13 research outputs found
Long-distance frequency transfer over an urban fiber link using optical phase stabilization
We transferred the frequency of an ultra-stable laser over 86 km of urban
fiber. The link is composed of two cascaded 43-km fibers connecting two
laboratories, LNE-SYRTE and LPL in Paris area. In an effort to realistically
demonstrate a link of 172 km without using spooled fiber extensions, we
implemented a recirculation loop to double the length of the urban fiber link.
The link is fed with a 1542-nm cavity stabilized fiber laser having a sub-Hz
linewidth. The fiber-induced phase noise is measured and cancelled with an all
fiber-based interferometer using commercial off the shelf pigtailed
telecommunication components. The compensated link shows an Allan deviation of
a few 10-16 at one second and a few 10-19 at 10,000 seconds
High-resolution microwave frequency dissemination on an 86-km urban optical link
We report the first demonstration of a long-distance ultra stable frequency
dissemination in the microwave range. A 9.15 GHz signal is transferred through
a 86-km urban optical link with a fractional frequency stability of 1.3x10-15
at 1 s integration time and below 10-18 at one day. The optical link phase
noise compensation is performed with a round-trip method. To achieve such a
result we implement light polarisation scrambling and dispersion compensation.
This link outperforms all the previous radiofrequency links and compares well
with recently demonstrated full optical links.Comment: 11 pages, 5 figure
86-km optical link with a resolution of 2.10-18 for RF frequency transfer
RF frequency transfer over an urban 86 km fibre has been demonstrated with a
resolution of 2.10-18 at one day measuring time using an optical compensator.
This result is obtained with a reference carrier frequency of 1 GHz, and a
rapid scrambling of the polarisation state of the input light in order to
reduce the sensitivity to the polarisation mode dispersion in the fibre. The
limitation due to the fibre chromatic dispersion associated with the laser
frequency fluctuations is highlighted and analyzed. A preliminary test of an
extended compensated link over 186 km using optical amplifiers gives a
resolution below 10-17 at 1 day
Cold atom Clocks and Applications
This paper describes advances in microwave frequency standards using
laser-cooled atoms at BNM-SYRTE. First, recent improvements of the Cs
and Rb atomic fountains are described. Thanks to the routine use of a
cryogenic sapphire oscillator as an ultra-stable local frequency reference, a
fountain frequency instability of where
is the measurement time in seconds is measured. The second advance is a
powerful method to control the frequency shift due to cold collisions. These
two advances lead to a frequency stability of at 7\times 10^{-16}^{87}^{133}$Cs fountains.
Finally we give an update on the cold atom space clock PHARAO developed in
collaboration with CNES. This clock is one of the main instruments of the
ACES/ESA mission which is scheduled to fly on board the International Space
Station in 2008, enabling a new generation of relativity tests.Comment: 30 pages, 11 figure
Phase- coherent comparison of two optical frequency standards over 146 km using a telecommunication fiber link
We have explored the performance of two "dark fibers" of a commercial
telecommunication fiber link for a remote comparison of optical clocks. The two
fibers, linking the Leibniz University of Hanover (LUH) with the
Physi-kalisch-Technische Bundesanstalt (PTB) in Braunschweig, are connected in
Hanover to form a total fiber length of 146 km. At PTB the performance of an
optical frequency standard operating at 456 THz was imprinted to a cw trans-fer
laser at 194 THz, and its frequency was transmitted over the fiber. In order to
detect and compensate phase noise related to the optical fiber link we have
built a low-noise optical fiber interferometer and investigated noise sources
that affect the overall performance of the optical link. The frequency
stability at the remote end has been measured using the clock laser of PTB's
Yb+ frequency standard operating at 344 THz. We show that the frequency of a
frequency-stabilized fiber laser can be transmitted over a total fiber length
of 146 km with a relative frequency uncertainty below 1E-19, and short term
frequency instability given by the fractional Allan deviation of
sy(t)=3.3E-15/(t/s)
High resolution frequency standard dissemination via optical fiber metropolitan network
International audienceWe present in this article results on a new dissemination system of an ultrastable reference signal at 100 MHz on a standard fiber network. The 100 MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solutions are suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100 km, with a relative frequency resolution of 10 −14 at 1 s integration time and 10 −17 for 1 day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks
Design and realization of a flywheel oscillator for advanced time and frequency metrology
International audienceIn this article, we describe a new frequency synthesis system that includes a low phase noise cryogenic sapphire oscillator (CSO) and an H-maser to provide metrological low-noise signals to time and frequency experiments. Implementing this system as a local oscillator for a Cs cold atom fountain, a record frequency stability of 1.6×10-14tau-1/2 is obtained
Carrier generation using a dual-frequency distributed feedback waveguide laser for phased array antenna (PAA)
Abstract Background Carrier generation based on optical heterodyning techniques where a beat signal is generated from the mixing of two light sources can be interesting solution due to ease on tunability. The free running heterodyning scheme benefits with a very wide tuning capability and the generated carrier can be freely adjusted. However, the drawbacks come in the form of frequency stability. Heterodyning of two optical frequencies coming from a single laser cavity has shown its potential on improvement of frequency stability. Methods The impact of the laser parameters (i.e., optical power and linewidth) on the quality of the generated carrier (i.e., phase/frequency stability and carrier-to-noise ratio) is analyzed for a 25×64 elements PAA system. An optically generated carrier signal using a dual-frequency distributed feedback waveguide laser in ytterbium doped aluminum oxide (Al2O3:Yb3+) is analyzed and experimentally demonstrated in this paper. The carrier signal is used for downconversion of the signal received from a phased array antenna (PAA) of a DVB-S (Digital Video Broadcasting-Satellite) system. Results An optical frequency locked loop (OFLL) to stabilize the generated carrier is implemented which results in a microwave frequency at ∼14 GHz with a phase noise of -75 dBc/Hz at 1 MHz offset from the center frequency and gives a loop settling time of 12 μs. By using the proposed OFLL, the long term and the short term frequency stability of the generated carrier has an Allan deviation of more than 1×10−10 for an averaging time of 1000 s and a standard deviation of 39.4 kHz, respectively. The lasers linewidth should be in the order of tens of Hz, with a maximum relative intensity noise (RIN) of -107 dB/Hz and a minimum optical power of 0.94 mW. Conclusions The optical carrier generation by OFLL using a DFL to comply with the requirements of the standard carrier used in commercial LNBs has been investigated. The detailed analysis of the OFLL scheme is presented. Specifications requirement on carrier power, linewidth and relative intensity noise of the optically generated carrier have been addressed. The optical carrier generation is experimentally demonstrated and the requirements on CNR have been determined by measuring the noise floor and the optical carrier power. The measured values are compared with the calculated values and found to be very close