Bi-Directional SFP transceivers use a single strand of fiber to transmit and receive data. This is possible by using two different wavelengths. Different combinations of wavelengths are available for BiDirectional communications, most used being 1310/1550nm, 1310/1490nm, 1490/1550nm or 1490/1590nm. The BiDi transceivers are also known as WDM (Wavelength Division Multiplexing). BiDi SFPs are only available for single-mode 9/125um fiber and only for Fast Ethernet and Gigabit Ethernet data rates. Some special solutions can be built on order for 4G data rates. All models have Digital Dignostic Monitoring features (SFF-8472 compatible).