Single-mode QSFP optical module

Single-mode QSFP modules are high-speed, hot-pluggable optical transceivers designed for 100G Ethernet over single-mode fiber, supporting long-distance transmission with compact form factors.

Overview

A QSFP (Quad Small Form-factor Pluggable) module is a compact, hot-swappable optical transceiver that carries four independent transmit and receive lanes, multiplying bandwidth density without increasing port count . Single-mode QSFP modules are specifically designed to operate over single-mode fiber (OS1/OS2), enabling long-distance connectivity in data centers, enterprise networks, and service provider environments .

Common Types

QSFP28 LR4

• Transmission Distance: Up to 10 km over OS2 single-mode fiber .
• Wavelength: Uses four separate wavelengths in the 1310 nm region, each carrying 25G, combined to form a 100G data stream .
• Connector: Duplex LC for transmit and receive fibers.
• Functionality: Splits a 100G signal into four 25G channels, enabling long-reach connectivity while supporting CWDM spacing for cost-effective deployment .

QSFP28 PSM4

• Transmission Distance: Up to 2 km over OS2 single-mode fiber; limited to 500 m on OS1 fiber .
• Connector: MPO-12 APC, supporting parallel single-mode fiber lanes.
• Functionality: Uses parallel single-mode fibers to transmit 100G signals, suitable for medium-range interconnects in data centers .

Key Features

• Hot-swappable: Can be replaced or upgraded without powering down the switch or server .
• High-density: Supports four lanes in a single module, increasing port density.
• Digital Diagnostic Monitoring (DDM/DOM): Provides real-time monitoring of temperature, voltage, transmit/receive power, and laser bias current .
• IEEE Compliance: Compatible with 100GBASE standards, ensuring interoperability across devices .

Deployment Considerations

• Fiber Type: OS2 single-mode fiber is recommended for long-distance LR4 modules; OS1 may limit reach .
• Distance Requirements: Choose LR4 for long-haul links (up to 10 km) and PSM4 for shorter interconnects (up to 2 km).
• Connector Compatibility: Ensure the network infrastructure supports LC duplex (LR4) or MPO-12 APC (PSM4) connectors.
• Power and Heat: QSFP modules are low-power but require proper airflow in high-density racks.

Summary

Single-mode QSFP modules, such as LR4 and PSM4, provide flexible, high-speed 100G Ethernet connectivity over single-mode fiber. LR4 is ideal for long-distance links up to 10 km using duplex LC connectors, while PSM4 supports medium-range parallel fiber connections up to 2 km with MPO-12 APC connectors. Both types offer hot-swappable operation, high port density, and real-time diagnostics, making them essential for modern high-performance networks .