Abstract: A cable is provided with optical fibers for use for downhole monitoring such as inside an oil or gas well. The cable has a cable core (1) having one or more optical fibers, a first metal tube (2) surrounding the cable core (1), and a vault armouring layer (3) surrounding the first tube (2). The vault. armouring layer (3) has numerous armouring wires (3a, 3b), a second metal tube (4) surrounding the vault armouring layer (3), and an outer insulation jacket of a polymer surrounding said second tube (4). Such cable can be used inside of an oil or gas well for monitoring at high depths below 2000 meters, more preferable below 5000 meters, yet more preferable below 8000 meters.

Abstract: An optical cable unit has a metal tube with a longitudinal laser-welded seam and at least one optical waveguide in the interior of the metal tube. The metal tube has a first inner layer and a second outer layer, where the first inner layer is made from copper and the second outer layer is made from austenitic steel. The longitudinal seam of both layers is laser welded and the seams of the layers are in superimposed alignment, where the laser welding is performed by a CO2 laser.

Abstract: An optical cable unit has a metal tube with a longitudinal laser-welded seam and at least one optical waveguide in the interior of the metal tube. The metal tube has a first inner layer and a second outer layer, where the first inner layer is made from copper and the second outer layer is made from austenitic steel. The longitudinal seam of both layers is laser welded and the seams of the layers are in superimposed alignment, where the laser welding is perfromed by a CO2 laser.

Abstract: An optical submarine cable with a sheath 8 and a core is proposed. It comprises optical fibers 1 which are enclosed in a metal tube 3. The tube is disposed near the axis of the cable. The cable comprises at least two metal tubes 3 and the tubes are SZ-stranded.