A novel concept of pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) is presented. It is shown that by pulse amplitude modulation of the subcarriers used, the resulting PAM-DMT time signal can be clipped asymmetrically to achieve a unipolar signal for transmission. The distortion resulting from this asymmetric clipping is orthogonal to the information signal itself, causing no additional penalty. Especially in intensity-modulated direct-detection optical channels, where a unipolar signal is to be transmitted, it is shown that this idea can improve system performance.
- Intensity modulation
- Optical fiber communication
- Orthogonal frequency-division multiplexing (ofdm)