Frequency- and phase-tunable optoelectronic oscillator based on a DPMZM and SBS effect

• The proposed OEO has flexible phase tunability feature: from 0° to 360°.
• The proposed OEO has frequency tunability feature: from 8.950 to 9.351 GHz.
• The frequency tuning step of our proposed OEO is low: 6 MHz/nm.

A novel approach to the optoelectronic oscillator (OEO) for the generation of a microwave signal with simultaneously frequency and phase tunability is proposed and experimentally demonstrated. In the proposed OEO, a carrier phase-shifted double-sideband modulated optical signal generated using a dual-parallel Mach–Zehnder modulator (DPMZM) is split into two parts. For one part, the signal is injected into a photodetector (PD) after passing through a section of high nonlinear fiber and then fed back into the DPMZM to form an OEO loop. The stimulated Brillouin scattering effect is used to select the oscillation frequency which equals to the Brillouin frequency shift. For the other part, a carrier phase-shifted single-sideband modulated signal is achieved by a tunable filter, and then converts to a microwave signal by a second PD. The tunable phase of the generated microwave signal is achieved by controlling the bias voltage of the DPMZM to change the phase difference between the optical carrier and the sideband. Thanks to the wavelength-dependent effect of the Brillouin frequency shift, the tunable frequency is realized by tuning the frequency of the laser source. Microwave signals with a tunable frequency from 8.950 to 9.351 GHz and a tunable phase from 0° to 360° are experimentally generated.