Wednesday, September 19, 2007

How long of a loop? / Quelle longueur pour la boucle locale?

It's clear to me that one of the most challenging elements for network operators is actually mapping out the most efficient topology in terms of capacity and cost. I thought I had decided how I would lay out the network but now I'm starting to wonder if I should readjust after certain developments here in France.

One of my big struggles now is how long to make the "local loop" element of the network. I know that "local loop" typically refers to a copper twisted pair but I'm not sure exactly what you would call its replacement in FTTH-speak.

Initially I had imagined putting a concentration point in the middle of our residence (100 meters away) where I could install active equipment. Then any operator could come and patch into us to offer services at the edge of our network. However, now I'm beginning to wonder if I should plan on taking all fibers all the way back down to the exchange 600 meters away.

If I thought that I would surely stop at just laying fiber in our residence then locating the active equipment next to us would probably be a good idea. However, the situation becomes a bit more complicated if I ever decide to spread out the fixed costs of connecting to exchange by expanding the project to other subdivisions at a later date.

I'm not sure that it makes good economic sense to place active equipment in each subdivision of a small village. It's not cost effective for the equipment and it surely introduces more potential points of failure. At the same time, it may not be cost effective to run a large amount of fiber to the edges of the village several kilometers away either.

Right now this is playing out in Paris. France Telecom's PON network requires less physical space than Iliad/Free's point-to-point network. That means that Free is likely looking for property all over Paris where it can locate active equipment to terminate its fiber closer to users.

I don't need to make all these decisions now since I can wait to see how the project progresses and if other subdivisions are interested in connecting with us. One of the important decisions for now though is how big of conduit I should put in leaving our residence out to the exchange? Do I plan for something big enough to accommodate future growth - even if it will increase my up-front fixed costs?


Zed said...

You should definately put all the equipment in the exchange. Small POPs and/or equipment in the field is a bad idea. 600 m is also a very short distance and won't bring any significant costs. Furthermore, instead of putting in a big duct, you should place multiduct in the trench and fill it up as needed.

Vincent said...

You can also create a kind of "carrier hotel". A multiple operators POP (3-4 racks space) and empty ducts that cross your residence.
Other operators can use you POP as a head end and spread their network ourside your residence by pulling their own cables in your ducts.

Anyway, Zed is right : 600m is nothing for a fibre connection.

Tad said...

Thank you Zed and Vincent for your comments. The more I hear from people the more I realize that it will probably be better try to limit the amount of active equipment as much as possible.

The 600 meters to the exchange is a bit of a hurdle because I'd be leaving private property and having to dig up some major roads in the village. The estimate from Yvelines Numeriques to to reach their network 300 meters away was around EUR 27'000 if I remember correctly. I'd only have to go a bit farther to reach the exchange itself.

If I were to build the POP here in the residence (solely on private property) then I could avoid much of the municipal red-tape of digging in public roads. That would mean that I'd have to rely on other operators to build out to me but France Telecom probably has existing ducts they could already use.

I'd love to build all the way back out to the exchange but that will likely be a second step.

I'd be very interested in the idea of a carrier hotel although I'm not familiar with it. The exchange near our house (which isn't used for residential DSL) is very small so I'd have build something on village land next to it. The Mayor did mention that France Telecom came to him asking for more land at the exchange. Hopefully he'd be able to accommodate us as well.

Zed said...

90 euro per meter sounds a bit exorbitant. Even directional boring isn't that expensive and with that you don't have to tear up the streets.

That being said, if there are any pre-existing ducts you are probably better of just renting.

FT will likely rent the ducts on request and if they don't feel like it, remaind them that they are going to be forced to rent ducts to third parties in the near future, so just get with the program.

A carrier hotel is not something you build for you and your neighbours, that's what the POP is for. I think you will have a hard time to get anybody to co-locate with you outside the POP. If you haven't done so by now, I suggest you start talking to presumtive service providers.

- Zed

Tad said...


I'm writing a post about possible business scenarios and it will be ready soon. There are a number of options and many of them depend on whether I am the person who pays to dig the road 400 meters to the exchange or not.

For our residence, I think it would probably be easier for us to bury our own conduit if they end up redoing the streets and sidewalks. If not it may be easier to try and get space in either FT's or the cable company's existing ducts/conduit.

However, when it comes to getting from our residence (subdivision) to the exchange I think ducts and existing conduit are going to be the best option if they are available.

The other day my boss passed along part of the French law which talks about access to ducts and their rental charges. I thought I had blogged about it but it seems as I didn't. I'll have to look it up again and post it.