100G optical modules use multiple interface types including QSFP28, CFP, CFP2, SFP-DD, and SFP56-DD, with electrical lanes and optical connectors standardized by IEEE and MSA specifications.

Common 100G Form Factors and Interfaces

• QSFP28 (Quad Small Form-Factor Pluggable 28): Uses four 25 Gbps electrical lanes aggregated to 100 Gbps. Supports both parallel optics (e.g., SR4, PSM4) and duplex single-mode or multimode fiber (e.g., SR1.2 BiDi, DR) with MPO or LC connectors. Widely used in data centers for high port density and low power consumption .
• CFP and CFP2 (C Form-Factor Pluggable): Larger modules supporting 100G and beyond, often used in telecom and metro networks. CFP2 reduces size and power compared to CFP while maintaining compatibility with 100GBASE-LR4 and ER4 standards .
• SFP-DD (Small Form-Factor Pluggable Double Density) and SFP56-DD: Compact modules using two lanes at 50 Gbps each (SFP-DD) or 25 Gbps per lane (SFP56-DD), suitable for high-density switch ports and breakout applications .

Electrical and Optical Interfaces

• Electrical Lanes: Most 100G modules use a 4×25G lane architecture (QSFP28) or 2×50G lanes (SFP-DD), with PAM4 or NRZ modulation to achieve 100 Gbps per module .
• Optical Connectors:
  • MPO/MTP: Used for parallel multimode fiber connections (e.g., 100GBASE-SR4, PSM4).
  • LC Duplex: Used for single-mode or BiDi short-reach links (e.g., 100GBASE-DR, SR1.2 BiDi) allowing reuse of existing duplex fiber infrastructure .
• Standards Compliance:
  • IEEE 802.3 defines 100GBASE-SR4, LR4, DR, and other Ethernet standards.
  • MSA (Multi-Source Agreement) defines additional module types like CWDM4 and PSM4 for medium-distance interconnects, complementing IEEE standards .

Deployment Considerations

• Short-Reach (SR): Multimode fiber, typically 70–100 meters, using parallel optics or BiDi modules.
• Long-Reach (LR/ER/DR): Single-mode fiber, 500 meters to several kilometers, often using wavelength-division multiplexing (WDM) or coherent optics (e.g., QSFP28 ZR for 80–300 km) with LC connectors .
• Breakout Capability: Many QSFP28 modules support 4×25G breakout to connect to multiple 25G ports, enhancing flexibility in data center networks . In summary, 100G optical modules offer a variety of interface types tailored for different distances, fiber types, and deployment scenarios, with QSFP28 being the most common in data centers, while CFP/CFP2 and SFP-DD provide options for telecom and high-density applications. Electrical lanes, connector types, and modulation schemes are standardized to ensure interoperability across vendors and network equipment.