Buying fibre optic cable

[OverWorked]

I recently been dropped in it by the head and need to buy a fibre cable in the next couple of weeks. (See my other thread)

 

The electrical contractor will start on site soon, and can pull in our fibre cable with the phone cables to be terminated by others later when the extension is completed.

 

I've asked around and done some research and it seems that this is the type I should buy.

 

Loose tube

62.5 / 125

multimode

Indoor / Outdoor

LSOH

 

This certainly seems to be the most common type, and so I imagine is the type used in gigabit fibre ethernet comms. This is the type of fibre we also have going to another part of the building.

 

Any advice (apart from the obvious - get a specialist contractor to do it)?

[Face-Man]

Hi,

 

We are using 62.5/125 loose tube for Gigabit SX backbone. The only dificult we had was when the contractor terminated it with ST fitting when it is alot easier using SC (can't be pluged in the wrong way around). Appart from that the only thing I would recomend is making sure nobody else tryes to put things in your fibre trunking. We had an alarm company that nicked a fibre and brought half the school down. So think carefully about routes and built in resiliance if possible.

[OverWorked]

Thanks, face-man. The existing cable terminates at the fibre tray with ST connectors. It would be easy to get them the wrong way round, but would be easy to spot the mistake and put them right again.

[MkII]

Not seen any SC terminators in a while - thought they'd become extinct.

[Norphy]

I'd spend the extra and get 50/125 (OM3) cabling if I were you. It can transmit at gigabit distances for longer distances and it will support 10gbps when its affordable.

[CyberNerd]

Definately go 50 micron as it potentially allows higher data rates unless you need to couple to 62.5 micron (not through a switch).

 

The biggest mistake I made w.r.t fibre is laying 'internal/external' fibre in tunnels between some huts - within 3 months the rats had eaten large sections of it - through the kelvar!. Last week we had to re-lay the lot using steel/polymer gel-filled armoured cable and this week we are terminating it.

 

I would recommend you talk to John from techoptics http://www.techoptics.com/

+44(0) 173 277 0466

John has been in the business 20+ years and really knows his stuff! He will be able to provide exactly what you need.

Techoptics also do really good training sessions.

 

Also be aware of some contractors terminations, insist that they give you a magnified printout of each termination and the total light loss (in Decibels) for each connection - after we had our termination training we checked all our existing cable for light loss and found that the work was a really poor standard, we have since re-terminated most of the cabling ourselves.

[CyberNerd]

tutorial here:

 

http://www.techoptics.com/pages/Fiber%20Optics%20-%20Home.html

[MkII]

Great link CN!

 

How much is that training then? And how much did you pay for the terminating kit?

 

Ta!

[CyberNerd]

IIRC the training was about £400 per person (full day).

not sure how much the kit was, it was either £500 or £1000 ish.

 

It sounds quite expensive but has been worth it for us. We've done a lot of terminations and layed over 1.5km of cable, because we have so many 'external' buildings. There is more glass in this site than brick now

[MkII]

Thanks

 

Good to have an idea in case it should come up. Sounds a good price to me.

[OverWorked]

Thanks CyberNerd,

 

That's a good website. I'm ploughing through the tutorial.

 

One thing I'm concerned about 50 micron is connecting it to the switch. Do manufacturers (like 3com) make 50 micron fibre modules for their switches? I'm guessing that the module would have to match the cable (or would it?). Please tell me if I'm taking rubbish!

 

It's only a short distance (about 120m), and it is only a sports hall with a small office, so I doubt we'll want 10Gigabit in the forseeable future.

[OverWorked]

Also: whats the difference between OM2 and OM3 cable? They're both 50/125 aren't they?

[CyberNerd]

One thing I'm concerned about 50 micron is connecting it to the switch. Do manufacturers (like 3com) make 50 micron fibre modules for their switches? I'm guessing that the module would have to match the cable (or would it?). Please tell me if I'm taking rubbish!

 

All the fibre modules will take 50/125 or 62.5/125 cabling so it would be fine to plug a 50/125 cable into any module, *but* the patch cables must also be 50/125. The problem comes when coupling the cables, not pluging them into a fibe module/switch: a 50 micrometer core can be coupled to a a 62.5 core but you would expect signal loss when doing so.

 

I still reckon its worth going with 50/125 because it 'future proofs' the network a bit. Its not much more expensive and if/when you start adding things to the network, it should make life easier.

[CyberNerd]

Also: whats the difference between OM2 and OM3 cable? They're both 50/125 aren't they?

 

I think its related to the quality (transparency??) of the glass. OM3 can do higher data rates at longer distances than OM2. I guess they can be either core diameter.

 

As I posted earlier: I would recommend you talk to John from techoptics http://www.techoptics.com/ +44(0) 173 277 0466 He knows far more about this than me... the rats ate the last cables I layed !

[OverWorked]

@ Cybernerd,

 

I spoke to John, jolly nice chap.

 

He did say that OM3 would be overkill for our little project, and OM1 would be more than enough.

 

He's recommended a cable type and given me a price - very cheap too. He said I should get tight buffered instead of the loose tube I was going to get. I'm only vaguely aware of what this means, but I trust his opinion.

 

It's also saved money - from £1.70/m for what I was going to get to 86p/m.

 

Thanks a lot!