Reach to 40km Transmission – 100G QSFP28 ER4 Lite Module


Today’s world is undergoing an infrastructure transformation, which requires higher speed, greater scalability, higher performance, flexibility and reliability to meet the demands. Take 100G data rate as an example, the MSA groups keep driving development of 500m, 2km, 10km and 40km cost-effective 100G optics targeting modern data center. The 100G QSFP28 ER4-Lite standard was sampling several months ago, but now we are glad to announce that 100G QSFP28 ER4 modules are available in several vendors, e.g. FS.COM, Flexoptics, Smartoptics, etc. Today’s article will explain this long-reach 100G optics in detail.
100G QSFP28 ER4 Lite

How Does It Develop?

A heated topic—how to reach beyond 10km in 100G network aroused much attention in Reddit. For applications beyond 10km, 100GBASE-ER4 is proposed. This type of optical transceivers are manufactured by using a semiconductor amplifier (SOA) inside the transceiver to increase power budget. However, 100G ER4 is available in CFP and CFP2 form factors, but because of the large form factor and power consumption, they are seldom utilized in 100G long-reach applications. What’s worst, the newly launched 100G optical switches are commonly equipped with compact QSFP28 ports instead of larger CFP interface.

These extended reaches are preferring to use high-density 100G QSFP28 modules to maximum capacity and minimize space, power usage and maintenance cost. The CWDM4 MSA defined the first duplex low-cost 100G specification for 2km reaches based on a CWDM grid and using RS (528,514) FEC. Now the 4WDM MSA is extending the value proposition of the CWDM4 MSA and RS-FEC to define an even more cost-effective set of specifications for reaches from 10 to 40 km. Customers, particularly hyperscale cloud service providers and carriers, are looking for optimized solutions for up to 40 km.

What’s New with QSFP28 ER4-Lite Solution?

QSFP-100G-ER4L-S is designed for extended reach 100 Gigabit Ethernet link. The 100GBASE-ER4-Lite QSFP28 supports both 100GbE and OTU4 applications over single-mode fibers, and supports up to 40km with FEC and up to 30km without FEC. 100G QSFP28 ER4 Lite module consumes 4.5W power in max.

QSFP28 optics in 100G optical switch

The 100 Gigabit Ethernet signal is carried over four independent channels over four LAN-WDM wavelengths—1296nm, 1300nm, 1305nm, 1309nm. Multiplexing and demultiplexing of the four wavelengths are managed within the device. This QSFP28 was standardized by ITU-T as G.959.1 4L1-9D1F and 4-Wavelength WDM MSA Group. The following table displays the existing 100G QSFP28 MSA optics in detail.

Product Description Connector Type
QSFP-100G-SR4-S 100GBASE SR4 QSFP Transceiver, 100m over OM4 MMF MPO-12 (12 fibers)
QSFP-100G-LR4-S 100GBASE LR4 QSFP Transceiver, 0km over SMF LC
QSFP-100G-CWDM4-S 100GBASE CWDM4 QSFP Transceiver, 2km over SMF LC
QSFP-100G-PSM4-S 100GBASE PSM4 QSFP Transceiver, 500m over SMF MPO-12 (12 fibers)
QSFP-100G-ER4L-S 100GBASE ER4 Lite QSFP Transceiver, 25-40km over SMF LC

The 100G QSFP ER4-Lite module will interoperate with existing ER4 solutions in the field up to 30km. Foe example, QSFP100 ER4-Lite provides backward compatibility with Cisco’s CPAK ER4-Lite, whose reach is up to 25km, and with IEEE 100GBASE-ER4 standardized transceivers, such as CFP 100G ER4, up to 30km. It also interoperates with QSFP28 and CPAK IEEE 100GBASE-LR4 modules up to 10km.

40km Transmission With FEC Turn On

To reach 40km transmission, QSFP ER4 lite requires the use of FEC on the host platform. So what is FEC? Forward Error Correction (FEC) can turn a mediocre to bad BER into a good BER. Ethernet network usually uses FEC in 1000BASE-PX (EPON), 10GBASE-KR, 10GEPON, 10GBASE-T, DSL, etc. High end long haul telecom industry also requires FEC. P802.3ba links have limited power budgets and SNR, for e.g. eye safety reasons.


The migration of current network infrastructure to 100G systems is inevitable, and a growing number of enterprises require 100G client interface to extend up to 40km without the use of expensive optical amplifiers. Thus, the new ER4-Lite specification enables cost-effective 100G 40km pluggable solutions in compact QSFP28 transceivers that use Forward Error Correction (FEC) and APD-based receivers. Such evolution is very exciting for not only everyone involved in its development and construction, but also for all those who seek a simple, reliable and cost-effective solution to extend the reach of their networks, without expensive network upgrades. FS.COM is devoting to change the world with our cost-effective self-developed devices, if you are interested, please feel free to contact us.

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