Abstract: In an internal combustion engine with externally supplied ignition, the compressed air-fuel mixture is ignited, at least partially, with the use of at least one laser beam, which is introduced into a combustion chamber via at least one optical waveguide and is focused onto an ignition location. In order to achieve a simple and compact design, the optical waveguide is positioned in a sealing element bounding the combustion chamber, wherein the sealing element is located in a cutting plane through the combustion chamber and preferably is constituted by a cylinder head gasket.

Abstract: For optical detection of the velocity of gas bubbles in the cooling liquid of an internal combustion engine, light is radiated into the coolant by means of at least one emitter, and the scattered light caused by the gas bubbles, or rather, the change in intensity of light radiation emitted into the coolant, is measured by an optical sensor. The scattered light or intensity change is measured in at least two adjacent areas, and the velocity of the bubbles is determined from the travel time between the measurement signals.