SR4 optical module

SR4 optical modules are 400G short-reach transceivers using four parallel channels, each transmitting 100G over multimode fiber for high-speed data center connectivity. OverviewSR4 stands for Short Reach with 4 channels, designed for 400 gigabits per second (Gbps) transmission over multimode fiber (MMF). Each module uses four optical lanes, each capable of 100G, leveraging parallel optics technology to achieve high-speed, short-distance connectivity, typically up to 100–300 meters depending on fiber type (OM3 or OM4) and standard compliance.

SR4 modules are ideal for intra-data center links, cloud computing, AI, and high-performance computing (HPC) workloads. Form FactorsSR4 modules are available in multiple pluggable form factors to suit different network designs: OSFP (Octal Small Form Factor Pluggable): Supports 400G/800G with higher thermal capacity, enabling advanced DSPs and future upgrades to 800G or 1. 6T interconnects.

QSFP112: Compact 400G module supporting 112G per lane across four lanes, suitable for dense data center deployments. QSFP-DD: Double-density QSFP modules for high port density and backward compatibility with QSFP28 interfaces.

Technical Features

Modulation: Uses PAM4 (4-level pulse amplitude modulation) to double data rate per lane compared to traditional NRZ signaling. Channels: 4 parallel channels, each at 100G, totaling 400G bandwidth. Wavelength: Typically 850 nm for multimode fiber.

Distance: Up to 100 meters on OM4 fiber and around 70 meters on OM3 fiber for standard SR4 modules. Applications: Short-reach interconnections within data centers, high-bandwidth server-to-switch links, and AI/HPC networking.

Vendor Examples

Huawei offers a range of SR4 modules, including the QSFP112-400G-SR4, which provides plug-and-play flexibility for short-reach data center connections. These modules perform photoelectric and electro-optic conversions, converting optical signals back into electrical signals for network devices. Comparison with Other 400G StandardsDR4: Up to 500 meters over single-mode fiber for inter-data center links.

FR4: Up to 2 km over single-mode fiber for longer connections. LR4: Up to 10 km over single-mode fiber for wide-area networks. SR4 modules are optimized for short-range, high-density, multimode fiber environments, making them distinct from DR4, FR4, and LR4 modules.

SR4 optical modules provide a cost-effective, high-performance solution for modern data centers requiring 400G connectivity, supporting scalable and future-proof network architectures.