As the need for training and inference infrastructure grows rapidly, there is demand for increased campus sizes, with the growth mandating campus links have 5 km reach or more. Full Coherent systems are predominantly used in long-haul communications, which ends up being overkill for distances less than 10 km due to stringent laser requirements, better modulator parameters (including a larger drive swing) and a complex DSP. Coherent-lite is an attempt to bring Coherent detection to the datacenter links since IM-DD gets strained with future generations, particularly 400G/lane. (1/5)🧵