— Combining the existing approaches for optical intelligence and the speed and capacity of light is undoubtedly the only viable strategy for building future-proof, highspeed networks. Future optical networks are also expected to provide added value through service quality. However, the performance parameters included in current service level agreements (SLA) require the termination of a channel (wavelength) at an optical-electrical (O/E) conversion point to measure them. In all-optical networks, this is associated with higher cost. Therefore, the optimal monitoring solution for all-optical networks will be one that implements the minimum amount of O/E conversions required to measure or estimate the SLA parameters. This is very challenging due to the complex relations of electrical and optical parameters. Taking the bit error rate (BER) as the key performance parameter to quantify the reliability of a transmission system, this paper discusses the applicability of in-service BER estima...