Method and system for distributed acoustic sensing

A method of distributed acoustic sensing, the method including:

• selecting an optical fibre cable installation having a path extending across a selected geographical area, the optical fibre cable installation including a bundle of optical fibres that form part of an established and dedicated fibre-optic communications network, the bundle of optical fibres including (1) a first subset comprising at least one optical fibre or channel to carry communication traffic, and (2) a second subset comprising at least one optical fibre or channel that is unused or unlit for communication;
• repurposing the second subset of at least one optical fibre or channel in the bundle of optical fibres for distributed acoustic sensing;
• determining characteristics associated with at least part of the bundle of optical fibres in the selected optical fibre cable installation, including geospatially mapping between one or more positions along a length of the bundle of optical fibres and a corresponding one or more locations in the selected geographical area;
• transmitting outgoing light through the second subset of at least one optical fibre or channel;
• receiving reflected light back scattered along the second subset of optical fibre or channel, the reflected light including fluctuations over time;
• and
• based on the fluctuations and the determined characteristics, generating an alert signal representative of an acoustic event.