60-GHz System-on-Packaging Transmitter for Radio-Over-Fiber Applications

Using ultra-high-speed electroabsorption modulator (EAM) devices for RF/optic conversion, we fabricated system-on-packaging (SOP) transmitter (Tx) modules and characterized their performance in 60-GHz RF/radio-over-fiber (ROF) applications. Both an EAM and low-noise amplifiers (LNAs) were co-packaged with internal bias circuits into a butterfly-type metal housing. At the EAM temperature,T~ 25degC and the EAM reverse bias, V
_R
~1.6 V was the largest RF gain obtained that was very susceptible to the change of T . The impedance matching in the 60-GHz band was accomplished with both a microstrip-line bandpass filter and a 500- Omega shunt resistor, which defined the 2-GHz passband of the SOP transmitter. In 60-GHz two-tone experiments, we observed that the spurious free dynamic range of an SOP module with two LNAs was 78 dB middot Hz
^2/3
while that of the narrowband EAM module showed 82 dB middot Hz
^2/3
. In contrast, the noise figure exhibited a large reduction of up to 30 dB for the SOP module compared with the narrowband EAM module. Using the SOP Tx module, we achieved successful transmission of commercial high-definition digital CATV signals in 64-quadrature amplitude modulation (QAM) format through the 60-GHz RF/ROF link. The total throughput of the link was estimated to be 6.5 Gb/s.