A spark plug assembly, comprising: a spark plug (102, 402, 502), wherein the spark plug (102, 402, 502) comprises: a high voltage connector disposed at one end of the spark plug (102, 402, 502); an insulator body having a first side and a second side, wherein the insulator body is coupled to the high voltage connector at the first side; a metallic shell having a first side and a second side, wherein the first side of the metallic shell is coupled to the second side of the insulator body; an electrical conductor (120, 412, 508) at least partly disposed in the insulator body and the metallic shell; a detection unit (104, 206, 404, 504), comprising: a transmitter device (134, 208, 406, 510) coupled to the spark plug (102, 402, 502) and electrically disposed between the high voltage connector and the electrical conductor (120, 412, 508), wherein the transmitter device (134, 208, 406, 510) is configured to draw an excitation current from the electrical conductor (120, 412, 508), and wherein the transmitter device (134, 208, 406, 510) comprises an optical signal generator, wherein the optical signal generator is configured to generate an optical signal being representative of an identification parameter of the spark plug (102, 402, 502) and/or a diagnostic parameter of an engine (200, 300) in response to the drawn excitation current, wherein the transmitter device (134, 208, 406, 510) further comprises a coder and an energy storage device and wherein the energy storage device is coupled to the coder and the coder is coupled to the optical signal generator; and a receiver device (214, 408, 512) disposed in optical communication with the transmitter device (134, 208, 406, 510) and configured to receive the optical signal from the transmitter device (134, 208, 406, 510). a spark plug (102, 402, 502), wherein the spark plug (102, 402, 502) comprises: a high voltage connector disposed at one end of the spark plug (102, 402, 502); an insulator body having a first side and a second side, wherein the insulator body is coupled to the high voltage connector at the first side; a metallic shell having a first side and a second side, wherein the first side of the metallic shell is coupled to the second side of the insulator body; an electrical conductor (120, 412, 508) at least partly disposed in the insulator body and the metallic shell; a high voltage connector disposed at one end of the spark plug (102, 402, 502); an insulator body having a first side and a second side, wherein the insulator body is coupled to the high voltage connector at the first side; a metallic shell having a first side and a second side, wherein the first side of the metallic shell is coupled to the second side of the insulator body; an electrical conductor (120, 412, 508) at least partly disposed in the insulator body and the metallic shell; a detection unit (104, 206, 404, 504), comprising: a transmitter device (134, 208, 406, 510) coupled to the spark plug (102, 402, 502) and electrically disposed between the high voltage connector and the electrical conductor (120, 412, 508), wherein the transmitter device (134, 208, 406, 510) is configured to draw an excitation current from the electrical conductor (120, 412, 508), and wherein the transmitter device (134, 208, 406, 510) comprises an optical signal generator, wherein the optical signal generator is configured to generate an optical signal being representative of an identification parameter of the spark plug (102, 402, 502) and/or a diagnostic parameter of an engine (200, 300) in response to the drawn excitation current, wherein the transmitter device (134, 208, 406, 510) further comprises a coder and an energy storage device and wherein the energy storage device is coupled to the coder and the coder is coupled to the optical signal generator; and a receiver device (214, 408, 512) disposed in optical communication with the transmitter device (134, 208, 406, 510) and configured to receive the optical signal from the transmitter device (134, 208, 406, 510). a transmitter device (134, 208, 406, 510) coupled to the spark plug (102, 402, 502) and electrically disposed between the high voltage connector and the electrical conductor (120, 412, 508), wherein the transmitter device (134, 208, 406, 510) is configured to draw an excitation current from the electrical conductor (120, 412, 508), and wherein the transmitter device (134, 208, 406, 510) comprises an optical signal generator, wherein the optical signal generator is configured to generate an optical signal being representative of an identification parameter of the spark plug (102, 402, 502) and/or a diagnostic parameter of an engine (200, 300) in response to the drawn excitation current, wherein the transmitter device (134, 208, 406, 510) further comprises a coder and an energy storage device and wherein the energy storage device is coupled to the coder and the coder is coupled to the optical signal generator; and a receiver device (214, 408, 512) disposed in optical communication with the transmitter device (134, 208, 406, 510) and configured to receive the optical signal from the transmitter device (134, 208, 406, 510).