Microwave generation with photonic frequency sextupling based on cascaded modulators

A novel scheme to optically generate a microwave signal with frequency sextupling is proposed. The proposed scheme is based on cascading an intensity modulator (IM) and a dual-parallel Mach-Zehnder modulator (DPMZM), without any optical or electrical filter. The low frequency local oscillator signal is divided into two paths, with one path driving the IM at the minimum transmission point and the other path driving the upper arm of the DPMZM. By controlling the three dc biases of the DPMZM, the third-order sidebands are generated, with other sidebands well suppressed. A 20-dB electrical spurious suppression ratio is demonstrated in the experiment. The phase noise measurements show that the phase noise performance of the generated microwave signal is not deteriorated by the optical system. The proposed scheme has no strict requirements for the modulation indexes and the generated signal exhibits advantages of high frequency tunability and purity.