Strange fibre issue - only 3 pairs out of 4 working

[hallb15]

I've got a strange issue with the fibre running between our two buildings.

Its an 8 core cable with 3 pairs being used for curriculum and 1 for admin.

 

At the beginning of this week the admin office reported an issue saying that opening and saving files was taking ages. I checked the SIMS server VM, but couldn't find anything of note.

Then printing started taking an age, I'm talking several minutes to spool one page before printing.

Then SIMS started playing up with application errors.

I checked all the obvious connections and power cycled the admin edge network switch, no joy.

After various group policy updates and a couple of server reboots we were still no nearer to finding the fault.

I tried power cycling the fibre media convertor and it refused to re-connect the fibre link between the buildings.

Next, I tried a different, known good, media convertor and it still refused. So I changed the media convertor at the other end and it still wouldn't connect.

 

So I moved both the media convertors onto one of the other fibre pairs and it connected straight away.

 

I've since tried another set of known working media convertors on the faulty fibre pair and it refuses to connect. So the question is, what has happened to break the fibre and how can I fix it? OK, so that's 2 questions

[FN-GM]

Mice?

[hallb15]

I thought that but its a thick armoured cable with the 8 fibres inside - how come only one pair has stopped working?

The majority of the run is underground. I can't see any damage on the above ground cable.

[deano3693]

Get someone in with a tester and they will be able to locate the point from either end in terms of distance at which the cable is broken. If this is accessible it may be as cheap as a re-splice/join failing that your potentially looking at a new fibre.

[hallb15]

The strange thing for me was the way it degraded over the past few days but it wasn't until I disconnected and reconnected the media convertors it died completely. Can anyone recommend a decent fibre testing company in the Leeds area?

[Achandler]

How are the ends attached?

 

Often they are glued, not spliced, the glue can degrade over time, and they you unplugging and replugging might have been the final straw, thats just make the end disconnect.

[hallb15]

I've not looked in the box on the wall above the cabinet where the fibres are terminated - I didn't touch that end at all, only the fibre patch lead at the media convertor end.

I'll have a look and see if I can see anything obvious but I'm not too sure what degraded glue will look like...

[Achandler]

1 might have simply fallen out (it had on an old cable for us, im talking a 20 year old fibre, the end just fell off!)

[IrritableTech]

I hate media converters - they are possibly the most unreliable bit of kit we've now thankfully eradicated from the network here. We had a similar issue to this - had a company out to test and they found no issue on any of the cores. Popped a proper fibre module into the switch and away it went and five or six years later it is still working fine.

 

Leeds fibre people... perhaps SICL or Datacable can help?

[hallb15]

@IrritableTech I could test that out as we do have a couple of switches with gbic fibre modules in, however I can't do it in normal working hours without taking down half the network...

[IrritableTech]

@IrritableTech I could test that out as we do have a couple of switches with gbic fibre modules in, however I can't do it in normal working hours without taking down half the network...

 

I might have a couple of spare switches and modules for the next week. I'll pm you.

[IrritableTech]

@IrritableTech I could test that out as we do have a couple of switches with gbic fibre modules in, however I can't do it in normal working hours without taking down half the network...

 

I might have a couple of spare switches and modules for the next week. I'll pm you.