Highly-tunable optoelectronic microwave oscillator

We report on a tunable optoelectronic microwave oscillator stabilized with an optical frequency-locked loop. The microwave signal is generated by heterodyning two cross-polarized optical waves. Its frequency is then locked with an electrooptical frequency discriminator realized with a 100 m long optical fiber delay line. The tunability is obtained by thanks to a birefringent optical phase modulator and a polarizer. We implemented this principle with a dual frequency laser at 1.5 μm and we obtained a chirp over a 1 GHz bandwidth with a 1 kHz precision and an average chirp rate of 500 MHz/ms.