Single-Channel Two-Bit Photonic DAC via Delta-Sigma Noise Shaping and Talbot Enhancement

Simultaneously achieving a high sampling rate, broad bandwidth, and high conversion resolution while maintaining reduced optical-channel complexity remains a fundamental challenge for photonic digital-to-analog converters (PDACs). To address this challenge, we propose and experimentally demonstrate a single-channel two-bit PDAC integrating delta–sigma (ΔΣ) noise shaping and fractional Talbot pulse repetition-rate enhancement. The proposed scheme jointly exploits digital-domain noise shaping and optical-domain sampling rate enhancement to suppress in-band quantization noise and expand the effective bandwidth within a compact single-channel configuration. A dual-drive Mach–Zehnder modulator (DDMZM) is adopted to realize linear four-level optical intensity mapping, eliminating the inter-channel mismatch issues in conventional multi-channel PDAC architectures. Experimentally, a 10.2 GHz optical pulse train is passively enhanced to 30.6 GHz, yielding an effective sampling rate of 30.6 GSa/s. Broadband X-band linear frequency-modulated waveforms (LFMs) with carrier frequencies of 7.5 GHz and 10 GHz are successfully generated, achieving effective numbers of bits (ENOBs) of 4.83, 3.96, and 3.64 for 2 GHz single-chirp, 4 GHz single-chirp, and 4 GHz dual-chirp signals, respectively. In addition, high-fidelity reconstruction of 1 GHz square and triangular waveforms is demonstrated. The proposed PDAC combines sampling-rate enhancement and noise suppression in a single-channel configuration, enabling high-speed broadband microwave photonic arbitrary waveform generation.