Short reach optical communicationtechnologies are increasinglydemandedin several fast-evolvingapplication scenariosin both telecom and datacom.Low-cost and low-complexity intensity modulation and direct detection (IM/DD) technologies are challengedtoscaleup the link ratebeyond 400Gbpsby increasing thesingle-lane rate towards 200Gbps,to maintaina low lane countin client-side optics. Limited by the bandwidth ofboth electronics and optoelectronics, and the more pronounced chromatic dispersion in the fiber, such high baud ratesystemsrequire the use of digital signal processing techniques with forward error correction(FEC)coding. Therefore, in this work, we first summarize a few potential alternative technologies to the IM/DD for future developmentand then focus on extending the IM/DD systems towards200Gbps lanerate. Westudyboth theircapability and theirperformancelimitsusingnumerical simulations andtransmission experiments.