What optical modules are available for single-fiber bidirectional transmission

BiDi modules are transceivers that can send and receive at the same time over one fiber cable using two wavelengths. This full-duplex allows both directions without requiring a separate fiber for receiving. Instead of using separate fibers for transmit and receive signals, BiDi modules rely on wavelength division multiplexing (WDM) to send signals in opposite. A BiDi SFP module is a bidirectional fiber optic transceiver that enables simultaneous transmit and receive over a single strand of single-mode fiber, instead of the traditional two-fiber setup. [pdf]