A 100G single-mode optical module transmits 100Gbps data over single-mode fiber by converting multiple 25G electrical channels into a single 100G optical signal, often using single-wavelength (single-lambda) or bidirectional (BiDi) techniques.

Working Principle

A 100G single-mode optical module, such as a QSFP28 DR or single-lambda transceiver, operates by converting electrical data into optical signals for high-speed transmission over single-mode fiber (SMF). Typically, the module takes four 25G electrical channels and combines them into a single 100G optical signal using advanced modulation techniques like PAM4 (Pulse Amplitude Modulation) for single-lambda modules, or separates them into different wavelengths for BiDi operation . At the receiving end, the optical signal is converted back into four 25G electrical channels.

Single-Lambda vs BiDi

• Single-Lambda Modules: Use a single wavelength to carry 100G data, simplifying optical design, reducing component count, and lowering power consumption. These modules are ideal for short to medium distances in data centers, typically up to 500 meters for DR modules .
• BiDi (Single Fiber) Modules: Enable full-duplex communication over a single fiber strand by using Wavelength Division Multiplexing (WDM). One wavelength transmits data in one direction (Tx), while a complementary wavelength receives data (Rx) on the same fiber. A WDM coupler inside the module separates and combines these signals .

Key Features

• High-Speed Transmission: Supports 100Gbps data rates, suitable for high-density data center interconnects .
• Long-Distance Capability: Single-mode fiber allows transmission over hundreds of meters to several kilometers, depending on the module type (DR, LR, ER), .
• Digital Optical Monitoring (DOM): Monitors temperature, optical power, and other parameters in real time to ensure reliability .
• Low Power Consumption: Optimized design reduces energy costs in large-scale deployments .
• Compact Form Factor: QSFP28 modules provide high port density and easy integration into switches and routers .

Applications

100G single-mode optical modules are widely used in:

• Data Center Leaf-Spine Networks: Short-reach high-speed interconnects using DR modules .
• Metro and Enterprise Networks: BiDi modules maximize fiber utilization where fiber is limited .
• 5G Fronthaul/Midhaul: High-capacity links with constrained fiber infrastructure . In summary, the principle of a 100G single-mode optical module is to efficiently convert high-speed electrical signals into optical signals for transmission over single-mode fiber, using either single-wavelength or bidirectional techniques to optimize speed, distance, and fiber utilization while maintaining reliability and low power consumption .