Sunday, July 22, 2007

Diagnosing faulty fibre splices

I go to lots of facilities where other engineers have run in fibre and the story is often the same - broadcast engineer who knows a bit about fibre and knows a firm who'll pre-make him tight buffered cable. Now - aside from the fact that tight-buffered cable for installation is never optimal why do they always choose the cheapest patch-cord cable rather than robust cable?

Anyhow - after a chance comment made by the instructor at Tyco last Tuesday I realised you can light up a fibre with a visible laser and the light will spill out at a bad splice. How often have I puzzled over which end of a loose-tube cable has the bad splice? The tester tells you you're loosing 5dBs of optical power but without a Fluke DTX-1800 (with the OTDM module - an extra £4k on the £5k basic!) you can never tell which splice to to blame.
The picture shows a bad splice (but not that bad - it was only loosing 5.5dBs - so would be fine on 2gig and probably fine on 4gig, but not optimal). The little red dot in the middle of the splice protector was a lot clearer than this 'phone-photo shows.

The Maplin keyfob laser pointer was the best fiver I spent this weekend. I just had two 12-hours days of fibre action and it saved a lot of time.

No comments: