Optical modules are the backbone of high-speed networking and data transmission, playing a critical role in enabling seamless connectivity across modern data centers. With the growing demand for higher bandwidth and more efficient systems, choosing the right optical module has become a vital decision for network engineers and IT professionals. This blog aims to provide a clear understanding of the differences between QSFP-DD (Quad Small Form-factor Pluggable Double Density) and QSFP28, two widely-used optical module standards. By examining their specifications, performance capabilities, and use cases, we seek to equip readers with the knowledge to make informed decisions for their networking needs.
QSFP-DD, or Quad Small Form-factor Pluggable Double Density, is an advanced optical module standard designed to support data rates of up to 400Gbps. It achieves this through 8 lanes, each capable of handling 50Gbps, making it ideal for high-bandwidth applications in data centers and cloud computing environments.
On the other hand, QSFP28 is a predecessor supporting data rates of up to 100Gbps. It utilizes 4 lanes, each with a 25Gbps capacity, making it suitable for lower bandwidth requirements compared to QSFP-DD.
The primary distinction lies in their density and scalability—QSFP-DD offers higher bandwidth and backward compatibility with QSFP28 ports, while QSFP28 remains a cost-effective solution for networks where lower throughput suffices.
QSFP-DD, or Quad Small Form Factor Pluggable Double Density, is an advanced interconnect solution designed to meet growing bandwidth demands. It features a form factor with eight electrical lanes, supporting aggregate data rates of up to 400Gbps. The form factor is aligned with the IEEE and MSA standards to ensure interoperability across vendors.
Physical Specifications:
Size: QSFP-DD maintains the same dimensions as QSFP28, allowing for seamless backward compatibility, with an additional row of electrical contacts to support the double-density interface.
Connector type: 8-lane electrical interface, compatible with PCIe Gen4 signaling.
Thermal performance: Designed to handle an operating power of up to 12W, depending on specific implementations.
Key Data Rates:
Per lane speed: Up to 50Gbps with PAM4 (Pulse Amplitude Modulation) signaling.
Aggregate throughput: Up to 400Gbps using all 8 lanes.
Applications:
The QSFP-DD module is ideal for high-performance applications like data center spine-leaf architectures, high-speed network switches, and edge computing platforms that demand ultra-high bandwidth and scalability. It is also power-optimized to reduce total cost of ownership in large-scale environments, ensuring performance efficiency even under high workloads.
The QSFP28 (Quad Small Form-Factor Pluggable 28) transceiver supports a data rate of 100Gbps, divided across four 25Gbps channels. Designed for high-speed data communications, it is commonly used in 100G Ethernet, data center interconnects, and cloud computing environments. Leveraging advanced technologies such as PAM4 (Pulse Amplitude Modulation), some QSFP28 modules have now been enhanced to support even higher data rates, including up to 200Gbps in certain configurations. These advancements ensure that QSFP28 remains a key component in scalable and future-proof network infrastructures, balancing performance, energy efficiency, and cost for modern IT ecosystems.
QSFP-DD (Quad Small Form-factor Pluggable Double Density) and QSFP28 modules differ significantly in terms of power consumption due to their design and performance capabilities. QSFP28 modules typically consume between 3.5W to 5W, depending on the data rate and operational conditions, making them highly efficient for 100Gbps network applications. On the other hand, QSFP-DD modules, which are designed to support higher speeds of up to 400Gbps, generally require between 7W to 12W per module due to their increased functionality and higher processing demands.
These differences in power consumption highlight the trade-off between performance and energy efficiency. QSFP28 modules are optimal for environments prioritizing lower power usage, while QSFP-DD modules are better suited for high-performance infrastructures where bandwidth demands outweigh energy considerations. These metrics are essential for planning scalable, energy-efficient networks tailored to specific operational needs.
Below is a detailed comparison of the technical specifications of QSFP-DD and QSFP28 modules, highlighting their contributions to high-speed data transmission:
Bandwidth Capacity:
QSFP28: Supports up to 100 Gbps per module, achieved via 4 lanes of 25 Gbps each.
QSFP-DD: Delivers up to 400 Gbps per module, using 8 lanes of 50 Gbps each.
Form Factor:
QSFP28: Compact design optimized for power efficiency while supporting high-speed connectivity.
QSFP-DD: Slightly larger than QSFP28 to accommodate higher lane counts, maintaining backward compatibility with QSFP28 ports.
