Photonics/Optics

Stabilization of Phase of a Sinusoidal Signal Transmitted Over Optical Fiber

Two-way transmissions allow for rapid correction of common reference tones. NASA’s Jet Propulsion Laboratory, Pasadena, California In the process of connecting widely distributed antennas into a coherent array, it is necessary to synchronize the timing of signals at the various locations. This can be accomplished by distributing a common reference signal from a central source, usually over optical fiber. A high-frequency (RF or microwave) tone is a good choice for the reference. One difficulty is that the effective length of the optical fiber changes with temperature and mechanical stress, leading to phase instability in the received tone. This innovation provides a new way to stabilize the phase of the received tone, in spite of variations in the electrical length of the fiber.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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Optical Tapers as White-Light WGM Resonators

Such resonators could be attractive for broad-band optical processing applications. NASA’s Jet Propulsion Laboratory, Pasadena, California A theoretical analysis has revealed that tapered optical waveguides could be useful as white-light whispering-gallery-mode (WGM) optical resonators. The compactness and the fixed-narrow-frequency-band nature of the resonances of prior microdisk and microsphere WGM resonators are advantageous in low-power, fixed-narrow-frequency-band applications. However for optical-processing applications in which there are requirements for power levels higher and/or spectral responses broader than those of prior microdisk and microsphere WGM resonators, white-light WGM resonators in the form of optical tapers would be preferable.

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Moving Machine Vision to 64-Bits

A nearly geometric growth in the data requirements for many machine vision applications is pushing 32-bit processing to its limits. The challenge is not in processing power, however, but in addressing memory buffers as systems fill them with ever-increasing volumes of data. Moving vision systems to 64-bit operation can solve the data challenge, but will require fully-updated hardware and software support.

Posted in: Articles, Features, ptb catchall, Photonics

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Designing 3D Capabilities Into Handheld Displays

For 3D viewing to be convenient on small, portable devices, it must be autostereoscopic, thus eliminating the requirement for 3D “glasses.” The display devices must also provide 2D and 3D capability simultaneously, without sacrificing resolution or color vibrancy.

Posted in: Application Briefs, Applications, ptb catchall, Photonics

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Solar Rejection Filter for Large Telescopes

Filters help avoid thermal loading of the receiver by incident sunlight. NASA’s Jet Propulsion Laboratory, Pasadena, California To reject solar radiation photons at the front aperture for large telescopes, a mosaic of large transmission mode filters is placed in front of the telescope or at the aperture of the dome. Filtering options for effective rejection of sunlight include a smaller filter down-path near the focus of the telescope, and a large-diameter filter located in the front of the main aperture. Two types of large filters are viable: reflectance mode and transmittance mode.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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Free-Space Optical Interconnect Employing VCSEL Diodes

These optical interconnects are applicable for large-capacity interconnection between information-processing equipment. John H. Glenn Research Center, Cleveland, Ohio Sensor signal processing is widely used on aircraft and spacecraft. The scheme employs multiple input/output nodes for data acquisition and CPU (central processing unit) nodes for data processing. To connect 110 nodes and CPU nodes, scalable interconnections such as backplanes are desired because the number of nodes depends on requirements of each mission. An optical backplane consisting of vertical-cavity surface-emitting lasers (VCSELs), VCSEL drivers, photodetectors, and transimpedance amplifiers is the preferred approach since it can handle several hundred megabits per second data throughput. Conventional electrical interconnects severely limit the performance of high-speed networks because of parasitic resistance and capacitance, which limit bandwidth and cause clock signals to skew. Moreover, they cause pin congestion and require large and bulky multi-pin connectors.

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Critical Coupling Between Optical Fibers and WGM Resonators

Recipes address issues of phase matching, aperture matching, and suppressing intermodal coupling. NASA’s Jet Propulsion Laboratory, Pasadena, California Two recipes for ensuring critical coupling between a single-mode optical fiber and a whispering-gallery-mode (WGM) optical resonator have been devised. The recipes provide for phase matching and aperture matching, both of which are necessary for efficient coupling. There is also a provision for suppressing intermodal coupling, which is detrimental because it drains energy from desired modes into undesired ones.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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