The induced optical phase change produced when a static pressure is applied to the test arm of an interferometric single-mode fiber optic hydrophone is examined in terms of hydrostatic and radial mechanical models. The expressions for the models are given in terms of a 3-D solution to the equations of elastostatics for multilayered cylinders. The induced phase change is calculated using both models for various values of the diameter and elastic properties of fiber jacket materials. It is shown that the phase change predicted from the 3-D approach for each model can be adequately described in terms of much simpler 2-D plane strain models. Calculations show that the hydrophone sensitivity of a jacketed fiber is amplified compared with a bare fiber. The largest increase in sensitivity is predicted with the radial model. Calculated sensitivities for the hydrostatic model are shown to correspond closely in value with static pressure sensitivity measurements for the experimental arrangement used here.

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Automated pedestrian detection systems provide the means to detect the presence of pedestrians as they approach the curb prior to crossing the street, and then these systems call the Walk signal without any action required on the part of the pedestrians. These detectors can also extend the clearance interval in order to allow slower persons to finish crossing. Whether automated pedestrian detectors, when used in conjunction with standard pedestrian push buttons, would result in fewer overall pedestrian-vehicle conflicts and fewer inappropriate crossings (i.e., pedestrians’ beginning to cross during a Don’t Walk signal) was evaluated. Before and after video data were collected at intersection locations in Los Angeles, California (infrared and microwave), Phoenix, Arizona (microwave), and Rochester, New York (microwave). The results indicated a significant reduction in vehicle-pedestrian conflicts, as well as a reduction in the number of pedestrians beginning to cross during the Don’t Walk signal. The differences between microwave and infrared detectors were not significant. Detailed field testing of the microwave equipment in Phoenix revealed that fine-tuning of the detection zone is still needed in order to reduce the number of false calls and missed calls.

Elastic and elastooptic coefficients used to predict acoustic response sensitivity for two single-mode optical fibers have been determined from Brillouin scattering measurements. These measurements were made on two ITT single-mode fiber preforms currently of interest in the fabrication of fiber-optic acoustic sensors. Previous predictions of acoustic sensitivity assumed the optical fiber waveguides as homogeneous fused silica cylinders. It was found that this assumption introduces no more than a 5% error in the pressure sensitivity for a low numerical aperture (N.A.) fiber and a 30% error for a high N.A. fiber.