In the field of high-speed optical communication, when transmission requirements extend from within data centers to campus and metropolitan areas, the QSFP28 100G ER4 optical module becomes a critical component for achieving ultra-long-distance 40 km, 100 Gbps high-speed interconnection.

QSFP28 100G ER4 Product Overview

The QSFP28 100G ER4 is an optical transceiver module that complies with the QSFP28 form factor standard and the IEEE 802.3ba 100GBASE-ER4 standard. The "ER" in its name stands for "Extended Range," clearly indicating its core advantage: the ability to transmit over single-mode fiber for distances up to 40 kilometers.

Within the family of 100G optical modules, the positioning of the ER4 is clear. Compared to multi-mode SR4 modules (typically under 100 meters), CWDM4/PSM4 modules (around 2 km), and LR4 modules (10 km), the ER4 module significantly extends the effective transmission distance to 40 km. This enables it to excel at connecting networks distributed across different urban districts, large campuses, or between core data centers, effectively simplifying network architecture, reducing the need for repeater equipment, and thereby lowering overall construction and maintenance costs.

How It Achieves 40 km Transmission

The long-distance transmission capability of the ER4 module stems from a series of precise designs and advanced technical solutions:

●Four-Wavelength Multiplexing Technology: Internally, the module does not use a single wavelength. Instead, it converts four lanes of 25.78 Gbps electrical signals into four independent LAN WDM optical signals (centered near the 1310nm window) with closely spaced wavelengths. These four optical signals are combined into one via a multiplexer at the transmitter and travel over a single fiber. At the receiver end, they are separated by a demultiplexer and converted back into four electrical signals. This greatly improves the bandwidth utilization of a single fiber.

●High-Performance Optoelectronic Components: To overcome signal attenuation over long distances, ER4 modules commonly employ a combination of high-performance EML lasers and APD receivers. EML lasers produce high-quality, low-chirp optical signals, while APD receivers feature internal gain, significantly improving receiving sensitivity. This combination provides a solid physical layer foundation for long-haul transmission.

●Forward Error Correction (FEC): This is key to achieving the nominal 40 km distance. FEC allows the receiver to detect and correct a certain number of bit errors during transmission by adding error-correcting codes to the data stream. With FEC enabled, the system can tolerate a lower signal-to-noise ratio, thereby extending the effective transmission distance from about 30 km without FEC to the full 40 km.

QSFP28 100G ER4 Application Scenarios

Leveraging its high-speed and long-distance characteristics, the QSFP28 100G ER4 optical module plays an irreplaceable role in several key areas:

●Data Center Interconnect (DCI): This is the primary application for ER4 modules. They are used to connect two or more data centers located within 40 km in the same metropolitan area, building high-speed, stable Data Center Interconnect (DCI) networks to meet demands for data synchronization, backup, and load balancing.

●Telecom Metropolitan Area Networks & 5G Backhaul: In the core and aggregation layers of telecom operators' metro networks, as well as in 5G mid-haul and backhaul networks, ER4 modules can provide high-bandwidth, low-latency connections, supporting 5G and fixed-network broadband services.

●Enterprise Campus & University Network Backbones: For large enterprise headquarters, universities, or technology parks where core equipment rooms and branch buildings may be several to tens of kilometers apart. ER4 modules can be used to build high-speed backbones for campus networks, carrying all internal data traffic.

●High-Performance Computing Networks: In scenarios requiring remote interconnection between supercomputing centers and massive storage resource pools, 100G ER4 provides the necessary high-speed channels.

Selecting QSFP28 100G ER4 Modules

When deploying QSFP28 100G ER4 modules, it is recommended to focus on the following points:

Compatibility Verification: Despite adhering to universal standards, it is still necessary to confirm the module's compatibility with the target network equipment (such as switches and routers from brands like Cisco, Juniper, etc.). Choosing a supplier that provides comprehensive compatibility testing is particularly important.

●FEC Function Configuration: As mentioned, to achieve the maximum 40 km transmission distance, FEC must be enabled on the host equipment at both ends. Before deployment, ensure the network equipment supports and is correctly configured for the relevant FEC settings.

●Link Budget Calculation: Prior to actual deployment, calculate the total loss of the entire fiber link (including fiber loss, connector loss, splice loss, etc.). Ensure it does not exceed the module's power budget (received optical power must be between the receiver sensitivity and overload points), and maintain a sufficient margin.

●Quality and Warranty: Optical modules are critical physical layer components of a network. It is advisable to choose brands and suppliers that offer warranties and reliable technical support to ensure long-term stable network operation.

The QSFP28 100G ER4 optical module is a key bridge for connecting medium- to long-distance high-speed networks. Through sophisticated WDM technology, high-performance optoelectronic components, and intelligent FEC, it achieves stable 40 km, 100 Gbps transmission within the compact standard QSFP28 form factor. In the era of large-scale data center interconnection and deepening 5G network deployment, the ER4 module will continue to serve as a core building block for constructing efficient and reliable metropolitan optical networks, providing an unimpeded high-speed channel for the data flow of the digital world.