An Overview on 100G QSFP28 4WDM and 100G QSFP28 ER4 Lite

There are two new QSFP28 optical transceiver products appeared in the optical module market: 100G QSFP28 4WDM 40km optical transceiver and 100G QSFP28 ER4 Lite optical transceiver in last month. However, many people don’t know too much about the 100G QSFP28 4WDM 40km optical transceiver and 100G QSFP28 ER4 Lite optical transceiver. Here Gigalight is going to have a brief introduction about the two products to help you have a better understanding and make the right choice when purchasing them.

Introduction on 100G QSFP28 4WDM:

4WDM MSA ( defines our familiar CWDM4 and 4WDM products with different distances and wavelengths (2km/10km/20km/40km). It’s shown as follows.

2km and 10km use CWDM wavelength; 20km and 40km use LAN WDM wavelength.

Because of the difference in the size of the CWDM and LAN WDM wavelengths, the wavelength-transmitting TOSA for LAN WDM must be carried with a TEC (Thermo Electric Cooler). As the stable wavelength drifts with temperature, TEC consumes an extra 0.5W of power, so the overall power consumption of optical transceivers with LAN WDM wavelengths will be higher than that of CWDM optical transceivers.

The BER requirement of module product defined by 4WDM MSA is better than 5E-5, because the system or switching equipment has the FEC front-end error correction function to meet the overall link bit error rate requirements. FEC has pros and cons, it increases packet delay and overall power consumption of the device while enabling. For example, when multiple devices in the network architecture enable FEC, the delay of FEC is cumulative, which is fatal for a dedicated network requiring high real-time performance, like financial trading system and so on.

Introduction on 100G QSFP28 ER4 Lite:

IEEE 802.3ba defines that the 100GBASE-LR4 / 100GBASE-ER4 series has a BER requirement of better than 1E-12 w / o FEC for optical modules. Since the receiving sensitivity of 100GBASE-ER4 is not satisfied with the existing APD technology, the SOA size is too large for the QSFP28 series; many optical module companies in the industry defined a non-standard 100GBASE-ER4 Lite with QSFP28 package that the largest transmission distance is up to 30km without FEC.

The receiving sensitivity of 100GBASE-ER4 Lite 30km has no clear definition in IEEE802.3ba. At the current level of 100G APD ROSA, the average of OMA Sensitivity is around -17dbm (BER 1E-12@25.78125Gbps). The description of the100GBASE-ER4 Lite products in the industry is defined as 30km w/o FEC, 40km with FEC. During product development, I deliberately tested 40km OTU 27.95Gbps 70-degree long-distance running error in a laboratory environment. It meets the 1E-12 BER w / o FEC. The receiver sensitivity data cannot meet the requirements of protocol 100GBASE-ER4. The running fiber can meet the 40km application.

Difference between 100G QSFP28 4WDM and 100G QSFP28 ER4 Lite

The 100G QSFP28 ER4 Lite supports dual rate 100GE and OTU4 applications, while the 100G QSFP28 4WDM 40km only supports 100GE applications.


With the development of device packaging technology, there is a plan to develop a small SOA + PIN integrated ROSA in the industry. When the technology is mature, the QSFP28 products meeting the 100GBASE-ER4 standard will also be released. And now Gigalight has released the latest 100G QSFP28 4WDM 40KM optical transceiver and 100G QSFP28 ER4 Lite 40KM optical transceiver. For more product details, you can directly visit its official website.

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