Single-fiber bidirectional (BiDi) optical modules enable full-duplex communication over a single fiber strand using wavelength division multiplexing (WDM), reducing fiber usage by 50% while supporting high-speed data transmission.

Overview of BiDi Technology

BiDi optical modules transmit and receive data simultaneously over a single strand of single-mode fiber by using two distinct wavelengths—one for transmitting (Tx) and one for receiving (Rx). This is achieved through wavelength division multiplexing (WDM), where an internal WDM coupler separates incoming and outgoing signals to prevent interference . BiDi modules are commonly used in campus networks, metro access networks, data center interconnects, and building-to-building links, where fiber resources are limited .

Key Specifications

• Data Rates: Common BiDi modules include 1G, 10G, and 25G SFP/SFP+ modules, with some supporting up to 11.3 Gbps for 10G BiDi SFP+ .
• Wavelengths: Typical wavelength pairs are 1310 nm/1550 nm or 1270 nm/1330 nm, depending on the module type. Modules must be paired with complementary wavelengths for proper operation (e.g., SFP-10G-BXD1 with SFP-10G-BXU1), .
• Transmission Distance: Distances vary by module and fiber type, ranging from 10 km to 40 km for single-mode fiber, with some modules optimized for shorter or longer spans .
• Power Consumption: Efficient BiDi modules consume ≤1W, reducing heat output and energy costs .
• Connector Type: Typically simplex LC connectors are used, simplifying cabling and reducing fiber requirements by half .
• Compatibility: BiDi modules are hot-swappable and standards-compliant with SFP/SFP+ MSA, CPRI, and eCPRI protocols, ensuring interoperability with major switches and NICs .

Common Models

• FS 10G BiDi SFP+ Modules: Designed for 10G full-duplex over single-mode fiber, supporting distances up to 10 km and integrating DFB lasers, PIN photodiode receivers, and internal WDM couplers .
• Huawei 10G BiDi Modules: Examples include SFP-10G-BXD1/BXU1 and SFP-10G-ER-SM1270-BIDI/SFP-10G-ER-SM1330-BIDI, which must be used in complementary pairs to ensure proper bidirectional communication .
• SFP28 BiDi Modules: Support 25G data rates for high-density networks, leveraging the same WDM principles to maximize fiber utilization .

Deployment Considerations

• Pairing Requirement: BiDi modules must always operate in matched pairs with reversed Tx/Rx wavelengths to maintain full-duplex communication .
• Fiber Savings: Using BiDi modules can reduce fiber usage by 50%, which is particularly beneficial in environments with limited fiber infrastructure .
• Installation and Maintenance: Fewer physical connections simplify deployment, reduce potential failure points, and streamline network upgrades .
• Optical Isolation: Integrated filters or WDM components ensure Tx and Rx signals do not interfere, maintaining data integrity .

Summary

Single-fiber bidirectional optical modules provide a cost-effective, fiber-efficient solution for high-speed network connectivity. By leveraging WDM technology, these modules enable full-duplex communication over a single fiber strand, support a range of data rates (1G–25G), and require careful pairing of complementary wavelengths. Popular models include FS 10G BiDi SFP+, Huawei 10G BiDi modules, and SFP28 BiDi optics, all designed to optimize fiber usage, reduce cabling complexity, and maintain reliable network performance .