Disclosed herein, among other things, is an implantable medical device header assembly with an optical interface. The header assembly can include a housing defining a cavity; an electrical contact disposed along the cavity; an electrical conductor configured to electrically couple the electrical contact with the implantable medical device; and an optical conductor. The header assembly can include a housing defining a first cavity for receiving a proximal end of an electrical lead; and a second cavity for receiving a proximal end of an optical lead. The header assembly can include a housing configured to be coupled to the implantable medical device, the housing defining a lead port for receiving a proximal end of a lead, the port configured to be in electrical and optical communication with the lead; a transducer disposed within the housing, and an electrical conductor disposed within the housing. Other aspects and embodiments are provided herein.