Pigtails are short pieces of 0.9mm buffered fibre connectorised at one end and the other end free to be spliced with the optical fibre cable. The No. of pigtails is generally equal to no of fibres in the cable unless some fibres in the cable are left unspliced. It is a good practice to splice all the fibres with pigtails and have all fibres ready for use.You will find the pigtails inside the LIU as you can see from the pictures in the attached file.
Adapters aka Mating sleeves aka couplers are mating points of the pigtail and patchcord. The pigtail is plugged into the adapter at the end inside the LIU and the patchcord is plugged into the end outside the LIU.
Patch cords are flexible fibre optic cable assemblies that facilitate connection between the LIU and the active equipment viz. Ethernet switches and media converters. Patch cords can be simplex or duplex. Simplex means one fibre and duplex means two fibres. Generally fibre optic communication is full duplex meaning a dedicated fibre for the transmit signal and a dedicated fibre for the the receive signal. Accordingly the patch cords are more often duplex than simplex particularly for data communications.
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