Modulation Schemes for Single-Laser 100 Gb/s Links: Single-Carrier

We evaluate single-carrier modulation techniques for 100 Gb/s single-laser data center interconnects. We present numerical performance analysis for various single-carrier schemes including pulse amplitude modulation (PAM), carrierless amplitude phase modulation, and orthogonal multipulse modulation in the presence of optical modulator bandwidth limitations and nonlinearity, clipping, quantization noise, and fiber chromatic dispersion. The performance is evaluated in terms of the required average optical power to achieve a target bit-error ratio for a given modulator bandwidth. We compare the complexity of different designs in terms of the required resolution and sampling rate of digital-to-analog (DAC) and analog-to-digital (ADC) converters, as well as the number of complex operations required for digital signal processing. We find that 4-PAM is the most power efficient scheme among those considered, and that it can be implemented with DAC/ADC resolution as low as 5 bits.