By Jim Vana, Application Engineer – High-Speed Interconnects, 3M Electronic Solutions Division
June 12, 2012
The 2011 Data Center Industry Census from Datacenter Dynamics reported that energy costs are the primary worry of data center operators, a concern that has prompted many to implement green data center initiatives. While thermal management is critical to maintaining hardware performance, employing cooling systems to manage heat further increases energy consumption and complexity. Meanwhile, space remains a constant concern as companies are continually asked to produce more and more processing power within existing infrastructures.
Interconnect suppliers are doing their part to help data centers address these pressing concerns. New trends in cable assemblies can help reduce energy consumption and carbon footprint, manage thermal efficiency, and conserve space in the data center.
Low-power AOCs reduce energy consumption
Active Optical Cables (AOCs) typically are used in data centers for long-reach applications of more than five meters. An AOC can consume up to one-third of the power used by a 10Gb/s port.
In response to data center operators’ efforts to lower carbon footprint and energy costs, interconnect suppliers have worked to reduce the power consumption of AOCs. In the past few years, cable assembly manufacturers have released increasingly efficient AOC interconnects. For example, in late 2009, one supplier released a QSFP+ AOC assembly that used 800mW per end, making it the most efficient available assembly at the time, according to the manufacturer. Late last year, 3M launched a competing product that decreased power usage to approximately 540mW per end.
In just two years, power savings of more than 30% were achieved. 3M achieved this improvement by using the latest power-efficient integrated circuits and by carefully optimizing signal integrity performance for specific application requirements.
This trend toward lower-power AOC technology will continue to help data centers reduce power consumption and operating costs. Additionally, lower power active cable assemblies imply lower heat output, further driving down power consumption by reducing the need for cooling.
Foldable, high-performance copper cable saves space in the rack
High-performance, low-cost passive copper cabling remains the preferred alternative for short-reach applications in the data center. However, standard round copper cables can be bulky and consume precious space. A recent innovation in manufacturing technology by 3M has resulted in the development of a uniquely shielded, thin, ribbon-style copper cable. The cable has the ability to fold multiple times and maintain signal integrity, allowing for higher-density racks and space savings.
A major barrier to decreasing the size and stiffness of a round cable is inherent in the construction of traditional cable. This is an issue because a round copper cable can extend up to nine inches when routed behind a cabinet. In conventional, twin axial constructions, the shield is applied by wrapping it spirally around the insulated wire pair. This layer is then overwrapped to provide support and retain the primary shield wrap, increasing the stiffness of the pair. Multiple pairs are then cabled and an overall foil and braided shield are typically applied, thus further increasing the cable bulk and stiffness.
The individual pair spiral shielding has inherent, repeated discontinuities along the cable length, which can create an unwanted resonance effect in attenuation. This unpredictable non-linear response makes it very difficult for system designers to apply essential signal conditioning algorithms typically required to compensate for data rates beyond 5Gb/s per channel.
Alternatively, the uniquely shielded, ribbon-style cable replaces the traditional wrapped shielding with a shield structure that is continuous in both the transverse and the longitudinal directions. This shield design provides a transmission path with no significant resonances up to 43GHz, even when folded or bent.
While cable technology cannot address all the issues inherent in the data center ecosystem, cable suppliers are doing their part to help operators meet their most pressing challenges.
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