Detailed Introduction of 40G QSFP+ MPO SR4 Transceiver

QSFP+40GBASE SR4 (Short Range 4-Channel) is the most commonly used 40Gb SFP module in data centers, mainly used for short distance multimode fiber transmission. Its core feature is parallel transmission through four independent 10Gbps channels, ultimately aggregated into a total bandwidth of 40Gbps.

Technical parameters

Encapsulation format: QSFP+ (Quad Small Form factor Pluggable Plus).

Interface type: MPO/MTP-12 (usually using 8 cores, i.e. 4 transmitter and 4 receiver).

Center wavelength: 850nm.

Fiber type: multimode fiber (MMF).

Transmission distance:

• Combined with OM3 fiber to 100 meters.
• Combined with OM4/OM5 fiber to 150 meters.

Power consumption: Typical power consumption is less than 1.5W.

Working principle

The MPO MTP QSFP+ 40GBASE SR4 transceiver adopts VCSEL (vertical cavity surface emitting laser) array technology. It converts electrical signals into 4 optical signals, each with a rate of 10.3125 Gbps, and transmits them in parallel through 4 channels of MPO interface; and the receiving end is converted by a PIN photodetector array.

Main application scenarios of QSFP+ 40Gbase SR4 transceiver

The QSFP 40Gbase SR4 transceiver is mainly used for short range interconnection within data centers (Internal Data Centers), with specific application scenarios including:

High bandwidth interconnection between switches (Switch to Switch)

High bandwidth interconnection between switches is the most common use. Quickly establish a 40G link between the core layer and aggregation layer, or between the aggregation layer and access layer (ToR/Leaf), in a data center using MPO multi mode fiber optic cables.

Breakout application

Using MPO to 4xLC fiber breakout cable, we can split a 40G port into four independent 10G ports.

• Scenario: Connect one 40G core switch to four servers or access switches with 10G SFP+ports.
• Advantages: Greatly improves device port density and reduces wiring costs per unit bandwidth.

High speed access between servers and storage

For high performance computing (HPC) or large storage area networks (SAN), connect high-end servers or all flash arrays directly to 40G switches through SR4 transceivers to eliminate bandwidth bottlenecks. Plug and play, hot swappable, no need for settings.

Campus backbone network

If the wiring distance between different floors of the same building is within 100 to 150 meters (using OM3/OM4 fiber), 40GBASE SR4 is the most economical 40G solution.

Is ESR4 module a SR4 transceiver?

The QSFP 40G ESR4 (Enhanced Short Range 4) enhanced optical module is not a standard SR4 (Short Range 4) optical module, but a high-power, long-distance version of the 40G QSFP+ SR4 transceiver. Although both use multimode fiber and MPO/MTP interfaces, ESR4 is typically an enhanced version of SR4, which improves the laser’s quality and the sensitivity of the receiver, supporting longer distance transmission at high rates (such as 40G/100G 300m-400m, higher than the standard SR4’s 100m-150m).

Key Features:

Fully Compatible: Both ESR4 and SR4 transceiver use the same MPO-12 interface and the same form factor (e.g., 40G QSFP+ or 100G QSFP28). It serves as a direct drop-in replacement, requiring no modification to existing multimode fiber patch cords. However, the ESR4 features superior power budget and transmission distance performance with OM4 multimode fiber.

Applicable Scenarios: The 40G SR4 is typically suited for interconnects within small data center server rooms. But if the distance between racks within a data center exceeds 150 meters, but not have enough budget to use single mode fiber (40GBASE PSM4 or LR4 transceiver), 40GBASE ESR4 is the best solution.

Beakout Support: Much like the QSFP SR4, the 40GBASE ESR4 supports port splitting. By utilizing a MPO to 4xLC fiber breakout cable, a single 40G port can be split into four 10G SFP-SR (or enhanced 10G SFP-ESR) ports.

ESR4 vs SR4 Transceiver Comparison

Conclusion

Compared to long distance single mode fiber module, the QSFP+ 40GBASE SR4 transceiver generates less heat and consumes less power, and it is the cheapest 40GB SFP module among all QSFP+ transceivers, so it is widely used for cabling within data center cabinets.

When selecting optical modules, please keep the following points in mind:

• Polarity requirement: In 40G direct connection scenarios, MPO crossover cable type B are usually required to ensure transmission and reception matching.
• Digital Diagnosis Monitor (DDM/DOM): Most mainstream 40G SR4 modules support real-time monitoring of optical power, temperature, and voltage.
• Compatibility: 40G SR4 follows the IEEE 802.3ba standard and is typically compatible with various brands of 40G ports, but it needs to be confirmed whether the switch has a specific brand lock.

FAQ