Low cost bidirectionnal QPSK transmission with optical frequency conversion

We propose and demonstrate a low cost bidirectional radio-over-fiber system based on the use of a simple p-i-n photodiode (PD) and a VCSEL. PD provides both photodetection and frequency conversion capabilities and its mixing efficiency is evaluated through the measurement of the PD non-linear parameter. The functionality of the RoF up-link and down-link systems is verified experimentally for microwave (MW) subcarrier frequency conversion of a 10 Mbaud QPSK digital signal in the 10 GHz band, measuring conversion gain and error vector magnitude (EVM). The experimental results demonstrate that the proposed bidirectional RoF system performs efficiently without significant distortion on the digitally modulated subcarrier, and could be advantageously used for mm-wave applications.