Versatile Microwave Photonic Signal Processor Based on a Quantum-Dash Mode-Locked Laser

Microwave photonic (MWP) signal processing offers the advantage of large time-bandwidth capability to overcome the inherent limitations of electronic systems. Optical frequency combs (OFC), providing many wavelengths, are particularly useful for transversal filter systems, while quantum-dash mode-locked lasers (QD-MLL), known for their ability to generate flat OFCs with low power consumption and simple operation, are promising candidates as the OFC sources. Here, we demonstrate for the first time a versatile MWP signal processor using a QD-MLL that generates an OFC with 49 comb lines and a free spectral range of 25 GHz. By tailoring the OFC spectrum, the MWP signal processor can be reconfigured to perform a variety of functions, including integral and fractional Hilbert transform (HT), differentiator, and integrator, with operation bandwidths of 7.5 GHz, 20 GHz, and 25 GHz, respectively. Owing to the large number of comb lines, the proposed HT exhibits small amplitude and phase and ripples, which are ±1.66 dB and ±6.2∘, respectively, for integral HT. We also simulate the time-domain response for the different signal-processing functions based on the measured frequency responses. Our simulation and experimental results show that the QD-MLL is a promising OFC source for developing a high-speed, reconfigurable MWP processing engine.