Optical networking in future-land: from optical-bypass-enabled to optical-processing-enabled paradigm

The evolution of optical networks is enabled by both technological and architectural advances with the goal of reducing operational and capital expenditure per transmitted bit. While the former one stimulates significant system capacity, the latter paves the way for reducing the effective traffic load in network so that more traffic can be carried. Accordingly, optical node architectures have been transitioning from optical-electrical-optical mode to all-optical one, leveraging the scalability and efficiency of fully optical cross-connecting. Conventional wisdom in designing and architecting such switching nodes is nevertheless rooted in the intuition that when an optical channel crossing an intermediate node, it should be maximally isolated from other optical channels in order to avoid interference which may result in degrading signal quality. Such long-established paradigm perceiving the interference of optical channels transiting at the same node as an adversarial factor and should therefore circumvent, albeit reasonable, may leave vast unexplored opportunities. Indeed, the rapid advances in all-optical signal processing technologies has brought opportunities to re-define the optical node architecture by upgrading its naive functionalities from simply add/drop and cross-connecting to proactively mixing optical channels in photonic domain. Specifically, all-optical channel aggregation and de-aggregation technologies have been remarkably advancing in recent years, permitting two or more optical channels at lower bit-rate and/or modulation formats could be all-optically aggregated to a single channel of higher-rate and/or higher-order modulation format and vice versa. Such evolutionary technique is poised to disrupt the existing ecosystem for optical network design and planning, and thus necessitates for a radical change to unlock new potentials. To that end, this paper presents a new paradigm for future optical networks, namely, optical-processing-enabled networks, which are powered by in-network all-optical mixing capability. We introduce the operational principle of optical channel aggregation (de-aggregation) and show how spectrally beneficial such innovative operations could yield by an illustrative example. Next, in order to maximize the aggregation opportunity, we present a mathematical model for optimal routing based on integer linear programming model. Numerical results on the realistic network topology COST239 are provided to quantify the spectral gain of aggregation-aware routing compared to the conventional one.

Automated summary

The evolution of optical networks is driven by technological and architectural advances, aiming to reduce operational and capital expenditure per transmitted bit. Optical node architectures have transitioned from optical-electrical-optical to all-optical, enabling the aggregation of multiple optical channels into a single channel with higher capacity. This paradigm shift unlocks new potentials for optical network design and planning by leveraging all-optical mixing capabilities.