Second-Order Intermodulation Distortion in Heterodyne Detection Fiber-Optic Millimeter-Wave Links

We analyzed intermodulation distortion by a photodiode in heterodyne detection optical-fibermillimeter-wave links. As a result, we show that the second-order distortion occurs close to the signal frequency, which is different from the IM-DD links. We generated two millimeter-wave signals (38.5 GHz and 38.6 GHz) in the experiment and measured the distortion. This result demonstrated the validity of the analysis. In three optical carriers, we show the reduction technique of second-order distortion close to the signal frequency by the appropriate arrangement of optical carrier frequencies. It is found that reduction of the second-order intermodulation distortion is important for the improvement of system performance.