The ability to understand and monitor the distributed behaviour of extended, critical structures is recognized as a matter of increasing importance. Optical fibres offer unique advantages for spatially distributed measurement.

This article reviews the field of distributed optical-fibre sensing (DOFS), tracing its origins and its evolution, and discussing the present and future positions.

Examples of the use of both linear and non-linear optics in pursuit of DOFS development are presented, together with details of a range of systems which have been investigated for particular applications.