What is a 100G SFP-DD transceiver and how does it differ from standard SFP?

A 100G SFP-DD (Small Form-Factor Pluggable Double Density) transceiver is a next-generation optical module designed to support 100 Gbps data rates while maintaining the same compact footprint as traditional SFP modules. The key difference is that SFP-DD features a dual-lane design (hence "Double Density"), with each lane supporting 50 Gbps using PAM4 modulation. This allows it to deliver four times the bandwidth of SFP28 (25G) while maintaining backward compatibility with existing SFP infrastructure, making it an ideal solution for network upgrades.

What are the advantages of using 100G SFP-DD compared to QSFP28 transceivers?

The primary advantages of 100G SFP-DD over QSFP28 include: - Higher port density: SFP-DD's compact size allows for more ports in the same rack space compared to the larger QSFP28 form factor. - Cost efficiency: SFP-DD typically offers a more cost-effective solution for high-density scenarios. - Migration path: SFP-DD provides backward compatibility with existing SFP modules, allowing for a smoother, gradual infrastructure upgrade. - Familiar form factor: Network operators already familiar with SFP can easily adapt to SFP-DD without significant changes to handling procedures or equipment. While both support 100 Gbps data rates, SFP-DD is optimized for high-density, high-performance networks, while QSFP28 is better suited for core and aggregation networks where individual port count might be less critical.

MSA standards explanation and compliance

Posted at June 17, 2025 in Technical Questions by Gints Golubs

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As optical transceiver providers, we and also our customers already know the term MSA. The three letters stand for Multi-Source Agreement. It is a document explaining the optical transceiver size, shape, electrical and optical interface standard. By following these standardized guidelines, manufacturers can design transceivers that are mechanically and electrically compatible with networking equipment from other vendors. This allows devices from different suppliers to work together seamlessly in the same network environment. But in general why is it so important and why do everyday we mention MSA internally and to our customers?

Firstly, you can buy transceivers from different suppliers and use them in the same equipment

Secondly, overall flexibility. Network operators have more options to choose from (variability of different type of transceivers) and are not locked into one supplier.

Thirdly, lower costs as many companies provide MSA compatible goods, which increases competition.

List of relevant MSA standards

The standards may differ from optical transceiver data rate/ form factor. Here is a list of all MSA standards and what are they described for. All other SFF MSA specification can be seen in the SNIA SFF Specifications database. Newer standards like the QSFP-DD and OSFP are defined by either QSFP-DD MSA group or OSFP MSA group, as the transceivers are more complicated, it requires multiple standard explanations in design and parameters.

SFP/ SFP+

INF-8074 / INF-8074i: SFP Transceiver definition
SFF-8472: Digital Diagnostic Monitoring Interface (DDM)
SFF-8431: SFP+ 10G Electrical Interface
SFF-8432: SFP+ Mechanical dimensions (Module + Cage)
SFF-8470: SFP+ Direct Attach Cable (DAC)
SFF-8418: SFP+ Electrical Interface
SFF-8089: SFP Rate and Application Codes
SFF-8079: Application Selection for SFPs

XFP

INF-8077i: XFP (10G) Transceiver MSA
SFF-8477: Tunable XFP for ITU Frequency Grid Applications (additions to the INF-8077i)

QSFP+/ QSFP28

SFF-8436: QSFP+ 40G Transceiver
SFF-8665: QSFP28 100G Electrical Interface
SFF-8679: QSFP28 100G Electrical Connector
SFF-8680: QSFP28 Module and Cage
SFF-8636: Common Management Interface Specification (CMIS)

OSFP/ QSFP-DD

OSFP MSA: 400G OSFP Transceiver (Non-SFF, defined by the OSFP MSA group)
QSFP-DD MSA: 200G/400G/800G QSFP Double Density Transceiver

CFP/ CFP2/ CFP4

CWDM MSA: Coarse Wavelength Division Multiplexing
LWDM MSA: LAN-WDM for 100G over single fiber
Open ZR+ MSA: 400G coherent pluggables for long-range use (developed by OIF and other industry bodies)

MSA compatible SFP

We daily use the sentence “MSA compatible SFP (or other form factor)”. Let us explain what do we mean by it – every SFP is coded with special coding, so the transceiver can work seamlessly in switches/ routers. Some SFPs may need different coding for different manufacturer devices, for example, in Cisco equipment the optic need different code, same as Huawei need different coding. MSA compatible SFP states that the transceiver can be used in variety of different manufacturer devices, if all switches/ routers comply with the MSA standard. This gives network engineers the freedom to use one transceiver in many different switches, without recoding them to fit a special device.

Common Exceptions and Vendor-Specific Deviations from MSA

Many switch and router vendors (like Cisco, Juniper, HP) program their devices to check the EEPROM of a transceiver for a specific vendor ID or checksum. If the transceiver isn’t “approved,” the device may either reject the module completely or show error, for example, unsupported/ unapproved.
This isn’t due to MSA incompatibility, but a firmware-level lock to encourage purchasing brand-certified optics.

EDGE Optical Solutions provide both MSA compliant standard and firmware-level locked transceivers for compatibility in such routers like Cisco, Huawei, Nokia and many other!

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