Abstract
We report electronic generation of optical Nyquist pulses using an arbitrary waveform generator (AWG) followed by a Mach Zehnder modulator (MZM), providing a simple, highly stable and flexible technique to perform photonic sampling. Here, we demonstrate the generation of 10 GHz periodic optical Nyquist pulses by synthesizing both all-positive and alternate positive-negative electrical pulse trains using a 25 GHz bandwidth AWG. Biasing the MZM at null ensures the meeting of the Nyquist ISI-free criterion in the optical domain and allows for pulse compression. Moreover, we report the first photonic sampling and demodulation of 1 Gbaud 16- and 32-QAM signals up to 22.5 GHz using 10 GHz optical Nyquist sampling pulse trains.
Highlights
Digital signal processing (DSP) is a powerful technique for storing, analyzing and manipulating digital signals
We report electronic generation of optical Nyquist pulses using an arbitrary waveform generator (AWG) followed by a Mach Zehnder modulator (MZM), providing a simple, highly stable and flexible technique to perform photonic sampling
In [11], 200 fs pulse trains of up to 17 GHz were generated using a MZM based optical comb generator followed by frequency compensation with a single mode fiber (SMF) and further pulse compression with a dispersion-flattened dispersion-decreasing fiber
Summary
Digital signal processing (DSP) is a powerful technique for storing, analyzing and manipulating digital signals. All-optical generation of sinc-shaped Nyquist pulses has attracted increasing attention because of their tolerance to inter-symbol interference (ISI) and high spectral efficiency [13] which are important for optical time division multiplexing (OTDM) applications [14]. One such generation technique involves manipulating the spectral components of the Gaussian-shaped output pulses from a mode-locked laser into 40 GHz Nyquist pulses [13]. A more flexible generation technique directly synthesizes a 156 GHz wide rectangular-shaped and phase-locked optical frequency comb, required for a 26 GHz sinc-shaped pulse train, by externally modulating a CW laser source with a cascade of RF driven MZMs [15]. We report the first photonic sampling and demodulation of 1 Gbaud 16-QAM and 32-QAM signals using 10 GHz optical Nyquist pulse trains, achieving low error vector magnitude (EVM) values of less than 6% up to a carrier frequency of 22.5 GHz
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