ETU-LINK 25G BIDI SFP28 optical module is a type of single-fiber bidirectional optical module that utilizes BIDI (Bidirectional) technology to transmit and receive two different center wavelengths in both directions through a single optical fiber, achieving bidirectional data transmission. Two different wavelengths of light are employed to transmit data in separate directions, reducing fiber usage, cutting costs, and enhancing network density and flexibility. While conventional optical modules typically feature separate TX transmit ports and RX receive ports, BIDI optical modules have only one port, utilizing internal filters within the module to accomplish both the transmission and reception of light signals. Hence, BIDI modules must be used in pairs.