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QSFP28 40km Differences

Posted by Jon Zatlokowicz on Nov 29, 2021

An Approved Networks QSFP28 optical transceiver

Three standards and optics that address distances up to 40Km

There are three different standards and optics that address distances up to 40Km. The main differences among the three are the use of forward error correction (FEC) and the optic receivers, along with the application to achieve the various distances. Let’s take a look at the differences between the various optics and choices.

ER4 Lite

The ER4L transceiver is designed for optical communication applications compliant with the Ethernet 100GBase-ER4 Lite/OTU4 standard.

The module converts four input channels of 25Gb/s electrical data to four channels of LAN WDM optical signals and multiplexes them into a single channel for 100Gb/s optical transmission. The central wavelengths of the four LAN WDM channels are 1295.56,1300.05,1304.58 and 1309.14 nm.

The high-performance cooled LAN WDM transmitters and high sensitivity APD receivers provide superior performance for 100Gigabit Ethernet applications up to 30km links without FEC and up to 40km links with FEC.

ER4

The ER4 transceiver is designed for optical communication applications compliant with the Ethernet 100GBase-ER4/OTU4 standard.

The module converts four input channels of 25Gb/s electrical data to four channels of LAN WDM optical signals and multiplexes them into a single channel for 100Gb/s optical transmission. The central wavelengths of the four LAN WDM channels are 1295.56,1300.05,1304.58 and 1309.14 nm.

The high-performance cooled LAN WDM transmitters and high sensitivity SOA+PIN receivers provide superior performance for 100 Gigabit Ethernet applications up to 40km links without FEC.

4WDM-40

The 4WDM transceiver is designed for optical communication applications compliant to the 100g 4WDM-40 MSA standard.

The module converts four input channels of 25Gb/s electrical data to four channels of LAN WDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission. The central wavelengths of the four LAN WDM channels are 1295.56,1300.05,1304.58 and 1309.14 nm.

The high-performance cooled LAN WDM transmitters and high sensitivity APD receivers provide superior performance for 100Gigabit Ethernet applications up to 30km links without FEC and up to 40km links with FEC.

To sum things up:These three QSFP28 40km optics are very similar in that they all utilize the four LAN wavelengths as noted above. The key differences are the use of FEC to achieve the varying distances and the support of OTU4 data rates. The optics are cross compatible with each other depending on the use of FEC and optical distances. The impact of FEC vs. no FEC in the ER4 part is the decreased packet delay and overall power consumption reduction of the device while enabling 40 km reach. The tables below compare the optic's performance.

Chart listing MSA information for 100GBASE optical transceivers