The Difference Between 100G QSFP28 Multimode Transceiver: 100G SRBD vs. 100G SWDM4

In today's cloud computing and 5G networking environments, the need for high-speed data transfers is revolutionizing data center architectures. As more and more organizations begin to deploy 100G transceivers, these devices are becoming an integral part of the network construction costs. Fiber link distances of 100 meters or less are the norm for more than 90 percent of small and midsize data centers. In large data centers, this figure is more than 70 percent. This trend shows that multimode fiber is becoming increasingly important, as it can efficiently support most short-distance connectivity needs. In the 100G range, QSFP28 multimode modules, particularly the QSFP 100G SRBD and QSFP 100G SWDM4, offer attractive solutions for modern data centers to meet diverse network requirements. Next, we will compare these two popular transceivers and discuss their features, benefits, and application scenarios.

QSFP28 100G SRBD and QSFP28 100G SWDM4 Overview

As network demands continue to grow, the 100GBASE-SRBD and 100GBASE-SWDM4 optical modules have been created to address the bandwidth, transmission distance, and efficiency challenges in modern data centers. These two modules have excellent performance and are specifically optimized for different application scenarios to ensure efficient and reliable data transmission. Next, we will briefly examine the basics of these two modules.

QSFP28 100G SRBD

The QSFP28 100G SRBD is a 100G optical transceiver designed for short-range data centers, especially for high-density environments that require bi-directional data transmission - SRBD stands for Short Range Bi-Directional, SR stands for short-range transmission, and BD refers to bi-directional communication. This module enables bi-directional data transmission over a single multimode fiber, making it highly efficient in optimizing the use of ports in network equipment.

The QSFP28 100G SRBD module is a dual LC port design that simultaneously transmits and receives optical signals at two different wavelengths (850nm and 900nm). The laser type used is a dual-wavelength vertical cavity surface emitting laser (VCSEL) optimized for four-level pulse amplitude modulation (PAM4) signals.

Fiber selection allows for transmission distances of up to 70 m with OM3 fiber, up to 100 m with OM4 fiber, and up to 150 m with OM5 fiber. The QSFP28 100G SRBD is ideal for short-haul data center applications, especially for high-density environments requiring reliable data transmission.

QSFP28 100G SWDM4

The QSFP28 100G SWDM4 is another 100G optical module designed for short-haul data centers that need to optimize their existing multimode fiber infrastructure. SWDM4 stands for Short Wavelength Division Multiplexing Quad (SWDM4), indicating that the module uses four channels of different wavelengths for data transmission.

Similar to the 100G QSFP28 SRBD module, the QSFP28 100G SWDM4 module also uses a duplex LC interface and is capable of transmitting optical signals at four different wavelengths (850 nm, 880 nm, 910 nm, and 940 nm) on a single multimode fiber. MUX/DMUX technology lets the module use multiple wavelengths for transmission, boosting the optical link's capacity and enhancing network performance without needing extra fiber infrastructure.

With a transmission distance of 70 meters when using OM3 fiber and a maximum distance of 100 meters when using OM4 fiber, the QSFP28 100G SWDM4 is ideal for high-density data centers, especially when existing multimode fiber systems need to be optimized to cope with increasing data demands.

How Do QSFP 100G SRBD and QSFP 100G SWDM4 Work?

QSFP 100G SRBD

It uses optical components to achieve signal wavelength multiplexing on a single fiber, allowing for bidirectional signal transmission. The 100GBASE-SRBD module effectively doubles the transmission capacity in a 100G optic system. This drastically increases the networks' performance quality and allows for better data flow in multimode networks. The second construction relies less on supplementary fiber and lessens complexity in the network deployment while guaranteeing superior performance, as is the demand for contemporary data centers.

QSFP 100G SWDM4

The 100GBASE-SWDM4 module also utilizes a duplex LC interface. Still, it is unique because it uses Short Wavelength Division Multiplexing (SWDM) technology combined with the MUX/DMUX method to improve data transfer efficiency significantly. This design allows four different wavelengths (850 nm, 880 nm, 910 nm, and 940 nm) transmit simultaneously over a single multimode fiber. With transmission distances of up to 70 m (using OM3 fiber) and 100 m (using OM4 fiber), the SWDM4 module is particularly well suited for short-haul applications requiring large bandwidth and high density. This makes them ideal for short-haul data center applications that require large bandwidth and high density. This high-speed transfer capability is crucial to cater to the increasing data needs within modern data centers.

Further, the 100GBASE-SWDM4 module can be quickly adopted into the existing 100G Ethernet network architecture, enabling cost-effective upgrades for most common infrastructure and supporting a variety of multimode fibers. This allows the 100GBASE-SWDM4 module to be efficient on existing fiber infrastructure, avoiding the high cost of large-scale infrastructure replacement.

The diagram below shows how the 100GBASE-SWDM4 module works:

How To Choose The Right Transceiver?

The 100G-SWDM4 transceiver uses four wavelengths (850nm, 880nm, 910nm, 940nm), while the 100G-SRBD uses two wavelengths (850nm and 900nm). This makes the SWDM4 more efficient in spectrum utilization for high-density applications. Although SRBD transceivers have lower insertion loss and better resistance to mode dispersion, SWDM4 is a better choice for maximizing fiber utilization due to its high efficiency.

In terms of distance, the SWDM4 supports up to 70m over OM3 fiber and 100m over OM4 fiber, while the SRBD can support distances up to 150 meters over OM5 fiber. The SWDM4 optimizes existing OM3 and OM4 deployments, while the SRBD extends coverage using OM5 fiber.

Both modules are available in the QSFP28 form factor with LC connectors, but the SWDM4 offers energy and space savings that make it ideal for modern data centers. At the same time, the SRBD supports 100G and 40G ports, while the SWDM4 is primarily used for 100G applications.

While both SWDM4 and SRBD are compatible with OM3/OM4 duplex MMFs, they are not interoperable. Regarding future 400G compatibility, the SRBD module is more forward-looking due to its ability to interconnect with 400G optics.

Conclusion

When choosing a data center solution, QSFPTEK offers high-quality 100G optical transceivers, such as the QSFP 100G SRBD and QSFP 100G SWDM4, that meet modern networks' high performance, reliability, and energy efficiency requirements. Whether you want to optimize your existing multimode fiber infrastructure or plan for future scalability, QSFPTEK's products can support your network growth.