The ab end of the fiber optic transceiver is the transmitting end (a end) and the receiving end (b end), and the two ends of the single fiber transceiver are the A end and the B end respectively. There are also fiber-to-fiber versions that translate between different fiber types, wavelengths, or distances. SFP transceiver that supports 1G connections up to 3 km using single-mode fiber with a simplex LC UPC connector.