The deliberate introduction of controlled intersymbol interference (ISI) in Tukey signalling enables the recovery of signal amplitude and (in part) signal phase under direct detection, giving rise to significant data rate improvements compared to intensity modulation with direct detection (IMDD). The use of an integrate-and-dump detector makes precise waveform shaping unnecessary, thereby equipping the scheme with a high degree of robustness to nonlinear signal distortions introduced by practical modulators. Signal sequences drawn from star quadrature amplitude modulation (SQAM) formats admit an efficient trellis description that facilitates codebook design and low-complexity near maximum-likelihood sequence detection in the presence of both shot noise and thermal noise. Under the practical (though suboptimal) allocation of a 50% duty cycle between ISI-free and ISI-present signalling segments, at a symbol rate of 50 Gbaud and a launch power of -10 dBm the Tukey scheme has a maximum theoretically achievable throughput of 200 Gb/s with an (8,4)-SQAM constellation, while an IMDD scheme achieves about 145 Gb/s using PAM-8. Note that the two mentioned constellations have the same number of magnitude levels and the difference in throughput is resulting from exploiting phase information under using a complex-valued signal constellation.
翻译:在Tukey信号中有意引入受控的间相干扰(ISI)使信号振幅和(部分)信号阶段在直接探测下得到恢复,从而与直接探测(IMDD)的强度调制相比,数据率显著提高。使用集成和俯冲探测器使精确波形形成不必要的精确波形结构,从而使该计划具有高度的稳健性,以实际调制器对非线性信号变形的采用。从恒星二次振动调调制(SQAM)格式中提取的信号序列包含一个高效的三角形描述,便于在有射门噪音和热噪音的情况下进行代码设计以及接近最大类似序列的低复杂性检测。在实际(尽管次优化)中,在无ISISI和ISI提供信号段之间分配了50%的值周期,其符号率为50 Gbaud,发射力为10 dBm。 Tukey 计划在理论上可达到的200 Gb/s(8,4)-SQAM星座模型中,在使用IM-GMA-8号星座变等的星座图中,在使用GM-DDDSQSpeage Speage Speal Speal Pal Pal Pal Pal Pal Pal Pal Pal Pal上实现了中达到大约145。