Multiwavelength opaque optical-crossconnect networks

Over roughly the past decade. the lightwave-research community has converge d upon a broad architectural vision of the emerging national-scale core net work. The vision has been that of a transparent, reconfigurable, wavelength -routed network, in which signals propagate from source to destination thro ugh a sequence of intervening nodes without optoelectronic conversion. Broa d benefits have been envisioned. Despite the spare elegance of this vision, it is steadily becoming clear that due to, the performance, cost, manageme nt, and multivendor-interoperability obstacles attending transparency, the needs of civilian communications will not drive the core network to transpa rency on anything like a national scale. Instead, they will drive it to 'op aque' form, with critical reliance on optoelectronic conversion via transpo nders. Transponder-based network architectures in fact not only offer broad transmission and manageability benefits. They also make networking at the optical layer possible by offering to the nodes managed and performance-eng ineered standard-interface signals that can then be reconfigured for provis ioning and restoration purposes by optical-layer elements. Because of this, the more pressing challenges in lightwave networking are steadily shifting towards the mechanisms that will be used for provisioning and restoration. Among these are mechanisms based on free-space micromachined optical cross connects. We describe recent progress on these new devices and the architec tures into which they fit, and summarize the reasons why they appear to be particularly well-matched to the task of provisioning and restoring opaque multiwavelength core long-haul networks.