The problem isn't getting the SFPs to "listen" to different wavelengths. The 
problem is that SFPs "listen" to ALL the wavelenghts. 

This is why you have to use a demux to separate the wavelenght, so that you 
only "listen" to the one meant for you. Alternatively you can use a filter to 
block out all the other wavelenghts than the one you are interested in. 

NG-PON uses a mux in the OLT side and active filters on the ONU side. 

Jared


> Sent: Thursday, October 11, 2018
> From: [email protected]
> To: "AnimalFarm Microwave Users Group" <[email protected]>
> Subject: Re: [AFMUG] Dumb Fiber MUX question
>
> Well, I can some some of them listen to different wavelengths or else NG-PON 
> would never work.
> 
> But a CWDM mux is pretty cheap.
> 
> -----Original Message----- 
> From: [email protected]
> Sent: Wednesday, October 10, 2018 3:41 PM
> To: [email protected]
> Subject: Re: [AFMUG] Dumb Fiber MUX question
> 
> > Can I use a splitter instead of a Mux/Demux?
>   Not to separate wavelenghts.
> 
> 
> > I'm just thinking if I have color coded SFP's that only talk and listen
> > on their own wavelengths, and assuming I'm ok with the losses from
> > splitters, then do I actually need a Mux?
>   SFPs have broadband light detectors, so they don't actually "listen" to a 
> specific wavelenght.
>   So, yes, you need to demux the wavelenghts in order to filter away all 
> other wavelenghts than the one you want to "listen" to.
> 
>   If you are using just one TX and one RX wavelenght then you could use a 
> splitter on both ends assuming you have the optical budget and there aren't 
> too many impairments degrading the signal (reflections, self interference, 
> etc.). But if there's just one RX and one TX, why not use Bidi optics 
> instead?
> 
>   Anything with more then one TX or RX wavelenght will need muxers and 
> demuxers.
> 
> > I'm looking at a scenario where I could have a Mux at one end of a
> > fiber, but I don't have electric at the point where I'd like to split it
> > back into two connections.  That's what got me wondering.
>   If you use a passive mux/demux you don't need power.
> 
>   However, I feel like I'm missing something. Are you trying to use a 
> splitter instead of a OADM?
> 
>   Something funky like this?
> 
>   MUX--splitter--DEMUX A
>            |
>            \-- DEMUX B
> 
>   I guess that could work.
> 
> 
> Jared
> 
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