René P. Salathé

This paper describes the development of a novel medical x-ray imaging system adapted to the needs and constraints of low- and middle-income countries. The developed system is based on an indirect conversion chain: a scintillator plate produces visible light when excited by the x rays, and then, a calibrated multi-camera architecture converts the visible light from the scintillator into a set of digital images. The partial images are then unwarped, enhanced, and stitched through parallel field programmable gate array processing units and specialized software. All the detector components were carefully selected focusing on optimizing the system’s image quality, robustness, cost-effectiveness, and capability to work in harsh tropical environments. With this aim, different customized and commercial components were characterized. The resulting detector can generate high quality medical diagnostic images with detective quantum efficiency levels up to 60% (@2.34 μGy), even under harsh environments, i.e., 60 °C and 98% humidity.

Water sorption of 100% changes the POFBG peak wavelength by 8.1 nm (at 1.54 micron). The temperature sensitivity depends on water content and is -10, -34, and -138 pm/K in dry, wet, and ambient conditions.

We report, to our knowledge, the fastest longitudinal scans in optical low-coherence reflectometry published in literature. The use of a rotating glass cube as an optical path length variator results in a longitudinal scan speed of 42 m/s at a longitudinal scan repetition rate of 1240 Hz. The high-speed reflectometer is operated at the shot-noise limit corresponding to a sensitivity of -78 dB. The scalability of the scanning method with respect to scan speed, scan repetitiveness and scan length is demonstrated by the use of differently sized glass cubes.

Reflection, transmission and loss filters based on fiber Bragg gratings are key components in future wavelength division multiplexing telecommunication networks. A shift of the Bragg wavelength, λ _B , can be achieved by applying a strain or heating the fiber section containing the grating [1]. Here we report on Bragg grating devices that use a thin metallic coating to directly heat the fiber or a piezoelectric coating to strain it. Such integrated tunable filter devices show DC tuning [2-5] and modulation capabilities with promise for enhanced efficiency, reduced size, and low electrical power consumption.