100G QSFP28 ER4 is a well-defined technical standard specifying the optical module requirements for achieving a 100 Gbps data rate over SMF with a transmission distance of up to 40 kilometers.

100G: Refers to a transmission rate of 100 Gigabits per second.

ER4: "ER" stands for "Extended Reach," and the "4" typically indicates that the standard utilizes four independent optical wavelength lanes. These lanes are combined at the receiver using Wavelength Division Multiplexing (WDM) technology to achieve the total 100G bandwidth.

QSFP28: Denotes the module's form factor—an abbreviation for Quad Small Form-factor Pluggable 28. It supports an electrical interface of 25 Gbps per lane and is the dominant packaging for 100G optical modules.

1310nm & 40km: These are the core operational parameters of the 100G ER4 module. It employs 1310nm wavelength lasers and can achieve a maximum transmission distance of 40 kilometers over standard single-mode fiber (G.652).

Core Working Mechanism and Key Technologies of 100G ER4 QSFP28

The core technology of the 100G ER4 module lies in its use of LAN-WDM (Coarse Wavelength Division Multiplexing). On the transmitter side, it modulates four 25 Gbps electrical signals onto four distinct wavelength optical signals within closely spaced 1310nm bands (approximately 1271-1331nm range). These signals are then multiplexed into a single strand of single-mode fiber for transmission. At the receiver end, demultiplexing and optical-to-electrical conversion take place.

Achieving the extended 40km reach relies on several key technologies:

●High-Performance Lasers: Uses cooled DFB (Distributed Feedback) lasers to ensure wavelength stability and signal quality, overcoming chromatic dispersion and attenuation over long distances.

●High-Sensitivity Receivers: Employs APD (Avalanche Photodiode) receivers to significantly enhance receiver sensitivity, compensating for optical power loss after long-haul transmission.

●Advanced Signal Processing: Integrates sophisticated DSP (Digital Signal Processing) chips to perform signal equalization, dispersion compensation, and error correction, ensuring link performance.

Advantages and Application Scenarios of 100G ER4 QSFP28

The 100G ER4 module is a critical choice due to its following distinct advantages:

●Ideal 40km Reach: Perfectly bridges the gap between short-reach (within 10km) and ultra-long-haul (beyond 80km) solutions. It serves as the "golden distance" solution for data center campus interconnects, metro network access/aggregation, and backbone connections for large enterprise networks.

●High Density & Low Power: Compared to earlier large form factors like CFP, the QSFP28 packaging offers significantly higher port density (3-4 times that of CFP) and typically consumes less than 4.5 watts of power. This dramatically improves rack switching capacity and energy efficiency.

●Mature Ecosystem: As an important member defined by the IEEE 802.3ba standard, 100G ER4 is highly standardized and offers broad equipment compatibility. It is supported by major switch and router manufacturers.

Application Scenarios for 100G ER4 QSFP28

●Data Center Interconnect (DCI): Connects data centers across different campuses or buildings within the same city for data synchronization, backup, and load balancing.

●Telecom Metro Networks: Serves as a high-speed link between the core and aggregation layers of 5G backhaul and IP metro networks.

●Large Enterprise & Campus Networks: Connects geographically dispersed core nodes to build high-performance backbone networks.

●Positioning in the Optical Module Technology Spectrum

Compared to similar technologies, 100G ER4 has a clear positioning

●vs. 100G LR4: LR4 offers a 10km reach, using the 1310nm band but with wider wavelength spacing. ER4 achieves 4 times the reach using more precise technology within the same band, representing an extended upgrade over LR4.

●vs. 100G ZR4/Coherent Modules: Solutions like ZR4 use coherent detection to achieve 80km or greater reaches, but at a significantly higher cost, power consumption, and complexity than ER4. ER4 provides the best cost-performance ratio within the 40km range.

●vs. 400G/800G: While representing higher-speed technologies, current 400G and above modules offer more complex and costly solutions for the 40km distance. For the foreseeable future, 100G ER4 will remain the stable, reliable, and economical mainstream choice for this reach.

The 100G ER4 QSFP28 1310nm 40km optical module is a pivotal technology in modern optical communication networks. It meets the rigid demand for medium-long distance (40km), high-bandwidth, high-density interconnections. With its standardized design, excellent performance, and mature ecosystem, it continues to play a central role in data center expansion, metro network upgrades, and enterprise backbone network construction.

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