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How Does the QSFP28 ER4 Work?

Mar. 16, 2021

QSFP28 optical modules are very popular in the optical module market today due to their small size, low power consumption and high density. Common QSFP28 optical modules such as QSFP28 SR4, QSFP28 LR4, QSFP28 PSM4 and QSFP28 CWDM4 can transmit distances ranging from 500m to 10km. This article will introduce the QSFP28 ER4, an optical module that can transmit over distances of up to 40km, in terms of definition, working principle and applications.

The 100Gbase ER4 standard that must be mentioned

Before introducing the definition of the QSFP28 ER4 optical module, let's take a look at the 100Gbase ER4 standard, defined by the IEEE 802.3ba working group, which supports DWDM technology and allows the transmission of signals in the 1310nm wavelength band via single-mode fibre patch cables. The "ER" stands for extended reach, which is achieved by using SOA amplification before the optical signal passes through the PIN photodetector.

What is the QSFP28 ER4?

The 100G QSFP28 ER4 optical module is compliant with QSFP MSA, IEEE 802.3ba, 100GBASE-ER4 Lite and OTU4 standards and can reach distances of up to 40km over single-mode fibre, supporting 100G Ethernet and OTU4 with a maximum power consumption of 4.5W.

100G QSFP28 ER4

How does the QSFP28 ER4 work?

The QSFP28 100G ER4 optical module transmitter works on four LAN WDM wavelength bands - 1295nm, 1300nm, 1305nm and 1310nm. The optical signals on these four wavelength bands are multiplexed by WDM wavelength division multiplexers and transmitted over single-mode fibres via industry-standard LC connectors. At the receiving end, the WDM WDM multiplexer breaks up the signal into individual channels before the SOA can amplify the signal (the PIN receiver is used to convert the optical signal back into an electrical signal).

Applications for the QSFP28 ER4

For 100G long-distance transmission over 40km, the 100G QSFP28 ER4 optical module is the best choice. Whether in the enterprise or data centre, 100G direct or interconnect, QSFP28 ER4 optical modules are suitable.

Direct Connect Solutions

The QSFP28 ER4 supports direct 100G connectivity over distances of up to 40km by simply plugging two 100G QSFP28 ER4 modules into a 100G switch port and connecting them with an LC duplex single-mode patch cable.

Answers to frequently asked questions about QSFP28 ER4

1. What is the difference between QSFP28 ER4 and QSFP28 ER4 Lite modules?

The BER requirements for 100G QSFP28 ER4 are better than 1E-12 without FEC front-end error correction (FEC), however, existing APD technology does not meet the reception sensitivity of 100G QSFP28 ER4. As a result, many optical module manufacturers in the industry have defined non-standard 100Gbase ER4 Lite modules in QSFP28 packages that can transmit up to 40km when using FEC and up to 30km without FEC. The 100Gbase ER4 Lite standard fully meets the requirements of users with regard to harsh environmental conditions such as temperature, humidity and electromagnetic interference.

2. What is the difference between 100G QSFP28 ER4 and 100G SR10?

The main differences between the QSFP28 100G ER4 and the 100G SR10 are the transmission distance and the fibre patch cable used with it. The latter can be terminated with MPO/MTP-24 connectors for 100m on OM3 multicore cables and 50m on OM4 multicore cables, and can also be connected to MTP to duplex branch patch cables for 10x10G links from 100G ports to 10G SR ports.