[c-nsp] DSL signals vs DOCSIS

Arie Vayner (avayner) avayner at cisco.com
Fri Dec 11 08:59:44 EST 2009


Yuri,

If you have fiber between the CPE and the "DSLAM", then you do not need
DSL... You just deliver FTTH (Fiber to the Home).
If you have fiber for only part of the way, then you deploy a mini-DSLAM
(which is what is being done in many places), and then use the fiber for
upstream connectivity for the the mini-DSLAM.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Yuri Bank
Sent: Friday, December 11, 2009 14:46
To: Yuri Bank; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] DSL signals vs DOCSIS

I understand that they use different frequency ranges, but why can't the
DSL
freqencies be converted and sent over fiber somewhere between the CPE
and
the DSLAM ?

On Thu, Dec 10, 2009 at 11:41 PM, Dmitry Kiselev <dmitry at dmitry.net>
wrote:

> Hello!
>
> On Thu, Dec 10, 2009 at 08:48:27PM -0800, Yuri Bank wrote:
>
> > Why can't DSL signals pass through fiber optics, yet we have HFC
networks
> > that obviously have no issues going from copper to fiber.
> > The modulation techniques DOCSIS and DSL use are similar, so what
> prevents
> > this from working with DSL? Is it that the RF is to weak and the
> conversion
> > process messes up the signal?
>
> It is becouse very different frequency ranges:
> DSL   0.02-1.1 MHz for both up and downstreams
> DOCSIS   16-30 MHz for upstream
>         50-800 MHz for downstream
>
> --
> Dmitry Kiselev
>
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