Generation of Triangular Pulses Based on an Optoelectronic Oscillator

A novel scheme for the generation of full-duty-cycle triangular pulses based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The fundamental tone corresponding to the repetition rate of the pulses is generated by the OEO. Biasing the Mach-Zehnder modulator at the quadratic point, the small-signal gain of the OEO is maximized, while even-order harmonics in the optical intensity are suppressed. By properly setting the gain of the OEO loop, the amplitude of the first-order harmonic is nine times that of the third-order harmonic. After a 90° electrical phase shifter adjusts the phase of the electrical signal at the output of the photodetector, triangular pulses are obtained in the time domain. The oscillating frequency is tuned from 2 to 10 GHz by the yttrium-iron-garnet filter, and the phase noise of generated signal is also investigated. Triangular pulses with repetition rates of 3 and 6 GHz are successfully generated. The root-mean-square errors between the generated and the ideal triangular waveforms are 6.4927e-4 and 9.0932e-4 at 3 and 6 GHz, respectively.