We experimentally demonstrate 200 Gb/s/λ downstream transmission for a passive optical network (PON) with a minimal coherent receiver at optical network unit (ONU). The low complexity receiver required at the cost-sensitive ONU employs heterodyne detection and requires a single photodiode, a 3-dB optical coupler and a local oscillator, and is the simplest coherent receiver. At the optical line terminal (OLT), digital pre-emphasis and Alamouti-coding is applied to the 50 GBaud signal. A power budget of 29 dB is experimentally demonstrated, increasing to 34.5 dB if a balanced receiver is utilized.