This paper describes an investigation of the effect of the extinction ratio and the chirp parameter of the first intensity modulator on the transmission performance of a proposed duobinary transmitter based on two intensity modulators without using electrical low-pass filters. This modulation scheme can generate duobinary signals using only two-level electrical signals without the conversion process to three-level electrical signals using electrical low-pass filters. The simulation results suggest that the appropriate chirp and extinction ratio of the first intensity modulator provide larger dispersion tolerance, compared with the conventional duobinary transmitter. The duobinary transmitter based on two intensity modulators can increase the dispersion tolerance without using electrical low-pass filters.
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