Abstract
In this paper we present the theory and the experimental setup used to transfer a standard frequency, to synchronize two clocks linked by an optical fiber. In order to verify the accuracy on frequency transfer over fiber link, we prepared an experiment that allows testing the performance of the setup for a variable set of environmental conditions, namely associated to temperature and vibration variations. The experimental setup shows the fiber optic link between one laboratory, where the standard frequency is generated, and another laboratory, where the equipment for simulating temperatures and vibrations are installed. The standard frequency, traceable to UTC(IPQ), is used to modulate two lasers with different wavelength,, injected in the optical fiber. At the end of the optical fiber the signals will be out of phase due to the inherent chromatic dispersion, which is also dependent on the temperature of the propagation media. Measuring the phase variations, caused by temperature gradients in the fiber, we can compensate the frequency transfer and synchronize the clocks. Evaluating all uncertainty components in this model, allows the metrological characterization of the synchronization and obtain the associated uncertainty of this quantity.
Highlights
Ultra-stable time and frequency sources, primary time standards or even commercial time standards, that contribute to the realization of the Coordinated Universal Time (UTC), have an important role in fundamental physics and in time and frequency metrology, such as clock evaluation, tests in relativity, work in fundamental constants, among others
This paper presents the initial work in this experiment, where temperature variation effect on the frequency transfer accuracy is evaluated
The optical signals from the lasers, after modulation, go to a Wavelength Division Multiplexing (WDM), where they are injected into a 500 m optical fiber
Summary
Ultra-stable time and frequency sources, primary time standards or even commercial time standards, that contribute to the realization of the Coordinated Universal Time (UTC), have an important role in fundamental physics and in time and frequency metrology, such as clock evaluation, tests in relativity, work in fundamental constants, among others. The dissemination in long distances of a standard frequency is achieved using the satellites of the Global Navigation Satellite Systems (GNSS), with a stability in the order of 10-15 in one day This value could be overcome replacing the satellites by optical fiber, being a matter of study in the last decade. This paper presents the initial work in this experiment, where temperature variation effect on the frequency transfer accuracy is evaluated. For this purpose, a fiber link of 500 m in length was mounted on the roof top of the laboratory and the environment conditions were recorded
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