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Understanding QSFP28 Optical Modules: A Comprehensive Guide


Abstract: In today's rapidly evolving technological landscape, high-speed data transmission is no longer a luxury but a necessity. With the proliferation of data-intensive applications such as cloud computing, artificial intelligence, and high-definition video streaming, the demand for faster and more reliable data transmission solutions has skyrocketed. In this context, the QSFP28 optical module has emerged as a critical component, enabling organizations to achieve blazing-fast data transfer rates of up to 100Gbps over optical fiber connections. In this article, we'll delve into the intricacies of QSFP28 optical modules, explore the different types available, discuss the key factors to consider when choosing the right module for your needs, and provide practical guidance on selecting 100G QSFP28 optical modules.


Understanding QSFP28 Optical Modules

QSFP28 (Quad Small Form-factor Pluggable 28) optical modules are high-speed, hot-pluggable transceiver modules used for high-speed data communication applications. They are designed to meet the ever-increasing demand for bandwidth in data centers, enterprise networks, telecommunications, and other high-performance computing environments.

The QSFP28 standard defines a compact form factor that allows for four independent channels of high-speed data transmission, each operating at rates of up to 25Gbps or 28Gbps per channel. This enables a single QSFP28 module to support aggregate data rates of up to 100Gbps, making it ideal for high-bandwidth applications.


Types of QSFP28 Optical Modules

There are several types of QSFP28 optical modules, each designed to meet specific application requirements. The most common types include:


QSFP28 SR: QSFP28 SR4 (Short Range 4) is a short-distance multi-mode optical fiber module that supports a maximum transmission distance of 100 meters. It uses 850nm wavelength optical signals to transmit data and is commonly used for internal interconnection in data centers. The maximum transmission rate of this module is 100Gbps and supports two types of multi-mode optical fibers, OM3 and OM4.


When the 100GBASE-SR4 QSFP28 optical module transmits signals at the transmitter end, the electrical signals are converted into optical signals by the laser array. They are then transmitted in parallel over a ribbon of multimode fiber, and upon reaching the receiving end, a photodetector array converts the parallel optical signals into parallel electrical signals.


QSFP28 LR:qsfp28 LR4 (Long Range 4) is a long-distance single-mode optical fiber module that supports a maximum transmission distance of 10 kilometers. It uses 1310nm wavelength optical signals to transmit data and is commonly used for interconnection between data centers. The maximum transmission rate of this module is 100Gbps.


The 100GBASE-LR4 QSFP28 optical module converts 4 channels of 25Gbps electrical signals into 4 channels of LAN WDM optical signals, and then multiplexes them into a single channel to achieve 100G optical transmission. At the receiving end, the module demultiplexes the 100G optical input into 4 LAN WDM optical signals, and then converts them into 4 electrical signal output channels.


QSFP28 ER: ER4 (Extended Range 4) is an ultra-long-distance single-mode optical fiber module that supports a maximum transmission distance of 40 kilometers. It uses 1310nm wavelength optical signals to transmit data and is typically used for long-distance transmission between data centers. It has the characteristics of low power consumption and high performance. The maximum transmission rate of this module is 100Gbps.

The 100GBASE-ER4 QSFP28 optical module uses advanced modulation technology to achieve high-speed data transmission over single-mode optical fiber. In addition, the optical module also supports digital diagnostic monitoring (DDM) function, which can monitor the working status, optical power, temperature and other parameters of the module in real time to improve the reliability and stability of the system.


QSFP28 CWDM: The QSFP28 CWDM4 optical module has a transmission rate of 103.1Gbp and is mainly used in computing, high-frequency trading and other fields. Its cost is significantly higher than the QSFP28 PSM4 optical module.


Through coarse wavelength division multiplexing (CWDM) technology, the QSFP28 CWDM4 optical module multiplexes four wavelengths of 1270nm, 1290nm, 1310nm and 1330nm onto a single-mode optical fiber for transmission.


