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.kuh...@gmail.com> Sent: Friday, July 8, 2016 10:40 PM To: Rod Beck Cc: nanog@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.b...@unitedcablecompany.com<mailto:rod.b...@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>
