Conformity Magazine - February 2009 - (Page 37)

EMC and EMI Issues in High Speed Data Communication Optical Systems Internet video, high-definition television, Voice over Internet (VoIP), and the exploding volume and growth of enterprise data are all factors driving a global explosion in the world’s need for information and bandwidth. Optical communications are the foundation. EMC issues for optical transceivers must be considered at two levels. For the transceiver itself, high frequency radiation can leak from holes, gaps and seams that are inherent features of transceivers. Problems emerge when transceivers are placed into systems that are bound by emissions limits, including radiating transceivers coupled to air vents, cavities, and seams and holes that are inherent features of systems. Accurate analysis of the transceivers themselves and their effect on a system could mean the difference between passing and failing emissions compliance tests. This section of the article addresses radiation from a small factor, pluggable optical transceiver, when modeled as a single, non-mounted device. In a real system employing optical transceivers, the geometry is highly complex and involves small details, like multiple layer PCBs and vast numbers of components on the PCBs, along with complex track paths. To model all of this detail would take a tremendous amount of time, and lead to large models with very long run times. Therefore, the simulation strategy already presented in this article is applied to this case as well. Figure 10 illustrates multiple views of the optical transceiver, including a detail of one of the small PCBs located inside it. The overall dimensions of the module are 30mm x 15mm; therefore, it is challenging to accurately mesh the structure due to the level of detail. The small board (see Figure 11) is simulated by means of PCBs, and the near field (surface current) distribution is used to excite the transceiver in order to analyze the radiated emissions and verify compliance. A preliminary signal integrity (SI) analysis is executed, and S-parameters are calculated for the two differential nets, as illustrated in Figure 9b (the frequency range is 0-40GHz). By considering a figure of merit of -3dB insertion loss, it is possible to see how this value is achieved within the range 0-8GHz. However for higher frequencies, multiple reflections are observed and the insertion loss is quite poor (see Figure 12a). february 2009 Conformity 37 a b Figures 10a and 10b: 3D electromagnetic model of the optical transceiver: a) perspective view; b) top view and detail of the PCB located inside the module http://www.fair-rite.com http://www.fair-rite.com http://www.fair-rite.com

Table of Contents Feed for the Digital Edition of Conformity Magazine - February 2009

Conformity Magazine - February 2009 Contents Editor's Note FCC Clarifies Closed Captioning Requirements for DTV Receivers Commission Cracks Down (For the Fifth Time!) On Junk Fax Marketer FDA Requests Comments on Global Harmonization Documents Australia Now Requires Solar Panel Testing and Certification EU Drafting New Directive on Toy Safety EU Commission Revises Standards List for EMC, R&TTE Directives Additional Standards Published For the EU's Medical Devices Directive EU Commission Publishes Additional Standards for Directives on Active Implantable, In Vitro Medical Devices EMC For the Functional Safety of Automobiles ESD Open Forum The ILAC Arrangement: Facilitating Trade Efficient Methodology for the EMI Analysis of Optical Transceivers Including PCBs and/or Flex Circuits The EuP Directive - Implementation, Design Requirements and Issues Chambers, Shielding, and Accessories Buyer's Guide CPSIA Lead Requirements Apply to Existing Inventory, Says CPSC CPSC Clarifies Certifcation Requirements Other CPSC Actions in the News IEC Standards Update Product Reviews UL standards Update Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - February 2009

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