DWDM on 250 Km dark fiber without re-amplification

Brian R briansupport at hotmail.com
Tue Dec 27 17:41:00 UTC 2016

I have to agree with Brandon.  I have not worked with Ciena equipment directly but have work with carriers that use it.  I worked with Adtran on this kind of setup and like Brandon said they require a lot of information to build what is needed for each specific run (fiber type, quality, wave length optimization, number of splices, etc).  I've seen the tools Adtran uses to calculate exactly what equipment is required and it is pretty complex for distances even close to what you are talking about.

Definitely check for a re-gen site(s), most likely the carrier has to re-gen their own runs down this fiber path (another thing to consider in the calculation matrix especially if you are not trying to re-gen your run).

I have to give Baldur kudos for finding that I'm still amazed that Fiberstore is claiming that's possible without a lot of information.  I have worked with Fiberstore and they are a cooperative vendor and their products work for what we have used them for.

My suggestion is to reach out to Fiberstore, Ciena, Adtran, and other vendors that people recommend with a detailed email of what you would like to accomplish and the information you can get.  Ask for a design engineer (I know Adtran has them and assume others do) to get the info you need and see what they can mock up for you.


From: NANOG <nanog-bounces at nanog.org> on behalf of Brandon Martin <lists.nanog at monmotha.net>
Sent: Sunday, December 25, 2016 12:41 AM
To: nanog at nanog.org
Subject: Re: DWDM on 250 Km dark fiber without re-amplification

On 12/23/2016 07:14 PM, Jeremy wrote:
> Hi all,
> First, i'm sorry for my english, i'm french and i don't have a good
> level in this language. But i want some informations and i'm sure,
> someone will be give the good anwser about my question.
> So, i'm regarding to rent a dual dark fiber in France, the estimated
> distance is 225 Km, but i know there are a lot of optical switching on
> the highway where it's fiber is installed (in theory, all 80 Km). So, i
> used the bad scenario, in adding 25 Km on my need.
> I would like to buy a amplificator and multiplexer DWDM to add some
> 10Gb/s waves on this dark fiber. I've see that the amplification is
> better on 100 Gb/s synchronised ports, but we don't have enoug capacity
> on our router to add 100 Gb/s interfaces.
> So, someone has installed this type of hardware on a dark fiber without
> regeneration  on 250 Km of distance ?
> If yes, with what kind of hardware ? If you are commercial for this
> hardware, please contact me in private message.

Look up Raman amplification.  The short of what this does is it pumps a
ton of power into the near end of the fiber span and creates what looks
somewhat like a typical color-blind amplifier somewhere several dozen km
out on the span.  You'll also need to dump a ton of power into the span
at the far end using an EDFA or similar.  Even with both of those, that
distance is still going to push the raw optical power budget of even
most state-of-the-art transceivers especially if the fiber is old or of
low quality (high loss, high dispersion, etc.).

The longest span I've ever gotten a vendor to commit to an engineered
design for was about 140km, and of course they needed full
characterization of the span before they'd do it.  At those distances,
distance alone is no longer sufficient to throw together a design.

It seems highly likely that there's at least one re-gen facility along
that span.  I'd definitely see if there is one and if you can get some
space in it.  That will knock you down into the 100-130km range on both
sides of the re-gen, hopefully, which is perfectly doable.

You are somewhat correct that 100Gb interfaces often handle longer
distances better, but it's because they are often using coherent
receivers and carrier-synchronous transmitters rather than raw power
receivers and ASK pulsed transmitters.  There are vendors that sell
coherent 10Gb transceivers, too, and they'll be cheaper than 100Gb
solutions especially if you don't need the extra capacity anyway.  I'd
definitely check them out for this type of application especially if you
can't get any dispersion compensation in the middle since coherent
optics are usually much more tolerant of chromatic dispersion.

The big vendor I've worked with in the past on this sort of stuff is
Ciena (and they're certainly a juggernaut in the industry) though I have
no connection to them other than as a satisfied (if occasionally broke
after a PO or out of breath after seeing a quotation) customer/integrator.

Brandon Martin

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