20 research outputs found
Characterization of Optical Frequency Transfer Over 154 km of Aerial Fiber
We present measurements of the frequency transfer stability and analysis of
the noise characteristics of an optical signal propagating over aerial
suspended fiber links up to 153.6 km in length. The measured frequency transfer
stability over these links is on the order of 10^-11 at an integration time of
one second dropping to 10^-12 for integration times longer than 100 s. We show
that wind-loading of the cable spans is the dominant source of short-timescale
noise on the fiber links. We also report an attempt to stabilize the optical
frequency transfer over these aerial links.Comment: 4 pages, submitted to Optics Letter
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
Simple Stabilized Radio-Frequency Transfer with Optical Phase Actuation
We describe and experimentally evaluate a stabilized radio-frequency transfer
technique that employs optical phase sensing and optical phase actuation. This
technique can be achieved by modifying existing stabilized optical frequency
equipment and also exhibits advantages over previous stabilized radio-frequency
transfer techniques in terms of size and complexity. We demonstrate the
stabilized transfer of a 160 MHz signal over an 166 km fiber optical link,
achieving an Allan deviation of 9.7x10^-12 Hz/Hz at 1 s of integration, and
3.9x10^-1414 Hz/Hz at 1000 s. This technique is being considered for
application to the Square Kilometre Array SKA1-low radio telescope.Comment: 4 pages, 2 figures, submitted to Optics Letter
High-precision optical-frequency dissemination on branching optical-fiber networks
We present a technique for the simultaneous dissemination of high-precision optical-frequency signals to multiple independent remote sites on a branching optical-fiber network. The technique corrects optical-fiber length fluctuations at the output of the link, rather than at the input as is conventional. As the transmitted optical signal remains unaltered until it reaches the remote site, it can be transmitted simultaneously to multiple remote sites on an arbitrarily complex branching network. This technique maintains the same servo-loop bandwidth limit as in conventional techniques and is compatible with active telecommunication links.Sascha W. Schediwy, David Gozzard, Kenneth G. H. Baldwin, Brian J. Orr, R. Bruce Warrington, Guido Aben and Andre N. Luite