11,063 research outputs found
Microwave analog fiber-optic link for use in the deep space network
A novel fiber-optic system with dynamic range of up to 150 dB-Hz for transmission of microwave analog signals is described. The design, analysis, and laboratory evaluations of this system are reported, and potential applications in the NASA/JPL Deep Space Network are discussed
Power system applications of fiber optics
Power system applications of optical systems, primarily using fiber optics, are reviewed. The first section reviews fibers as components of communication systems. The second section deals with fiber sensors for power systems, reviewing the many ways light sources and fibers can be combined to make measurements. Methods of measuring electric field gradient are discussed. Optical data processing is the subject of the third section, which begins by reviewing some widely different examples and concludes by outlining some potential applications in power systems: fault location in transformers, optical switching for light fired thyristors and fault detection based on the inherent symmetry of most power apparatus. The fourth and final section is concerned with using optical fibers to transmit power to electric equipment in a high voltage situation, potentially replacing expensive high voltage low power transformers. JPL has designed small photodiodes specifically for this purpose, and fabricated and tested several samples. This work is described
Cascaded multiplexed optical link on a telecommunication network for frequency dissemination
We demonstrate a cascaded optical link for ultrastable frequency
dissemination comprised of two compensated links of 150 km and a repeater
station. Each link includes 114 km of Internet fiber simultaneously carrying
data traffic through a dense wavelength division multiplexing technology, and
passes through two routing centers of the telecommunication network. The
optical reference signal is inserted in and extracted from the communication
network using bidirectional optical add-drop multiplexers. The repeater station
operates autonomously ensuring noise compensation on the two links and the
ultra-stable signal optical regeneration. The compensated link shows a
fractional frequency instability of 3 \times 10-15 at one second measurement
time and 5 \times 10-20 at 20 hours. This work paves the way to a wide
dissemination of ultra-stable optical clock signals between distant
laboratories via the Internet network
Population-scale organization of cerebellar granule neuron signaling during a visuomotor behavior.
Granule cells at the input layer of the cerebellum comprise over half the neurons in the human brain and are thought to be critical for learning. However, little is known about granule neuron signaling at the population scale during behavior. We used calcium imaging in awake zebrafish during optokinetic behavior to record transgenically identified granule neurons throughout a cerebellar population. A significant fraction of the population was responsive at any given time. In contrast to core precerebellar populations, granule neuron responses were relatively heterogeneous, with variation in the degree of rectification and the balance of positive versus negative changes in activity. Functional correlations were strongest for nearby cells, with weak spatial gradients in the degree of rectification and the average sign of response. These data open a new window upon cerebellar function and suggest granule layer signals represent elementary building blocks under-represented in core sensorimotor pathways, thereby enabling the construction of novel patterns of activity for learning
Quantum information processing with space-division multiplexing optical fibres
The optical fibre is an essential tool for our communication infrastructure
since it is the main transmission channel for optical communications. The
latest major advance in optical fibre technology is spatial division
multiplexing (SDM), where new fibre designs and components establish multiple
co-existing data channels based on light propagation over distinct transverse
optical modes. Simultaneously, there have been many recent developments in the
field of quantum information processing (QIP), with novel protocols and devices
in areas such as computing, communication and metrology. Here, we review recent
works implementing QIP protocols with SDM optical fibres, and discuss new
possibilities for manipulating quantum systems based on this technology.Comment: Originally submitted version. Please see published version for
improved layout, new tables and updated references following review proces
Astronomical verification of a stabilized frequency reference transfer system for the Square Kilometre Array
In order to meet its cutting-edge scientific objectives, the Square Kilometre
Array (SKA) telescope requires high-precision frequency references to be
distributed to each of its antennas. The frequency references are distributed
via fiber-optic links and must be actively stabilized to compensate for
phase-noise imposed on the signals by environmental perturbations on the links.
SKA engineering requirements demand that any proposed frequency reference
distribution system be proved in "astronomical verification" tests. We present
results of the astronomical verification of a stabilized frequency reference
transfer system proposed for SKA-mid. The dual-receiver architecture of the
Australia Telescope Compact Array was exploited to subtract the phase-noise of
the sky signal from the data, allowing the phase-noise of observations
performed using a standard frequency reference, as well as the stabilized
frequency reference transfer system transmitting over 77 km of fiber-optic
cable, to be directly compared. Results are presented for the fractional
frequency stability and phase-drift of the stabilized frequency reference
transfer system for celestial calibrator observations at 5 GHz and 25 GHz.
These observations plus additional laboratory results for the transferred
signal stability over a 166 km metropolitan fiber-optic link are used to show
that the stabilized transfer system under test exceeds all SKA phase-stability
requirements under a broad range of observing conditions. Furthermore, we have
shown that alternative reference dissemination systems that use multiple
synthesizers to supply reference signals to sub-sections of an array may limit
the imaging capability of the telescope.Comment: 12 pages, accepted to The Astronomical Journa
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