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Copper Cabling Options: QSFP + Direct Attach Copper Cable

Today’s enterprise data centers and networking environments are undergoing an infrastructure transformation, requiring higher speeds, greater scalability, and higher levels of performance and reliability to better meet the demands of business. As speed and performance needs increase, modern copper cables have become an integral part of overall system design. QSFP+ direct attach copper breakout cables are designed to meet emerging data center and high performance computing application needs for a short distance and high density cabling interconnect system capable of delivering an aggregate data bandwidth of 40Gb/s. These high speed cables provide a highly cost-effective way to upgrade from 10G to 40G or 40G to 40G interconnect connection.

What Is QSFP+ Direct-Attach Twinax Copper Cable?

QSFP+ DAC is also called QSFP+ to QSFP+ cable. It has a QSFP+ module at one end and another QSFP+ module at the other end, and uses integrated duplex serial data links for bidirectional communication. Used to connect the 40 Gbps QSFP+ port of a switch at one end to another QSFP+ port of a switch at the other end, it can provide high quality of 40G end-to-end connection. Usually, maximum transmission distance of QSFP+ DAC is 10 m, which makes these cables are suitable for in-rack connections between servers and Top-of-Rack (ToR) switches. Besides, since its price ($30-$200) is much lower than QSFP+ optics, it’s a more cost-effective option to connect within racks and across adjacent racks.

How to Use a QSFP+ Direct Attach Copper Cable?

QSFP+ direct attach copper cables can be mainly divided into two types. One is QSFP+ to 4 SFP+ direct attach breakout copper cable, and the other is QSFP+ to QSFP+ direct attach copper cable. In fact, there is a third type QSFP+ direct attach copper cable called QSFP+ to 4 XFP breakout cable. However, regardless of what type of cables, they are both used to connect switch to switch or switch to sever. For a QSFP+ to 4 SFP+ direct attach breakout copper cable, it has a QSFP+ connector on one end and four SFP+ connectors on the other end. In terms of a QSFP+ to QSFP+ direct attach copper cable; it has a QSFP+ connector on both ends of the cable. When we use a fiber optic transceiver and patch cable to establish a fiber link, we should firstly plug the transceiver to the switch and then plug the patch cable to the transceiver. But for a QSFP+ direct attach copper cable, either SFP+ connector or QSFP+ connector, can be both directly inserted into the switch and don’t need a transceiver at all, which provides a really cost-effective solution for interconnecting high speed 40G switches to existing 10G equipment or 40G switches to 40G switches.


QSFP+ Direct Attach Copper cables are hot-removable and hot-insertable. A cable consists of a cable assembly that connects directly into two QSFP+ modules, one at each end of the cable. The cables use integrated duplex serial data links for bidirectional communication and are designed for data rates up to 40 Gbps. Direct Attach Copper cables have no signal amplification built into the cable assembly.

About the author

Milana Rose, AppLecture news editor. Kind, sympathetic and very inquisitive person, who loves to help people with the "computer", and not only those challenges sufficiently due to her knowledge. Hobbies - Apple products, drawing, dancing, swimming, a healthy lifestyle. In a private use - MacBook Air, iPad 2, iPhone 4, iPod Nano 5, iPod touch, Mac Mini.
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