All three modules utilize the 40G QSFP+ form factor and support a 10km transmission distance, making them suitable for medium- and long-distance interconnects in data centers (e.g., aggregation-to-core and inter-building connections).
Key Differences and Features
QSFP-40G-LR4-S: An Economical Single-Mode Solution
Technology: Based on the IEEE 40GBASE-LR4 standard, it utilizes a 1310nm wavelength (quad-channel CWDM: 1271nm/1291nm/1311nm/1331nm) to transmit 40G signals over single-mode fiber (SMF) via an LC duplex interface.
Core Positioning: Part of the Cisco S-Class family, it offers the same performance as the standard LR4 at a lower cost, making it suitable for budget-conscious scenarios.
Limitations: Does not support OTU3 data rates or breakout applications.
QSFP-40G-LR4: Full-featured single-mode module
Technical basis: Also complies with the 40GBASE-LR4 standard, with the same wavelength and interface as LR4-S (LC duplex, SMF).
Key advantages: Supports OTU3 data rates (used in carrier-grade optical transport networks) and is suitable for hybrid service environments requiring OTN (Optical Transport Network) compatibility.
Application scenarios: Finance, carriers, and other scenarios requiring high reliability and multi-protocol support.
QSFP-4X10G-LR-S: Split-type 10G aggregation module
Technical basis: Splits 40G into four independent 10G channels, each based on the 10GBASE-LR standard (1310nm) and connected via an MPO-12 interface.
Key benefits: Allows connection of four 10G devices (such as servers or switches) via breakout cables (e.g., MPO to 4xLC), maximizing port utilization and reusing existing 10G infrastructure.
Typical deployments: Suitable for high-density 10G access layers (such as TOR switch uplinks).
Comparison Summary Table
| Features | QSFP-40G-LR4-S | QSFP-40G-LR4 | QSFP-4X10G-LR-S |
| Wavelength | 1310nm (4×CWDM) | 1310nm (4×CWDM) | 1310nm (4×Independent Channels) |
| Fiber Type | Single-Mode (SMF) | Single-Mode (SMF) | Single-Mode (SMF) |
| Interface | LC Duplex | LC Duplex | MPO-12 |
| Breakout Support | × | × | √ (4×10G) |
| OTU3 Data Rate Support | × | √ | × |
| Power Consumption | Low (S-Class Optimized) | Medium | Medium |
| Typical Scenarios | Cost-Sensitive 40G Links | Telecom/Multi-Protocol Environments | 10G Equipment Aggregation |
Selection Guide
Require 40G Direct Connect and Prioritize Cost → QSFP-40G-LR4-S (Saving Costs, Meets Performance Standards)
Requires OTN compatibility or carrier-grade transmission → QSFP-40G-LR4 (critical support for OTU3).
Live network with 10G equipment, for smooth future upgrades → QSFP-4X10G-LR-S (multiplexing and reusing existing racks/fiber resources).
Deployment Notes:
QSFP-4X10G-LR-S requires an MPO-12 to 4xLC breakout cable to achieve split 1.
All modules support digital diagnostic monitoring (DDM/DOM), but cannot be mixed (wavelength and interface physical incompatibility).
Conclusion
Although all three are 40G QSFP+ 10km modules, their design goals differ:
- LR4-S is a cost-saving tool suitable for pure 40G Ethernet;
- LR4 is a versatile solution that meets OTN convergence requirements;
- 4X10G-LR-S is the key to a smooth upgrade, unlocking the value of existing 10G equipment.
Accurately matching service needs with existing network architecture can maximize return on investment. In some scenarios, choosing 20km optics might be more cost-effective than 10km optics and accommodate future expansion needs. For example, the Cisco compatible QSFP-LR4-40G-20 from a third-party vendor supports a maximum distance of 20km at a slightly higher price than the standard QSFP-40G-LR4 .
