The distance for a 25G SFP (Small Form-factor Pluggable) module can vary depending on the specific model and specifications. However, in general, a 25G SFP module can support distances of up to 10 kilometers over single-mode fiber and up to 100 meters over multi-mode fiber. It's important to consult the manufacturer's documentation for the specific distance capabilities of a particular 25G SFP module.

1、Q：What are the types of 25G SFP28 optical modules?

A: There are three types of 25G modules, namely: 25G dual-fiber bidirectional module (SR, LR, ER), 25G single-fiber bidirectional module (BIDI), 25G WDM color optical module (CWDM, DWDM, LWDM).

2、Q：What is the longest transmission distance of 25G module?

A: At present, theoretically the farthest transmission distance can be realized 40KM.

3、Q：Can SFP28 optical module support backward compatibility?

A: It can support backward compatible 10G rate.

4、Q：Can SFP28 ports be interconnected with QSFP28 ports?

A: Yes, it can be interconnected, which can be realized by using module + patch cord or branch cable.

Module + Patchcord: Use 25G SR module for 25G end and 100G SR4 module for 100G end, and use multimode MTP/MPO-4xLC harness branch cable in the middle to connect.

Branch cable: use 100G to 4x25G breakout AOC/DAC cable to interconnect.

5、Q：Can 25G SFP28 ports support 10G modules?

A: Generally, the 25G port of the device can support multiple rates, such as 1G/10G/25G, in which the port can meet the use of 1G, 10G, 25G three rate modules.

6、Q：What is the farthest transmission distance of 25G DAC and AOC?

A: The farthest transmission distance of DAC is 5m, and the farthest transmission distance of AOC can reach 100m.

7、Q：Do I need to turn on FEC when using 25G module?

A: FEC can reduce the BER (bit error rate) of the module to 10-12, for 25G module, turn on RS-FEC when the current FEC BER is higher than 5×10-5, and turn on FC-FEC when the current FEC BER is higher than 10-8, for more details, please refer to Clause 74 of IEEE802.3 FC-FEC and Clause 91 of RS-FEC.

8、Q：Does the device need to enable FEC function when using 25G DAC?

A: According to the IEEE 802.3by protocol specification, 25G DAC does not need to turn on the FEC when the transmission distance is 1, 2 or 3m; when the transmission distance is 5m, it needs to turn on the RS-FEC.

9、Q：What is 25G dual-rate module?

A: Dual-rate is to support two types of rate, 25G dual-rate module can support 10G and 25G two types of rate, in the supported equipment port can be rate switching.

10、Q：What are the application scenarios of different types of 25G optical modules?

A: 25G SFP28 conventional optical modules (SR, LR, ER and BIDI) are mainly used for interconnecting servers, switches and routers in data centers.

25G CWDM SFP28 optical module is a single-mode duplex CWDM module, with a maximum rate of up to 25.78125Gbps, and a transmission distance of up to 40km through single-mode fiber, which is mainly applied to 25G Ethernet switches, routers, Network Interface Cards (NICs), and storage network equipment, and is capable of solving the problem of 5G millimeter-wave forward propagation well at the current stage;

25G DWDM SFP28 optical module is mainly used to meet the needs of 5G forward transmission service, the device adopts EML+APD scheme, the maximum rate is up to 25.78125Gbps, and the transmission distance can reach up to 10km through the single-mode optical fiber, which is widely used in the 25G Ethernet and single-mode SMF on the CPRI/eCPRI link, in which the wavelengths are tightly packed together to increase the bandwidth of existing fiber networks.

25G LWDM SFP28 optical module adopts high-performance and low-cost DML laser to provide 12-wave multiplexing, which is more advantageous than other similar 25G pre-transmission products in 5G pre-transmission applications. It makes up for the problems of large dispersion of 25G CWDM module and high cost of 25G DWDM optical SFP module laser, and saves 5G pre-transmission transmission while ensuring stable transmission, and thus is a stable and high cost-effective product in 5G pre-transmission network. network is a stable and cost-effective solution.