Fig. 1. Schematic diagram of the proposed microwave signal generation approach.

Fig. 2. Spectra of (a) the direct modulation of a MZM and (b) fiber ring loop modulation.

Fig. 3. Schematic diagram of filtering strategy based on the FRMPFs.

Fig. 4. Measured harmonic spectra (a) without FRMPFs and (b) with one FRMPF (frequency of driving signal is 2.835 GHz).

Fig. 5. Measured spectrum of the generated fourth harmonic. Inset, detailed spectrum of the fourth harmonic.