The reliability of the production of complex thin film optical filters is highly dependent on a precise deposition control. On the one hand, layer thickness monitoring systems for accurate end-point detection are essential even within stable deposition processes. On the other hand, online monitoring concepts can be applied to further stabilize deposition processes by complementing or replacing open-loop control systems by the implementation of closed-loop control approaches. Today, indirect optical monitoring concepts are replaced more and more by direct monitoring solutions that measure optical properties of samples on the moving substrate holder. Also deterministic production strategies based on process and monitoring simulation packages as well as online error correction tools found their way into optical coating industry. Nevertheless, the process control algorithms and the simulation tools have to be further improved, for instance by integrating layer growth models to predict optical and non-optical thin film properties. Another promising approach is the development of optical monitoring systems, which are not limited to the measurement of the transmittance or reflectance. On the one hand, the online-evaluation of simultaneous transmittance and reflectance measurements allows for new process insights. On the other hand, a new monitoring system has been developed, which enables the measurement of the phase information directly on the moving samples being coated. For instance, this system can be used to monitor the group delay dispersion for depositing advanced femtosecond laser optics. In this contribution an overview of different monitoring approaches in combination with recent application examples will be given.