Abstract: This invention uses an interferometric fibre optic sensor, particularly a Sagnac or Michelson interferometer, in a first fibre to monitor a sensing length of the first fibre and to detect disturbances. Signals indicating disturbances are classified as being of interest or not of interest, depending on predetermined criteria. Disturbances of interest can be, for example, the breaking of reinforcement wires in concrete pipe, the breaking of wires in suspension cables, a fire, a pipeline leak, or an intrusion. A location sensor system is used to determine the location of disturbances of interest, and to confirm the interferometer signal to reduce noise. The location sensor system is a fibre optic sensor, such as a phase OTDR sensor or a Brillouin effect sensor, which can detect the location of events it senses. It is present either in the first fibre or in a separate fibre laid adjacent the first fibre along its sensing length, as for example in the same optical cable.

Abstract: Process and apparatus for sensing possible leaks in a pipeline. The pipeline is monitored continuously by acoustic monitoring means, and acoustic events indicating a possible leak are noted. The pipeline is also equipped with temperature monitoring means, and is monitored for temperature either continuously, periodically or on demand.