Abstract: A system comprises a tool arrangement (4) which is configured for measuring a property of an environment in, or adjacent to, an elongated space; a line (6) coupled to the tool arrangement, the line including an optical fibre for distributed optical sensing measurements, an electrically insulating material, and an electrically conductive member covered by, or embedded in, the electrically insulating material, the line having the outer profile of a slickline; and a termination-coupler (3) which mechanically connects the line to the tool arrangement, which electrically connects the electrically conductive member of the line to the tool arrangement, and which optically terminates the optical fibre of the line.