QSFP28 PSM4: PSM4 (Parallel Single Mode 4) is a parallel single-mode optical fiber module that supports a maximum transmission distance of 500 meters. Usually used for internal interconnection of data centers. The maximum transmission rate of this module is 100Gbps. It adopts parallel transmission technology and uses four single-mode optical fibers to transmit data simultaneously, which can improve transmission bandwidth and transmission distance.


The fiber transmission model of the 100G QSFP28 PSM4 optical module is similar to the 100G QSFP28 SR4 optical module. The biggest difference is that the transmission medium of the PSM4 optical module is single-mode fiber, using a laser light source of 1310nm, and the connector uses single-mode MTP/MPO.


Factors to Consider When Choosing QSFP28 Optical Modules

Selecting the right QSFP28 module for your specific application requires careful consideration of several key factors:


Transmission Distance: Determine the required transmission distance for your application, whether it's short-range connectivity within a data center or long-range connectivity between remote facilities.

Fiber Type: Consider the type of optical fiber infrastructure available in your environment, whether it's multimode fiber for short distances or single-mode fiber for longer distances.


Data Rate: Ensure that the module supports the desired data rate for your application, whether it's 25Gbps or 100Gbps per channel.


Compatibility: Verify compatibility with existing network equipment, including switches, routers, and other optical transceivers, to ensure seamless integration into your network infrastructure.


Reliability and Quality: Choose reputable manufacturers and suppliers that adhere to industry standards and provide high-quality, reliable products with low error rates and long-term reliability.

Cost: Consider the overall cost of the modules, including upfront procurement costs, maintenance expenses, and total cost of ownership over the module's lifespan.


How to Select 100G QSFP28 Optical Modules

When selecting 100G QSFP28 optical modules specifically, follow these guidelines to ensure you choose the right modules for your needs:

Evaluate Performance Requirements: Assess your application's performance requirements, including data rate, latency, and reliability, to determine the appropriate specifications for the QSFP28 modules.

Consider Future Scalability: Anticipate future growth and scalability needs to ensure that the selected modules can accommodate future upgrades and expansions without requiring significant infrastructure changes.

Review Compatibility: Verify compatibility with existing network infrastructure, including switches, routers, and other optical modules, to avoid compatibility issues and ensure seamless integration.

Assess Environmental Conditions: Consider environmental factors such as temperature, humidity, and airflow within your data center or network environment to ensure that the selected modules can operate reliably under varying conditions.

Seek Expert Advice: Consult with networking experts, system integrators, and optical engineers to gain insights and recommendations tailored to your specific requirements and challenges.

By following these guidelines and considering the aforementioned factors, you can confidently select 100G QSFP28 optical modules that meet your performance, compatibility, and reliability requirements, enabling you to build high-speed, robust, and scalable optical networks that support your organization's evolving needs.


In conclusion, QSFP28 optical modules play a crucial role in enabling high-speed data transmission in modern data centers, telecommunications networks, and enterprise environments. By understanding the different types of QSFP28 modules available, considering key factors when choosing modules, and following best practices for selecting 100G QSFP28 modules, organizations can build efficient, reliable, and future-proof optical networks that meet the demands of today's data-driven world.


What is the difference between QSFP28 and SFP28?

The main difference between QSFP28 (Quad Small Form-factor Pluggable 28) and SFP28 (Small Form-factor Pluggable 28) lies in their form factor and data transmission capacity. QSFP28 modules support four independent channels of up to 25Gbps or 28Gbps each, totaling up to 100Gbps, while SFP28 modules support a single channel of up to 25Gbps.

In terms of packaging method, is QSFP28 backward compatible with QSFP+?

Yes, in terms of packaging method, QSFP28 (Quad Small Form-factor Pluggable 28) is backward compatible with QSFP+ (Quad Small Form-factor Pluggable Plus). Both modules share the same form factor, allowing QSFP28 modules to physically fit into QSFP+ slots, although they may not support the same data rates.

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