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Amplifier-free slab-coupled optical waveguide optoelectronic oscillator systems

August 13, 2012
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Journal Article
Author:
William Loh
…
Published in:
Opt. Express, Vol. 20, No. 17, 13 August 2012, pp. 19589-19598.
Topic:
optics
R&D area:

Summary

We demonstrate a free-running 3-GHz slab-coupled optical waveguide (SCOW) optoelectronic oscillator (OEO) with low phase-noise (88 dB down from carrier). The SCOW-OEO uses highpower low-noise SCOW components in a single-loop cavity employing 1.5- km delay. The noise properties of our SCOW external-cavity laser (SCOWECL) and SCOW photodiode (SCOWPD) are characterized and shown to be suitable for generation of high spectral purity microwave tones. Through comparisons made with SCOW-OEO topologies employing amplification, we observe the sidemode levels to be degraded by any amplifiers (optical or RF) introduced within the OEO cavity.
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Summary

We demonstrate a free-running 3-GHz slab-coupled optical waveguide (SCOW) optoelectronic oscillator (OEO) with low phase-noise (88 dB down from carrier). The SCOW-OEO uses highpower low-noise SCOW components in a single-loop cavity employing 1.5- km delay. The noise properties of our SCOW external-cavity laser (SCOWECL) and SCOW photodiode (SCOWPD) are characterized...

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Amplifier-free slab-coupled optical waveguide optoelectronic oscillator systems

Probabilistic reasoning for streaming anomaly detection

August 5, 2012
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Conference Paper
Author:
Kevin M. Carter
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Published in:
2012 SSP: 2012 IEEE Statistical Signal Processing Workshop, 5-8 August 2012, pp. 377-380.
Topic:
intrusion detection & monitoring
R&D area:
R&D group:

Summary

In many applications it is necessary to determine whether an observation from an incoming high-volume data stream matches expectations or is anomalous. A common method for performing this task is to use an Exponentially Weighted Moving Average (EWMA), which smooths out the minor variations of the data stream. While EWMA is efficient at processing high-rate streams, it can be very volatile to abrupt transient changes in the data, losing utility for appropriately detecting anomalies. In this paper we present a probabilistic approach to EWMA which dynamically adapts the weighting based on the observation probability. This results in robustness to data anomalies yet quick adaptability to distributional data shifts.
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Summary

In many applications it is necessary to determine whether an observation from an incoming high-volume data stream matches expectations or is anomalous. A common method for performing this task is to use an Exponentially Weighted Moving Average (EWMA), which smooths out the minor variations of the data stream. While EWMA...

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Probabilistic reasoning for streaming anomaly detection

Toward matched filter optimization for subgraph detection in dynamic networks

August 5, 2012
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Conference Paper
Author:
Benjamin A. Miller
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Published in:
2012 SSP: 2012 IEEE Statistical Signal Processing Workshop, 5-8 August 2012, pp. 113-116.
Topic:
signal processing
R&D area:
R&D group:

Summary

This paper outlines techniques for optimization of filter coefficients in a spectral framework for anomalous subgraph detection. Restricting the scope to the detection of a known signal in i.i.d. noise, the optimal coefficients for maximizing the signal's power are shown to be found via a rank-1 tensor approximation of the subgraph's dynamic topology. While this technique optimizes our power metric, a filter based on average degree is shown in simulation to work nearly as well in terms of power maximization and detection performance, and better separates the signal from the noise in the eigenspace.
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Summary

This paper outlines techniques for optimization of filter coefficients in a spectral framework for anomalous subgraph detection. Restricting the scope to the detection of a known signal in i.i.d. noise, the optimal coefficients for maximizing the signal's power are shown to be found via a rank-1 tensor approximation of the...

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Toward matched filter optimization for subgraph detection in dynamic networks

Multifunction phased array radar (MPAR) spectral usage analysis

July 24, 2012
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Project Report
Author:
John Y. Cho
…
Published in:
MIT Lincoln Laboratory Report ATC-395
Topic:
radar
R&D area:
R&D group:

Summary

This report addressed two technical risks associated with replacing current air traffic and weather surveillance radars with a single type of multifunction phased array radar (MPAR). The first risk is whether radio spectrum usage would increase with the MPAR network and whether the allocated band will have enough spectral space. This question is addressed in two steps. First, single-radar spectrum usage is estimated based on certain assumptions regarding the radar design. Second, locations based on a previous radar placement study are used together with a terrain-dependent propagation model to compute the number of frequency channels needed at each site. We conclude that the overall spectrum usage is likely to increase with MPAR, but that the targeted window in S band will be able to accommodate the occupancy at all sites. The second risk is whether self-interference will limit the ability of the MPAR to operate asynchronously and adaptively on different antenna faces. This question is addressed by employing a simple bistatic ground clutter model to characterize the interference between adjacent faces. We conclude that some interference is unavoidable, but it would likely only occur during times when a transmit beam is at its maximum off-broadside angle (~2% of the time).
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Summary

This report addressed two technical risks associated with replacing current air traffic and weather surveillance radars with a single type of multifunction phased array radar (MPAR). The first risk is whether radio spectrum usage would increase with the MPAR network and whether the allocated band will have enough spectral space...

