Attenuation in waveguides on FR-4 boards due to periodic substrate undulations

Yin Jung Chang, Thomas K. Gaylord, Gee Kung Chang

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The guided-mode attenuation associated with optical-interconnect-polymer waveguides fabricated on FR-4 printed-circuit boards is quantified. The rigorous transmission-line network approach is used and the FR-4 substrate is treated as a long-period substrate grating. A quantitative metric for an appropriate matrix truncation is presented. The peaks of attenuation are shown to occur near the Bragg conditions that characterize the leaky-wave stop bands. For a typical 400 μm period FR-4 substrate with an 8 μm corrugation depth, a buffer layer thickness of about 40 μm is found to be needed to make the attenuation negligibly small.

Original languageEnglish
Pages (from-to)2234-2243
Number of pages10
JournalApplied Optics
Issue number12
StatePublished - 20 Apr 2007


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