Search

A comparison is made of three device configurations which can be used as tunable filters: a Fabry-Perot etalon used in transmission (FPT), a Fabry-Perot etalon used in reflection (FPR), and a variable birefringence filter used in transmission (VBF). Initial conditions are defined for the achievement of a contrast ratio of 100:1, and the implications of these results on material choice discussed. The effect of nonuniform device thickness on contrast ratio is analyzed for all three cases. Analytic expressions are derived which predict the behavior of the contrast ratio under differing device conditions and which give rule-of-thumb values for the maximum acceptable thickness variation for a given contrast ratio. Using these expressions it is shown that the configuration least sensitive to variations in thickness is the VBF, with the FPT coming second and the FPR last. Experimental studies were carried out on three devices-a piezoelectric tunable air-spaced Fabry-Perot etalon, an electrooptically tunable liquid-crystal Fabry-Perot etalon, and an electrooptically tunable liquid-crystal variable birefringence filter. >

A means of approximating light-traffic performance of RAD (random-arrivals-with-deadlines) systems for four basic preemptive scheduling policies is presented. The design goal is to keep congestion low enough to make the probability of rejection acceptably small. These designs must have low processor utilization. The study analyzes rejection probabilities at utilizations up to 20% and rejection probabilities up to about 10% for various well-known preemptive scheduling disciplines (shortest job first, earliest due date, and least laxity first), as well as first-come, first-served. Good approximations for the rejection probability and for a number of other properties, such as the distribution of time-to-go at rejection, are found. >