[AusNOG] Water in Fibre cables

Fri Mar 9 10:48:51 EST 2012

·         whether moisture directly against a fibre changes the refractive index of the fibre to an extent that communications is affected.

Unless the moisture somehow penetrates the glass, no. Fibres are constructed with a coaxial core and cladding both made of glass with different refractive indexes. The internal reflective boundary (that keeps the light inside the core) is between the grades of glass, not an external  glass/air boundary.

·         The construction profile of fibre cables being laid by the NBN from the exchange (redundant term in the NBN world??) to the home.

I remember in a previous life specifying optical cables with an armoured housing designed to resist burrowing wombats…. 

Not sure NBNCo is going that far.

Mike.

From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Rod Veith
Sent: Friday, 9 March 2012 9:50 AM
To: ausnog at lists.ausnog.net
Subject: [AusNOG] Water in Fibre cables

There are many things that can pierce cable sheaths allowing moisture in without necessarily breaking communications.

The odd rat bite, tree roots, ants, backhoe, termites etc as many years of sheathed copper has shown. 

What I‘m curious about now is:

·         whether moisture directly against a fibre changes the refractive index of the fibre to an extent that communications is affected.

·         The construction profile of fibre cables being laid by the NBN from the exchange (redundant term in the NBN world??) to the home.

It has been many many years since I was last inside a manhole looking into cables. Still remember some on-the-job training and once beating a lead joint into submission  shape and turning some brown paper coated wires a slightly darker shade of brown. Gotta respect those blow torches J

Rod

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