The cost of labor to pull a new cable far outweighs the cost of fiber
cable itself, so if you are pulling new cable, always pull much more
than you need today, even if you don't terminate all of the strands
now. This especially holds true for outside plant cabling.
Given that each link typically needs 2 strands, and each piece of
equipment may need multiple links for redundancy, 4 strands only gets
you one piece of redundantly-linked equipment and no spare strands.
Always plan on having at least 2 spare strands at each equipment
location so you can swap over to them in case something happens.
Common cable strand counts are 6, 12, 24, 36, 48, 72, 144, 288. For
small locations with one or two equipment closets I would pull at
least a 12 strand cable, if not 24. Perhaps 12 strands per closet,
but it depends on your topology (whether you plan to home-run closets
to a main distribution point inside the building, or to an aggregation
point in another building). Terminating the fiber ends with
connectors can be a time consuming (labor intensive) process, so if
you are tight on budget you can opt to leave some strands unterminated
for future use--just be sure to have good documentation of what you
pulled where and what you did and did not terminate.
I wouldn't bother with multimode for outside plant, unless you have a
legacy application that requires it or you think you can reach
everywhere you need to within 300 meters for 10gig/40gig or 100 meters
for 100gig multimode OM3/OM4 links. For inside a building or
datacenter, using multimode might be worth it depending on the port
density since the multimode optics can be 1/3 to 1/4 of the cost of
equivalent singlemode optics. But keep in mind that even in this use
case, and even with the best OM4 multimode fiber, eventually higher
speeds will require an upgrade to singlemode or the use of
multi-strand connections to support a single link (like 12-strand MPO
If you do need multimode for some legacy reason, check that you get
the correct/compatible type. 62.5/125 micron (legacy FDDI cable)
won't mate with 50/125 micron (OM2 or the so-called "laser optimized"
OM3/OM4) without significant signal loss.
Overall, plan for any fiber infrastucture you install to last at least
On Thu, Jan 02, 2014 at 08:16:48PM +0000, Finnel, Michael wrote:
> I have recently taken over the roles and responsibiliteis of someone who spent the last 20 years managing our campus fiber backbone. As you can imagine, there was some knowledge that walked out the door. We are in the process making decisions on how many strands of fiber, and what kind, to pull to buildings going through renovations. Each of these buildings are getting new data closets with upgraded equipment. As a team, we decided multi mode fiber may not be needed in a couple buildings because of who will be occupying the location. Because of that, we are wonder what might be best practice in determining how many strands of single mode fiber we should pull in. In one building we have 4 strands of single mode going to a location where we are considering not pulling multi mode. So the question is...how many strands of single mode should we have going to that location with scalability and flexibility in mind? My immediate/limited experience with structured cabling has me wondering if anyone has come across this type of scenario, and what they did about it?
> Mike Finnel | Technical Services Supervisor | Marquette University IT Services | 414-288-8010
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