Investigation of the packaging-induced RF attenuations and resonances in a broadband optoelectronic modulator module

In this paper, the influence of packaging-induced RF signal degradation on an optoelectronic modulator module is investigated. A directly modulated laser (DML) is modeled and packaged in a butterfly-type package. A distributed 3-D electromagnetic model is built based on this laser module. In the packaging assembly procedure, impedance mismatching and ground discontinuity on microwave transmission will cause unwanted signal decays and resonances. We specify the RF degradation in three regions: 1) the RF connector, 2) the RF substrate, and 3) the mode transition region between the optoelectronic subsystem and the package. The RF transmission characteristics in these regions are extracted and analyzed in detail. The results indicate that by optimizing the packaging design, strong resonances and signal decays can be eliminated or compensated over a wide frequency range. The measured scattering parameters show that the proposed packaging assembly has a resonance-free bandwidth of 31.2 GHz, and the DML module exhibits a wide 3 dB bandwidth of 15.1 GHz.