AOCs vs DACs

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Introduction

Active Optical Cables and Direct Attach Cables are popular connectivity options in today’s data centers. They are cost-effective alternatives to transceiver modules and structured cabling. Think of them as basically transceivers connected by either copper or fiber. Main use cases for these wired solutions are inside data centers where only short reaches are required. So, what are the differences between AOCs and DACs? And why does an AOC cost 10 x more than a DAC?

DACs – pros and cons

DACs stand for direct attach cables and they are constructed out of copper cables of different gauges. The chief advantage of a DACs is its’ low cost. DACs are ideal for short reach, top of rack (ToR) applications.

There are two types of DACs in the market today – active and passive. Active DACs incorporate signal processing inside them to amplify the signal. In the case of passive DACs, the signal is transmitted without any processing. Active DACs are slightly more expensive owing to this additional electronic circuitry.

DACs are heavier and more rigid than AOCs. Also, since higher data rates and longer reaches require thicker copper gauge, the cables become heavier and bulkier as you go up from 40G to say, 400G. So, the reach limit for a 400G DAC is typically 2m, beyond which AOCs are recommended. Fiber management becomes a nightmare at long reaches. DACs have the benefit of being economical and their power consumption is negligible.

AOCs – pros and cons

AOCs have transceivers connected at the ends of a Multi-mode fiber. They are typically used in Top of Rack and Middle of rack applications. Because of their fiber inter connections, they are lighter and more secure than DACs which have copper connections. AOCs find favor at reaches from 3m to 50m. In comparison to DACs, AOCs have a lower bend radius. For links beyond 50m, optical transceivers are typically preferred for easy fiber management. AOCs are generally more expensive than DACs and consume more power.

Why optical transceivers?

There are use cases in which neither AOCs or DACs are suitable. Pre-terminated DACs and AOCs are not suitable for applications where they need to be pulled through cable trays. These are situations for transceivers. Network upgrades are also easier with stand-alone  optical transceivers.

Conclusion

AOCs and DACs are both widely deployed in data centers. DAC is cost-effective, offers low power consumption and is very effective at short reaches. AOCs are preferred for longer reaches. Vitex range of AOCs and DACs are available in various configurations including breakouts. Contact us at sales@vitextech.com for pricing and availability.

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