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100G QSFP28 Optical Transceiver: How to Choose?

Due to the increasing demand for network bandwidth, 100G transceivers are also more widely used. But when choosing, many people cannot accurately understand the type they need, such as SR4, LR4, CWDM4, ER4, etc. This article will show you how to determine the type of 100G transceiver you need.

What is a 100G QSFP28 Transceiver

The 100G QSFP28 transceiver is a fiber optic communication module used to increase data transmission rates to 100Gbps, typically employing PAM4 modulation technology. It consists of an optical transmitter, optical receiver, module housing, and chipset. This module typically utilizes multimode or single-mode fiber optic cables as transmission media and converts electrical signals to optical signals through electro-optical modulation technology, enabling high-speed data transmission and communication over optical fibers.

Considerations for Choosing 100G Optical Modules


When selecting a 100G optical module, compatibility is the first consideration. If you are using Cisco switches, make sure that the module is compatible with your equipment when purchasing it. If you buy modules from other brands, such as HP compatible modules, they may not work properly on Cisco devices. 6COM provides modules compatible with various brands, including Cisco, Juniper, Dell, and Arista.

Transmission Distance

After considering compatibility, you need to estimate the transmission distance based on your application requirements. When purchasing optical modules, it is recommended to choose specifications that exceed the estimated transmission distance. For example, if you estimate a transmission distance of 1.2 kilometers, it is advisable to purchase a 2-kilometer optical module. Because the maximum transmission distance of the module is measured under extreme test conditions, selecting specifications greater than the actual transmission distance can improve the stability and reliability of data transmission.

Operating Temperature

Optical modules are typically available in three temperature specifications: commercial, extended, and industrial. Commercial temperature modules usually operate between 0 and 70 degrees Celsius, extended temperature modules between -20 and 85 degrees Celsius, and industrial-grade modules between -40 and 85 degrees Celsius. Choose the appropriate module based on the actual temperature conditions of your environment, but try to select specifications with a wider coverage range to ensure the stability of the optical module.

Laser Types

Laser is a key component of optical modules, and different types of lasers are suitable for different application scenarios. 100G optical modules typically include VCSEL, DFB, and EML lasers. VCSELs are small in size, low in price, and low in power consumption, making them suitable for short-distance transmission of 100G. EMLs have small dispersion and stable wavelengths at high speeds, making them suitable for transmissions of around 10 kilometers. DFB lasers are suitable for long-distance transmission because of their narrow spectral linewidth, which reduces dispersion and distortion of optical signals during transmission, and they also have higher output power, making them more suitable for long-distance transmission.

Connector Types

The most common connector types for 100G QSFP28 optical modules are MTP/MPO-12 and LC duplex. Although the connector types between two optical modules do not necessarily need to match, ensure that the connectors correspond to the interfaces of the optical modules when in use.

How to Choose 100G Optical Modules in Different Applications

When purchasing an optical module, you first need to determine under what circumstances you need to use it. Next, I will recommend suitable optical modules for you based on different transmission distances:

Transmission distance: 1-5M

When connecting within a rack at distances of 1-5 meters, 100G DAC (Direct Attach Cable) presents an economically efficient connectivity solution. With negligible power consumption and minimal heat generation, DAC offers lower costs compared to optical modules.

Transmission distance: 5-30M

For distances ranging from 5 to 30 meters, 100G AOC (Active Optical Cable) emerges as the optimal choice. AOC, a simplified device, integrates optical modules and fibers into a single unit, facilitating convenient deployment.

Transmission distance: 100M

Within a 100-meter distance range, the combination of 100G SR4 and 12-core MTP OM3/OM4 cables meets basic requirements, suitable for transmissions within 100 meters. Specific selection depends on cost-effectiveness and application scenarios.

Transmission distance: 2KM

For distances up to 2 kilometers, options include CWDM4 or PSM4 100G modules. While 100G PSM4 can transmit 500 meters through 12-core MTP single-mode fibers, 100G CWDM4 achieves 2 kilometers through LC duplex single-mode fibers.

Transmission distance: 10KM

Within distances of 10 kilometers, such as interconnecting adjacent buildings, consider using 100G LR4 paired with LC duplex single-mode fibers. Not only does it ensure stable transmission, but it also offers relatively high cost-effectiveness.

Transmission distance: More Than 10KM

When distances exceed 10 kilometers, opt for higher-specification optical modules. For instance, at a distance of 40 kilometers, 100G ER4 delivers exceptional performance, meeting long-distance, high-bandwidth transmission demands. It converts 25Gb/s electrical data from four input channels into LAN WDM optical signals across four channels, then multiplexes them into a single channel to achieve 100Gb/s optical transmission.


Types Fiber Mode Interface Wavelength Distance
100G QSFP28 DAC / / / ≤5M
100G QSFP28 AOC / / / ≤30M
100G QSFP28 SR4 MMF MPO-12 850nm 100m
100G QSFP28 PSM4 SMF 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 40km


For current network applications, 100G optical modules still play an irreplaceable role. If you need to choose a module that suits your needs, the content provided in this article applies to most situations and will help you successfully deploy your business.

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