A multi-optical fiber measurement technique is presented which can determine spatial flame propagation with a high temporal resolution. With this measurement technique it is possible to investigate the combustion process in both Diesel and SI engines. The measurement technique can also be applied for the detection of flame propagation in research engines and in actual production engines for performing analysis of special problems such as knocking combustion, combustion chamber design studies which concern flame propagation, the influence of engine parameters on flame propagation, ignition and inflammability behavior.The new measurement technique is discussed in detail and the application of optical measuring points in the combustion chamber walls is demonstrated. A special non-contacting optical transmission system has been developed for the observation of flame propagation. Unlike previously developed optical transmission systems, the new non-contacting system presents no restriction on engine speed. Results obtained with this measurement technique, which employs a new, non-contacting transmission system, are presented for different engines under different operating conditions.