Free-space micromachined optical-switching technology has emerged as a promising candidate for the large-scale optical cross connects that are needed in next-generation optical-transport networks. Although this technology has demonstrated good optical performance, its ability to expand to the required port-count while remaining within reasonable optical loss budgets has yet to be demonstrated. In this paper, we theoretically analyze the expandability of free-space micromachined optical switches. The chief loss mechanisms-Gaussian-beam divergence and angular misalignment-are analyzed both theoretically and experimentally. We find that micromirror angular repeatability in such a cross connect must be accurate within about 0.1, and show that integrated mechanical structures are capable of achieving this goal. These results in general suggest that free-space micromachined optical-switching technology appears capable of achieving the port-count required by core-transport networks while remaining within cross-office optical-loss budgets.
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