Dark fiber usage info request - know-how pointers and experience sharing

Looking at dark fiber leasing as an alternative for existing ISP-acquired
MPLS, MetroE, P2P, etc. services. I would appreciate some pointers (links)
into specific technologies used with dark fiber, as direct consumer (not
ISP). I am not looking for the theory behind (C)DWDM, but rather real life
implementations and experience with folks operating such.

Highly appreciated would also be extra info on what the learning curve
required for traditional network engineering crew to operate devices
terminating into such, and maybe even work (installation and operation)
needed to maintain plants with this infrastructure.


In the USA the Federal School Lunch program has built out a parallel fiber
network equal to or superior to telco fiber in many urban locations, under
the E-Rate program. TheE-Rate backbone fiber is leased typically on a
10-20 year IRU basis. Sunesys is a provider of dark fiber, and their web
site interfaces with Google Maps to provide detailed fiber maps where they
have deployed fiber (I do not work for Sunesys, or any other dark fiber

My own experience with dark fiber using off the shelf long reach sfps
(GiGE, CWDM wavelengths with passive mux technology, h, connecting Ethernet
switches from various vendors) is that dark fiber networks are extremely
stable,and require little maintenance once operational. An experienced
network engineer will have no trouble deploying such a network.


Your people will need to come to grips with the fact that just being
able to see light coming out the end of the fiber is no longer
sufficient. Depending on the length you will have to deal with
Chromatic Dispersion and compensation for that. People will need to
understand that waves that are coming into a filter at -3 will totally
blow out waves coming in at -15, especially when EDFA (amps) are
concerned. DWDM (in the metro instance) is all about light levels and
making sure that all waves are within 3-5db of each other as they go
from site to site. Also documentation of exactly which waves are used
on each part of a path and management of your waves is important,
especially to the NOC when troubleshooting or determining exactly
everything that's affected when a path or wave goes down. Also fiber
cleanliness and proper handling becomes really important. With 850nm
and SMF you can pretty much lick the end of it and it will stick work
fine. When running 20 lambdas over 50km it becomes a much bigger
issue. I would recommend investing in good fiber cleaning/scoping
gear and proper training for your physical plant folks. Also invest
in a couple of decent OSA's to check levels of all waves coming off a
fiber. You don't have to drop $80k (or lots more) on gear, but you'll
need something capable of determining the power of different waves at
once and checking for noise. JDSU, EXFO, and Fluke make some good
gear and should have options to meet just about whatever your budget
is. An OTDR is nice to have but not crucial, whoever is leasing you
the fiber should be able to provide OTDR shots and characterization of
the paths. Normal light level checking at various points should be
able to provide you enough info to determine whether its your gear or
the long fiber.

With fixed wave gear you can start pretty cheap and build a decent
enough system. If you're making lots of moves/add/changes all the
time, I'd recommend tunable optics, especially for sparing. Then move
to ROADM gear if needed. For the most part if your system is fairly
static once you get it up and going you don't have to touch it much,
it just works. The things that then change are when fiber is cut or
stretched due to weather conditions or backhoes. The gear is pretty

Hope that helps a little bit. Enjoy!


Thank you all who answered. I got a few good leads to follow, and
information on operation gotchas.