Measurement and Multiplexing of Ultra-Low Duty Cycle Nyquist Pulse Sequences.

In this paper, we propose a novel, to the best of our knowledge, method to our knowledge for generating and accurately measuring Nyquist pulse sequences with an ultra-low duty cycle of only 0.037, which breaks the limitations caused by the noise and bandwidth of the optical sampling oscilloscope (OSO) by using a narrow-bandwidth real-time oscilloscope (OSC) and an electrical spectrum analyzer (ESA). By this method, it is found that the bias point drift of the dual parallel Mach-Zehnder modulator (DPMZM) is the main cause of the distortion of the waveform. In addition, we increase the repetition rate of Nyquist pulse sequences by a factor of 16 by multiplexing the unmodulated Nyquist pulse sequences.