The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters [1]. The 400 Gbps client-side links are demanding cost efficient solution: to reduce the number of lanes and increase the bandwidth for a single lane. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100G since it reduces complexity, power consumption and costs [2]. However, it requires silicon and InP opto-electronic components with more than 70 GHz bandwidth [3]. In this talk, we report on a cost-efficient integrated externally modulated laser (EML) with high bandwidth for record high-speed intensity modulation and direct detection system demonstration with up to 100G OOK, PAM4/8 and duobinary signaling, as well as analog modulations e.g. DMT, paving the way for high speed multilevel modulation formats [4–6]. Related techniques including digital signal processing algorithms for timing recovery, adaptive/static equalization are also discussed in terms of practical implementation and complexity. In addition, techniques constructively using time domain super-Nyquist image induced aliasing for mitigating modulator driver nonlinearity for high speed DMT transmission will be presented [6], [7].