[LINK] Anticipated service life of fibre

[Paul Brooks]

On 5/04/2016 10:45 AM, Karl Auer wrote:
> Even glass is touched by time. Perhaps it will become slowly more opaque, carry
> certain wavelengths better (or less well), become more fragile, or deform (as old
> windows have flowed down so they are fatter at the bottom).

Given the educational/informational origins of this list, may I chime in here to point
out that this 'old glass flows/deforms and gets thicker at the bottom' is an urban
myth that has been debunked. The glass doesn't flow, the thickness gradient is a
byproduct of the pouring process, and panes have been found that were installed
upside-down, with the thicker part still at the top.

http://io9.gizmodo.com/the-glass-is-a-liquid-myth-has-finally-been-destroyed-496190894
http://www.scientificamerican.com/article/fact-fiction-glass-liquid/

That doesn't stop the rest of the comments being very valid - the likely service
lifetime of an optical fibre cable is certainly decades, but beyond that - who knows.
Certainly the glass fibres aren't prone to the deterioration, corrosion, and shorting
that copper is, but there may be other effects which become evident.
Optical fibre cable is much more 'brittle' and more easily broken by excessive
stretching, and being bent around corners too tight than metallic cables.
Suspended aerial fibre cables swing in the breeze and may develop micro-fractures.
Other components of the cable - the protective jacket, plastic bits, waterproofing,
fibreglass strength members, insect-resistant coatings etc wont last infinitely long.

And they are all just as susceptible to being chewed through by cockatoos and rats,
and ants
(http://www.networkworld.com/article/2367202/lan-wan/hungry-ants-knock-out-my-fios-service-again.html).

For a vaguely on-topic reference point - subsea optical fibre cable systems are
generally guaranteed for 25 years. The actual cable may well last longer before it
deteriorates to the point of being unusable, but nobody knows when that might be, so
nobody is willing to provide a warranty for it.

Paul.