A single fiber passive optical network (PON) wavelength division multiplex (WDM) overlay includes a central office, a fiber optic network, and a plurality of optical network termination (ONT) units. The central office has a baseline optical link that receives a baseline communication signal and converts the baseline communication signal into a downstream baseline optical signal within a first optical bandwidth, and has an additional optical link that receives a second type of communication signal and converts the second type of communication signal into a second downstream optical signal within a second optical bandwidth. The downstream baseline optical signal generated by the baseline optical link is combined with the second optical signal generated by the additional optical link to generate a broadband optical signal. The fiber optic network is coupled to the central office and receives the broadband optical signal on at least one optic fiber. The fiber optic network splits the broadband optical signal to a plurality of fiber drops. The optical network termination (ONT) units are each coupled to a fiber drop. At least one of the ONT units is a baseline ONT unit that receives the broadband optical signal from the fiber drop and splits the downstream baseline optical signal from the broadband optical signal, and at least one other of the ONT units is an upgraded ONT unit that receives the broadband optical signal from the fiber drop and splits the downstream baseline optical signal and the second downstream optical signals from the broadband optical signal. In addition, the installation of the upgraded ONT unit to the PON does not effect baseline optical service to any other ONT unit.