Analysis of Non-Idealities in the Generation of Reconfigurable Sinc-Shaped Optical Nyquist Pulses

Abstract

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.INDEX TERMS Nyquist pulse, optical frequency combs, ripple, side band suppression, optical sampling.

High-Bandwidth Coherent OFDM-Nyquist-TDM Transceiver With Low-Bandwidth Electronics

“…The effect of non-idealities on the sinc-shaped Nyquist pulse generation has been studied in detail for different rollof-factor, ripple and sideband suppression ratios [34], [35]. Compared to an ideal flat comb, a 2 dB ripple in a 3-line comb only increases the root mean square error of the pulses by 3%.…”

A New Family of Nyquist Pulses With Improved Performance

“…Moreover, the second derivatives y ′′ i can be obtained as the solution of the following linear system of equations b = Ey (6) where y = [y ′′ 1j , y ′′ 2j , . .…”

“…The most popular design satisfying the above mentioned requirements is the socalled raised-cosine (RC) pulse [3], which has been widely employed in numerous practical digital communications systems, e.g. see [5], [6], [7], [8], [9], [10], and [11] and references therein.…”

“…For example, in [5], a linearly pulse modulation scheme has been proposed improve the performance of visible light communication (VLC) system. In [6], the impact of the rolloff factor, the side band suppression ratio and the ripple of sinc-shaped reconfigurable optical Nyquist pulse sequences has been investigated. In [7], the impact of the optical filter roll-off factor on Nyquist pulses generated by an on-chip silicon Mach-Zehnder modulator, has been investigated.…”

Comb flatness dependence for orthogonally sampled high bandwidth signals

“…23,24 Previously, the effect of non-idealities for the frequency comb generation by Mach-Zehnder modulators at the transmitter side has been studied in detail for the research project Metrology for THz Communications (Meteracom). [25][26][27][28] For the receiver side, it has been shown that orthogonal sampling can effectively enhance the ENOB. 23,24 In this study, we investigate the impact of the case that the carrier is higher than the sidebands (positive ripple) on the performance of orthogonal sampling.…”