Triangular Pulse Generation by Polarization Multiplexed Optoelectronic Oscillator

A novel triangular pulse generator is proposed based on a polarization multiplexed optoelectronic oscillator (OEO). Employing a dual-polarization modulator, the proposed OEO can simultaneously oscillate at two frequencies of $f$ and $3f$ along the two orthogonal polarizations of the same optical carrier. Thanks to the harmonic injection coupling between the two OEO oscillations, the generated two signals have an exact frequency ratio of 1:3 and can be tuned to be in phase with each other. By properly setting the amplitudes of the two signals, a triangular pulse train can be generated. The generation of a 4.44-GHz triangular pulse train is experimentally demonstrated. A very clean electrical spectrum incorporating the 4.44- and 13.32-GHz components is obtained, and the two tones have good phase noises of −100.6 dBc/Hz at 10 kHz and −99.2 dBc/Hz at 10 kHz, respectively. The generated triangular waveform is very close to an ideal waveform, and the root-mean-square error between the generated and the ideal waveforms is $5.145\times 10^{-4}$ .