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The Difference Between Various Types of Fiber Optic Transceivers(Part 2)

Sep. 03, 2020

QSFP28 (quad small form-factor pluggable 28)

QSFP28 is suitable for applications with 100G network requirements. It provides 4 high-speed differential signal channels, supporting rates from 25 Gbps to 40 Gbps. It also meets the requirements of 100 Gbps Ethernet (4×25 Gbps) and 100 Gbps unlimited bandwidth enhanced data rate (EDR).

SFP vs. SFP+:

1. Appearance: Both are almost the same in size and appearance. This allows equipment manufacturers to reuse existing SFP physical designs for network switches with SFP+ ports.

2. Transmission speed: SFP is up to 4 Gbit/s, while SFP+ is 10Gbit/s. In addition, they meet different specifications. SFP is based on SFF-8472 protocol, SFP+ complies with SFF-8431 and SFF-8432.

3. Compatibility: SFP+ ports can also be backward compatible with SFP, but the speed is reduced by 1 Gbit/s. The SFP+ transceiver cannot be inserted into the SFP port, otherwise the product or port will be damaged.

SFP28 vs. SFP+:

1. Appearance: almost the same.

2. Transmission speed: SFP28 is an upgraded version of SFP+. SFP28 has been upgraded to handle 25 Gbit/s per channel, while SFP+ only supports 10 Gbit/s.

3. Compatibility: SFP28 can also be backward compatible with SFP+, but the speed will be reduced to 10 Gbit/s. If the SFP+ module is used on the SFP28 port, then the port needs to be set to 10G transmission so that the SFP+ module can work normally, otherwise the SFP+ module cannot work.


SFP28 vs QSFP28:

1. Appearance: SFP28 and QSFP28 have different sizes.

2. Transmission speed: SFP28 only supports one 25Gbit/s channel, while QSFP28 supports 4 independent 25Gbit/s channels. They can all be used in 100G networks.

3. Compatibility: SFP28 is a disconnected cable applied to SFP28 in the form of QSFP28. The following shows the direct connection from 100G QSFP28 to 4x SFP28 DAC.

QSFP+ vs. QSFP28:

1. Appearance: Although both QSFP+ and QSFP28 transceivers integrate 4 transmit and 4 receive channels, they are the same size. In addition, the product series of QSFP+ and QSFP28 both include transceiver modules and DAC/AOC cables, but at different speeds.

2. Transmission speed: QSFP+ module supports 1x40gbit/s, QSFP+ DAC/AOC cable supports 4x10Gbit/s. The QSFP28 module can transmit 100 Gbit/s data, and the QSFP28 DAC/AOC cable can run at 4x 25 Gbit/s or 2x 50 Gbit/s.

3. Compatibility: Please note that usually, QSFP28 modules cannot break into 10G links. But inserting a QSFP+ module in the QSFP28 port is another situation if the switch supports (how to implement 4x 10G mode on the QSFP28 100G port, please visit QSFP28 100G port to play 40G, 25G, and 10G). In this case, QSFP28 can break through 4x10G like the QSFP+ transceiver module.

to sum up:

SFP and SFP+, SFP28 and SFP+, QSFP+ and QSFP28 can be seen from the comparison, the main driving force for the development of optical transceivers is the need to use a smaller form-factor to obtain higher bandwidth rates. For example, in the same form-factor, QSFP28 provides more bandwidth than QSFP+.

The information is provided by the transceiver supplier.