Introduction of SFP+ Direct Attach Copper Cable

The SFP+ interface provides the highest density, cheapest, and lowest power 10 Gigabit Ethernetsolution commercially available today. Further SFP+ enables mass migration of the 1GbE network to10 GbE by providing an extremely low priced 10G SFP+ 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(10G SFP+ Cu), which replaces two optical modules and a connectorized optical fiber with a twinaxial copper cable assembly. The 10G SFP+ Cu option is defined for 10GbE applications over passive copper with a reach of 8.5m. The 10G SFP+ Cu link utilizes a receive equalizer from the host PHY/SerDes to be able to compensate for the Inter Symbol Interference (ISI) introduced by the cable. Electrical and mechanical specifications for SFP+ optical modules, 10G SFP+ Cu, and hosts are defined in the SFF-8431 specification developed by the SFF Committee, with broad industry participation.

What's SFP+ Direct Attach Copper Cable

10G SFP+ Cu(10G SFP+ Cable) 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+ Direct Attach, 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+ interfaces. SFP+ Direct Attach has a 10 meter distance limitation, thus the target application is interconnection of top-of-rack switches with application servers and storage devices in a rack.

Pasive and Active SFP+ DAC Cables

Passive cables are much less costly but require the host to do the work of driving it properly.
Benefits:

• Lower Costs
• Higher Reliability

Tradeoffs:

• No LOS
• No TX Disable
• No Interrupts
• Limited Management Interface
• Host must drive Cu cable

Active cables provide the added benefit of being "optical-module" like.
Benefits:

• Enhanced Signal Integrity
• Longer Cable Lengths
• Transmit Pre-emphasis
• Active/Adaptive Receive Equalization
• Tx Disable
• Loss of Signal (LOS)
• Interrupts
• Management Interface
• Looks like an optical module
• Don’t have to worry about host Tx/Rx for Cu cables

Tradeoffs:

• More Expensive

You can also get the SFP+ Direct Attach Cable and other Fiber Optic Transceivers easily from Fiberstore.