An optical network unit (ONU) circuit that combines both analog and digital components is provided. It was developed in the late 1990s and early 2000s, converting optical signals from the ISP into electrical signals usable by routers, computers, IP phones, or Wi-Fi access points. Use the resources below to design a system with our most advanced microcontroller, interface and power delivery. An Optical Network Unit, as a key node in a passive optical network, is responsible for the "last mile" of fiber optic network access to homes and buildings. In a PON system, a single fiber typically connects the OLT device to the ONU to achieve Fiber to the x.