  Among various aspects in optical network architectures, handling transit
traffic at intermediate nodes represents a defining characteristic for
classification. In this context, the transition from the first generation of
optical-electrical-optical (O-E-O) mode to the second generation of
optical-bypass marked a paradigm shift in redesigning optical transport
networks towards greater network efficiency. Optical-bypass operation has then
become the \textit{de facto} approach adopted by the majority of carriers in
both metro and backbone networks in the last two decades and has remained
basically unchanged. However, in optical-bypass network, the fact that
in-transit lightpaths crossing a common intermediate node must be separated in
either time, frequency or spatial domain to avoid adversarial interference
appears to be a critical shortcoming as the interaction of such lightpaths in
optical domain may result in efficient computing and/or signal processing
operations for saving spectral resources. Inspired by the accelerated
progresses in optical signal processing technologies and the integration of
computing and communications, we introduce in this paper a new architectural
paradigm for future optical networks and highlight how this new architecture
has the potential to shatter the \textit{status quo}. Indeed, our proposal is
centered on exploiting the superposition of in-transit lightpaths at
intermediate nodes to generate more spectrally efficient lightpaths and how to
harness this opportunity from network design perspectives. We present two case
studies featuring optical aggregation and optical XOR encoding to demonstrate
the merit of optical-processing-enabled operation compared to its counterpart,
optical-bypass. Numerical results on realistic network typologies are provided,
revealing that a spectral saving up to $30\%$ could be achieved thanks to
adopting optical-processing network.

Networking and Internet Architecture