Single fiber SFPs are always deployed in matched pairs, sometimes referred to as “A-end” and “B-end” modules. These paired modules use complementary wavelengths. For instance, if the local SFP transmits at 1310nm and receives at 1550nm, the remote SFP must transmit at 1550nm and. BIDI module only has 1 port, wave filtering through the filter of module, and finished the transmitting of 1310nm optical signal and receiving of 1550nm optical signal, or opposite., one end TX1310/RX1550, the other end. While both are compact fiber optic modules for switches and routers, BiDi SFPs uniquely enable bidirectional data transmission over a single fiber strand using Wavelength Division Multiplexing (WDM), contrasting with standard SFP modules requiring two fibers. Single-fiber BiDi SFP optics play an important role in saving fiber resources in fiber optic communication. Think of it as the “translator” for your network equipment, converting electrical signals into optical signals. Short answer: Usually yes, you use them in pairs, but the “pair” can be a media converter on one end and a fiber switch (or SFP in a switch) on the other, as long as both sides speak the same speed, wavelength, and optical mode.