FO-SAG Fibre Optic Detection System
The detection system is based on a single mode fibre optic cable that has the highest level of detection while at the same time has a very low false alarm rate. It is completely immune to electromagnetic interference generated by fast transients of current /voltage or atmospheric phenomena (lightning).
The system is particularly suited to deployment in the protection of gas, water and oil pipelines where the main pipe is above ground but can also be used to protect very long perimeter fences.
The fibre, clamped to the pipe or fence, will detect attempts to drill into or damage the pipe and attempts to cut or climb the fence and then pass this information to a processing unit. The cable detects vibrations, pressure disturbances and movement. At least 20km of pipe/fence can be protected in this way using go and return fibres.
A laser diode in the processor injects an impulse of coherent light into the optical fibre. This light propagates along the fibre and is returned to the launch processor by a return fibre.
A mechanical disturbance on the fibre (generated by vibration, pressure or movement) changes the light transmission characteristics of the fibre. The changes are very small but using a very accurate light source (such as obtained with a laser diode) and with a very sophisticated inteferometric analysis between the light transmitted and the light returned it is possible to generate a voltage signal that is representative of disturbance that created it, in both amplitude and frequency content.
The connection between the processing unit and the sensitive fibre is made by sections of non-sensitive fibre so that the sensitivity of the system is limited to the zone to be protected.
The fibre optic cable does not require power supplies of any type and therefore power supplies are not required at any point along the perimeter to be protected.
The length of the actual detection zones is programmable with a resolution of approximately 2% of the total fibre length. |
