40G QSFP+ Transceiver

56G QSFP+ DAC Vs. 40G QSFP+ DAC

High speed data transmission is the prerequisite for enterprise network deployment. For big data centers, 40G is still the mainstream. For 40G network, 40 gbps transceiver and 40gb ethernet cable are important components, and they can be classified according to transmission distance. For long transmission distance, there are 40G LR4 QSFP+ transceiver and singlemode fiber cable; for short transmission distance, there are 40G SR4 QSFP+ transmission and multimode fiber cable. In addition, for 40G short link, there is QSFP+ DAC cable. Two types of QSFP+ DAC cables are available on the market: 56G QSFP+ DAC vs. 40G QSFP+ DAC, what’s the difference between them? This article will make a comparison.

56G QSFP+ DAC Vs. 40G QSFP+ DAC: Same construction

We know that DAC cable is a kind of high speed passive copper cable with one connector on each end. The connectors are not real optical transceiver modules but in the form of optical transceiver module. DAC twinax cable Therefore, QSFP+ DAC consists of two QSFP+ transceiver style connectors and one twinax copper cable. With the same construction, the operation of 56G QSFP+ DAC and 40G QSFP+ DAC in 40G network deployment is the same, too. Just plug the connector into 40G QSFP+ port on the switch on both sides, and then you can get 40G link. Here is a figure of QSFP+ DAC cable for you.

QSFP DAC

56G QSFP+ DAC Vs. 40G QSFP+ DAC: Different protocols

As qsfp+ passive copper cable, both 56G QSFP+ DAC and 40G QSFP+ DAC are QSFP MSA compliant. But 40G QSFP+ DAC supports 40G InfiniBand 8x DDR, 4x QDR, 10G/40Gigabit Ethernet, Fibre Channel, while 56G QSFP+ DAC supports 40G InfiniBand 4x FDR, 56Gigabit Ethernet, Fibre Channel. What’s the different between InfiniBand DDR, QDR and FDR? InfiniBand (abbreviated IB) is a computer-networking communications standard used in high-performance computing that features very high throughput and very low latency. It is used for data interconnect both among and within computers. InfiniBand is also used as either a direct or switched interconnect between servers and storage systems, as well as an interconnect between storage systems. And the following figure shows InfiniBand specification. We know that QSFP+ DAC cable uses four channels for data transmission. And for 40G QSFP+ DAC, it supports 40G InfiniBand 8x DDR, 4x QDR, so each channel can achieve 10G data rate; for 56G QSFP+ DAC, it supports 40G InfiniBand 4x FDR, so the maximum data rate of each channel is 14G.

InfiniBand Specification

Conclusion

Characterized by low Insertion loss and power consumption, qsfp+ passive copper cable is a cost-effective option for 40G data transmission over short distance. As for 56G QSFP+ DAC vs. 40G QSFP+ DAC, the only different is that the former can operate high bandwidth than the latter one. Therefore, if your network needs 40G data transmission, then 40G QSFP+ DAC cable; if you need more than 40G bandwidth, then choose 56G QSFP+ DAC.

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