How Much Do You Know About 100G SFP-DD Transceivers?

Author Yana

Date 04/01/2025

Discover the key features, advantages, and types of 100G SFP-DD transceivers, including their dual-channel design, PAM4 modulation, and high-density performance. Compare DSFP vs. SFP-DD differences and discover their role in networks.

Currently, the most common 100G transceiver form factor is QSFP28, which meets the needs of most applications. However, with the increasing demand for greater port density, SFP-DD (Small Form-factor Pluggable-Double Density) emerged. This article will explain the characteristics, advantages, common types, and differences between 100G SFP-DD vs 100G DSFP transceivers.

SFP-DD 100G Overview

What is 100G Optical Transceiver?

Simply put, a 100G optical module is a transceiver with a rate of 100G. Here, the G is the unit of optical signal transmission rate, which is Gbps. The commonly used form factor is QSFP28, which has four independent optical signal transmission channels, and the transmission rate of each channel is 25G.

What is Double Density SFP-DD Form Factor？

Based on the development trend of high throughput and large bandwidth in data centers, server network cards and access switches are evolving toward the next-generation 100GE interface. The next generation 100GE interface consists of two 50GE physical channels, which is half the number of physical channels of the previous generation QSFP28 interface, and the port density is improved. SFP-DD is this next-generation 100GE interface.

The SFP-DD (Small Form-factor Pluggable-Double Density) form factor was proposed by Alibaba at the 2017 OFC. Under the initiative and promotion of Alibaba, the SFP-DD MSA organization was established on July 12, 2017. The SFP-DD MSA organization aims to develop the optoelectronic interface standards, mechanical structure and heat dissipation standards for the connection between servers and switches in the next-generation 400G data center network.

The SFP-DD replaces the traditional 4-channel data center module with two channels, running up to 25 Gbps NRZ modulation or 56 Gbps PAM4 modulation, providing up to 50 Gbps or 112 Gbps PAM4 aggregation solutions, and even in the future it can provide access solutions such as 200G (2x 100G) required by the next generation of data centers, saving space for the installation of data centers and meeting the requirements of small size, high density and low power consumption of the next generation of data centers.

The SFP-DD form factor is backward compatible with the current SFP/SFP+ interface solution, laying the foundation for the smooth upgrade of 25G SFP28 solution to 100G, and also establishing a basic technical platform for the upgrade of single-channel optical port 50G to 100G. SFP-DD and QSFP-DD can form a complete solution for 100G access in data center networks and interconnection between 400G switches.

Why Do We Need 100G SFP-DD Fiber Optic Transceiver?

The SFP-DD module is needed because it has many advantages.

Firstly, SFP-DD uses dual-channel architecture and PAM4 high-order modulation technology, doubling the data throughput compared to traditional NRZ modulation. This feature perfectly adapts to bandwidth-intensive services such as AI model training, 8K ultra-high-definition video streaming, and real-time big data analysis, ensuring non-blocking transmission under data torrents.

Secondly, the SFPDD module adopts dual-channel, which can increase port density within the same physical space to improve space utilization.

Then, SFP-DD optical modules are compatible with SFP/SFP+, ensuring a transition at a low cost.

Finally, SFP-DD optical modules can significantly improve network performance. Their stronger data processing capability and lower latency make the network more stable and efficient when dealing with high-demand applications such as large-scale data streaming, video streaming or cloud computing, ensuring the network's stability and responsiveness in large-scale data transmission.

What Are the Common Types of 100Gb SFP-DD Transceiver Modules?

100GBASE-DR SFPDD Optical Module

The 100GBASE-DR Single Lambda SFPDD optical module delivers 100GbE connectivity, supporting up to 500m over single-mode fiber (SMF) via duplex LC connectors at a 1310nm wavelength. Compliant with the SFPDD MSA and SFP-DD MIS Rev 2.0 standards, this transceiver converts 2x26.5625G PAM4 electrical lanes into a single 53.125G PAM4 optical channel, adhering to IEEE 100GBASE-DR specifications.

100GBASE-FR SFPDD Fiber Module

The 100G FR SFP-DD modules are designed to support 100G Ethernet transmission over single-mode fiber operating at 1310nm. The transmission distances can be up to 2km. The module uses duplex LC connectors, complies with the SFP-DD MSA and SFP-DD MIS Rev 2.0 standards, and combines two 26.5625G PAM4 electrical channels into a single 53.125G PAM4 optical channel to meet the requirements of the IEEE 100GBASE-FR standard.

100GBASE-LR SFPDD Optical Transceiver Module

The SFP-DD Single Lambda 100GBASE-LR module is designed for 100GBASE Ethernet transmission over single-mode fiber (SMF) with a reach of up to 10km, utilizing a 1310nm wavelength and duplex LC connectors. This transceiver also complies with the SFP-DD MSA and SFP-DD MIS Rev 2.0 standards. It consolidates two 26.5625GBd PAM4 electrical lanes into a single 53.125GBd PAM4 optical channel, fully compliant with the IEEE 100GBASE-LR specification.

100G DSFP vs. SFP-DD, What's the Difference?

Before explaining the difference between 100G DSFP and 100G SFP-DD, we need to understand what DSFP 100G is.

The DSFP (Dual Chanel Small Form-factor Pluggable) MSA standard defines 10G point-to-point application optical modules. It is a dual-transmit and dual-receive optical module that supports two electrical lanes and is compatible with the SFP+ packaging specification. It can provide high-density, low-cost optical module solutions for 5G networks. The installation density of DSFP is twice that of SFP and is compatible with the existing SFP specification.

DSFP can support up to 28Gbps in NRZ format and 56Gbps per electrical channel through PAM4, which is twice the number of channels of the existing SFP. Therefore, DSFP will be able to support 56Gbps NRZ or 112Gbps PAM4 transmission, and in the future, it will also support 224Gbps transmission based on PAM4.

The core difference between DSFP and SFP-DD lies in application scenarios and scalability: DSFP is suitable for efficient bandwidth management of medium-speed (such as 100G) and is often used in enterprise networks or ordinary data centers; while SFP-DD can achieve 400G ultra-high speed through a higher-density channel design (has the capacity expansion of eight lanes), mainly for large data centers with dense traffic, and is compatible with traditional SFP/SFP28 modules, making it more suitable for future upgrades. In short, DSFP focuses on practical medium-speed needs, while SFP-DD focuses on high density and future expansion.

Conclusion

The 100G SFP-DD optical transceiver adopts dual-channel and PAM4 technology. It doubles the port density and is compatible with SFP/SFP+. Compared with 100G DSFP modules, SFP-DD 100G performs better in future scalability and high-density applications. Overall, due to its high density and future scalability, SFP-DD 100G has become a key choice for developing 100G and higher-speed networks.