In today’s high-performance networks, cost-effective and reliable cabling solutions are essential. For 40G connections, QSFP+ cables, specifically DAC (Direct Attach Copper) and AOC (Active Optical Cable), are increasingly popular in data centers and enterprise networks due to their plug-and-play capabilities. This article explores the distinctions between these two types and their applications.
QSFP+ DAC Cable Overview
The 40G QSFP+ DAC is a high-speed twinaxial cable terminated with QSFP+ connectors at both ends. It utilizes silver-plated conductors and foam insulation, employing line-pair or complete shielding to transmit electrical signals. The cable gauge ranges from 24 to 30AWG, with longer cables requiring larger gauges to minimize signal loss. For instance, a 1-meter DAC cable typically uses 28 AWG, while a 7-meter cable might use 24 AWG.
Types of QSFP+ DAC Cables
DAC cables are categorized into passive and active types. Passive DACs lack electronic components, relying on the host network equipment to regenerate signals, with a maximum reach of 7 meters. Active DACs, equipped with signal conditioning chips, extend this reach to over 10 meters.
Applications of QSFP+ DAC Cables
QSFP+ DAC cables are available as 40G QSFP+ to QSFP+ direct cables and QSFP+ to 4x SFP+ breakout cables. The former connects two 40G ports on different switches, while the latter splits a 40G signal into four 10G signals, facilitating upgrades from 10G to 40G networks.
QSFP+ AOC Cable Overview
The QSFP+ AOC cable is a duplex fiber optic cable with QSFP+ connectors at both ends. It uses multimode fibers and incorporates optical transceivers, making it more complex and costly than DAC. AOC requires external power for signal conversion and can reach up to 100 meters.
Applications of QSFP+ AOC Cables
Various QSFP+ AOC cables are available for 40G applications, including direct cables and breakout cables. The direct cables connect 40G ports on two switches, while breakout cables are ideal for upgrading from 10G to 40G. Custom services for breakout cables with different connector types are also offered.
Comparing QSFP+ DAC and AOC Cables
The primary differences between DAC and AOC cables lie in their working principles, transmission distances, and costs. DAC cables transmit electrical signals via copper, with passive DACs requiring no signal conditioning and active DACs using internal chips for signal boosting. AOC cables, on the other hand, convert signals from electrical to optical and back to electrical, using optical fibers for transmission.
Transmission Distance and Cost
AOC cables, designed with optical fibers, offer longer transmission distances than the 10-meter limit of DAC cables. They are also thinner and have a more flexible bend radius, potentially improving airflow cooling in racks. DAC cables are generally less expensive, making them a cost-effective choice for short distances.
FAQs
Q: How do QSFP+ cables differ from QSFP+ transceivers with connected fibers?
A: QSFP+ DAC and AOC cables offer several advantages, including lower costs due to simplified direct connections, reduced power consumption compared to transceivers designed for longer distances, and a plug-and-play design that minimizes field maintenance.
Choosing Between 40G QSFP+ DAC, AOC, and Transceivers
The choice depends on factors like network budget and transmission distances. For distances under 10 meters, passive QSFP+ DAC cables are recommended. For 10 to 100 meters, AOC cables are more suitable. Beyond 100 meters, consider 40G QSFP+ SR4 transceivers with OM3 or OM4 fibers, or LR4 transceivers with single-mode fiber for longer deployments.
