Bi-Directional (BiDi) Transceiver is a compact optical transceiver module that uses WDM (wavelength division multiplexing) technology and is compliant with the SFP multi-source agreement (MSA). Bi-Directional technology means a communication mode that processes data in both directions (send and receive) over optical fiber, which allows transceiver modules to transmit and receive data to/from the interconnected network devices (like network switches or routers) via a single optical fiber.
BiDi modules are equipped with WDM couplers/diplexers to combine or separate data transmitted over a single fiber using the different wavelengths of the light. Like traditional transceivers, BiDi transceivers should be deployed in pairs. However, for BiDis, we should use two modules: one for the upstream (“U”) direction and another for the downstream (“D”)—each part transmits at an opposite wavelength. For example, from point A we have installed a transceiver that transmits TX on 1310nm towards point B on a single fiber. In point B there is a transceiver that receives RX on 1310 nm and transmits back to point A on 1490nm on the same fiber. In point A the RX frequency is listening on 1490nm.