Rapide DAC and AOC

High-speed, High-performance

High-speed and High-performance DAC Cables

Pactech’s Rapide DAC Cable Series offers a comprehensive portfolio of high-speed copper Ethernet interconnect solutions for switches, servers, and storage in data center deployments:

  • No crosstalk and source jitter, and extremely low insertion loss
  • Proprietary PCB termination technology for superior impedance and crosstalk control
  • Patented latching mechanism for easy engagement and disengagement
  • Small bend radius for higher density bundling
  • 360° shielding for superior EMI/EMC performance
  • Smallest die cast back shell in the market for space saving easier management
  • Robust pull tab and strain relief system against mechanical stress
  • High performance with rich set of test data

An Overview of Direct Attach Cables

Direct Attach Cable, short for DAC, is a form of high speed cable with hot swappable “transceivers” on either end. They can be used to connect switches to routers or servers. They are becoming increasingly popular in the network industry and widely applied in storage area network, data center, and high-performance computing connectivity etc. Because RJ-45 10G is not widely adopted, and most high density 10 G switches are delivered with 24 or 48 x SFP+ ports in one unit rack.

DACs are cheaper than the regular optics. Because the "transceivers" on both ends of DACs are not real optics. Compared with the regular optics, they are without the real components and just used to transmit the optical signals. So, the cost of DAC twinax cable is much lower without those expensive optics components. Thus, though using the same port as an optical transceiver, DACs are with significant cost savings and power savings in short reach applications.

DAC Components

DAC composed by signal wires, SFP+, shielding and PCB board as below figure 2. SFP+ DAC cable assembly is fully compliant to the SFF-8431 SFP+ MSA. The cable construction is a 100 two pair shielded twinax with drain wires for digital ground. SFP+ DAC cable allows for a serial data transmission up to 12Gbps in each direction. Electronic Dispersion Compensation (EDC) is typically used on host board designs when passive copper cable assemblies are utilized. The mechanical design of the braid crimp and EMI skirt ensure that EMI radiation is sufficiently suppressed. Additionally, the copper cable acts as a natural heatsink. The low power consumption assists in making the DAC copper cable assembly an economic solution for within rack or rack to rack applications.

Passive DAC vs. Active DAC

There are two options for users to consider depending on the transmission distance. When the transmission distance is over 5 meters, active DAC cable is more suitable than passive DAC cable. Because it will cause the signal issue when using passive DAC cable for long-haul transmission. But some users think the thickness and weight may depend on the active or passive. They actually are divided according to their characteristic of AWG. For instance, AWG24 DAC cable is thicker and heavier than the AWG30. Because of the difference of wire diameter, the longer the cable, the more inconvenience AWG24 DAC twinax cable is, compared with the AWG30. Moreover, there is also limited bend radius. Thus, the longer the distance, the higher the AWG rating should be. The main difference between active DAC cable and passive DAC cable is that there is a driving chip in the design of active DAC.