Disclosed in a wearable electronic device including an optical keypad supported by a keypad housing. The optical keypad may include a plurality of keys disposed along the keypad housing, and a plurality of illumination sources and optical receivers with a corresponding illumination source and optical receiver for each of the plurality of keys. The keypad signal interface may be limited to three connections, to provide a connection for power, a connection for ground, and a connection for data between the keypad housing and the main housing. The electronic device may also include at least one optical receiver configured to be optically coupled to at least one of the plurality of illumination sources, and configured to convert a received optical signal representing data into an electrical signal representing data. The illumination sources may provide optical signals during key presses, and may in addition provide key illumination for unpressed keys.