Analysis of Non-Idealities in the Generation of Reconfigurable Sinc-Shaped Optical Nyquist Pulses
Optical sinc-shaped Nyquist pulses are widely used in microwave photonics, optical signal processing, and optical telecommunications due to their numerous advantages, like rectangular shape in the frequency domain, the orthogonality and the consequential possibility to use these pulses to transmit data with the maximum possible symbol rate. Ideal sinc pulses with the rectangular spectrum are just a mathematical construct. However, high-quality sinc pulse sequences offer the same advantages and can be generated by a phase-locked rectangular frequency comb with mode-locked lasers, intensity modulators, and integrated devices. Nevertheless, any non-idealities in the pulse and comb generation might lead to a degradation of the system performance, especially for metrology. Here, we investigate and analyze the effect of three major non-idealities, namely, the roll-off factor, the side band suppression ratio (SSR), and the ripple of sinc-shaped reconfigurable optical Nyquist pulse sequences based on 3, 5, and 9-line optical phase-locked frequency combs. We compare these results with the existing literature for the three-line comb followed by the experimental verification of the simulation results. We illustrate that by increasing the number of comb lines, the pulse sequences have superior performance and contribute to lesser root-mean-square (r.m.s.) error. We also discuss the trade-off between the r.m.s. error and the optical power loss for increasing the SSR.