SFP vs SFP+ and SFP28 vs SFP+ and QSFP28 vs QSFP+ Compatibility
When connecting two networking equipment such as two Ethernet switches, we use a pair of the same transceiver modules to ensure symmetrical TX and RX power at both ends. However, there are circumstances of mix-using different optics in the same system in actual application, which brings hot discussion on module interoperability compatibility issues. Frequently asked questions include: Is SFP+ backward compatible with SFP? Is SFP28 compatible with SFP+? Is QSFP28 compatible with QSFP+? This post will give some insights into the transceiver compatibility issue on three themes - SFP SFP+ compatibility, SFP28 SFP+ compatibility, and QSFP28 QSFP+ compatibility.
SFP vs SFP+ Compatibility
Let us dive into the SFP and SFP+ compatibility and interoperability in three applications.
Scenario 1: Plug SFP Transceiver into SFP+ Port
SFP and SFP+ are identical in appearance but SFP+ supports ten times the data rate of SFP. Does it work to insert the 1G SFP optics into 10G SFP+ ports? Theoretically yes. It will work but run at 1Gb/s. In most cases, the SFP+ port can auto-negotiate to 1Gbps to fit the SFP module. But exceptions exist for some devices with fixed port data rates. Be mind to check with your system providers.
Figure 1: Deploying a pair of 1G SFPs to achieve 1G fiber connectivity between 1G SFP port and 10G SFP+ port over OM3 MMF.
1/2. 1000BASE-SX SFP transceiver module
3. OM3 multimode fiber optic patch cable
Scenario 2: Plug SFP+ Transceiver into SFP Port
How about installing SFP+ optics into the SFP port? Will the SFP port accept the SFP+ module? This case is not likely to happen as 10G SFP+ in an SFP port will not run at 10Gbps. A more realistic solution is to use the 1G module.
Scenario 3: Connectivity between SFP+ Transceiver and SFP Transceiver
Imagine the following case: On the data center rack a 10G switch SFP+ port is loaded with an SFP+ module, and another switch SFP port is plugged with an SFP module. The question is: will it work to connect the two optics with a patch cable? In this scenario the modules at both ends are asymmetrical. Regular fiber 10G SFP+ modules often work at fixed 10Gbps. Therefore it won't communicate while the other end is 1Gbps. However, it works in the following two cases.
1. Using copper modules via copper patch cables
Though fiber SFP+ does not support auto-negotiating 10/100/1000Mbps, the 10GBASE-T SFP+ copper transceiver does. Thus the SFP+ port end keeps the same data rate as the SFP port end.
A direct connection solution is:
a. Plug a 10GBASE-T SFP+ module into a switch 10G SFP+ port
b. Plug a copper SFP on a switch 1G SFP port.
c. Connect the two modules with an Ethernet patch cable such as Cat5e.
1. 10GBASE-T SFP+ copper transceiver
2. 1000BASE-T SFP copper transceiver
3. Cat5e/Cat6 Ethernet patch cable
2. Using dual-rate 1G/10G SFP+ fiber module
1G/10G Dual-rate optics have optional 1G or 10G speed, which guarantees the SFP+ port end to stay the same 1G/s with the SFP port end. QSFPTEK provides dual-rate 1000BASE-SX and 10GBASE-SR SFP+, 1000BASE-LX and 10GBASE-LR SFP+, 10G/25GBASE-SR SFP28, all at the industry-leading price and quality.
SFP28 vs SFP+ Compatibility
Is SFP28 compatible with SFP+? Yes, the SFP28 port does take the SFP+ port but not vice versa. SFP28 is backward compatible with SFP+. For instance, if inserting an SFP+ module into the switch SFP28 port, the SFP+ module will work well but the max transmission speed will auto-negotiate down to 10Gb/s.
QSFP28 vs QSFP+ Compatibility
Is QSFP28 compatible with QSFP+? Similarly, QSFP+ optics works in QSFP28 ports but QSFP28 optics cannot work in QSFP+ ports. it is functional to use QSFP+ optics in QSFP28 ports to run at 40Gbps.
The issue of SFP SFP+ compatibility, SFP28 SFP+ compatibility, and QSFP28 QSFP+ compatibility is similar. Take SFP SFP+ compatibility as an example, SFP+ ports can take SFPs, and it is possible to plug SFP+ into SFP28 ports to run 10G, but not vice versa.
To prevent SFP compatibility issues, make sure the same speed at both ends of the link and double-check with your equipment supplier. For Cisco products, you can refer to optics-to-device or optics-to-optics interoperability for compatibility matrix. If you have any questions or product inquiries, please contact us. We will also be glad to help.
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