Local Oscillator Free Frequency Up-Conversion at Millimeter-Wave Band

We have demonstrated all-optical frequency upconversion at millimeter-wave band without using local oscillators. By launching a low bit rate signal into a Fabry-Pérot laser diode (FP-LD), a microwave subcarrier is generated based on the four wavelength mixing and injection mode locking. Due to the dynamic charge carrier density response during the injection locking, the wavelength of the leading part of the subcarrier will be red-shifted while that of the falling part will be blue-shifted. By compensating the generated chirp with a suitable negative dispersion device, the time-domain pulses will be compressed and the second harmonic of the subcarrier will be generated. A polarization interferometer is used to further suppress the foundational frequency. In our experiment, a subcarrier of 30.8 and 34.8 GHz is obtained by launching a 2.5-Gb/s NRZ signal into the FP-LD. We also show that the photonic frequency upconversion can go up to ~60 GHz with the proposed scheme.