Abstract: A method and a system are for detecting at least one leak or at least one leak property in an underground pipeline, the underground pipeline being arranged near an underground conduit which is either a sewage conduit or a surface water conduit. The method has the steps of: providing at least one optical sensing fiber that extends inside and along underground conduit; obtaining distributed acoustic sensing data from the optical sensing fiber; and using the obtained distributed acoustic sensing data to detect the leak the at least one leak property in the underground pipeline.

Abstract: A flexible elongate member has at least one optical sensing fiber and is configured to be at least partially submerged or float in waste fluid inside a sewage pipeline or channel for obtaining distributed measurement data along the waste fluid flow. An apparatus is for use in obtaining distributed measurement data from a sewage pipeline or channel. The apparatus has a flexible elongate member in and deployment means for deploying the flexible elongate member in the waste fluid of the sewage pipeline or channel. Furthermore, a method is for obtaining distributed sensor measurements along a sewage pipeline or channel and a method is for deploying a flexible elongate member in a sewage pipeline or channel.