Power Consumption:
QSFP28: Consumes between 3.5 to 5 watts per module, designed for energy-conscious applications.
QSFP-DD: Consumes 7 to 12 watts per module, reflecting its higher data rate capabilities.
Backward Compatibility:
QSFP28: Not compatible with QSFP-DD as it lacks the necessary lane count.
QSFP-DD: Fully backward compatible with QSFP28 modules for flexible deployment in hybrid environments.
Applications:
QSFP28: Ideal for data centers with moderate bandwidth demands and stringent energy efficiency targets.
QSFP-DD: Suited for next-generation networking environments with significant throughput requirements, such as 5G networks and AI-driven infrastructures.
These specifications underline how QSFP-DD modules leverage advanced technology to meet growing data traffic demands compared to QSFP28, which prioritizes energy-efficient performance for existing frameworks.
Optical transceivers play a critical role in ensuring efficient and scalable data transmission within modern data centers. With the increase in cloud computing, IoT, and AI workloads, the demand for higher bandwidth and lower latency has grown exponentially. Optical transceivers, such as QSFP28 and QSFP-DD, facilitate high-speed data connections between servers, switches, and storage systems, enabling data centers to meet these demands effectively. Recent advancements in optical transceiver technology focus on achieving speeds of 400G and beyond, leveraging Dense Wavelength Division Multiplexing (DWDM) and Coherent Optics to optimize data transfer while reducing power consumption and operational costs. These innovations are essential for addressing the challenges posed by escalating data traffic and evolving network requirements.
Compatibility and interoperability are critical for ensuring seamless communication between network components. Compatibility refers to the ability of hardware or software to function with other systems without modification, while interoperability focuses on the capability of different systems or devices to exchange and utilize information effectively. Ensuring both aspects requires adherence to industry standards, such as IEEE or ITU-T, which define the parameters for interface design and communication protocols. This guarantees efficient integration and operational consistency across diverse platforms.
QSFP-DD (Quad Small Form-factor Pluggable Double Density) technology delivers numerous advantages in data center environments, particularly in addressing the increasing demand for higher bandwidth and improved efficiency. Below is a detailed list highlighting the key benefits of adopting QSFP-DD:
Higher Bandwidth Capacity
QSFP-DD modules support up to 400Gbps data transmission rates, enabling data centers to handle growing demands for high-speed connections and scalable network performance.
Backward Compatibility
The design of QSFP-DD allows compatibility with existing QSFP-based infrastructure, providing a seamless upgrade path while protecting previous investments in networking hardware.
Compact Form Factor
Despite the increased density, QSFP-DD retains a relatively small footprint, allowing for better utilization of rack space in data centers and enhanced equipment scalability.
Energy Efficiency
QSFP-DD modules are optimized for lower power consumption while maintaining high-performance levels, reducing operational costs in energy expenditure over time.
Support for Next-Generation Applications
This technology is ideal for applications such as cloud computing, artificial intelligence (AI), and high-performance computing (HPC), where bandwidth, latency, and efficiency are critical.
Scalability and Flexibility
QSFP-DD provides a versatile solution for scaling networks without requiring significant system overhauls, allowing data centers to adapt to evolving workload demands.
Adherence to Industry Standards
QSFP-DD technology complies with MSA (Multi-Source Agreement) standards, ensuring reliable and interoperable solutions are available from multiple vendors.
The adoption of QSFP-DD technology offers significant advantages for modern data centers, ensuring they remain equipped to handle the challenges of a data-driven future.
QSFP-DD modules are designed to optimize power consumption while maintaining high data throughput. The use of advanced materials and thermal management systems helps reduce heat generation, ensuring efficient operation. This minimizes cooling requirements in data centers, contributing to overall energy savings and improved system reliability.
QSFP-DD (Quad Small Form Factor Pluggable Double Density) modules are engineered to meet the demanding requirements of high-speed data networks. Below are the detailed key features and specifications:
Data Rate Support: Capable of supporting up to 400 Gbps, with scalability for future network upgrades up to 800 Gbps.
Backward Compatibility: Fully compatible with existing QSFP ports, ensuring seamless integration with legacy equipment.
Thermal Design Power (TDP): Modules operate within a power envelope of 7–12 watts, balancing performance and energy efficiency.
Connector Density: Features higher port density by utilizing an 8-lane electrical interface, doubling the capacity over standard QSFP modules.
