Low Time Jitter Microwave Pulse Train Generation Based on an Optoelectronic Oscillator

We demonstrate an approach to ultra-short microwave pulse train generation with a low time jitter based on pulse compression of a frequency comb generated by a dual-loop optoelectronic oscillator (OEO). The frequency comb is generated due to the use of cascaded phase modulator and Mach Zehnder modulator in the OEO cavity. By adjusting the phase relationship between the comb lines using a dispersion compensating fiber (DCF), a stable optical pulse train with compressed pulses is generated. Thanks to the low phase noise nature of an OEO, the generated pulse train has a low time jitter. The proposed approach is evaluated experimentally. A pulse train with a repetition frequency of 2.023 GHz and a pulse width of 40 ps is generated. The phase noise of the carrier frequency generated by the OEO is measured to be -118 dBc/Hz at a 10-kHz offset frequency, corresponding to a time jitter of the pulse train of 391.2 fs. The phase noise can be further reduced if an active cavity stabilization mechanism is adopted, enabling further reduction in the time jitter to the order of tens of femtoseconds.