BiDi SFP (Bidirectional Small Form-Factor Pluggable) transceivers use a single optical fiber for bidirectional communication. Unlike traditional transceivers that use separate wavelengths for transmitting and receiving, BiDi SFP modules use two different wavelengths, one for upstream and one for downstream communication, over the same fiber strand.

1.25G SFP BIDI

The two common types of BiDi SFP modules are often referred to as "BX-U" (Upstream) and "BX-D" (Downstream), and they operate on different wavelengths. The specific wavelengths used may vary among different BiDi SFP implementations, but a common pairing is as follows:

1. BX-U (Upstream): Typically uses a longer wavelength (e.g., 1310nm) for upstream transmission. 

2. BX-D (Downstream): Typically uses a shorter wavelength (e.g., 1490nm) for downstream transmission.

These wavelength pairings allow for bidirectional communication on a single fiber strand. The exact wavelengths used can depend on the specific vendor and product implementation, so it's essential to check the datasheet or specifications provided by the BiDi SFP manufacturer for accurate information.

BiDi SFP modules are commonly used in scenarios where deploying additional fibers for separate transmit and receive paths is challenging or expensive. They are often employed in metropolitan area networks (MANs), access networks, and fiber-to-the-home (FTTH) deployments to optimize the use of available fiber infrastructure.