The most common sentence you hear when purchasing optical modules is "Bring me an SFP module", but SFP is just the name of the package and does not represent the speed. There are also SFP+, QSFP+, QSFP28 and other branches under the same form factor series, but the speed is several times different. If the wrong port is inserted, the link will not work at best, or the module will not be recognized at all. This article explains the differences between the four packages at once.

Check the numbers first: What speed does each package run at?

SFP packaging corresponds to 100M or Gigabit (1.25G and below), and some 2.5G modules also use this shape; SFP+ is a small package of 10G, with a single channel of 10G; QSFP+ is a four-channel package, with four 10G channels totaling 40G; QSFP28 is similar in appearance to QSFP+, with a single channel upgraded to 25G and a total of four channels of 100G. When judging the speed, don't guess the package, just look at the model label, for exampleSFP+ 10G single-mode dual-fiber 10km optical moduleIt is clear about SFP+ packaging, 10 Gigabit speed, and 10 kilometers transmission.

Let's look at physical size and slot compatibility

• SFP and SFP+ have the same width, the main difference is the internal circuit speed level;
• SFP+ slots are usually backward compatible with SFP Gigabit modules, which are supported by most switches, but please refer to the device specifications;
• Conversely, if the SFP+ 10G module is inserted into the SFP Gigabit port, the link will only slow down or not light up, which is not suitable for use;
• QSFP+ and QSFP28 ports are wider and have a four-channel structure and are not interchangeable with the SFP series; many QSFP28 ports can be split into four 25G links through cable splitting.

How to choose not to waste in the computer room

For short-distance stacking in the cabinet, copper cables are preferred, such as100G DAC high speed cable, the cost is lower than the combination of optical modules with the same speed; only optical fibers and optical modules are installed across buildings and campuses. For long-distance single-mode scenarios, please refer toData center high-speed interconnection solutionlayered design. Also note: The same package does not mean the same wavelength and distance. It is more reliable to check the four parameters of speed, package, wavelength and distance before placing an order than to memorize a bunch of abbreviations. All EB-LINK optical modules support coding according to mainstream equipment brands, so there is no need to replace the entire module when changing equipment.