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Search Publications by: Paul A. Williams (Fed)

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Displaying 51 - 75 of 119

Long distance frequency transfer through an optical carrier

August 2, 2009
Author(s)
Paul A. Williams
Fiber optic networks are an attractive means for the remote distribution of highly stable frequencies from optical clocks. The highest performance is achieved by use of the frequency of the optical carrier itself as the transfer frequency. We will review

Word-synchronous linear optical sampling of 40 Gb/s QPSK signals

March 20, 2009
Author(s)
Tasshi Dennis, Paul A. Williams, Ian R. Coddington, Nathan R. Newbury
We demonstrate word-synchronous measurements of QPSK format 40 Gb/s PRBS signals using linear optical sampling with a precision time-base, which allows us to average waveforms and distinguish between signal distortion and noise in eye diagrams.

Coherent measurements with fiber-laser frequency combs

February 2, 2009
Author(s)
Nathan R. Newbury, Ian R. Coddington, Tasshi Dennis, William C. Swann, Paul A. Williams
The coherent and broad spectral output of fiber-laser frequency combs can be exploited for a variety of high-resolution measurements outside of conventional frequency metrology. We will discuss recent measurements in spectroscopy, ranging, and

Bilateral comparison on polarization mode dispersion between KRISS and NIST

October 10, 2008
Author(s)
Seung-kwan Kim, Paul A. Williams
We made an international bilateral comparison on polarization mode dispersion between KRISS and NIST. Three mode-coupled artifacts were used for comparison. The average values of differential group delay measured by both institutes agreed well within their

High-stability transfer of an optical frequency over long fiber-optic links

August 1, 2008
Author(s)
Paul A. Williams, William C. Swann, Nathan R. Newbury
We present theoretical predictions and experimental measurements for the achievable phase noise, timing jitter, and frequency stability in the coherent transport of an optical frequency over a fiber-optic link. Both technical and fundamental limitations to

Practical performance limits on optical frequency transfer over fiber optic links

May 4, 2008
Author(s)
Paul A. Williams, William C. Swann, Nathan R. Newbury
We present theory and experiment quantifying the limitations to stable transport of optical frequencies over optical fiber. These are fundamental fiber noise, propagation delay, bidirectional propagation and system noise in the measurement interferometers.

Fiber lasers for frequency standards in optical communications

February 24, 2008
Author(s)
Nathan R. Newbury, William C. Swann, Ian R. Coddington, Paul A. Williams
Optical light with millihertz relative frequency stabilities and subfemtosecond timing jitter can be produced from stabilized cw or mode-locked fiber lasers. We will discuss the generation, fiber-optic distribution and some applications of these coherent

Coherent transfer of an optical carrier over 251 km

October 15, 2007
Author(s)
Nathan R. Newbury, Paul A. Williams, William C. Swann
We transfer of an optical frequency over 251 km of optical fiber with a residual instability of 6×10 -19 at 100 s. This instability and the associated timing jitter are limited fundamentally by the noise on the optical fiber and link length. We give a

Coherent fiber-based frequency combs and cw lasers at 1550 nm

August 26, 2007
Author(s)
Nathan R. Newbury, William C. Swann, Ian R. Coddington, Paul A. Williams
Coherent optical sources in the 1550 nm region of the spectrum have a number of applications in frequency metrology, stable frequency transfer, precision spectroscopy and remote sensing. A narrow-linewidth (~ 1 Hz) single-frequency source can be generated

Biophotonic tools in cell and tissue diagnostics

May 1, 2007
Author(s)
Michael Brownstein, Robert A. Hoffman, Richard Levenson, Thomas E. Milner, Marla L. Dowell, Paul A. Williams, Grady S. White, Adolfas Gaigalas, Jeeseong C. Hwang
In order to maintain the rapid advance of biophotonics in the U.S. and to enhance our competitiveness worldwide, key measurement tools must be in place. As a part of a wide-reaching effort to improve the U.S. technology base, the National Institute of

High Sensitivity Measurements of the Scattering Dispersion of Phantoms using Spectral Domain Optical Coherence Tomography

January 26, 2006
Author(s)
Shellee D. Dyer, Tasshi Dennis, Paul A. Williams, Lara Roberson, Shelley M. Etzel, Robert J. Espejo, Thomas Germer, T E. Milner
We demonstrate a novel technique to determine the size of Mie scatterers with high sensitivity. Our technique is based on spectral domain optical coherence tomography measurements of the dispersion that is induced by the scattering process. We use both Mie

Noise model for polarization-sensitive Optical Coherence Tomography

January 26, 2006
Author(s)
Paul A. Williams, Nate J. Kemp, David Ives, Jesung Park, Dwelle C. Jordan, H. Grady Rylander, Thomas E. Milner
Characterizing and quantifying noise sources in birefringence imaging with polarization-sensitive optical coherence tomography (PS-OCT) is necessary for the development of efficient noise reduction techniques for real-time clinical PS-OCT imaging. We

Fundamental limits in fiber Bragg grating peak wavelength measurements

January 1, 2005
Author(s)
Shellee D. Dyer, Paul A. Williams, Robert J. Espejo, Jonathan Kofler, Shelley M. Etzel
We discuss the fundamental limits of fiber Bragg grating (FBG) wavelength metrology. High-accuracy wavelength measurements are critical for FBG strain sensors, because wavelength measurement uncertainties even as small as 1 pm lead to an uncertainty of
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