What is the difference between QSFP and SFP module？

QSFP (Quad Small Form-factor Pluggable) and SFP (Small Form-factor Pluggable) are both types of optical transceiver modules used in networking equipment, but there are several key differences between the two:

1. Size and Density: QSFP modules are larger and denser than SFP modules, meaning they can support more ports and provide higher bandwidth. QSFP modules have four transmit and receive channels, while SFP modules have only one.

2. Data Rates: QSFP modules are designed to support higher data rates than SFP modules. QSFP modules can support data rates of up to 40Gbps or even 100Gbps, while SFP modules typically support data rates of up to 10Gbps.

3. Form Factor: QSFP modules have a larger form factor and use a different type of connector than SFP modules. QSFP modules use a 38-pin connector, while SFP modules use a 20-pin connector.

4. Applications: QSFP modules are typically used in high-density applications and high-speed data center networks, while SFP modules are more commonly used in lower-speed applications and smaller form factor devices.

In summary, the main differences between QSFP and SFP modules are in size, density, data rates, form factor, and applications. QSFP modules are bigger, support higher data rates, and are used in high-density and high-speed applications, while SFP modules are smaller and support lower data rates, and are used in lower-speed applications and smaller form factor devices.

Form factor & connectors

The term "form factor" refers to the standardized size and shape (or footprint ) of the optic, but other design features also help create each standard's definition. While there are many different transceiver form factors to consider, a few standards are more universal than the others.

Which you need is primarily determined by what form factors are compatible in the switch or router the optic is to be plugged in to, so it is always good to check what your system accepts.

AddOn's SFP-10G-SR-S-AO Cisco Compatible 1G SFP+ 40km LC Transceiver

Without the right form factor for your network environment, the optic may not fit into your switch or router at all. If it does connect, it may have impaired performance.

Can I use 100G QSFP28 port based with 40G QSFP+ transceiver?

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Most Switches, Network Packet Broker (NPB), and other Network Element allow the use of 40G QSFP+ optics within QSFP28 slot to support 10G using fanout/Breakout cable or 40G Multimode straight conectivity using MTP to MTP fiber cable.

SFP vs SFP+ vs XFP vs QSFP+ vs CFP vs QSFP28 Differences

Through the above definitions of each type of fiber optic transceiver module, you may have a further understanding of them. Now, we are comparing these transeiver one by one.

SFP vs SFP+ (SFP+ vs SFP): Simple to understand, SFP+ is an updated vision of SFP. SFP usually support 1.25Gbit/s to 4.25 Gbit/s while SFP+ supports data rates up to 10 Gbit/s. When it comes to SFP vs SFP+, they have the same size and appearance, but in a different standard which SFP is based on IEEE802.3 and SFF-8472.

SFP+ vs XFP (XFP vs SFP+): In comparison to earlier XFP modules, SFP+ modules leave more circuitry to be implemented on the host board instead of inside the module. The size of SFP+ is smaller than XFP, thus it moves some functions to motherboard, including signal modulation function, MAC, CDR and EDC. XFP is based on the standard of XFP MSA while SFP+ is compliance with the protocol of IEEE 802.3ae, SFF-8431, SFF-8432.

SFP+ vs QSFP+: QSFP+ has four-channel SFP+ interfaces which can transfer rates up to 40Gbps. And of course, they have different standards.

CFP vs QSFP+: QSFP+ (Quad Small Form-Factor Pluggable Plus) modules offer customers a wide variety of high-density 40 Gigabit Ethernet. The CFP is a hot-pluggable transceiver module form factor that supports a wide range of 40Gb/s and 100Gb/s applications such as 40G and 100G Ethernet.