FPS - Fibre-optic Cable Detection System

The FPS detection system is based on a 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.

The fibre, clipped to the pipe, will detect attempts to drill into or damage the pipe and pass this information back to the processing unit. At least 20km of pipe can be protected in this way using a single fibre.

Principle of Operation

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 amplification and processing system it is possible to generate a voltage signal that is similar to that generated by a microphonic cable (see the CPS Plus perimeter protection system).

The laser diode injects an impulse of coherent light into the optical fibre. This light propagates along the fibre and is reflected from the extreme opposite end of the fibre. An inteferometric analysis between the light transmitted and the light reflected allows the generation of an optical signal that is converted by an opto-electric converter and sent to a processing unit.

The processing unit passes the electrical signal to an analogue bus and generates two synchronisation signals: one to the coherent light generator (laser) and one to the zone processing devices. The zone processors operate in a very similar way to the microphonic cable sensor (CPS Plus) and, like these, are compatible with the COM115 bus, used in the latest generation of perimeter sensors, managed by the UCP2000/MX2000 system.

(Click image to enlarge)

The analogue signal, generated by the processor unit, is digitised by a high precision A/D converter and then processed by a DSP (Digital Signal Processing) microprocessor with a very high processing capability. The accurate time domain and frequency domain analysis (with Fourier transformation) and the capability to adjust specific operating parameters of the system, using a commissioning and monitoring software, make it possible for the product to give excellent performance.

The sensor detects vibrations, pressure disturbances and movement. 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 system allows the management of very long perimeters (up to 20 Km) with identification of the zone of intrusion down to tens of metres.