This paper discusses the issue of pulse shaping in unipolar orthogonal-frequency-division-multiplexing-based modulation schemes for intensity modulation/direct detection systems. Three previously presented schemes, asymmetrically clipped optical OFDM, pulse-amplitude-modulated discrete multitone modulation, and unipolar orthogonal frequency division multiplexing, are investigated. The current work demonstrates how both unipolar and bipolar pulse shapes can be used for the generation of unipolar continuous-time signals.
- pulse shapes
- modulation schemes