Singlemode fibre optic adapter LC/APC, also called fibre optic coupler, is used to terminate or link the fibre optic cables or fibre optic connectors between two fibre optic lines. By connecting two connectors precisely, fibre optic adapters allow the light source to transmit the most with the lowest possible loss. At the same time, the fibre optic adapter has the advantages of low insertion loss, good interchangeability and good reproducibility.