Tag Archives: EX-QSFP-40GE-DAC-50CM

Two Main Questions About Direct Attach Cables

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The increasing bandwidth demands in data centers call for new cost-effective network solutions that are able to provide great bandwidth and improved power efficiency. As such, direct attach cables (DACs) are designed to replace expensive fiber optic cables in some Ethernet applications, like choosing SFP+ DACs and QSFP+ DACs accordingly as 10 Gigabit Ethernet (GbE) and 40GbE cabling solutions to achieve high performance. How much do you know about this kind of cable? Do you know its such basic information as classifications? If not, then you can follow this article to understand DAC in depth based on the two main questions.

Question 1: What Is DAC?

DAC, a kind of optical transceiver assembly, is a form of high speed cable with “transceivers” on either end used to connect switches to routers or servers. Often referred to as twin-ax, this direct attach twin-axial cable is very similar to coaxial cable, except for one additional copper conductor core. DACs are much cheaper than the regular optics, since the “transceivers” on both ends of DACs are not real optics and their components are without optical lasers. In some 10GbE and 40GbE infrastructures, DACs have been selected to replace fiber optic patch cord when the required link length is relatively short. And in storage area network, data center, and high-performance computing connectivity, DACs are preferable choice because of their low cost, low power consumption and high performances.

Question 2: How DAC Is Classified?

When it comes to DAC’s classifications, there exist two primary standards: Ethernet transmission rate, material of cables.

Based on Ethernet transmission rate and construction standard, 10G SFP+ DACs, 40G QSFP+ DACs, and 120G CXP+ DACs are all available, meaning that DAC can be used as transmission medium for 10GbE, 40GbE, and 120GbE applications when combined as transceivers. Typical DAC assemblies have one connector on each end of the cable. Take SFP-10G-AOC1M for example, this Cisco compatible SFP+ to SFP+ Direct-Attach Active Optical Cable assembly has one SFP+ connector on each end of the cable, designed for relatively short reach that is 1m.

SFP-10G-AOC1M, one SFP+ connector at each end

According to material of cables used, DACs are available in direct attach copper cables and active optical cables (AOCs).

Direct Attach Copper Cable

Direct attach copper cables are designed in either active or passive versions, providing flexibility with a choice of 1-, 3-, 5-, 7-, and 10-meter lengths. The former provides signal processing electronics to avoid signal issue, thus to improve signal quality. What’s more, the former can transmit data over a longer distance than the latter which offers a direct electrical connection between corresponding cable ends. Both direct attach passive copper cables and direct attach active copper cables have gained popularity in data centers. For instance, EX-QSFP-40GE-DAC-50CM, the Juniper 40G cabling product, hot-removable and hot-insertable, is the QSFP+ to  QSFP+ direct attach passive copper cable assembly, really suitable for short distances of up to 0.5m(1.6ft), appropriate for highly cost-effective networking connectivity within a rack and between adjacent racks.

EX-QSFP-40GE-DAC-50CM, for short reach

Active Optical Cable

AOC is also one form of DAC. It uses electrical-to-optical conversion on the cable ends to improve speed and distance performance of the cable while mating with electrical interface standard. Compared with direct attach copper cable, its smaller size, electromagnetic interference immunity, lower interconnection loss and longer transmission distance make it popular among consumers.

DACs offer great flexibility in cabling length choices, simplify server connectivity in top-of-rack deployments, and reduce the power needed to transmit data. More importantly, DACs ensure high system reliability after going through rigorous qualification and certification testing, helping network designers to achieve new levels of infrastructure consolidation while expanding application and service capabilities.

Conclusion

DACs are able to provide an end-to-end solution that is easy to maintain, thus helping improve the availability of networks that support mission-critical applications. Fiberstore offers a broad selection of DACs with high quality for state-of art performance, 10G SFP+ DACs, 40G QSFP+ DACs, and 120G CXP+ DACs all included. For more information about DACs, you can visit Fiberstore.

