Lots of work being done with pulse amplitude modulation (PAM-16) at the moment. 
 

From: Eric Kuhnke via Af 
Sent: Thursday, October 23, 2014 1:03 PM
To: [email protected] 
Subject: Re: [AFMUG] fiber signaling

here's a decent intro, covering RZ-OOK (return to zero, on-off keying) vs 
coherent modulations.

http://www.jdsu.com/ProductLiterature/optical_modulation_methods.pdf



At least in the next few years I doubt any of us will be using coherent optics 
for WISP type applications. If you need 40 Gbps to an upstream transit provider 
right now it's still much more economical to create a Juniper LAG (or cisco 
portchannel) of four relatively inexpensive 10Gbps SFP+ based interfaces.


On Thu, Oct 23, 2014 at 11:47 AM, Adam Moffett via Af <[email protected]> wrote:

  Something came up in fiber training that I attended recently that I found 
hard to believe.

  The instructor said that the signaling was simply on/off.  I.E.: light on = 1 
and light off = 0.

  I would have assumed they would use some sort of more advanced modulation 
than that.  In fact, I'm sure I've read about creating an optical carrier wave 
and modulating it.  

  Was the instructor correct?  Is it just blinky blinky on/off and that's it?  
If so, then why the hell would they do that?  Wouldn't they get another order 
of magnitude of capacity by applying a more advanced modulation scheme? 

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