Noob question - Fibre Optic Cables

[TonyR]

Please can someone point me in the direction of a dummies guide to understanding fibre optic cables. We have a cabling guy who is putting in our new network fibre optics to link buildings and across one building.

 

He speaks of installing a 4 channel fibre optic but keeps asking about 65s or 157s or similar....

 

I get the basic of what a fibre optic is and how it works, the supposed unlimited bandwidth etc. The installation will be linking 3 HP switches in serial...

 

But, what is all the technical explanations for current cables etc please?

 

Many thanks,

 

Tony.

[CyberNerd]

This is quite a good site, and the company is good too:

 

Fiber Optics - Home

[featured_spectre]

Fibre is not unlimited, its capacity is very very high, but not unlimited.

 

To my knowledge there are 3 different types of fibre (someone please correct me if I am wrong)... OM1, OM2 and OM3

Each OM has a different capacity and length it can be run...

 

beyond that you would need someone else to help as fibre is not my strong point.

[sonofsanta]

Speed is decided by the signalling gear at each end, not the cable itself, for the most part - ou can only send data down it as fast as your little lights can blink, after all.

 

Gauge is important as well - you normally get 50/125 and 62.5/125 as the two sizes - don't ever mix and match down one stretch of cable as it devastates performance, something along the lines of halving it. When I say don't mix, I mean - don't have a long run of one, then use the other gauge as your patch cable.

[synaesthesia]

We've had a guy in recently who's taught us a lot about it, and we hope to get some decent training in it soon (which itself isn't cheap).

 

Basically you've got a fair few standards of cable, starting easy you've got "single mode" and "multimode" - singlemode is typically used for longer distances and multimode for short runs.

The 50/125 and 62.5/125 are referring to the wavelengths/width of the actual fibre core - so naturally when you transfer from one to the other (i.e. don't!) you'll lose some or all signal.

 

The amount of "cores" are referring to the amount of actual data carrying cables although they will usually always be in a single larger cable/sheath.

 

Don't worry too much about the ends, there's a million and one different ways to terminate fibre and I can never remember any of them!

 

Rule of thumb we go by is simple: if it can be done with copper, do it with copper

Long runs however are all fibre.

[john]

Depending on the distance between the switches you are linking with fibre I would be asking for OM3 fibre to be installed now, this will be good for 10 gig links going forth for a good distance (were talking 100's of meters), the cost for cores in the cable is minimal now, so don't just get enough for the job, we tend to put a minimum of 8 core to each cabinet now unless its a main building feed / special job AKA digging the car park up etc... then we stick in a 24 core then there is scope for the future

[synaesthesia]

Plus with the extra cores you can always trunk connections for a mixture of speed and failover reliability

[fr4j0]

Assuming your connecting 4core to provide trunks between switches (theoretically 20G connection - depending on fibre type)

 

And the distances and type shown below.

 

fibre optic info.pdf