Attenuators made from doped fibre are used in-line, in an optical transmission system to reduce the signal strength to safe and acceptable levels. This signal attenuation prevents unplanned outages due to equipment failure. These items are used in systems such as: Telecommunication Networks, CATV Networks, Data Communications Networks, Instrumentation and Local Area Networks. The Attenuator is manufactured to recognised and approved industry standards, and will achieve a 20 year service lifetime, under typical operational conditions. Each attenuator assembly is capable of a reasonable number (eg 500) of matings/unmatings, and for withstanding normal (not excessive) operational handling forces/loads without suffering any damage or significant increase in optical performance. The complete assembly is capable of reliable operation in Exchanges or Repeaters over the temperature range of –40° to + 80°, and up to high levels of RH. The attenuator can be safely stored, in suitable accommodation, over the temperature range of –50° to + 85°.