Analysis of Simultaneous Photonic Frequency Downconversion and Optical Subcarrier Modulation in an Electroabsorption Modulator

We present theoretical analysis of simultaneous photonic frequency downconversion, based on four-wave mixing (FWM), and optical subcarrier modulation in an electroabsorption modulator (EAM) for broadband millimeter wave (mm-wave) over fiber uplinks. A model of FWM generation in an EAM is established. The FWM efficiency with an EAM at dc bias with and without RF modulation is analyzed, including the impact of bias voltage, modulation voltage, and frequency detuning. The calculated FWM efficiency agrees well with the measured. The signal-to-noise ratio (SNR) of photonic frequency downconverted RF signal is also analyzed, considering the nonlinear distortion due to the EAM nonlinearities. Moreover, calculated error vector magnitude using theoretical SNR is compared with the measured for multiband orthogonal frequency division multiplexing ultrawideband mm-wave signals.