Radiation physics and EMI coupling path determination for optical links

Optical transceiver modules are used in high-end and low-end switches and routers. These modules, located in the optical i/o ports at the front-end of the system chassis, can contribute significantly to the system level EMI at high frequencies. In this paper, a mode stirred reverberation chamber (RC) is used to analyze the EMI performance of the optical modules. Three EMI leakage points are identified from the optical i/o ports. Using the results from four experimental configurations, coupling paths and unintentional current paths are proposed for the optical link. This can help provide insight to EMC design engineers about the radiation physics associated with optical links and potential mitigation solutions.