Re: Pluggable Coherent DWDM 10Gig

[Mikael Abrahamsson <swmike () swm pp se>]

On Fri, 25 Apr 2014, Phil Bedard wrote:

> What are you trying to do?  Why do you need the receive side to be tuned
> to a specific narrowband wavelength?

Because he doesn't want to use filters. A coherent receiver s like a FM 
radio, you can tune what it listens so. So if you send it all waves the 
receiver can decide what to listen to.

>  Coherent doesn't really make sense in 10G becaue 10G long-haul is still 
> on/off keyed and doesn't care about phase. Coherent detectors are needed 
> where phase of the signal is important like long-haul 100G where 
> multiple analog photonic signals are mixed on the transmit side.  It 
> also requires DSPs to process the received information. You aren't going 
> to put a DSP inside a SFP+ cage.  With CFP2/CFP4/QSFP28 the optics 
> vendors would like people to start building the DSP onto line cards, 
> whether it be a router or transport shelf, because there just isn't the 
> packaging room to make it happen.

If you're today building a new DWDM system, putting in dispersion 
compensation isn't something you want to do really. Having pluggable 
coherent 10G would make a lot of sense for some.

> Terastream today doesn't use integrated router optics, they use Cisco's 
> nV-Optical solution. The connection between the router and transport 
> shelf is still gray optics, but the system is managed as a single 
> logical entity, with a 1:1 correlation between router port and 
> transponder.  You "tune" the wavelength on the router because of the 1:1 
> correlation. Terastream just uses passive DWDM muxes/demuxes, also part 
> of the same Cisco transport solution, and Cisco VOAs/amps.

That is correct, but the plan is to have integrated optics. It just isn't 
available yet. The plan is to make 100G so cheap you can use it 
everywhere, which includes actually having a royalty free standard for 
100G including FEC.

Ask your router vendor to support http://www.stupi.se/Standards/

--
Mikael Abrahamsson    email: swmike () swm pp se