Cisco QSFP-40G-CSR-S
40GBASE-CSR QSFP Transceiver Module with LC Connector, Original Cisco
Product Highlights
Upgrading your data center or campus backbone to 40 Gigabit Ethernet shouldn't mean ripping out your existing fiber plant. The Cisco QSFP-40G-CSR-S is a 40GBASE-CSR QSFP+ transceiver module with a duplex LC connector that lets you leverage your current 10G duplex multimode fiber infrastructure for 40GbE connectivity — no costly re-cabling required.
The QSFP-40G-CSR-S uses SWDM4 (Shortwave Division Multiplexing) technology, operating at four distinct wavelengths near 850 nm. Each wavelength carries a 10G lane, and all four are multiplexed over a standard duplex MMF link using familiar LC connectors. This delivers 40 Gbps aggregate throughput over distances of up to 300 meters on OM3, 400 meters on OM4, and 440 meters on OM5 multimode fiber.
Designed for Cisco switching and routing platforms with QSFP+ slots, this genuine Cisco transceiver is hot-swappable and supports Digital Diagnostics Monitoring (DDM) for real-time insight into link health. Whether you're building out a new leaf-spine fabric, extending inter-building links on campus, or migrating access-layer uplinks from 10G to 40G, the QSFP-40G-CSR-S provides a cost-effective, infrastructure-friendly path to higher bandwidth.
Features & Benefits
Duplex Fiber Infrastructure Reuse
Unlike parallel-optic 40G solutions that require 12-fiber MPO/MTP ribbon cables, the QSFP-40G-CSR-S operates over standard duplex LC-terminated multimode fiber. This means you can upgrade from 10GbE to 40GbE on the same cabling you already have in place — dramatically reducing migration costs and deployment time.
SWDM4 Multi-Wavelength Technology
The module multiplexes four 10G channels across four distinct wavelengths near 850 nm over a single duplex fiber pair. This innovative approach delivers full 40 Gbps throughput without the fiber count overhead of SR4-based solutions, making it ideal for environments where fiber strand availability is limited.
Extended Multimode Reach
With support for link lengths of 300m on OM3, 400m on OM4, and 440m on OM5 laser-optimized multimode fiber, the QSFP-40G-CSR-S covers the vast majority of intra-building and campus backbone distances. This extended reach gives network architects greater flexibility in physical topology design.
Hot-Swappable & DDM-Enabled
The QSFP+ form factor supports hot-swap insertion and removal, minimizing disruption during maintenance windows. Built-in Digital Diagnostics Monitoring provides real-time telemetry on optical TX/RX power, module temperature, laser bias current, and supply voltage — enabling proactive fault detection before link degradation impacts users.
Genuine Cisco Quality
As an original Cisco transceiver, the QSFP-40G-CSR-S is fully validated and supported across Cisco's QSFP+-equipped platforms. Genuine modules ensure eligibility for Cisco TAC support and SmartNet coverage, giving you confidence in mission-critical deployments.
Deployment Scenarios
Data Center Leaf-Spine Uplinks
Deploy the QSFP-40G-CSR-S in top-of-rack or leaf switches to provide 40GbE uplinks to spine switches over existing duplex MMF. This simplifies cabling in dense rack environments and provides a cost-effective bandwidth upgrade path without re-cabling.
Campus Backbone & Building Interconnects
Connect distribution-layer switches across floors or buildings using the extended 400m reach on OM4 fiber. The duplex LC interface integrates seamlessly with standard campus fiber plants, enabling 40G backbone links without deploying new ribbon cable.
10G-to-40G Migration
Organizations running 10GbE over duplex MMF can upgrade to 40GbE by simply swapping SFP+ modules for QSFP-40G-CSR-S transceivers on compatible platforms — reusing the same LC-terminated fiber runs and patch panels already in place.
High-Performance Computing Clusters
Provide high-bandwidth, low-latency interconnects between compute nodes and aggregation switches in HPC environments. The 40 Gbps throughput and short-reach multimode design are well-suited for tightly coupled cluster fabrics within a single facility.
General
Performance
Environmental
Physical
Compatibility Notes
The QSFP-40G-CSR-S is designed for Cisco platforms equipped with QSFP+ ports. Always verify transceiver compatibility with your specific platform and running software version using the Cisco Transceiver Compatibility Matrix before ordering. This module requires duplex LC-terminated laser-optimized multimode fiber (OM3, OM4, or OM5).
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| QSFP-40G-SR4 | Cisco 40GBASE-SR4 QSFP+ | Uses 12-fiber MPO/MTP parallel optics instead of duplex LC; supports 4×10G breakout mode but requires ribbon fiber cabling. |
| QSFP-40G-SR4-S | Cisco 40GBASE-SR4-S QSFP+ | S-Class SR4 module with MPO connector; 100m/150m reach on OM3/OM4 — does not support breakout or duplex fiber reuse. |
| QSFP-40G-CSR4 | Cisco 40GBASE-CSR4 QSFP+ | Extended-reach SR4 variant with MPO connector supporting up to 400m on OM4; uses parallel optics rather than SWDM4 over duplex LC. |
| QSFP-40G-LR4-S | Cisco 40GBASE-LR4-S QSFP+ | Long-reach 40G module over single-mode fiber with duplex LC; supports up to 10 km — choose this for inter-building SMF links. |
