This work addresses the topic of optical networks cross-layer design with a focus on physical-layer-impairment-aware design. Contributors captures both the physical-layer-aware network design as well as the latest advances in service-layer-aware network design. Treatment of topics such as, optical transmissions which are prone to signal impairments, dense packing of wavelengths, dispersion, crosstalk, etc., as well as how to design the network to mitigate such impairments, are all covered.