Understanding QSFP28 100G DR1: Applications, Switch Compatibility, and Key Advantages

Understanding QSFP28 100G DR1: Applications, Switch Compatibility, and Key Advantages

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Understanding QSFP28 100G DR1: Applications, Switch Compatibility, and Key Advantages

As data centers scale out to support cloud, AI, and high-density virtualization workloads, 100G Ethernet has become the mainstream speed at the ToR (Top-of-Rack) and leaf layer. Among the many 100G optical interface types, QSFP28 100G DR1 stands out as a simple, cost-effective, and power-efficient option for 500 m single-mode fiber links.

QSFP28 100G DR1 is designed for 500m transmission over single-mode fiber (SMF) using 1310nm and PAM4 modulation. It provides higher data transmission between Leaf switch and ToR switch.

This makes DR1 an ideal choice for short to medium-reach interconnects inside modern leaf–spine data center fabrics.

What Is QSFP28 100G DR1?

QSFP28 100G DR1 is a single-lane 100G optical module in QSFP28 form factor:

  • Form factor: QSFP28

  • Data rate: 100 Gbps (1 × 100G lane)

  • Fiber type: Single-mode fiber (SMF)

  • Wavelength: 1310 nm

  • Modulation: PAM4

  • Reach: Up to 500 m over SMF

  • Connector type: LC duplex

Compared to older 4-lane 100G standards such as 100G SR4 or 100G PSM4, DR1 uses one optical lane at 100G instead of 4 × 25G or 4 × 50G, which simplifies cabling and reduces fiber count.

Typical Application Scenarios for QSFP28 100G DR1

1. Leaf–ToR (Top-of-Rack) Interconnects

One of the primary use cases is connecting leaf switches to ToR switches within the same data hall. In a modern spine-leaf architecture, it’s common to have:

  • ToR switch ↔ Leaf switch at distances of 50–300 m

  • Requirement for 100G uplinks from the rack to the aggregation layer

In this scenario, QSFP28 100G DR1 modules on both sides, connected with LC-terminated SMF, provide a clean, simple 100G link up to 500 m without the complexity of breakout cabling.

2. Short-Range Spine Links in Compact Data Centers

In smaller or more compact data centers, the spine and leaf switches may still be within a few hundred meters. DR1 can be used for:

  • 100G leaf ↔ 100G spine connections

  • Migration from legacy 40G or 10G uplinks to flat 100G fabric

This allows operators to standardize on single-lane 100G optics and use uniform SMF infrastructure across the fabric.

3. 100G Access for Storage and GPU/AI Nodes

Many storage servers, AI training nodes, and NVMe-oF appliances now use 100G NICs. QSFP28 100G DR1 can be used for:

  • Direct 100G links from ToR switch ↔ storage node / GPU node

  • Low-latency and high-bandwidth connections for RoCEv2 or iWARP environments

Because DR1 runs on SMF, it’s more future-proof than multimode solutions when distances increase or when fiber plant must support higher rates in future.

4. Migration Path Toward 400G/800G Architectures

In newer data centers using 400G or 800G at the spine, DR1 still fits in as part of a migration strategy:

  • 400G ports (e.g., QSFP-DD 400G DR4) can be broken out into 4 × 100G DR1 links using the right breakout cables and optics mapping.

  • This enables a gradual upgrade path where the spine runs 400G, and the leaf or ToR side remains on 100G DR1.

Switches and Platforms That Support QSFP28 100G DR1

QSFP28 100G DR1 modules are broadly compatible with many modern data center switches that have QSFP28 ports and support 100G PAM4 optics. Example categories include:

1. NVIDIA / Mellanox Switches

  • NVIDIA Spectrum / Spectrum-2 / Spectrum-3 series

  • Common platforms: SN2010, SN2100, SN2700, SN3700, SN3800, SN4700, etc.

These switches often operate in RoCEv2 environments and can use 100G DR1 for low-latency east-west traffic between racks.

2. Arista Data Center Switches

  • Arista 7050X, 7060X, 7260X, 7280 series with QSFP28 100G ports

  • Used widely in cloud, web-scale, and colocation data centers

Arista’s EOS typically supports a wide range of third-party and OEM QSFP28 DR1 optics via proper coding.

3. Cisco Nexus Series

  • Cisco Nexus 9000 series (e.g., 93180YC-FX, 9364C, 9336C, 93108TC-FX3) with 100G QSFP28 ports

  • DR1 can be used for N9K leaf–spine or leaf–ToR links over SMF

Cisco supports multiple 100G 1310 nm SMF solutions, and DR1 is used where 500 m reach is sufficient.

4. Other Vendors: Juniper, Huawei, H3C, Broadcom-based Whitebox

  • Many whitebox and ODM switches based on Broadcom Trident/Tomahawk chips

  • Juniper QFX series, Huawei CloudEngine, H3C S-series data center switches

As long as the switch port supports 100G QSFP28 and DR/FR optical profiles, QSFP28 100G DR1 can typically be used (with correct EEPROM coding if brand-locked).

In practice, compatibility is usually validated through lab testing or vendor interoperability lists, especially in RoCE or latency-sensitive deployments.

Key Advantages of QSFP28 100G DR1

1. Simpler Cabling and Lower Fiber Count

Unlike parallel 4-lane solutions (such as 100G SR4 or PSM4), DR1 uses 1 × 100G lane over LC-terminated SMF:

  • No need for MPO connectors or breakout cables

  • Easier to label, manage, and reconfigure links

  • Reduced risk of fiber polarity errors

This is especially valuable when scaling to hundreds or thousands of 100G links.

2. Cost-Effective for 100G at ≤500 m

For distances up to 500 m, DR1 often hits a sweet spot between cost, distance, and simplicity:

  • Cheaper and less power-hungry than many 4-lane or long-haul coherent options

  • Adequate reach for intra-data center aggregation and cluster connectivity

3. Future-Proof Single-Mode Infrastructure

Because DR1 uses single-mode fiber, it aligns with the long-term trend of:

  • Moving away from multimode in new builds

  • Supporting higher-speed migrations (100G → 400G → 800G) on the same fiber plant

Investing in SMF for DR1 helps avoid expensive recabling later.

4. Higher Bandwidth Between Leaf and ToR

As you requested to highlight:

QSFP28 100G DR1 is designed for 500m transmission over single-mode fiber (SMF) using 1310nm and PAM4 modulation. It provides higher data transmission between Leaf switch and ToR switch.

This is critical when:

  • Running east-west traffic-heavy workloads, such as distributed databases, big data platforms, or microservices

  • Aggregating multiple 25G/10G server connections into a single 100G uplink

5. Energy Efficiency

Single-lane PAM4 100G optics generally offer better energy efficiency per bit compared to older multi-lane NRZ implementations. For large deployments, this translates into:

  • Lower power consumption per port

  • Reduced cooling pressure in dense racks

When Should You Choose QSFP28 100G DR1?

DR1 is a strong choice if:

  • Your link distance is ≤500 m within a data center

  • You want simple LC SMF cabling

  • You need 100G point-to-point links between leaf and ToR or leaf and spine

  • Your switches/NICs support 100G PAM4 DR optics

For longer distances (2 km / 10 km), you might consider 100G FR or LR. For legacy compatibility or multimode fiber, SR4 or BiDi variants may be more appropriate.

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