What is the bidirectional sfp?

As we learned, a common SFP transceiver is generally with two ports, one is TX port to transmit the signal, and the other one is RX port to receive signals. BiDi SFP transceiver is only with one port which uses an integral WDM coupler to transmit and receive signals over a single strand fiber.

At present, the BiDi SFP is mostly used in FTTx deployment P2P (point-to-point) connection. A FTTH/FTTB active Ethernet network consists of a central office (CO) connecting to the customer premises equipment (CPE). BiDi SFP allows a bi-directional communication on a single fiber by using wavelength multiplexing (WDM), which makes CO and CPE connection more simple.

The Small Form-Factor Pluggable (SFP) is a compact and hot-pluggable transceiver utilized for both telecommunication and data communication applications. The form factor and electrical interface are specified by a Multi-Source Agreement (MSA) supported by the SFF Committee. It represents a popular industry format jointly developed and endorsed by numerous network component vendors. A common implementation of the SFP transceiver involves a two-fiber configuration: one for the transmission (TX) port and one for the receiving (RX) port. In this scenario, the same frequency can be employed for both transmission and reception, as long as the communication channels operate in parallel on separate fibers. A communication link occupies two fibers within cabling channels traversing data centers.