I. Introduction
Transparent optical network architectures help reduce expensive optoelectronic conversions, while offering high data rates, flexible switching, and multiple types of services. However, physical layer impairments (PLIs) caused by network devices degrade the quality of transmission (QoT) [1], [2], [3], which can be measured by the bit error rate (BER). The process of handling PLIs as a part of the establishment of a connection results in an increased set-up delay of the connection [4] or may even cause its blocking. To meet the requirements of a variety of services, transparent optical networks should be quality-of-service (QoS) [5] capable to support differentiated services in terms of BER and set-up delay.