Direct Attach Copper (DAC) SFP cables are high-speed, factory-terminated twinax copper assemblies designed for short-range, low-latency connections between network devices, available in passive and active versions.

Overview

DAC cables are twinax copper cables with SFP connectors permanently attached at both ends, used for connecting servers, switches, and storage arrays in data centers . They provide a cost-effective, low-latency alternative to fiber optics for short-distance links, typically within racks or between adjacent racks . These cables are plug-and-play, requiring no additional transceivers or modules, and are available in various data rates including 10Gbps, 25Gbps, 40Gbps, 50Gbps, 100Gbps, and higher .

Types of DAC Cables

• Passive DAC: Contains no active electronics. Ideal for very short distances (1–3 meters, sometimes up to 5–7 meters). Offers lowest cost, zero power consumption, and minimal heat generation .
• Active DAC: Includes signal conditioning electronics such as equalizers or pre-emphasis to extend reach up to 10–15 meters. Slightly more expensive and consumes less than 1W per cable . Active DACs are suitable for inter-rack connections or high-density deployments where cable flexibility is important .

Key Features

• High reliability and performance: 100% tested for signal integrity with serial number traceability .
• Customizable options: Cable lengths, wire gauges, low-smoke zero-halogen jackets, pull-tab colors, and EEPROM programming are available .
• Low latency: Electrical signals over copper introduce minimal delay, making DAC ideal for high-speed, latency-sensitive applications .
• Ease of deployment: Factory-terminated assemblies reduce installation complexity and risk of errors .
• Bend radius considerations: Minimum bend radius is typically 4x the cable diameter (~1 inch); exceeding this can damage the cable .

Use Cases

• In-rack connections: Short links between servers and switches within the same rack.
• Inter-rack connections: Active DACs can extend reach for connections between adjacent racks.
• High-density data centers: Flexible active DACs help manage cabling in dense environments.
• Cost-sensitive deployments: Passive DACs provide a low-cost alternative to fiber optics for short distances.

Summary

Retail DAC SFP cables are high-speed, reliable, and cost-efficient solutions for short-range networking in data centers. Choosing between passive and active DAC depends on the required distance, power consumption, and deployment density. They are widely used for 10G, 25G, 40G, and 100G connections, offering plug-and-play simplicity and predictable performance for modern high-speed networks .