Nyquist pulses, which are defined as responses of Nyquist filter, can be used in time-division multiplexing transmission which can simultaneously achieve ultrahigh data rate and spectral efficiency (SE). Generally, the methods for Nyquist pulse generation are based on optical Nyquist filters, nonlinear effects in fiber and phase-locked frequency comb. In this paper, we focus on the third method of phase-locked frequency comb. However, this method has a problem which the large duty cycle of generated Nyquist pulses limits their applications. To address this issue, we proposed a new setup in which one optical intensity modulator and an electrical arbitrary function generator (AFG) are employed. The various duty cycles of ideal Nyquist pulses are generated using one optical intensity modulator so that the phase-locking between the different RF signals is no need any more. And the ideal Nyquist pulses in microwave domain are generated successfully. The duty cycles ranging from 21% to 11% are obtained by programming the number of frequency comb lines in the RF signal which is generated by the AFG. The method has a potential to generate ideal Nyquist pulses in radio frequency domain if a high bandwidth AFG is used to replace the low bandwidth AFG used in this paper.
Cheng Guo, Tianxin Yang, Zhaoyu Lu, Chunfeng Ge, and Zhaoying Wang, "Nyquist pulse generator by techniques of frequency synthetization
," Proc. SPIE 10103, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X, 101030W (Presented at SPIE OPTO: January 31, 2017; Published: 30 March 2017); https://doi.org/10.1117/12.2256798.
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