Cisco QSFP-40G-SR-BD
QSFP40G BiDi Short-reach Transceiver, Original Cisco
Product Highlights
Migrating from 10G to 40G shouldn't mean ripping out your entire fiber plant. The Cisco QSFP-40G-SR-BD is a 40GBASE-SR Bi-Directional QSFP+ transceiver that delivers 40 Gigabit Ethernet over standard duplex multimode fiber using familiar LC connectors — the same cabling you already use for 10GbE links.
Unlike traditional QSFP-40G-SR4 modules that require eight fibers and MPO/MTP connectors, the QSFP-40G-SR-BD uses wavelength-division multiplexing (WDM) to transmit and receive simultaneously on two wavelengths (850nm and 900nm) across a single fiber pair. This bidirectional architecture consolidates four 10Gbps electrical lanes into two 20Gbps optical channels, achieving an aggregate 40Gbps data rate while cutting fiber consumption by 75%.
The transceiver supports link distances of up to 100 meters over OM3 and 150 meters over OM4 multimode fiber, making it well-suited for top-of-rack to end-of-row connections, spine-leaf fabric links, and short-reach data center interconnects. With hot-swappable operation, built-in digital diagnostics (DDM/DOM), and compliance with IEEE 802.3ba and the QSFP+ MSA, the QSFP-40G-SR-BD provides a cost-effective, operationally simple path to 40GbE without infrastructure disruption.
Features & Benefits
Bidirectional (BiDi) Fiber Efficiency
The QSFP-40G-SR-BD uses two distinct wavelengths (850nm TX / 900nm RX on one channel, reversed on the other) to achieve full-duplex 40Gbps over a single duplex fiber pair. This eliminates the need for 8-fiber MPO ribbon cables, dramatically reducing cabling cost and complexity while preserving your existing LC-based multimode infrastructure.
Seamless 10G-to-40G Migration
Because the QSFP-40G-SR-BD uses standard LC duplex connectors and multimode fiber, organizations can upgrade from 10GbE to 40GbE without re-cabling. Simply swap the transceiver and switch — the fiber stays in place. This makes the BiDi module the most practical upgrade path for brownfield data centers with established duplex MMF runs.
Short-Reach Performance
Supporting up to 100m over OM3 and 150m over OM4 multimode fiber, the QSFP-40G-SR-BD covers the vast majority of intra-data-center link distances. It is optimized for rack-to-rack, top-of-rack to aggregation, and spine-leaf fabric connections where low latency and high bandwidth are essential.
Digital Diagnostics Monitoring (DDM/DOM)
Built-in digital diagnostics provide real-time visibility into key operating parameters including optical TX/RX power, temperature, voltage, and bias current. This enables proactive fault detection and simplifies troubleshooting, reducing mean time to repair and improving overall network uptime.
Hot-Swappable & Standards-Compliant
The QSFP-40G-SR-BD is fully hot-swappable, allowing field replacement without powering down the host device. It complies with IEEE 802.3ba, QSFP+ MSA (SFF-8436), and RoHS directives, ensuring broad interoperability and regulatory compliance across enterprise and data center environments.
Deployment Scenarios
10G-to-40G Data Center Migration
Organizations upgrading from 10GbE to 40GbE can leverage the QSFP-40G-SR-BD to reuse existing duplex LC multimode fiber runs. This avoids the cost and disruption of deploying new MPO/MTP ribbon cabling, making it the most economical migration path for brownfield data centers.
Spine-Leaf Fabric Interconnects
In modern spine-leaf architectures, the QSFP-40G-SR-BD provides 40Gbps uplinks between leaf and spine switches over short-reach duplex MMF. Its LC connector compatibility simplifies structured cabling and patch panel management in high-density environments.
Top-of-Rack to Aggregation Links
For connecting top-of-rack switches to end-of-row or aggregation-layer switches within the same data hall, the QSFP-40G-SR-BD delivers reliable 40Gbps throughput over distances well within its 100m (OM3) or 150m (OM4) reach, using only two fibers per link.
Fiber-Constrained Environments
In facilities where fiber strand counts are limited or conduit space is at a premium, the BiDi architecture of the QSFP-40G-SR-BD reduces fiber consumption by 75% compared to SR4 modules, freeing capacity for future growth without pulling new cable.
General
Performance
Physical
Electrical
Environmental
Compliance
Compatibility Notes
The Cisco QSFP-40G-SR-BD is compatible with Cisco platforms that support QSFP+ 40GbE transceiver modules, including various Nexus and Catalyst series switches. The Meraki variant (MA-QSFP-40G-SR-BD) is listed for use with MS355, MS390, and MS425 switches. Always verify transceiver support against the Cisco Transceiver Compatibility Matrix for your specific platform and software release.
Fiber Requirements:
- OM3 MMF (2000 MHz·km): up to 100m
- OM4 MMF (4700 MHz·km): up to 150m
- OM2 MMF (500 MHz·km): up to 30m
- Connector: LC duplex
Note: The QSFP-40G-SR-BD must be paired with another QSFP-40G-SR-BD at the remote end. It is not interchangeable with QSFP-40G-SR4 modules, which use MPO connectors and parallel optics.
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| QSFP-40G-SR4 | Cisco 40GBASE-SR4 QSFP+ | Uses 4 parallel lanes over 8 fibers with MPO connector; supports 4x10G breakout but requires MPO cabling infrastructure. |
| QSFP-40G-SR4-S | Cisco 40GBASE-SR4 S-Class QSFP+ | S-Class variant of SR4 with Class 1 laser safety (vs. 1M); same MPO/8-fiber requirement, no BiDi capability. |
| QSFP-40G-CSR4 | Cisco 40GBASE-CSR4 QSFP+ | Extended-reach SR4 supporting up to 300m (OM3) / 400m (OM4) with MPO connector; ideal when longer distances are needed. |
| QSFP-40G-LR4 | Cisco 40GBASE-LR4 QSFP+ | Long-reach 40G transceiver over single-mode fiber up to 10km using 1310nm CWDM; for inter-building or campus links. |
