Frequency-Sextupling Optoelectronic Oscillator Using a Mach–Zehnder Interferometer and an FBG

A frequency-sextupling dual-loop optoelectronic oscillator (OEO) without any electronic microwave filters is proposed and demonstrated. In the proposed OEO, a modulated signal that consists of an optical carrier and odd-order sidebands is generated using a Mach–Zehnder interferometer (MZI). The modulated signal is then divided into reflection components and transmission components by a fiber Bragg grating (FBG). The reflection components, including the optical carrier and the ±1st-order sidebands, are sent to a photodetector (PD1) and then fed back to the MZI to form the OEO loop. The transmission components, including the ±3rd-order sidebands, are sent to another PD (PD2) to generate a frequency-sextupled microwave signal. Meanwhile, a microwave photonic filter is formed by the joint operation of the MZI, the FBG, and an optical domain dual-loop composite cavity that performs the selection of the oscillation mode. As a result, a fundamental oscillation signal at 4.03 GHz and its frequency-sextupled microwave signal at 24.18 GHz are generated with their performance being evaluated.