1,721,051 research outputs found
Realization of a phase-coherent optical fiber link for the comparison of remote atomic clocks
No full textThis thesis describes the realization of a facility for the high-accuracy frequency dissemination on a continental scale. This project was developed at the Optics division of the Italian National Metrology Institute (INRIM), which is in charge of the realization and operation of the atomic primary frequency standards, of their dissemination, and cooperates to the International Atomic Time generation. Frequency dissemination is now based on satellite techniques; however, the resolution provided by these methods does not cope with the accuracy and stability of newgeneration frequency standards. For instance, more than 10 days of measurement are needed to effectively compare primary standards, and years would be necessary to compare optical clocks via satellite links. On the other hand, it has been demonstrated that systems based on optical fibers can improve the resolution by about 5 orders of magnitude with respect to satellite techniques. This is the reason why many national metrology institutes in Europe are cooperating to develop a network for frequency dissemination and clocks comparisons all across the continent. This technique is based on the transmission of a narrow-linewidth laser along a standard telecom fiber. At the metrological laboratory, the frequency is measured with respect to a frequency standard, while at the remote link end it is extracted and used as a frequency reference. However, temperature changes, acoustic noise, air flows can degrade the stability of the delivered frequency, and must therefore be compensated. This is done through a Doppler cancellation technique, in which the light travels twice in the optical fiber in opposite directions. This is different from what happens in telecom links, which are inherently bidirectional. Dedicated instruments have therefore been developed. This thesis describes the realization of a phase-stabilized optical link between INRIM and the European Laboratory for Non Linear Spectroscopy in Florence, where an optical clock based on Sr atoms was under development at the time of measurements. This clock has been compared to the INRIM primary standard via the optical link. I worked on the realization of the ultrastable laser sources, on the development and characterization of the optical and electronics apparatus, and at the development of the metrological chain for the remote clocks comparison. This thesis also describes some novel techniques which we investigated in the framework of this project, and new applications of optical fiber links. During my studies I spent two months at the Laboratoire National d'Essais-Systemes de Référence Temps-Espace (LNE-SYRTE) in Paris, where I cooperated to the realization of an ultrastable laser source based on an optical delay line. This is reported in the thesis as wel
Avoiding Aliasing in Allan Variance: An Application to Fiber Link Data Analysis
Full text linkOptical fiber links are known as the most performing tools to transfer ultrastable frequency reference signals. However, these signals are affected by phase noise up to bandwidths of several kilohertz and a careful data processing strategy is required to properly estimate the uncertainty. This aspect is often overlooked and a number of approaches have been proposed to implicitly deal with it. Here, we face this issue in terms of aliasing and show how typical tools of signal analysis can be adapted to the evaluation of optical fiber links performance. In this way, it is possible to use the Allan variance (AVAR) as estimator of stability and there is no need to introduce other estimators. The general rules we derive can be extended to all optical links. As an example, we apply this method to the experimental data we obtained on a 1284-km coherent optical link for frequency dissemination, which we realized in Italy
Spectral purity transfer with 5 × 10−17 instability at 1 s using a multibranch Er:fiber frequency comb
Full text linkIn this work we describe the spectral purity transfer between a 1156 nm ultrastable laser and a
1542 nm diode laser by means of an Er:fiber multibranch comb. By using both the master laser
light at 1156 nm and its second-harmonic at 578 nm, together with the 1542 nm slave laser,
we investigate the residual noise between the main comb output, the octave-spanning output,
and a wavelength conversion module including non-linear fibers, second-harmonic generation
crystal and amplifiers. With an ultimate stability of the system at the level of 5E−17 at 1 s
and accuracy of 3E−19, this configuration can sustain spectral transfer at the level required
by the contemporary optical clocks with a simple and robust setup
Sistema per il monitoraggio strutturale di strutture e corrispondente procedimento per il monitoraggio strutturale di strutture
No full textDistributed Raman Amplification for Long-Haul Optical Frequency Dissemination
No full textThis work describes the use of Distributed optical
Raman Amplification for the realization of coherent optical fiber
links for frequency dissemination. The main advantages of this
technique are high gain and feasibility of long fiber spans with a
simple apparatus, without degrading the link stability
Datasets related to publication "Improving the Resolution of Comb-Based Frequency Measurements Using a Track-And-Hold Amplifier"
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LinkO: un’infrastruttura in fibra ottica per confronti remoti di tempo e frequenza ad alta accuratezza
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