The signal injection efficiency of electroabsorption modulator integrated lasers (EMLs) is improved to suit 10-Gb/s applications. For a typical EML module design with a conventionally designed 50-Ω signal feeder to meet the input return loss requirement for 10-Gb/s applications, a reduction in device capacitance of the electroabsorption modulator (EAM) section by 65% from its typical value is necessary. By optimizing the characteristic impedance of the signal feeder, the required 65% reduction in device capacitance of the EAM section is reduced to 45%, which would naturally lead to enhanced extinction ratio and optical output power. With the addition of a series 5-Ω thin-film resistor along the signal feeder, the device capacitance reduction of the EAM section is further reduced to approximately 33% of the typical value.
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