In these days of increased cable theft and also data intrusion businesses must protect their infrastructure from damage. Losing a major power cable on your site or having a multi-pair copper cable stolen can inflict significant economic damage on your organisation. Fortunately there are optical fibre monitoring technique which can monitor the entire length of your cable and/of ducting. Some systems can protect up to 80 Km with a single controlling device yet pinpoint the site of the damage/intrusion to within a few metres. Such techniques can detect the vibration of interference with the cable before actual damage occurs and then trigger suitable alarms. To achieve the monitoring you'll need a spare dark fibre or lay a suitable fibre along the route you want to protect.
There are several companies providing such protection but FFT Secure Link is a good example.
Some people think data transmitted over optical fibre is inherently secure. In fact it is relatively easy to tap a fibre by exposing the fibre and bending it over a curved form. This will induce a slight laser leakage which can be monitored without alerting the owner of the cable. If you install a vibration sensing alert on one of the fibres in the bundle you'll be able to raise an alert that the cable is being disturbed.
Of course another approach is to encrypt data/video/voice along the link, but this can be expensive if there are multiple fibres to protect.