# QSFP28 Passive Cable Overview and Applications

## Introduction to QSFP28 Passive Cables

QSFP28 passive cables are high-speed interconnect solutions designed for data center and high-performance computing applications. These cables utilize the Quad Small Form-factor Pluggable 28 (QSFP28) interface, which supports data rates up to 100Gbps per port. Unlike active optical cables, passive cables don’t contain any signal processing electronics, making them simpler and more cost-effective solutions for short-range connections.

## Key Features of QSFP28 Passive Cables

1. High-Speed Data Transmission

QSFP28 passive cables support data rates of 100Gbps (4×25Gbps or 4×28Gbps), making them ideal for modern high-bandwidth applications.

2. Low Power Consumption

Since they don’t contain active components, these cables consume significantly less power compared to active optical cables or transceivers.

3. Cost-Effective Solution

Passive cables are generally more affordable than their active counterparts, especially for short-distance connections.

4. Plug-and-Play Installation

These cables require no configuration or special setup, enabling quick and easy deployment.

## Types of QSFP28 Passive Cables

1. Direct Attach Copper (DAC) Cables

These are the most common type, featuring copper conductors with QSFP28 connectors on both ends. They’re available in various lengths, typically up to 5 meters.

2. Breakout Cables

These cables split one QSFP28 port into multiple lower-speed connections (such as 4×SFP28) for flexible connectivity options.

3. Custom Length Options

Many manufacturers offer custom-length cables to meet specific installation requirements.

## Applications of QSFP28 Passive Cables

1. Data Center Interconnects

QSFP28 passive cables are widely used in data centers for connecting switches, routers, and servers within racks or between adjacent racks.

2. High-Performance Computing

These cables provide the high-speed connectivity required for supercomputers and cluster computing environments.

3. Storage Area Networks

They’re used to connect storage arrays and servers in SAN environments requiring high bandwidth.

4. Network Infrastructure

Telecommunication providers and enterprise networks utilize these cables for backbone connections and aggregation points.

## Advantages Over Other Connectivity Options

Compared to active optical cables or separate transceivers with fiber, QSFP28 passive cables offer several benefits:

• Lower cost per connection
• Reduced power consumption
• Simpler installation and maintenance
• Lower latency due to direct electrical connection
• Reliability with fewer points of failure

## Considerations When Using QSFP28 Passive Cables

1. Distance Limitations

Passive copper cables are typically limited to 5 meters or less due to signal integrity concerns at high speeds.

2. Weight and Bend Radius

Thicker copper cables can be heavier and require proper management to avoid excessive bending.

3. Electromagnetic Interference

Proper shielding is essential in environments with significant EMI to maintain signal quality.

4. Compatibility

While generally interoperable, it’s important to verify