QSFP-40G-SR4 vs QSFP-40G-SR4-S vs QSFP-40G-SR-BD vs QSFP-40G-CSR4, Any Difference?

What is 40G QSFP+ Transceiver?

40G QSFP+ transceiver refers to the Quad-Small-Form-Factor-Pluggable Plus Module. It is a hot-swappable, parallel fiber-optic module with 4 independent 10G data tracks in each direction for a total speed of 40 Gbps. QSFP+ transceiver also called a QSFP+ module, and it is fully compliant with the QSFP+ MSA standard. According to the QSFP standard, the 40G QSFP + terminal can be either a duplex LC or 12 fiber MTP / MPO port. 40G QSFP+ modules provide customers with a wide range of high-density 40 Gigabit Ethernet connectivity options for data centers, high-performance computing networks, enterprise core, and distribution layers, and transport applications for service providers.

QSFP-40G-SR4 40GBASE-SR4 Transceiver

Cisco QSFP-40G-SR4 is a 40GBASE-SR4 QSFP+ transceiver. It fully complies with the 40GBASE-SR4 standard. The QSFP-40G-SR4 supports link lengths of 100m and 150m on laser-optimized OM3 and OM4 multimode fibers. Cisco QSFP-40G-SR4 enables high-bandwidth 40G optical links mainly through ribbon fiber optic cables terminated with fiber optic connectors, and can also be used along with ribbon fiber to breakout cables for connection to four 10GBASE-SR optical interfaces.

QSFP-40G-SR4-S 40GBASE-SR4 Transceiver

QSFP-40G-SR4-S is typically standing for Cisco S-Class 40GBASE-SR4 QSFP module. It supports link lengths of 100 and 150 meters, respectively, on laser-optimized OM3 and OM4 multimode fibers. It primarily enables high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP multifiber connectors. The QSFP-40G-SR4-S is optimized to guarantee interoperability with any IEEE-compliant 40GBase-SR4 QSFP module.

QSFP-40G-SR-BD 40GBASE-SR BiDi Transceiver

QSFP-40G-SR-BD is a 40GBASE-SR Bi-directional QSFP+ transceiver.  It is a short-range transceiver with max 100m or 150m over a duplex OM3 or OM4 MMF. The techniques used in these 40G BiDi QSFP+ modules allow for bidirectional connectivity of 40Gbps via OM3 or OM4 multimode fiber. Using two 20Gbps channels, these modules use the existing MMF cabling to transmit and receive on the same strand fiber. Therefore QSFP-40G-SR-BD transceiver supports connections via an LC duplex MMF cable.

QSFP-40G-CSR4 40GBASE-SR BiDi Transceiver

QSFP-40G-CSR4 is an extended version of QSFP-40G-SR4, allowing extended long reach link over OM3 or OM4 fiber. Each 10-gigabit lane of this transceiver complies with the IEEE 10GBASE-SR specification. It extends the tentacles of the 40GBASE-SR4 interface to 300 meters and 400 meters of laser-optimized OM3 and OM4 multimode parallel fibers. QSFP-40G-CSR4 is suitable for short 40G optical links on parallel cables with MPO/MTP connectors, as well as for parallel duplex optical fiber Disconnect cable 4x10G mode for connecting to four 10GBASE-SR SFP+ interfaces. QSFP-40G-CSR4 is optimized to ensure interoperability within the full specification range of 10GBASE-SR.

QSFP-40G-SR4 vs QSFP-40G-SR4-S vs QSFP-40G-SR-BD vs QSFP-40G-CSR4 Comparison, What is the difference?

The comparison between QSFP-40G-SR4 vs QSFP-40G-SR4-S vs QSFP-40G-SR-BD vs QSFP-40G-CSR4 is shared as below.

Transceiver TypeQSFP+ ModuleQSFP+ ModuleQSFP+ ModuleQSFP+ Module
Wavelength850 nm850 nm832~918 nm850 nm
Reach100m@OM3, 150m@OM4100m@OM3, 150m@OM4100m@OM3, 150m@OM4300m@OM3, 400m@OM4
Fibre TypeMultimode Fiber (MMF)Multimode Fiber (MMF)Multimode Fiber (MMF)Multimode Fiber (MMF)
Connector TypeMPOMPOLC DuplexMPO
Data Rate40 Gbps40 Gbps40 Gbps40 Gbps
Cabling TypeEthernet 40GBASE-SR4 CablingEthernet 40GBASE-SR4 CablingEthernet 40GBASE-SR BiDi CablingEthernet 40GBASE-CSR4 Cabling
DOM SupportYesYesYesYes
Operating Temperature0°C to 70°C (Commercial Grade)0°C to 70°C (Commercial Grade)0°C to 70°C (Commercial Grade)0°C to 70°C (Commercial Grade)
Storage Temperature-40°C to 85°C-40°C to 85°C-40°C to 85°C-40°C to 85°C
Weight0.05 kg0.05 kg0.05 kg0.05 kg
Other featuresNon-S-ClassS-ClassNon-S-ClassNon-S-Class


As the above comparison, you may choose the right QSFP+ module for your network. If your link distance is less than 150 meters, then QSFP-40G-SR4 or QSFP-40G-SR4-S transceiver is the right one. If your link distance is more than 150 meters, then QSFP-40G-CSR4 transceiver is the better one. If you need to transmit on duplex multimode fiber, then QSFP-40G-SR-BD will be the best choice, because it allows you to reach bidirectional connectivity over OM3 or OM4 multimode fiber.