High-Precision Triangular Waveform With Tunable Symmetry Photonic Generation Based on Image-Reject Down Conversion

A high-precision triangular waveform with tunable symmetry photonic generation scheme based on in-phase/quadrature-phase modulation and image-reject down conversion is proposed and analyzed. The optical carrier from the laser diode is split into two paths: one is injected into the I/Q modulator driven by a sinusoidal signal, while the other is injected into a frequency shifter to introduce a frequency offset. Different channels have different frequency offsets. The modulated and frequency-shifted signals enter the image-reject mixer to realize optical down conversion and suppress the frequency mixing interference in the frequency conversion process. Finally, the signals from both channels are coupled to synthesize the first to sixth-order harmonic fitting in the Fourier series. High-precision triangular waveforms generation with tunable symmetry coefficients and repetition frequency of 5 GHz are obtained by simulation. In order to verify the mechanism, a proof-of-concept experiment is carried out. This scheme effectively expands the multi-channel spectrum and enables high-precision functional waveform fitting.