The use of microwave photonic arbitrary function waveform generation (OAFG) technology can overcome the speed limitations encountered in electronic systems, enabling the generation of high-quality function waveform signals with broader applications. Various OAFG schemes have been proposed by research institutions worldwide, including direct spectral shaping, frequency-to-time mapping (FTTM), time-domain synthesis, and external modulation. Direct spectral shaping has gained considerable attention due to its flexibility. This technique utilizes Fourier transform principles to manipulate the amplitude and phase of the spectrum, altering the characteristics of optical pulses in the time domain. However, practical spectral manipulation can be affected by phase disturbances and precision issues, influencing signal quality and requiring further refinement. FTTM technology allows for spectral analysis of microwave signals, removing noise and unwanted frequency components to improve waveform quality and reliability. However, its implementation is complex and it may introduce nonlinear distortions, reducing the accuracy of the signals. Time-domain synthesis involves processing the optical intensity envelope to match the target waveform’s envelope, which is then detected to obtain the desired waveform. However, this method can introduce noise and nonlinear distortions during the synthesis process, affecting waveform quality. External modulation technology leverages the nonlinear characteristics of electro-optic modulators to adjust the modulation of optical signals by controlling parameters such as modulation coefficient and bias voltage, allowing the modulated photocurrent to approximate the Fourier series of the target waveform.

In this paper, we introduce a novel optical function waveform generation scheme based on image-frequency rejection mixer technology. By adjusting key parameters of the Mach-Zehnder modulator (MZM), including modulation coefficient, bias voltage, and phase difference between the upper and lower arm signals, this scheme enables control of harmonic components within the photocurrent expression. Moreover, by leveraging the image-frequency rejection mixer’s properties, interference to the target signal is effectively suppressed, allowing the generated waveform to closely match the Fourier series of the target waveform, resulting in high-quality functional waveforms. Simulation results confirm the scheme’s ability to generate diverse signals with excellent tunability, offering new avenues for function waveform research.

The proposed functional waveform generation scheme is shown in Fig. 1. For various target waveforms, system variables such as modulation coefficient, bias voltage, and phase difference are calculated and set to generate the desired functional waveform. The root mean square error (RMSE) is used to assess the waveform quality, and the effects of drift in modulation coefficient, phase difference, and bias voltage are analyzed with corresponding tolerance ranges.

A function waveform generation scheme based on an image-frequency rejection mixer is proposed. By controlling three variables of the MZM, i.e., modulation coefficient β, bias voltage Vbias, and phase difference θ between the upper and lower arms, each harmonic component can be adjusted to approximate the Fourier series of the target waveform, thus generating the desired signal. The scheme’s tunability, as well as the tolerance ranges for each MZM variable, is analyzed and discussed. This approach can generate triangular waves with adjustable symmetry, square waves with adjustable duty cycles, and triangular waves with adjustable duty cycles. When the RMSE is limited to ≤5%, high-quality adjustable symmetric triangular waves (with symmetry factor 30%≤σ≤70%) can be produced.