While most equipment vendors currently are SFP+ Passive DAC

The SFP + interface offers the highest density, lowest cost, and lowest power 10 Gigabit Ethernetsolution commercially available today. Further SFP + enables mass migration of the 1GbE network to10 GbE by offering a very low cost 10GSFP + Cu (direct attached copper cable assembly) option for short reach interconnects along with multimode and single mode fiber options. The SFP + interface accepts along with hot-pluggable, small-footprint, optical transceivers, a Direct Attach Cable SFP+ Passive DAC, which replaces two optical modules and a connectorized optical fiber with a twinaxial copper cable assembly.
The 10GSFP + Cu option is defined for 10GbE applications over passive copper with a reach of 8.5m. The 10GSFP + Cu link utilizes a receive equalizer in the host PHY / SerDes in order to compensate for the Inter Symbol Interference (ISI) introduced by the cable. Electrical and mechanical specifications for SFP + optical modules, 10GSFP + Cu, and hosts are defined in the SFF-8431 specification developed by the SFF Committee, with broad industry participation.What is SFP + Direct Attach Copper Cable? (SFP+ Passive DAC presentation 10GSFP + Cu (SFP + Direct Attach) is a copper interconnect using a passive twin-ax cable assembly that connects directly into an SFP + housing. It has a range of 10 meters and like 10GBASE-CX4, is low power, low cost and low latency with the added advantage of having the small form factor of SFP +, and smaller, more flexible cabling.SFP + Direct Attach is known as the successor technology to 10GBASE-CX4. SFP+ Passive DAC, as implied in the name, uses SFP + MSA and by using the inexpensive copper twinaxial cable with SFP + connectors on both sides, provides 10 Gigabit Ethernet connectivity between devices with SFP+ Passive cable.