How to Choose the Right 100G QSFP28 Optical Transceiver?

As an advanced manufacturing technology, QSFP28 optical transceivers have been highly favored by a large number of Ethernet users. We use large scale deployment and application of 100G optical transceivers in data center, Local Area Network(LAN), Wide Area Network(WAN), Ethernet switches and so on. Based on the unique low cost optical design package, we fully enjoy the great value crated by the new generation of 100G QSFP28 technology. There are many products with QSFP28 form factor like SR4, LR4, ER4, CWDM4, PSM4…

Facing so many different QSFP28 transceivers, we may be at a loss to choose an appropriate one for ourselves. At some extend, it really depends on our real demand. Due to limited space, we would mainly guide you how to choose a right one for your application from the perspective of transmission distance. Hope this article would help.

Transmission Distance

Different applications have given requirements for transmission distance, and the specific conditions and feasible measures will be fully covered in the following text.

Transmission Distance Is 100 m or Under 100 m

QSFP28 SR4 is highly recommended. The QSFP28 SR4 supports links of 70 m (OM3) and 100m (OM4) over multimode fiber with MPO connectors. It offers 4 independent transmit and receive channels, each capable of 25Gbps operation for an aggregated data rate of 100 Gbps. The QSFP28 SR4 modules are ideal for rack to rack connections in the data center and short reach telecom applications.

Transmission Distance Is Over 100 m But Under 10 km

QSFP28 LR4 is preferred. The QSFP28 LR4 is a fully integrated 4 × 25Gbit/s optical transceiver module, which supports distance up to 10 km. For long span 100GbE deployment, such a connectivity between two buildings, QSFP28 LR4 with duplex LC single-mode fiber cable is the perfect option.


Transmission Distance Exceeds 10 km

QSFP28 ER4 is ideal for very long transmission distance. The QSFP28 ER4 optical transceiver provides superior performance for 100G Ethernet applications up to 30 km links. The 100G QSFP28 ER4 module converts 4 input channels of 25Gb/s electrical data to 4 channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission.

Note: When an optic says “10 km”, this is only a guideline. Actual distances can be significantly better or worse. It depends on your actual usages at large extend, including regular cleaning and maintenance.

How to Choose Based on the Same Transmission Distance?

We discussed the optimal options according different transmission distances, but it seems that it is hard to make a decision when the transmission distance is identical. QSFP28 CWDM4 and QSFP28 PSM4 are designed to meet the requirement for intermediate or mid-reaches for datacenter applications (500 m to 2 km). They both use WDM and parallel single mode fiber technologies and support transmission distance up to 2 km.


The CWDM4 provides a 100G Ethernet high-speed link with a maximum transmission distance of 2 km, which interfaces with LC duplex connectors. The CWDM4 module uses Mux/Demux technologies with 4 lanes of 25Gbps optically multiplexed onto and demultiplexed from duplex single-mode fiber.



PSM4 does not need a MUX/DEMUX for each laser but it does need either a directly modulated DFB laser (DML) or an external modulator for each fiber. With an MTP interface, PSM4 modules can bus 100Gb/s point-to-point over 2 km or can be broken out into dual 50Gb/s or quad 25Gb/s links for linking to servers, storage and other subsystems.

How to Choose?

From the aspect of an inner transceiver module structure, PSM4 can be more cost effective because of its lower component costs. However, from an infrastructure viewpoint, PSM4 would be more expensive when the link distance is long, mainly because PSM4 uses 8 optical single-mode fibers while CWDMs uses only 2 optical single-mode fibers.

Where Can Buy QSFP28 Transceivers at Low Cost ?

You may dizzy about the mess online shopping websites about fiber optic, and it is hard to find one online store that provides fiber optic products with high quality but low cost. Under this condition, you can try FS.COM which is an online shopping store about fiber optic communication.

For the mentioned 100G QSFP28 SR4, there is a big slump on it recently. Buying it now only needs $269, which is tripled on other online shopping stores. Here, we made a comparison between FS.COM and on Cisco QSFP-100G-SR4-S price. You can see it clearly by clicking the following link.

100G QSFP28 SR4

Cisco QSFP-100G-SR4-S at FS.COM:

Cisco QSFP-100G-SR4-S at


According to the above provided information and suggestion, you can choose the right QSFP28 transceiver for your application.


Author: Joanna

6 thoughts on “How to Choose the Right 100G QSFP28 Optical Transceiver?

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