This disclosure is directed to devices and methods for facilitating the upgrade of optical networks. An optical network terminal (ONT) that terminates an optical fiber link of an optical network comprises two or more transport engines that each converts data transmitted via different transports to data corresponding to a service. For example, the ONT may include a first transport engine and a second transport engine. The first transport engine converts data received over the optical network via a first transport, e.g., a legacy transport, into data corresponding to a service for one or more subscriber devices. The second transport engine converts the data received over the optical network via a second transport, e.g., a next generation transport, into the data corresponding to the service for the subscriber devices. The ONT is selectively configurable to select one of the first and second transport engines, thereby making the ONT upgrade-resilient.