DWDM on 250 Km dark fiber without re-amplification

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.

Thanks you for your time,


I have not done this as our links are not that long. However in theory this is how I would do it. There are nice integrated solutions that will do it as a black box, but someone else will have to tell you about that. I am using Fiberstore as a reference because they have the necessary components with pricing directly online, but there is of course multiple alternatives.

So first off forget about 40G and 100G. This will be N x 10G and N can be as large as 96 channels. 100G would be the same equipment (possibly without dispersion compensation) but with each 100G stream as four 25G wavelengths. However the optics are very expensive and hard to get for 40G and 100G while 10G is relatively cheap and easy.

You need the following components:


They list all you need with a nice drawing. Get the components from them or someone else. The nice integrated solutions are just these components in a box.

They only list the solution as 200 km. You will have to send them a mail and ask if they can do 225 km.

Also you need to check that the black fiber provider allows amplified signals at this level. Not everyone do. Normally the signals are not that dangerous, but with this a unaware tech can go blind if he is unlucky. It is not clear if the Fiberstore equipment automatically turns of the laser in the case of a fiber cut and that might also be a requirement.



I agree with what Baldur suggested..

Only thing I would point out that ..
Hardly anyone installs 200km fiber runs without having some sort of a Regen facility.

While you can push the signal over the 200km link, in the long run you may be better off see if there a Regen facility (typically 70/80km) that you can use to re-generate the light.

Best of luck.

Faisal Imtiaz
Snappy Internet & Telecom

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.

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.



SmartOptics is one such vendor that I've used in the past that may be able
to do this.



You will want to request an OTDR characterization of the dark fiber path
from its owner. If you can post OTDR "shots" with full resolution images in
a lossless image format to the list, we may be able to take a guess if the
distance is feasible without amplification inline.

For equipment choices you're looking at the usual vendors for DWDM long
haul ROADM chassis such as Ciena, Adva, Huawei, ZTE, Infinera, etc.

If you simply want to do point to point DWDM mux:demux on the 250km fiber,
your choices will be different than if you want the ability to insert a
chassis at an intermediate location and drop or insert wavelengths.

It may be possible, at a lower cost than buying 100GbE capable DWDM chassis
type systems, to do a single router-to-router linecard link with coherent
100GbE signal with FEC on the 250km path. Again this will totally depend on
the OTDR results and link budget available.

Polarization and dispersion will come into play at these distances if you plan on running a DWDM system. In that world you get what you pay for as a rule. The more expensive gear is more forgiving to fiber that is not 100 % up to high quality. Most small one or two RU gear from all the vendors mentioned have 100 gig cards that will be 100 gig on the DWDM side and break it out to 10 sfp Plus ten gig ports for the client side. Another thing to look for in this is link down propergation ... you will want the client facing links on both sides of the optical span to go down if the span goes down. Good luck with your quest