Photonics

Opto-Electronic Oscillator Using Suppressed Phase Modulation

Phase noise would be much lower than in prior OEOs. NASA’s Jet Propulsion Laboratory, Pasadena, California A proposed opto-electronic oscillator (OEO) would generate a microwave signal having degrees of frequency stability and spectral purity greater than those achieved in prior OEOs. The design of this system provides for reduction of noise levels (including the level of phase noise in the final output microwave signal) to below some of the fundamental limits of the prior OEOs while retaining the advantages of photonic generation of microwaves. Whereas prior OEOs utilize optical amplitude modulation, this system would utilize a combination of optical phase modulation and suppression thereof. The design promises to afford, in the opto-electronic domain, the low-noise advantages of suppression of carrier signals in all-electronic microwave oscillators.

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Alternative Controller for a Fiber-Optic Switch

This controller communicates via a serial instead of a parallel port. NASA’s Jet Propulsion Laboratory, Pasadena, California The figure is a simplified diagram of a relatively inexpensive controller for a DiCon VX (or equivalent) fiber-optic switch — an electromechanically actuated switch for optically connecting one or two input optical fibers to any of a number of output optical fibers. DiCon VX fiber-optic switches are used primarily in research and development in the telecommunication industry. This controller can control any such switch having up to 32 output channels.

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Hardware and Software for Air-to-Air Schlieren Imaging

Accurate positioning and camera control are necessary for success in schlieren imaging. Software and electronic hardware are being developed to provide cockpit guidance and camera control for an air-to-air schlieren photography system that is to be used to take high-resolution pictures of shock waves generated by a full-scale airplane (see Figure 1). For success in schlieren imaging, it will be necessary to position two airplanes — an observing airplane and the one generating the shock waves — precisely along a line of sight to the Sun, which will be used for illumination. The shock-wave-generating airplane will fly at supersonic speed, while the observing airplane will have to fly at a much lower speed of 250 knots (129 m/s).

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Portable Airborne Multispectral-Imaging System

This system can be put into operation almost anywhere on short notice. A portable instrumentation system that includes an airborne and a ground-based subsystem acquires multispectral image data over swaths of terrain ranging in width from about 1/2 to 1 km. The system was developed especially for use in surveying coastal environments; it is also well suited for performing remote sensing in connection with agriculture, aquaculture, forestry, environmental decontamination, and general environmental monitoring. The system can be stowed in two suitcase-size containers that can be transported as check-in luggage on a commercial airline. Once the system has been delivered to its destination and unstowed, the airborne subsystem can be launched over unprepared terrain and controlled from the ground-based subsystem, which can be operated from a minivan or a similarly sized vehicle.

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Camera Images Hydrogen Fires in Three Wavelength Bands

The camera filters and processing can be customized for other multispectral imaging applications. A special-purpose multispectral video camera has been designed to provide an enhanced capability for viewing hydrogen fires. Hydrogen fires do not emit sufficient visible light to be seen by the unaided human eye, but they do emit strongly at other wavelengths — especially in the infrared and near-infrared portions of the spectrum. Therefore, like some other video cameras developed previously for the same purpose, this camera is designed to respond to infrared light emitted by hot water molecules in hydrogen flames. Going beyond previous designs, this camera provides a combination of imaging in three wavelength bands and processing of the three images, all for the purposes of (1) reducing spurious responses to background light and solar radiation, and (2) synthesizing an image of a hydrogen flame overlaid on an ordinary visible-light image of the scene that contains the flame.

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High-Performance Processor of Hyperspectral Images

Efficient algorithms analyze pixel spectra to estimate abundances of materials. The Remote Sensing Hyperspectral Engine (RSHE) is a special-purpose, portable computer that performs high-performance processing of hyperspectral image data collected by a remote-sensing optoelectronic apparatus. Typically, the remote-sensing apparatus is airborne or spaceborne, the images are of terrain, and the purpose of collecting and analyzing the image data is to estimate the spatially varying abundances of materials of interest. Remote-sensing applications in which the RSHE could prove beneficial include assessment of crops, exploration for minerals, identification of military targets, urban-planning studies, environmental assessment, and large-area search-and- rescue operations.

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Hand-Held Optoelectronic Particulate Monitors

Data on concentrations and sizes are obtained from diffraction of light. Optoelectronic instruments are being developed for use in measuring the concentrations and sizes of microscopic particles suspended in air. The instruments could be used, for example, to detect smoke, explosive dust in grain elevators, or toxic dusts in industrial buildings. Like some older, laboratory-bench-style particulate monitors, these instruments are based on diffraction of light by particles. However, these instruments are much smaller; exploiting recent advances in optics, electronics, and packaging, they are miniaturized into compact, hand-held units.

Posted in: Tech Briefs, ptb catchall, Physical Sciences, Photonics, Briefs, TSP

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