Generation of Triangular-Shaped Waveform With Frequency Doubling

A novel approach for triangular-shaped waveform generation based on a dual-polarization quadrature phase shift keying (DP-QPSK) modulator and balanced photo-detection is proposed and demonstrated by simulation and experiment. By properly biasing the child Mach-Zehnder modulators, the optical carrier and the ±4th-order sidebands can be obtained in the upper arm (X-polarization) of the DP-QPSK modulator and the ±2nd-order sidebands in the lower arm (Y-polarization). The polarization multiplexed optical signal is injected to a balanced photo-detector to generate full-duty triangular-shaped waveform. The repetition rate of the detected triangular-shaped waveform can be double frequency of the driving signal. In the simulation and experiment, a 10-GHz triangular pulse train is successfully generated using a 5-GHz driving signal.