Multimode fiber scenario ..


We have a school with several builings and dorms. Our server room is situated somehow in the middle and there are buldings lined up in two directions, the farthest away is around 400m from the servers.

We need to connect LANs in each of these buildings to the servers. I assume that multimode fiber is the way to go as the distance is within limits, but I need some hints on the available options.

Also we want to distrubute *two* different nets. Can the fiber be 'tapped' at each builidng or do we need separate fibers for each house?

I would appreciate tips on 'budget' solutions and links to pages with relevant informations

thanks in advance


Reply to
Geir Holmavatn
Loading thread data ...

Easiest is to pull in a twelve strand fiber cable between the buildings. buried cable and flown cable have special requirements that you ought to leave to the experts,

Each building ends up with a 12 or 24 port fiber patch panel. Patch through with short jumpers all but the ones you need in that particular building. Each building will need two strands for each physical network. As for multiple networks, check out the port subdividing available on CISCO switches. I'm blanking on the name of it right now. All I can think of is VPN, but I know that is the wrong one. blast! I need some caffeine!


Reply to
Dale Farmer


You can do the following:

A) Pull seperate fiber optic cables to each building and have them homerun back to your server room. Most expensive approach...


B) Pull a 24 strand fiber optic cable somewhere in between where the remote buildings are located and terminate this cable into a fiber patch panel, and then distribute shorter length runs of fiber cable from this point to your other buildings. Easier to do and a bit cheaper.

Reply to

"Dale Farmer" skrev i melding news:

So there is no prvision to just cut the needed strand and leav the other elven in a nice roll unopened?

Can I daisy-chain connectors for low-bandwidth users in several buildings or are fiber just a point to point thingy?

Which kind of connectors and cable type would be best for 500m max length multimode (in Europe, as of connector standard)?


Reply to
Geir Holmavatn

Rather than distrubute each 'net' over seperate fibre, is it practical for you to use 802.1Q tagged VLANs?

At the College I work at we have five out buildings; using Nortel Baystack

350-24T switches with 2 port 100Base-FX fibre MDA's I've built a ring (with spanning tree enabled on the fibre ports) and 802.1Q tagging to distribute staff and student networks over 62.5/12/5 multimode fibre.

In this configuration I only need two 100-Base FX fibre ports on the Ethernet switch in the main building to feed the outbuildings rather than five (ten if I didn't use 802.1Q tagging) and it's tolerant to any single switch failure, or more commonly our Tech Services department turning the power off.

We did it this way to keep cost down as the outbuildings only support about

50 users total. Even if you need seperate feeds to each building I would suggest that 802.1Q tagging for the two networks would halve the fibre you need.


Reply to

Understanding the difficulties with money at a school (I work at a state college) but I would highly recommend doing this on the cheap. When you get in to this realm of cabling, you've really got to do it all right or not at all. Because if you just sort of band-aid it in now, you'll be doing it again in 4-5 years, whereas if you do it right, you won't have to do anything with in in 25 years. And that's just considering technological advancement, not to mention maintenance which could be something you end up dealing with once a year if not more.

Having said that, how to do it right?

Yes, a fiber cable could be "tapped" (run a 24 strand, drop of 4 strands at each building), but you really wouldn't be saving much. Fiber isn't really all that expensive, it's the labor and the termination that kills ya'. Anyway, first off, I would suggest singlemode cable, unless the hardware you already have is multimode. Reason being, the only multimode I would put in is 50 micon laser optimized for 10gig @ 300m, (don't flip about the 10gig, it's really only a unit of measure here) and doing so would limit you're future usability as you're over 400m in some places. Also, singlemode fiber is cheaper than this particular multimode. Next, for cable counts, there are a couple options. First, I'd homerun a cable from your server room to each building with 12 strands. This is the most flexible, and the method that will last you the longest without having to do anything with it. Another option is to loop through each building, but to do that would require more strands. Example: if you have 7 buildings, 3 each direction from your central server room. Run one 48 count to the first building in each direction, then from those 24 strands to the next building, then from those 12 strands to the last building. You would have to patch through at each point, so for the furthest buildings, this gives you 2 additional points of failure as well as several dbs of additional loss, which may be too much for you signal loss budget.

The other option is to put extra fiber connection (GBICS) in your switches in each building and hang the next building out on the previous, but this could cause serious bandwidth/through-put issues. The would allow you to put in equal numbers of fiber counts (12 minimum).

For termination, the most cost effective is to do use a wall mounted LIU from any of the major manufactures. But that depends on what you have in the way of telecom space in each of the out buildings. If you have a full room with a rack, I would do rack mounted, again for the flexibility. I prefer Panduit's rack mount fiber trays/drawers.

And that's about as far as I can really speculate. You really should have a professional telecom designer put something together for you. A badly designed and installed system will cost you twice as much as a properly designed one from the beginning.

just> Hi,

Reply to
Justin Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.