Current and future flexible wavelength routing cross-connects

Existing and evolving telecommunication services rely upon transport infrastructure for their carriage, including that provided by Wavelength Division Multiplexing (WDM) based networking. In order to maximize reach in the photonic domain, thus limiting the total number of costly and power-greedy optoelectronic regenerators required for reliable transport, optimization of Wavelength Routing Cross-Connects (WRXC) properties is essential. There are several relevant WRXC properties including low physical impact on optical channels, enabling usage of advanced modulation formats with high spectral efficiency, support for flexible wavelength allocation as well as multi-directional, colorless, and contentionless insertion/extraction of traffic, resilience against failures, and automatic light path setup. Other factors supporting WRXC deployment involve fair initial cost, compactness and modularity, and scalability to high connectivity and to large add/drop capacity. Some of these features are "must have" whereas others are "nice to have". This paper reviews the primary trends affecting current and future WRXC evolution considering such functionalities, as well as the corresponding trade-offs.