QSFP56 and QSFP28 are both types of transceivers, which are used to transmit and receive data over fiber optic or copper cables in high-speed networking applications. The main difference between the two is the data transfer rate and the number of lanes used for transmission.

QSFP28 (Quad Small Form-factor Pluggable 28) supports data rates of up to 28 gigabits per second (Gbps) per lane, with four lanes for a total data rate of 100 Gbps. It is commonly used in applications requiring high-speed data transfer, such as data centers and telecommunications networks.

QSFP56 (Quad Small Form-factor Pluggable 56) supports data rates of up to 56 gigabits per second (Gbps) per lane, with four lanes for a total data rate of 200 Gbps. It is designed for even higher-speed data transfer requirements, such as emerging 5G network deployments and advanced data center architectures.

In summary, QSFP56 has a higher data transfer rate than QSFP28, making it suitable for applications requiring even greater bandwidth and speed.

    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?

    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.

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