Carry Gigabit Ethernet over a single strand of single-mode fiber with an upstream 1000BASE-BX20-U optical interface. This bidirectional SFP transceiver pairs complementary transmit and receive wavelengths on one simplex LC fiber connection, conserving fiber strands where a duplex run is unavailable or where existing plant capacity must support additional links. Its 20 km optical budget suits campus, municipal, industrial, and distributed-building connections. Axiom Memory AXG105105 is intended for ComNet network equipment that accepts the corresponding 1000BASE-BX20-U SFP optical interface. The hot-pluggable SFP form factor lets technicians install or replace the optic without replacing the host device. It operates at 1 GbE and uses single-mode fiber, making it appropriate for fixed point-to-point Ethernet uplinks rather than short-reach multimode runs. Within a bidirectional fiber optic pair, the upstream designation matters: this module must be matched with the complementary downstream optic at the far end of the link. Its simplex LC interface distinguishes it from standard duplex 1000BASE-LX-style optics, which require two fiber strands. TAA compliance supports deployments where that sourcing requirement applies.