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Multifunction phased array radar (MPAR) spectral usage analysis

Nanosatellites for Earth environmental monitoring: the MicroMAS project

July 23, 2012
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Conference Paper
Author:
William J. Blackwell
…
Published in:
IGARSS 2012, Int. Geoscience and Remote Sensing Symp., 22-27 July 2012, pp. 206-9.
Topic:
satellites
R&D area:
R&D group:

Summary

The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a 3U cubesat (34x10x10 cm, 4.5 kg) hosting a passive microwave spectrometer operating near the 118.75-GHz oxygen absorption line. The focus of the first MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit at approximately 500-km altitude. A MicroMAS flight unit is currently being developed in anticipation of a 2014 launch. A parabolic reflector is mechanically rotated as the spacecraft orbits the earth, thus directing a cross-track scanned beam with FWHM beamwidth of 2.4-degrees, yielding an approximately 20-km diameter footprint at nadir incidence from a nominal altitude of 500 km. Radiometric calibration is carried out using observations of cold space, the earth?s limb, and an internal noise diode that is weakly coupled through the RF front-end electronics. A key technology feature is the development of an ultra-compact intermediate frequency processor module for channelization, detection, and A-to-D conversion. The antenna system and RF front-end electronics are highly integrated and miniaturized. A MicroMAS-2 mission is currently being planned using a multiband spectrometer operating near 118 and 183 GHz in a sunsynchronous orbit of approximately 800-km altitude. A HyMAS- 1 (Hyperspectral Microwave Atmospheric Satellite) mission with approximately 50 channels near 118 and 183 GHz is also being planned. In this paper, the mission concept of operations will be discussed, the radiometer payload will be described, and the spacecraft subsystems (avionics, power, communications, attitude determination and control, and mechanical structures) will be summarized.
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Summary

The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a 3U cubesat (34x10x10 cm, 4.5 kg) hosting a passive microwave spectrometer operating near the 118.75-GHz oxygen absorption line. The focus of the first MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit at approximately...

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Nanosatellites for Earth environmental monitoring: the MicroMAS project

A preliminary investigation of Tower Flight Data Manager safety benefits

July 21, 2012
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Conference Paper
Author:
Amy L. Alexander
…
Published in:
Applied Human Factors and Ergonomics Conf., 21 July 2012.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Improvements to current air traffic management technologies and techniques are required to move toward the next generation air transportation system (NextGen). The Tower Flight Data Manager (TFDM) is a prototype air traffic control system consisting of the: (1) Flight Data Manager (FDM) facilitating interaction with electronic flight data, (2) Tower Information Display System (TIDS) providing enhanced surveillance information, and (3) Supervisor Display providing a means for front line managers and traffic management coordinators to interact with strategic and tactical planning and decision support tools. Given that TFDM aims to enable safe and efficient operations under NextGen, it is critical to analyze potential safety impacts and determine what types of real-world safety issues can be prevented or mitigated by TFDM. With this goal in mind, we reviewed 560 National Transportation Safety Board (NTSB) and Aviation Safety Reporting System (ASRS) reports focusing on commercial air carrier operations over a five year period. Over 100 reports were deemed relevant to TFDM and further analyzed to determine the likelihood that these safety-related events could have been mitigated or prevented by the key TFDM capabilities outlined above. A systematic method for generating probabilistic estimates of benefits for a technology not yet deployed was utilized to produce effectiveness ratings for the various TFDM components.
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Summary

Improvements to current air traffic management technologies and techniques are required to move toward the next generation air transportation system (NextGen). The Tower Flight Data Manager (TFDM) is a prototype air traffic control system consisting of the: (1) Flight Data Manager (FDM) facilitating interaction with electronic flight data, (2) Tower...

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A preliminary investigation of Tower Flight Data Manager safety benefits

Data-driven evaluation of a flight re-route air traffic management decision-support tool

July 21, 2012
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Conference Paper
Author:
Lianna M. Hall
…
Published in:
Applied Human Factors and Ergonomics Conf., 21 July 2012.
Topic:
decision support
R&D area:
R&D group:

Summary

Air traffic delays in the U.S. are problematic and often attributable to convective (thunderstorms) weather. Air traffic management is complex, dynamic, and influenced by many factors such as projected high volume of departures and uncertain forecast convective weather at airports and in the airspace. To support the complexities of making a re-route decision, which is one solution to mitigate airspace congestion, a display integrating convective weather information with departure demand predictions was prototyped jointly by MIT Lincoln Laboratory and the MITRE Corporation. The tool was deployed to twelve air traffic facilities involved in handling New York area flights for operational evaluation during the summer of 2011. Field observations, data mining and analyses were conducted under both fair and convective weather conditions. The system performance metrics chosen to evaluate the tool's effectiveness in supporting re-route decisions include predicted wheels-off error, predicted wheels-off forecast spread, and hourly departure fix demand forecast spread. The wheels-off prediction errors were near zero for half the flights across all days, but the highest 10% errors exceeded 30 minutes on convective weather days. The wheels-off forecast spread exceeded 30 minutes for 25% of forecasts on convective weather days. The hourly departure demand forecast spread was 9 flights or less for 50% of departures across all days except one. Six out of the seven days having the highest hourly departure demand forecast spreads occurred in the presence of long-lived weather impacts.
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Summary

Air traffic delays in the U.S. are problematic and often attributable to convective (thunderstorms) weather. Air traffic management is complex, dynamic, and influenced by many factors such as projected high volume of departures and uncertain forecast convective weather at airports and in the airspace. To support the complexities of making...

