This Interim European Telcommunication Standard (I-ETS) applies to optical fibre pigtailed fixed attenuators to be used in single-mode optical fibre transmission networks and which are designed to be spliced into the optical path.This includes splices which are fabricated to produce an attenuation and which are fitted with an appropriate protector. It does not include variable attenuators or attenuators that are based on connectors. This I-ETS is intended to establish uniform requirements for the following aspects: - optical, environmental and mechanical properties; - test conditions; - acceptance criteria. Acceptance criteria will be interpreted with respect to the consideration that some of the parameters specified in thsi I-ETS may be affected by measurement uncertainty arising either from measurement or calibration errors. The optical attenuator is: A passive optical component which produces a controlled signal attenuation when inserted in an optical path.