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Proceedings Paper

Simultaneous transfer of optical frequency and time over 306 km long-haul optical fibre link
Author(s): Vaclav Hucl; Martin Cizek; Lenka Pravdova; Simon Rerucha; Jan Hrabina; Bretislav Mikel; Vladimir Smotlacha; Josef Vojtech; Josef Lazar; Ondrej Cip
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Paper Abstract

Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.

Paper Details

Date Published: 23 December 2016
PDF: 6 pages
Proc. SPIE 10142, 20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics, 101420M (23 December 2016); doi: 10.1117/12.2264514
Show Author Affiliations
Vaclav Hucl, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Martin Cizek, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Lenka Pravdova, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Simon Rerucha, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Jan Hrabina, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Bretislav Mikel, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Vladimir Smotlacha, CESNET, z.s.p.o. (Czech Republic)
Josef Vojtech, CESNET, z.s.p.o. (Czech Republic)
Josef Lazar, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)
Ondrej Cip, Institute of Scientific Instruments of the CAS, v.v.i. (Czech Republic)


Published in SPIE Proceedings Vol. 10142:
20th Slovak-Czech-Polish Optical Conference on Wave and Quantum Aspects of Contemporary Optics
Jarmila Müllerová; Dagmar Senderáková; Libor Ladányi; Ľubomír Scholtz, Editor(s)

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