This Interim European Telecommunication Standard I-ETS specifies requirements of the connector set to be used in single-mode optical fibres telecommunication systems; the scope covers establishment of uniform requirements for the following aspects: - optical, environmental and mechanical properties; - test conditions; - acceptance criteria. Some users may have additional specific requirements, such as a need to verify perfprmance at lower temperatures. These users should specify connectors conforming to the basic ETSI performance standard, plus additional tests or more severe test conditions. Connectors for different applications which fall within the scope of this I-ETS have common environmental and mechanical stability requirements, but there are two grades of attenuation requirements and four grades of return loss. The attenuation grades are designated P and Q. The return loss grades are designated S, T, U and V. A connector set is defined as: The complete set of connector components require to provide demountable coupling between one or more pairs of optical fibre. The lenght of fibre or cable on each side of the connector shall be 1,5 metres (minimum). A minimum lenght of 1,5 m on each side of the test set must be exposed to the test conditions of all climats and environmental test.