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Ultra-stable frequency transfer using optical fibers

Preutz, Simon LU (2016) PHYM01 20161
Atomic Physics
Department of Physics
Abstract
A new era of precise time measurement came with the atomic clock. The
technology is vital to navigations systems like GPS and to accurate physical
measurements. Improvements in laser cooling and the development of frequency
combs have combined to enable the construction of clocks using optical reference transitions, which are more stable than the Cesium standard with references in the microwave regime.
Optical fiber networks have been used to transmit stable frequencies and
compare clocks but setups so far use specialized equipment. It would be advantageous to be able to use the existing optical fiber infrastructure.
In this thesis a frequency is stabilized over 80km of fiber in the lab, reaching an instability of 10^(-15) in 7000... (More)
A new era of precise time measurement came with the atomic clock. The
technology is vital to navigations systems like GPS and to accurate physical
measurements. Improvements in laser cooling and the development of frequency
combs have combined to enable the construction of clocks using optical reference transitions, which are more stable than the Cesium standard with references in the microwave regime.
Optical fiber networks have been used to transmit stable frequencies and
compare clocks but setups so far use specialized equipment. It would be advantageous to be able to use the existing optical fiber infrastructure.
In this thesis a frequency is stabilized over 80km of fiber in the lab, reaching an instability of 10^(-15) in 7000 seconds.
With a 1542.14 nm laser, frequency shifted with an acoustic optical modulator, the signal is transmitted along the fiber. A heterodyne detection scheme allows phase information to be received. A phase-locked loop regenerates the signal after the fiber and a PI controller locks the phase to a stable reference.
The maximum noise frequency that can be regulated is affected by the latency
in long fibers so the delays in two pairs of fibers are measured. The 80km
fiber displays a delay of 0.4ms, close to the theoretical calculated value. The 2x60km fiber that goes from SP Technical Research Institute of Sweden in Borås to Chalmers in Gothenburg display a delay of about 1ms, when the calculated value for such a distance of fiber is 0.6ms.
Further on polarization changes in the 80km fiber and the 2x60km fiber
between Boråas and Gothemburg is examined. The 2x60km fiber show regular
variations in time at 200Hz. (Less)
Popular Abstract (Swedish)
I antiken användes solen till att hålla reda på tiden. Teknologiska framsteg gjorde det möjligt att mäta bättre med hjälp av till exempel pendelklockor. Atomklockor upprätthåller dagens definition av sekunden och har möjliggjort bland annat GPS systemet.
Nyare optiska atomklockor är bättre än de som tidigare baserats på Cesium atomen. Men då krävs också bättre tekniker för att sända signalerna som klockorna genererar.
Genom att skicka signalerna genom optiska fiber kan de bli mindre brusiga i jämförelse med dagens utbredda metoder, till exempel satellittransmission. Men det finns fortfarande störningar i fiber som behövs kontrolleras. I detta arbete har sådana störningar detekterats och kompenserats.
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author
Preutz, Simon LU
supervisor
organization
course
PHYM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Optics, optical fibers, stability, time, optical clocks, control.
language
English
id
8879249
date added to LUP
2016-06-23 17:27:40
date last changed
2016-11-15 13:55:54
@misc{8879249,
  abstract     = {A new era of precise time measurement came with the atomic clock. The
technology is vital to navigations systems like GPS and to accurate physical
measurements. Improvements in laser cooling and the development of frequency
combs have combined to enable the construction of clocks using optical reference transitions, which are more stable than the Cesium standard with references in the microwave regime.
Optical fiber networks have been used to transmit stable frequencies and
compare clocks but setups so far use specialized equipment. It would be advantageous to be able to use the existing optical fiber infrastructure.
In this thesis a frequency is stabilized over 80km of fiber in the lab, reaching an instability of 10^(-15) in 7000 seconds.
With a 1542.14 nm laser, frequency shifted with an acoustic optical modulator, the signal is transmitted along the fiber. A heterodyne detection scheme allows phase information to be received. A phase-locked loop regenerates the signal after the fiber and a PI controller locks the phase to a stable reference.
The maximum noise frequency that can be regulated is affected by the latency
in long fibers so the delays in two pairs of fibers are measured. The 80km
fiber displays a delay of 0.4ms, close to the theoretical calculated value. The 2x60km fiber that goes from SP Technical Research Institute of Sweden in Borås to Chalmers in Gothenburg display a delay of about 1ms, when the calculated value for such a distance of fiber is 0.6ms.
Further on polarization changes in the 80km fiber and the 2x60km fiber
between Boråas and Gothemburg is examined. The 2x60km fiber show regular
variations in time at 200Hz.},
  author       = {Preutz, Simon},
  keyword      = {Optics,optical fibers,stability,time,optical clocks,control.},
  language     = {eng},
  note         = {Student Paper},
  title        = {Ultra-stable frequency transfer using optical fibers},
  year         = {2016},
}