Datacenters experience an enormous traffic growth due to the vast amount of data to be stored, transmitted and processed [1]–[4]. Technical and economic challenges arise to keep up the bandwidth scalability. Therefore, cost-efficient short reach optical interconnects for 400 GbE intra-datacenter links are critical. Attractive solutions are proposed based on eight optical lanes thanks to compatibility with 100 GbE building blocks, where two optical lanes based 100 GbE solution is already being deployed [4]. Solutions for 400 GbE based on four optical lanes or even two optical lanes using high bandwidth components may be more attractive to reduce cost, power consumption and complexity of parallelism [5], [6]. In this talk, we report on several experimental demonstrations for short reach optical interconnects in C-band. We experimentally evaluate high-speed on-off keying (OOK) and 4-level pulse amplitude modulation (PAM4) and 8-level PAM8 transmitter performance in C-band for short reach optical interconnects. We demonstrate 100 Gbaud PAM4 transmission over 400 meters long standard single mode fiber without optical amplification. We also show results of numerical simulations showing achievable transmission reach in C-band for multilevel modulation at 100 Gbaud over standard single mode fiber with simple decision feedback equalizer. This paves the way for cost-effective short reach optical interconnects with multilevel modulation at 100 Gbaud and higher.