The problem with digging is that in case of faults, it's far more difficult to service. Also, future upgrades (e.g. fibers with better optical properties, or more fibers) require re-digging.
When done properly, conduit is laid that fiber is then run through. You don't re-dig to lay new media, you simply drag it through the existing conduit. That's why "dig once" is such a big deal.
Comments
The problem with digging is that in case of faults, it's far more difficult to service. Also, future upgrades (e.g. fibers with better optical properties, or more fibers) require re-digging.
When done properly, conduit is laid that fiber is then run through. You don't re-dig to lay new media, you simply drag it through the existing conduit. That's why "dig once" is such a big deal.
http://www.muninetworks.org/tags/tags/dig-once
http://www.sfexaminer.com/sanfrancisco/san-francisco-seeks-t...
http://www.whitehouse.gov/the-press-office/2012/06/14/execut...
You don't redig for more fiber unless you really screwed up the initial dig. Always leave lots of room in the tubes to blow more glass down later.