Optical sinc-shaped Nyquist pulses of exceptional quality

Abstract

Sinc-shaped Nyquist pulses possess a rectangular spectrum, enabling data to be encoded in a minimum spectral bandwidth and satisfying by essence the Nyquist criterion of zero inter-symbol interference (ISI). This property makes them very attractive for communication systems since data transmission rates can be maximized while the bandwidth usage is minimized. However, most of the pulse-shaping methods reported so far have remained rather complex and none has led to ideal sinc pulses. Here a method to produce sinc-shaped Nyquist pulses of very high quality is proposed based on the direct synthesis of a rectangular-shaped and phase-locked frequency comb. The method is highly flexible and can be easily integrated in communication systems, potentially offering a substantial increase in data transmission rates. Further, the high quality and wide tunability of the reported sinc-shaped pulses can also bring benefits to many other fields, such as microwave photonics, light storage and all-optical sampling.

Design and Applications of In-Cavity Pulse Shaping by Spectral Sculpturing in Mode-Locked Fibre Lasers

“…Various techniques to optically generate Nyquist pulses have been demonstrated, including spectral reshaping of a mode-locked laser [44] or fibre optical parametric amplification [45]. Additionally, sequences of very high-quality sinc-shaped pulses were obtained by the direct synthesis of a phase-locked frequency comb [46]. Furthermore, a Nyquist laser that can directly emit an optical Nyquist pulse train was recently demonstrated [47].…”

Reconfigurable Filter-free Sinc-shaped RF Photonic Filters Based on Rectangular Optical Frequency Comb

“…φ2 (-1020ps/nm in our experiment) stands for dispersion induced group delay. The term sin(φ22π 2 Nf m f RF )/sin(φ22π 2 f m f RF ) is a periodic sinc function [6] with (N-1) nulls equally distributed between the main peaks. The quadratic phase term represents a linear group delay additional to the periodic sinc carver, while the linear phase term vanishes, when the laser frequency is set as reference.…”

“…In this paper, we present reconfigurable RF photonic filters with near perfect sinc response based on a simple versatile comb source. The comb is synthesized using a cascade of Mach-Zehnder modulators (MZMs) driven by synchronized RF frequencies [6], resulting in rectangular spectra without the need for spectral shaping. The proposed RF filter scheme can be easily reconfigured by modifying the RF signals (frequency, power) and DC bias driving the comb source modulators.…”

A simple all-optical format transparent time and wavelength demultiplexing technique for WDM & orthogonal-TDM Nyquist channels

“…A spool of 10 km long SMF is used to decorrelate the NRZ WDM channels. The method described in [5] is then implemented to perform high quality sincshaped Nyquist carving with f1 = 30 GHz and f2 = 10 GHz on all WDM channels. An optical clock multiplier (OCM) is then used to produce 8 Nyquist uncorrelated O-TDM tributaries on each WDM channel for a total 240 Gb/s aggregate rate.…”

“…After passing through the delay line, the chain of intensity modulators driven by specific RF tones with adjusted bias and amplitude voltages as in [5] and the tunable filter centred at f0, the signal becomes: …”