The 1000BASE-BX SFP modules include the 1000BASE-BX-U SFP module and the 1000BASE-BX-D SFP module. These two SFP modules are used together to permit a bidirectional Gigabit Ethernet connection using a single strand of SMF cable and LC connectors. The 1000BASE-BX-D SFP operates at wavelengths of 1490 nm TX/1310 nm RX, and the 1000BASE-BX-U SFP operates at wavelengths of 1310 nm TX/1490 nm RX.
The 1000BASE-BX-U SFP module is always connected to the 1000BASE-BX-D SFP module. The maximum transmission distance for this connection is 40 km. The 1000BASE-BX SFP modules conform to the IEEE 802.3ah 1000BASE-BX10 standard.
The 1000BASE-BX-D SFP operates at wavelengths of 1490 nm TX/1310 nm RX, and the 1000BASE-BX-U SFP operates at wavelengths of 1310 nm TX/1490 nm RX. The 1000BASE-BX-U SFP module is always connected to the 1000BASE-BX-D SFP module.