Fiberstore SFP+ DAC Cable Solution

SFP+ Direct Attach

Also known as Direct Attach (DA), Direct Attach Copper (DAC), 10GSFP+Cu, 10GBASE-CR, 10GBASE-CX1, SFP+, or 10GbE Cu SFP cables. Direct Attach uses a passive twinax cable assembly and connects directly into an SFP+ housing. SFP+ Direct Attach has a fixed-length cable, typically 1 to 7 m (passive cables) or up to 15 m (active cables) in length, and, like 10GBASE-CX4, is low-power, low-cost and low-latency with the added benefits of using less bulky cables and of having the small form factor of SFP+. SFP+ Direct Attach cable today is tremendously popular, with more ports installed than 10GBASE-SR.

SFP+ Direct Attach Copper (10GSFP+Cu)

SFP+ DAC is a copper 10 Gigabit Ethernet cable which comes in either an active or passive Twinax (twinaxial) cable assembly and connects directly into an SFP+ housing. The active Twinax cable has active electronic components in the SFP+ housing to improve the signal quality; the passive Twinax cable is just a straight "wire" and has no active components. Generally Twinax cables less than 5 meters in length are passive and greater than 5 meters in length are active, but this is a general rule of thumb and will vary from vendor to vendor. SFP+ Direct Attach Copper (DAC) is expected to be the optimum solution for 10G Ethernet reaches up to 10 m.

One of major applications includes Cisco, Juniper, Brocade and others' network hardware with SFP+ interfaces. This kind of connection has the capacity to transmit at 10 Gigabits/second full duplex speed over 5 meter distances. Moreover, this setup offers 15 to 25 times lower transceiver latency than current 10GBASE-T Cat 6/Cat 6a/Cat 7 cabling systems: 0.1 μs for Twinax with SFP+ versus 1.5 to 2.5 μs for current 10GBASE-T specification. The power draw of Twinax with SFP+ is around 0.1 watts, which is much better than 4-8 watts for 10GBASE-T.

As always with cabling one of the consideration points is bit error ratio or BER for short. Twinax copper cabling has BER better than 10-18 according to Cisco, and therefore is acceptable for applications in critical environments.

Cables must not be bent below their minimum bend radius, which is depending on cable size expressed in AWG. The table on the right summarizes minimum values typically admitted for SFP+ sustained bend radiuses.

This SFP+ Twinax DAC is also referred to as "10GBASE-CR" by some manufacturers, even though there is no IEEE or other standard with that name.

Cisco SFP+ Twinax Copper Cables

Cisco SFP+ Copper Twinax (Figure 1) direct-attach cables are suitable for very short distances and offer a cost-effective way to connect within racks and across adjacent racks. Cisco offers passive Twinax cables in lengths of 1, 1.5, 2, 2.5, 3, 5, 7 and 10 meters, and active Twinax cables in lengths of 7 and 10 meters.

Figure 1. Cisco direct attach passive SFP+ cables

Cisco SFP+ Active Optical Cables

Cisco SFP+ Active Optical Cables (Figure 2) are direct-attach fiber assemblies with SFP+ connectors. They are suitable for very short distances and offer a cost-effective way to connect within racks and across adjacent racks. Cisco offers Active Optical Cables in lengths of 1, 2, 3, 5, 7, and 10 meters.

Figure 2. Cisco active optical SFP+ cables

Platform Support

Cisco SFP+ modules are supported on a wide range of Cisco switches and routers^*:

Ordering Information

Notes

Direct Attach Copper (DAC) Cable is widely used in storage, data center, and high-performance computing connectivity. The DAC cables are widely-used to connect one mobility access switch with another when forming a stack. Fiberstore supplies different kinds of high-speed interconnect DAC cable assemblies including 10G SFP+ Cables, 40G QSFP+ Cables, and 120G CXP Cables. Fiberstore offers customized service for cable length.

References:

• http://en.wikipedia.org/wiki/Twinaxial_cabling
• DAC Cable