24-Fiber Trunk Cabling Solution for 40 Gigabit Ethernet

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Year by year, the amount of data transmitted at data centers is skyrocketing as networks need to support more devices and advanced applications than ever before. Typical transmission speeds in the data center are also increasing from 10Gbps to 40Gbps, to 100Gbps or beyond, and in 2010, the IEEE ratified the 40 and 100 gigabit Ethernet (GbE) standard.

Data centers, at the heart of tremendous amount of data to be transmitted, need fiber optic links greatly to provide high bandwidth and low latency for data operation. The 24-fiber trunk cables, one type of fiber optic links, are able to deliver higher data transmission speed and bandwidth, better performance and more efficient scalability. 24-fiber trunk cables are considered as the suitable solution for 40GbE transmission. This text mainly introduces one 40GbE cabling solution: 24-fiber trunk cables.

What Does the 40GbE Standard Define?

The efforts aimed to support speeds of 40Gbps led to the ratification of the 802.3ba standard. This standard for 40Gbps uses parallel optics, or multiple lanes of fiber transmitting at the same speed. Most 40GbE infrastructure uses a 12-fiber MPO connector, requiring 8 fibers, with each 4 fibers transmitting at 10Gbps and the other 4 fibers receiving at 10Gbps, while the inner 4 optical fibers are left unused. According to IEEE 802.3ba standard, multi-mode fiber (MMF) supports 40GbE with link lengths up to 100m over OM3 optical fiber and up to 150m over OM4. Single-mode fiber (SMF)supports 40GbE with link lengths up to 40km when applied for longer distance transmission. Besides, copper cable is is also capable of supporting 40GbE when very short distance is required, such as EX-QSFP-40GE-DAC-50CM and QFX-QSFP-DAC-3M. Take QFX-QSFP-DAC-3M for example, Fiberstore compatible Juniper QFX-QSFP-DAC-3M establishes 40GbE with the link lengths of 3m.

QFX-QSFP-DAC-3M establishes 40GbE with the link lengths of 3m

Here introduces a better standards-based 40GbE cabling solution with 24-fiber trunk cables.

The use of 24-fiber trunk cables between switch panels and equipment is a wise solution. In this approach, 24-fiber trunk cables with 24-fiber MPOs on both ends are used to connect from the back of the switch panel to the equipment distribution area. This solution is appropriate for 40GbE owing to its following advantages.

Reduced Cable Congestion

Another advantage of using 24-fiber trunk cables comes to the reduced cable congestion. Data centers’ priority is the space in infrastructure, since congested cables would make cable management more difficult. 24-fiber trunk cables are only appreciably larger than 12-fiber trunk cables at 3.8 mm in diameter, compared to 3 mm. That means the 24-fiber trunk cables provide twice the amount of fiber in less than 21% space. For a 40GbE application, it takes three 12-fiber trunk cables to provide the same number of links as a single 24-fiber trunk cable.

24-fiber trunk cableS reduce cable congestion

Maximum Fiber Utilization

As mentioned previously, 40GbE uses eight fibers of a 12-fiber MPO connector, the remaining four fibers unused. When using a 12-fiber trunk cable, those same four fibers are also unused. But with the use of 24-fiber trunk cables, all the fibers are actually used. The use of all the 24-fiber trunk cables create three 40GbE links. This recoups 33% of the fibers that would be lost with 12-fiber trunk cables, providing a much better return on investment.

Conclusion

24-fiber trunk cabling solution delivers high bandwidth to data-hungry applications along with low end to end latency, enabling data centers to operate with high performance and efficiency. Fiberstore supplies a large number of 24-fiber trunk cables, and other cables for 40G solution, including EX-QSFP-40GE-DAC-50CM and QFX-QSFP-DAC-3M mentioned above. Besides, Fiberstore also offers other 40G solution products, like 40G QSFP+ transceivers which are fully compatible with major brand, such as Cisco, HP and Dell (eg. Dell QSFP+), You can visit Fiberstore for more information about 40G solution.