Recommendation ITU-T L.78 describes the characteristics, construction and test methods for optical fibre cables to be installed in sewer ducts and drainpipes. The characteristics that a cable should have for an optical fibre to perform appropriately are described. Also, a method is described for determining whether or not the cable has the required characteristics. The required conditions may differ according to the installation environment; detailed test conditions need to be agreed upon between the user and manufacturer for the environment in which the cable is to be used.