Bidirectional WDM

A form of WDM that transmit and receive data over the same strand of fiber cabling.

It uses slightly shifted wavelengths to distinguish between Tx (1310 nm) and Rx (1490 nm) signals. BiDi transceivers must be installed in opposite pairs, so the downstream transceiver would have to use 1490 nm for Tx and 1310 nm for Rx.

BiDi is documented in the 802.3 standards as 1000BASE-BX and 10GBASE-BX.