The through connector (or adaptor) is mounted in a patch panel, of an optical fibre termination unit, or OFDF, and allows a pigtail to be connected to a patchcord. A through connector allows the optical transmission system connection to be quickly made and broken, as required. This enables fault finding and maintenance activities (such as service restorations & re-arrangements) to be undertaken quickly and efficiently. The A/SC through connector is a compact size unit. The adaptor unit comprises a plastic body, and inner part with a precision alignment zirconia sleeve; which is made to demanding specifications. The zirconia alignment sleeve and precision body ensures: reliable, long term, mechanical and optical performance for the through adaptor. The through adaptor is capable of a reasonable number (e.g. 500) of matings/unmatings, and of withstanding normal (i.e.not excessive ) handling forces/loads without suffering any damage or significant increase in optical performance. The assembly is capable of reliable operation in Exchanges or Repeaters over the temperature range of -20oC to + 70 oC, and up to high levels of RH. Two way and four way through connector modules are also available.