Photonic frequency sextupling scheme based on two intensity modulators and a Sagnac loop

A photonic scheme to generate frequency sextupled microwave signal is proposed and experimentally demonstrated. An intensity modulator (IM) and a Sagnac loop with another IM imbedded inside are cascaded in the scheme. A light wave is modulated by a local oscillator (LO) signal in the first IM at the minimum transmission point to generate the ±1st-order sidebands, and the modulated light wave is then sent to the Sagnac loop. The IM in the Sagnac loop is operating at the maximum transmission point and is driven by the same LO signal. The optical signal at the output of the Sagnac loop mainly contains ±3rd-order sidebands. In the experiment, a 15.1-dB electrical spurious suppression ratio (ESSR) is observed and no extra phase noise is introduced. In addition, the proposed system has no optical or electrical filter so that the generated frequency of the system can be tuned flexibly.