Optical Standards Support: Adheres to a range of optical network standards, including 100GBASE-SR4, LR4, and 400GBASE-DR4.
Cable and Module Interoperability: Supports both fiber-optic and copper cables, enabling flexibility in deployment scenarios.
Mechanical Design: Compact design optimized for thermal dissipation, ensuring durability and reliable long-term operation.
These specifications illustrate the versatility and advanced capabilities of QSFP-DD modules, solidifying their role as critical components in next-generation data center infrastructure.
QSFP-DD and OSFP differ primarily in their form factors, power consumption, and use cases. QSFP-DD is smaller in size, allowing higher port density, making it ideal for space-constrained environments. OSFP, being slightly larger, supports higher power levels per module, which makes it suitable for use cases requiring enhanced thermal management and higher power optics. Both standards support 400G speeds, but QSFP-DD is widely adopted in existing infrastructure due to backward compatibility with previous QSFP generations, offering more flexibility during deployment.
Form factor compatibility plays a crucial role in the adoption of network modules like QSFP-DD and OSFP. QSFP-DD is designed with backward compatibility in mind, supporting legacy QSFP transceivers such as QSFP+, QSFP28, and QSFP56. This ensures seamless integration into existing hardware without major overhauls, offering significant cost and operational efficiencies. On the other hand, OSFP, while not natively backward compatible, delivers superior thermal performance and supports higher power optics for evolving network demands. Organizations should evaluate compatibility concerns alongside thermal and performance requirements to determine the most suitable choice for their infrastructure.
Port density and data rates are critical factors to consider when evaluating network modules for scalable and high-performance deployments. QSFP-DD supports up to 36 ports per 1U switch, providing a potential aggregated bandwidth of 14.4 Tbps with 400 Gbps per port. This high port density makes QSFP-DD an attractive option for environments requiring maximum bandwidth in limited space.
Conversely, OSFP also offers strong performance by supporting 32 ports per 1U switch, delivering an aggregated bandwidth of 12.8 Tbps at 400 Gbps per port. While it has slightly lower port density compared to QSFP-DD, OSFP’s design accommodates higher-power optics, making it future-proof for applications requiring subsequent power scaling.
Both modules are envisioned for 800 Gbps capabilities in the future, with early testing and prototypes demonstrating promising results. Their suitability ultimately hinges on the specific architectural demands of the network, such as power, cooling, and space constraints.
The 400G QSFP-DD transceiver introduces a set of advanced features and specifications that make it a reliable and scalable solution for next-generation networking requirements. Below is a detailed list of its core characteristics:
Form Factor:
Compact QSFP-DD design fitting in a 1U chassis.
Supports up to 36 ports per 1U, allowing 14.4 Tbps of total bandwidth.
Data Rate:
Each port operates at 400 Gbps, ensuring high-speed data transmission.
Electrical Interface:
Utilizes an 8-lane electrical interface, compatible with existing QSFP standards.
Each lane supports 50 Gbps using PAM4 (Pulse Amplitude Modulation).
Thermal Management:
Features improved heat dissipation mechanisms.
Accommodates modules with power consumption up to 15 W, ensuring efficient cooling in dense configurations.
Backward Compatibility:
Fully interoperable with legacy QSFP-based systems.
Simplifies infrastructure upgrades by reducing compatibility concerns.
Connector Type:
Incorporates a Double Density (DD) connector, doubling the number of high-speed interfaces within the same form factor.
Applications:
Ideal for data centers, high-performance computing (HPC), and cloud-scale networks.
Suitable for Ethernet, Fibre Channel, and InfiniBand networking protocols.
Future-readiness:
Designed with a roadmap to achieve 800 Gbps performance capabilities through innovation in optics and signaling.
These specifications underscore the QSFP-DD’s pivotal role in optimizing network capacity and efficiency, making it a key component of 400G Ethernet deployment strategies.
Below is a comprehensive list of the key specifications and details for QSFP-DD:
Form Factor Dimensions:
Length: 72 mm (with pull tab)
Width: 18.35 mm
Height: 8.5 mm
Electrical Interface:
Supports 8 electrical lanes, each capable of 25 Gbps NRZ or 50 Gbps PAM4 signaling.
Total aggregate bandwidth of 200 Gbps (NRZ) or 400 Gbps (PAM4).
Thermal Management:
Provides optimal heat dissipation using thermal heatsink designs.
