iNTERCONNECT SFP + Enhancements Enable Network NEED FOR SPEED


improving emi and Thermal performance in sfp+ connecTors Smart Phones. Tablets. Social Media. Cloud Computing. Virtualization. Today’s consumer and enterprise data-intensive applications are driving the need for constantly increasing data throughput in every aspect of the computing, storage and data centre networks. IT managers, data system architects


and data communication equipment manufacturers are responding by increasingly driving system IO at even higher data rates. More and more servers, SANs, base stations and network switches implement IO at 10Gbps and higher at the physical layer. While the technical merits of copper


and optical physical layers must be considered, an increasing number of these data intensive equipment applications are adopting the SFP+ standard as the default physical layer interconnect. The SFP+ standard offers several benefits over competing solutions.


SFP+ interconnect solutions consume less power versus their copper equivalents. SFP+ cables have longer reaches and SFP+ optical modules have almost no system latency, thus optimizing system performance. Additionally, they have no cross talk sensitivity. How do the benefits of SFP+ interconnect solutions affect equipment


and system design? As an example, low cable and system latency ensures fast response time and reduced CPU idling. This increases data centre efficiency and maximizes ROI. Additionally, lower power consumption in SFP+ ports drive system and data centre power savings.


addressing sfp + design challenges While SFP+ connector technologies have many benefits, several design challenges need attention to drive the desired system performance. As port density increases and higher data rates (>10 Gbps) are supported, system EMI emission and thermal performance concerns must be addressed while allowing for several system design trade-offs. Many variables affect EMI emissions, including leakage from optical


transceivers, a myriad of types of board-level components (e.g. integrated chips, power supply module), and other improperly shielded connectors used in today’s communications equipment. If EMI emissions are not mitigated properly, these disturbances may degrade the effective performance of the circuit or prevent standards compliance. These effects can range from a decrease in performance to a total loss of data transmission. There are also internal and external variables that affect thermal


performance of pluggable IO products and dictate whether or not a cooling solution is required. Unfortunately there is no clear answer to this question and therefore system architects must consider many options and


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restrictions when designing end products. The form factor of the product


must be taken into account as different configurations have unique airflows. A “pizza box” (whether a 1U or 4U) that is mounted in a standard rack may have front-to-back airflow or side-to-side airflow. A blade style switch, or piece of equipment, may be mounted vertically within an enclosure that is in turn mounted in a standard rack. This type of configuration almost always has bottom-to-top airflow. The number and density of ports


mounted to the PCB must also be well considered. These ports can be single port cages, 1xN ganged cages, 2xN stacked cages or a combination of all three. This is in addition to other IO connectors at the


face of the product. The spacing between these cages must also be taken into account as well as port density, ambient air temperature, airflow and allowable temperature rise & backpressure created by baffling. Finally, heat dissipation of the optical transceiver itself must be


considered. Commercially available optical transceivers are rated up to 70 °


but there are extended temperature range transceivers that can operate up to 85°


C. Newer SFP+ connector modules that are used in short reach and


long reach applications are still dissipating 1 watt or less but extended reach and fixed DWDM (dense wavelength division multiplexing) transceivers can range from 1.25 to 1.5 watts per port. The industry has found that trying to cool these higher wattage


transceivers in SFP+ stacked cages is quite challenging. Managing the temperature of the inner lower row of ports that are not exposed to airflow is especially difficult. TE Connectivity (TE) has made several enhancements to its standard SFP+ connector portfolio to control EMI emissions while dissipating extra heat in dense, high-speed applications.


emi enhancemenTs Through extensive research and testing, TE engineers have redesigned two components to improve EMI performance. The first component identified was the gasket retention plate shown in figure 1. This component acts as a backer plate for the conductive elastomeric gasket that interfaces with the inside of the front bezel. This retention plate was redesigned to utilize a right angle design with more attachment points to the cage body. These additional attachment points minimize the chance for EMI emissions to escape between the cage body and gasket retention plate. The redesigned gasket retention plate can be seen attached to the cage body in figure 2.


10 C


figure 1


focus magazine - issue 16


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