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Data-driven evaluation of a flight re-route air traffic management decision-support tool

Loading of a surface-electrode ion trap from a remote, precooled source

July 20, 2012
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Journal Article
Author:
Jeremy M. Sage
…
Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 86, No. 1, 20 July 2012, 013417.
Topic:
quantum
R&D area:
R&D group:

Summary

We demonstrate loading of ions into a surface-electrode trap (SET) from a remote, laser-cooled source of neutral atoms. We first cool and load ~10^6 neutral 88Sr atoms into a magneto-optical trap from an oven that has no line of sight with the SET. The cold atoms are then pushed with a resonant laser into the trap region where they are subsequently photoionized and trapped in an SET operated at a cryogenic temperature of 4.6 K. We present studies of the loading process and show that our technique achieves ion loading into a shallow (15 meV depth) trap at rates as high as 125 ions/s while drastically reducing the amount of metal deposition on the trap surface as compared with direct loading from a hot vapor. Furthermore, we note that due to multiple stages of isotopic filtering in our loading process, this technique has the potential for enhanced isotopic selectivity over other loading methods. Rapid loading from a clean, isotopically pure, and precooled source may enable scalable quantum-information processing with trapped ions in large, low-depth surface-trap arrays that are not amenable to loading from a hot atomic beam.
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Summary

We demonstrate loading of ions into a surface-electrode trap (SET) from a remote, laser-cooled source of neutral atoms. We first cool and load ~10^6 neutral 88Sr atoms into a magneto-optical trap from an oven that has no line of sight with the SET. The cold atoms are then pushed with...

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Loading of a surface-electrode ion trap from a remote, precooled source

Ring array antenna with optimized beamformer for simultaneous transmit and receive

July 8, 2012
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Conference Paper
Author:
Kenneth E. Kolodziej
…
Published in:
2012 IEEE Antennas and Propagation Society International Symp. and USNC/URSI National Radio Sci. Mtg., 8-14 July 2012.
Topic:
antennas
R&D area:
R&D group:

Summary

In order to avoid self-interference, Simultaneous Transmit And Receive (STAR) systems require low mutual coupling between their respective transmit and receive antennas. This paper discusses the development of an 8-element transmit ring array antenna on a circular ground plane with a raised receive element. When combined with a beamformer that supplies linear progressive phase shifts to the array with opposing elements phased 180-degrees apart, the receive and transmit antennas are measured to exhibit 55 dB of isolation and omni-directional patterns in the 2.4 to 2.5 GHz band.
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Summary

In order to avoid self-interference, Simultaneous Transmit And Receive (STAR) systems require low mutual coupling between their respective transmit and receive antennas. This paper discusses the development of an 8-element transmit ring array antenna on a circular ground plane with a raised receive element. When combined with a beamformer that...

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Ring array antenna with optimized beamformer for simultaneous transmit and receive

Measurement of the third-order nonlinear optical susceptibility chi^(3) for the 1002-cm^-1 mode of benzenethiol using coherent anti-Stokes Raman scattering with continuous-wave diode lasers

July 1, 2012
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
J. Raman Spectrosc., Vol. 43, No. 7, July 2012, pp. 911-916.
Topic:
lasers
R&D area:
R&D group:

Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1 s^2 were measured for the xxxx, xxyy, and xyyx components of |3x^(3)|, respectively. We have calculated these quantities using a microscopic model, reproducing the same qualitative trend. The Raman cross-section sigma RS for the 1002-cm^-1 mode of neat benzenethiol has been determined to be 3.1±0.6 X 10^-29 cm^2 per molecule. The polarization of the anti-Stokes Raman scattering was found to be parallel to that of the pump laser, which implies negligible depolarization. The Raman linewidth (full-width at half-maximum) Gamma was determined to be 2.4±0.3 cm^-1 using normal Stokes Raman scattering. The measured values of sigma RS and Gamma yield a value of 2.1±0.4 X 10^-12 cmg^-1 s^2 for the resonant component of 3x^(3). A value of 1.9±0.9 X 10^-12 cmg^-1 s^2 has been deduced for the nonresonant component of 3x^(3).
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Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1...

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Measurement of the third-order nonlinear optical susceptibility chi^(3) for the 1002-cm^-1 mode of benzenethiol using coherent anti-Stokes Raman scattering with continuous-wave diode lasers
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