A transponder-equipped ID tag is provided, deriving its power from an incoming interrogating optical signal. The invention relates to a transponder-equipped ID tag that is able to extract power from the incident corresponding interrogation signal and temporarily store it in an internal energy storage device. Optionally, optical transmission is used as either a transmission mode only into the tag or a transmission mode only away from the tag. The inventive optical means of transmission may be combined with either RF transmission into the tag and/or RF transmission away from the tag.