Generator of Signals with Quadruple Frequency and Triangular Waveform Tunable in Symmetry Based on Dual-Parallel Mach-Zehnder Modulator and Balanced Photodetector

This paper proposed a generator of signals with a quadruple frequency and a triangular waveform tunable in symmetry based on the dual-parallel Mach-Zehnder modulator and balanced photodetector. In the scheme, modulation nonlinearity and multiparameter manipulation arc used to generate the target signals. An approximate characterization of the photocurrent expression using the first three terms of the Fourier expansion of microwave signals following the objective function can be achieved via the adjustments of the modulation index beta and time delay tau. As a result, signals with a periodic triangular waveform and a frequency four times the RF modulation frequency arc obtained. In the simulation verification, 20 GHz signals with a triangular waveform arc output at an RF modulation frequency of 5 GHz. Based on the fitting error, the error of the obtained time-domain waveform can be evaluated. The designed generator is capable of outputting signals with a symmetry factor between 209 and 80% while ensuring the fitting error within 8%.