A single-mode single-fiber transceiver (B-end) is a bidirectional optical module that transmits and receives data over a single strand of single-mode fiber using complementary wavelengths.

Overview

A single-mode single-fiber transceiver, also known as a BiDi SFP, is designed to enable full-duplex communication over a single strand of single-mode fiber. Unlike traditional SFPs that require two fibers—one for transmitting (TX) and one for receiving (RX)—a single-fiber transceiver uses wavelength division multiplexing (WDM) to send and receive signals simultaneously on different wavelengths . For example, one module may transmit at 1310 nm and receive at 1550 nm, while the corresponding B-end module uses the opposite configuration .

Functionality

• Bidirectional Communication: The B-end transceiver complements the A-end by reversing the TX and RX wavelengths, ensuring proper data flow.
• Single-Mode Fiber: Operates on single-mode fiber (SMF) with a core diameter of 9 microns, suitable for long-distance transmission ranging from 2 km up to 120 km depending on the module type .
• Wavelength Pairing: Each transceiver pair must have complementary wavelengths to function correctly. For instance, if the A-end transmits at 1271 nm and receives at 1331 nm, the B-end transmits at 1331 nm and receives at 1271 nm .
• Connector Type: Typically uses LC connectors for compact and reliable connections .

Advantages

• Fiber Conservation: Reduces fiber usage by half compared to dual-fiber SFPs, which is particularly valuable in metro networks, enterprise campuses, or areas with limited fiber infrastructure .
• Cost Efficiency: Lowers deployment costs by reducing the number of fibers, patch panels, and associated cabling .
• Simplified Network Expansion: Easier to scale networks without laying additional fiber.

Applications

• Telecom Access Networks: Ideal for FTTH (Fiber to the Home) or metro networks where fiber availability is limited .
• Enterprise Networks: Used in campus links or data center interconnects to maximize existing fiber capacity.
• Long-Distance Links: Single-mode fiber allows transmission over tens of kilometers, making it suitable for backbone connections .

Key Considerations

• Compatibility: Ensure the B-end transceiver matches the A-end in wavelength pairing, optical power budget, and connector type .
• Distance and Loss: Verify the link budget and fiber quality to avoid signal degradation. Inline optical attenuators may be required for short distances to prevent receiver overload .
• Form Factor: Available in SFP, SFP+, QSFP, and QSFP28 for different speeds and network requirements . In summary, a single-mode single-fiber transceiver (B-end) is essential for bidirectional communication over a single fiber strand, offering cost-effective, long-distance, and high-speed connectivity while conserving fiber infrastructure and simplifying network deployment.