Optical Modules: FAQ

1. SFP vs. SFP+

• SFP+ is an enhanced version of SFP, with the same physical size, but different in speed and compatibility. SFP complies with IEEE802.3 and SFF-8472 standards, while SFP+ follows SFF-8431. SFP+ ports can accommodate SFP optical fibers, but the speed is reduced to 1Gbit/s.
• SFP+ optical modules cannot be inserted into SFP ports, as this may damage the product or port. In general, SFP+ is more expensive than SFP.

2.SFP+ vs. SFP28

• SFP+ is primarily used for 10G connections, while SFP28 is typically used for 25G connections, with the same form factor, and SFP28 and SFP+ connectors are mating compatible

SFP28 can be used with SFP+ fiber, but the speed will be limited to 10 Gbit/s.

3.SFP+ vs. SFP28

• SFP+ is primarily used for 10G connections, while SFP28 is typically used for 25G connections, with the same form factor, and SFP28 and SFP+ connectors are mating compatible.

4.SFP28 vs. QSFP28

SFP28 and QSFP28 optical modules adopt different sizes and working principles

SFP28 supports a single 25 Gbit/s channel, QSFP28 supports 4 independent channels

• Both can be used in 100G networks

5.QSFP+ vs. QSFP28

Both consist of four transmit channels and four receive channels, and have the same physical size

QSFP+ module supports 1x40 Gbit/s

QSFP28 module achieves 100 Gbit/s transmission

QSFP28 modules cannot usually be split into 10G links.

If the switch allows, QSFP28 can be configured as 4x10G, similar to QSFP+ optical modules.

FAQs about different optical modules.

1. Can SFP/SFP+ optical modules be used in SFP28 ports?

Answer: In SFP28 ports, SFP optical modules can be used, but SFP+ optical modules cannot be used generally. Because SFP28 ports are backward compatible with SFP optical modules and cables (but they do not support the higher 25Gb/s data rate of the SFP28 standard), SFP+ optical modules designed for 10G data rates are not compatible with SFP28 ports that support 25G data rates, unless your switch allows the port data rate to be configured to 10Gbps, in which case SFP+ optical modules can be used in SFP28 ports (in this case, the SFP28 port is essentially used as a 10G SFP+ port).

2. Can SFP28 optical modules be used in SFP+ ports?

Answer: Yes. SFP28 optical modules are designed to be backward compatible with SFP+ ports. Just make sure that the SFP28 optical modules you use support dual rates of 10G/25G.

3. Can SFP+ be used with QSFP28?

Answer: Yes. Generally, new generation optical modules are backward compatible with previous versions, which means that SFP+ ports can accommodate SFP optical modules, and SFP+ optical modules can be inserted into SFP28 ports to achieve 10G speed

4. What is the maximum transmission distance of SFP+ optical modules?

Answer: The maximum transmission distance varies according to its speed. For example: 10G SFP+, most manufacturers provide 80km.

5. Is QSFP56 compatible with QSFP28?

Answer: Yes, it is. They both use the QSFP form factor.

6. Does QSFP28 support 10G?

Answer: Yes. QSFP28 optical modules can support 10G connections using 4 10GbE channels, and traditional QSFP optical modules also support 40G connections using 4 10GbE channels.

7. Can SFP+ be connected with XFP modules?

Answer: Yes. The premise is to ensure that they have the same transmission speed and wavelength. If these factors do not match, the connection may not be established.

8. Is QSFP-DD more suitable for 400G deployment?

Answer: Yes, and QSFP-DD is the first choice for 400G deployment. With the launch of the QSFP-DD800 specification, Xingxin Public Account Today's Optoelectronics Industry Trends also tend to use QSFP-DD for 800G deployment.