Meets the thermal operating range of 0°C to 70°C.
Power Consumption:
Maximum supported power per module is 15 W.
Connector Type:
Utilizes Double Density (DD) connector for higher port densities.
Designed for mechanical reliability with secure latching.
Protocol Support:
Compatible with Ethernet (100GBASE-SR4, 400GBASE-DR4, etc.).
Integrated with Fibre Channel and InfiniBand standards.
Backward Compatibility:
Fully interoperable with existing QSFP+ and QSFP28 systems.
Simplifies network upgrades by supporting hybrid configurations.
Applications:
Optimized for data center interconnects, enterprise networks, and high-capacity cloud solutions.
Suitable for deep learning, artificial intelligence (AI), and machine learning workloads.
Future-Readiness:
Engineered to scale performance up to 800 Gbps.
Designed with an advanced optical signaling roadmap.
This detailed breakdown highlights the advanced features and robust design of QSFP-DD, reinforcing its position as a critical enabler of next-generation high-speed networking technologies.
The development of optical modules is primarily driven by the demand for higher bandwidth, lower latency, and greater energy efficiency in network infrastructures. Key advancements include the adoption of silicon photonics, which integrates optical and electronic components for improved performance, and the utilization of digital signal processing (DSP) for enhanced error correction. Additionally, the shift toward co-packaged optics—embedding optical components alongside networking silicon—reflects an industry focus on reducing power consumption and footprint in high-performance systems. These trends underline the industry’s commitment to meeting scalability and sustainability goals.
A: The most prominent distinction between the two lies in the bandwidth as well as the design densities. Being a Double Density Quad Small Form-Factor Pluggable (QSFP-DD), it supports both 200G and 400G Ethernet which is double the capacity of QSFP28 as this only supports 100G Ethernet. This is done by including an extra row of electrical contacts which expands the amount of eight electrical signals to be encompassed within a Transceiver Module instead of four shown in QSFP28.
A: Both QSFP-DD and OSFP transceivers facilitate the same use case of 400 Ether but the difference lies within their sizes. QSFP-DD operates on a smaller form factor as it is designed as being backwards compatible to existing QSFP ports which allows for an easier upgrade, while OSFP is in form of a large factor meaning an increase in space requirements but this does endorse better thermal performance alongside additional power handling capabilities. The decision on applying either QSFP-DD or OSFP depends on the requirements set in place by the network as well as the infrastructure availability.
A: Due to its backward compatibility features with the QSFP28, the QSFP-DD can allow the use of QSFP28 transceivers in this port. This option allows network operators to use their already existing QSFP28 modules while planning to put systems in place that can facilitate an upgrade to the QSFP-DD which supports higher data rates.
A: The Most significant role of the QSFP28 form factor in a data center is that it facilitates 100G Ethernet and even higher speed which allows for wider adoption of the technology in comparison to other technologies available in the market. These features in addition to the small form factor and power consumption are suited for the dense networks environments as they allow for greater port density on network switches and routers.
A: SFP28 is known to support only 25G Ethernet only while QSFP28 transceiver can support 100G Ethernet. The SFP28 is also part of SFP form factor family which means that it is smaller in size than QSFP28 and is mostly used over shorter distance and lower data rate applications compared to its counterpart which is meant for long range neutron high data rate.
A: The efficiency of the networks is enhanced by the use of the transceiver, the provision of 400G Ethernet and automation of the data center is made possible by the increased data rate QSFP-DD compatibility achieves maximum port density. All of these attributes render transceivers QSFP-DD ideal for the contemporary data centers to scale up network performance and capacity.
A: QSFP-DD was able to add more electrical contacts which were able to electrically signal eight lanes rather than four opposing sides like seen in the QSFP28. There is more lane capacity for QSFP-DD which means it is able to facilitate 200G and 400G ethernet systems.
A: The differences between QSPF-DD vs OSFP in deployment wise is usually in the case of form factors and compatibility. In comparison to OSFP, a bigger size that requires new infrastructure is needed, while the integration of OSFP along with other ports into existing networks is made easier by its backwards compatibility.
A: Of course, ASMBL QSFP-DD was developed in line with the standards for the QSFP56 so both of these switch are part of the same family of transceivers. The backward compatibility of the QSFP-DD allows the use of QSFP56 transceivers which are used for 200G Ethernet applications thus enabling easy migration within the network.
