How to Choose the Right 100G QSFP28 Optical Transceivers?

December 22, 2021

As one of the most widespread and commonly used form factors for 100G applications, QSFP28 has been highly favored among mobile operators, Internet service providers, data centers, etc. There are many 100G QSFP28 transceivers with various different types of interface, such as SR4, LR4, PSM4, CWDM4, ER4, ZR4, etc. Among all these 100G QSFP28 transceivers, which one to choose for your 100G deployment? There are several factors you need to take into consideration.

Six Considerations When Selecting 100G QSFP28 Transceivers

Connector Type

The two most commonly seen connector types of QSFP28 transceivers are MTP/MPO-12 and Duplex LC. The connectors do not necessarily have to match between devices, but the cables connecting the two must be terminated in these connectors to bridge the two.

OEM Compatibility

The fiber in a port that is not coded to interoperate with an OEM router is likely to make the port inoperable because they use a different language, even if they physically fit. Thus, you'd better seek third-party 100G transceivers from trusted suppliers who guarantee it. FS provides those 100G QSFP transceivers that are compatible with its switches, as well as transceivers compatible with Cisco, Dell, Arista, Juniper, etc.

Operating Temperature

The environment temperature in which 100G QSFP transceivers work can significantly influence their performance. Generally, there are commercial use transceivers which work at 0°C to 70°C, industrial use ones that work at -40°C to 85°C. Make sure the 100G QSFP28 transceivers you select are acceptable for the environment.

Transmission Distance & Fiber Mode

There are 100G QSFP28 transceivers for many different transmission distances, such as 100m, 500m, 2km, 10km, 40km, 80km, etc. which come with different fiber modes. Generally, multimode QSFP28 transceivers cost less but the transmission distance is short (<2km), while single-mode modules have a longer transmission distance. What you need to do is to select those that can satisfy your needs on transmission distance.

Laser Type

Typical laser types of 100G QSFP28 modules in the market include VCSEL, DML, and EML. VCSEL laser features small size, high coupling rate, low power consumption, and low price. QSFP28 modules with VCSEL laser are mainly used for 100G multimode fiber networks. The EML has less wavelength dispersion and a stable wavelength at high-speed operation, mainly for applications over SMF reaching up to 10km. Compared to EMLs, DMLs have larger chromatic dispersion, lower frequency response, and relatively low extinction ratio, thus mainly used for relatively lower speeds (≤25Gbps), and shorter reaches (2-10km) in telecom and datacom applications.

Price and Warranty

For 100G deployment, you can choose to purchase OEM QSFP28 optical transceivers from distributors or those compatible ones from third-party suppliers. The main difference between these two choices may rely on prices. Also, make sure there is a warranty for your transceivers because it will help to avoid further loss.

Ways to Select 100G QSFP28 Transceivers

The first thing to make sure of before purchasing is the transmission distance you expect the transceivers to reach. Here are a few tips to choose the right QSFP28 transceivers for your 100G deployment based on different transmission distances.

1. Copper DAC Used Inside Racks: 1-5m

QSFP28 DACs are a very cost-effective I/O solution for 100GbE connectivity within 5m. If your 100G deployment is within 5m intra racks, the DACs would be good for you.

2. Multimode Fiber Use Between Switches: 5-100m

For 100G cabling between switches, there are two options to choose from. One is to use QSFP28 AOC for a distance of 3-20 meters. And the other option is to use a QSFP28 SR4 transceiver with 12-fiber MTP OM3/OM4 cable to reach a distance of up to 100m.

3. Single-Mode Fiber Use Between Switches: 100m-2km

For a distance of 100m-2km, there are two recommendations, QSFP28 PSM4 and CWDM4 transceivers. QSFP28 PSM4 can support up to 500m over 12-fiber MTP single-mode fiber cable. QSFP28 CWDM4 transceivers are suitable for 2km over duplex LC single-mode fiber cable.

4. Single-Mode Fiber for Long Span: ≤10km

For long-distance 100GbE deployment, such as connectivity between two buildings, mostly up to 10 km, QSFP28 LR4 with duplex LC single-mode fiber cable is the preferred option defined by IEEE. Some QSFP28 LR4 modules can even reach a maximum distance of 20km.

5. Transmission Distance Exceeds 10 km

The QSFP28 ER4 optical transceiver provides superior performance for 100G Ethernet applications up to 40 km links. It 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. There are also QSFP28 ZR4 100G module and DWDM PAM4 module for expended long-haul transmission up to 80km.


For most 100G applications, various QSFP28 transceivers are still playing an irreplaceable role. FS provides a variety of high-quality QSFP28 100G optical modules with full compatibility and here is a 100G QSFP28 Selection Guide for your reference.

FS 100G QSFP28 Modules

To be more specific, the following is a chart of those different 100G QSFP28 modules.

Types of 100G QSFP28 Fiber Mode Interface Wavelength Distance
100G QSFP28 SR4 MMF MTP/MPO-12 850nm 100m
100G QSFP28 PSM4 SMF MTP/MPO-12 1310nm 500m
100G QSFP28 CWDM4 SMF LC Duplex 1271nm/1291nm/1311nm/1331nm 2km
100G QSFP28 LR4 SMF LC Duplex 1310nm 10km
100G QSFP28 ER4 SMF LC Duplex 1310nm 25km-40km
100G QSFP28 ZR4 SMF LC Duplex 1310nm 80km

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