><http://www.unitedcablecompany.com>