Which port is the optical module for transmitting and receiving

Single-fiber bidirectional (BiDi) optical modules use one port to transmit and receive data simultaneously over a single fiber using different wavelengths.OverviewSingle-port optical modules, often called BiDi transceivers or WDM modules, allow bidirectional communication on a single optical fiber. Unlike dual-fiber modules, which require separate fibers for transmitting (TX) and receiving (RX), BiDi modules combine both functions into one port, saving fiber resources and reducing cabling complexity .How They WorkBiDi modules use wavelength division multiplexing (WDM) technology. Each module transmits and receives on different wavelengths. For example, one module may transmit at 1310 nm and receive at 1550 nm, while the paired module does the opposite . A WDM coupler inside the module separates or combines the wavelengths, ensuring signals do not interfere with each other . This allows simultaneous two-way communication over a single fiber.Key FeaturesSingle optical port: Both TX and RX signals share the same fiber.Paired operation: Modules must be used in matched pairs with complementary wavelengths.Wavelength options: Common BiDi SFP modules include TX1310/RX1550, TX1550/RX1310, TX1490/RX1550, and others .Compatibility: Typically used with single-mode fiber for long-distance transmission, though some multi-mode BiDi modules exist .Digital Diagnostic Monitoring (DDM): Many modules support real-time monitoring of optical power, temperature, and voltage .AdvantagesFiber savings: Only one fiber is needed per link, reducing infrastructure costs.Simplified cabling: Easier installation in environments with limited fiber availability.Flexibility: Ideal for network upgrades without laying additional fiber .ConsiderationsCost: BiDi modules are generally more expensive per unit than dual-fiber modules, but overall network costs may be lower due to reduced fiber usage .Distance and speed: Most BiDi modules are single-mode and support distances from 2 km up to 120 km, depending on the module type and wavelength .Paired requirement: Each BiDi module must be paired with a complementary module to function correctly.ApplicationsUpgrading existing fiber networks without adding new cables.Data centers and enterprise networks with limited fiber infrastructure.Long-distance single-mode fiber links where fiber conservation is critical. In summary, single-port BiDi optical modules provide an efficient solution for transmitting and receiving data over a single fiber using WDM technology, offering cost and space savings while maintaining high-speed, reliable communication .