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Distribution of the accurate optical frequency and time via photonic networks in the Czech Republic
Číp, Ondřej ; Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Řeřucha, Šimon ; Hrabina, Jan ; Lešundák, Adam ; Mikel, Břetislav ; Lazar, Josef ; Vojtěch, J. ; Smotlacha, V.
To verify the stability of the frequency of optical clock an intensive research in the transmission of stable frequency via optical fibers is in progress for many years. Interconnection of large cities and metropolitan networks with optical fiber running DWDM allowing to transfer many optical signals in parallel over one fiber at the same time contributes significantly to troubleshoot the problem. Between nodes of ISI Brno and the main center of CESNET there are several dedicated bi-directional channels through the DWDM technology. The first tests are ongoing with the transfer of accurate time, which are using the possibility of bi-directional communication over a single fiber, thus the phase delay including Doppler shift are reflected on the two signals as well. From periodic measurements can subsequently be evaluated daily, weekly and seasonal fluctuations of the delay and after deduction of such data from the measured data a mutual stability of used time normal can be determined. The second technique is a full compensation of phase of the laser wave through active control of phase changes of the wave during its transmission from the ISI to the node of CESNET. At present, a characterization of the behavior of individual system elements, including their commissioning is in progress.
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SMV-2014-27: Optical system for generation of stable optical frequency
Hrabina, Jan ; Číp, Ondřej ; Čížek, Martin ; Hucl, Václav
The work was oriented to design and development of a stable optical frequency laser standard based on ultra-low noise DFB laser. The laser frequency was locked to selected rotational-vibrational transition of isotopic acetylene gas by the method of linear absorption spectroscopy. The research included: design, investigation and development of narrow-linewidth DFB laser source including of development of ultra-low noise power-supply and control electronics; development of an optical setup equipped with opto-fiber output for automatic locking of the laser to selected transition of the ultra-pure acetylene gas, special custom-design absorption cell development, filled with isotopic acetylene, with optical windows equipped with custom-design antireflection coatings; development of control electronics for automatic searching of absorption lines and automatic locking of the laser frequency to this transition; development of control software.
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SMV-2012-29: Absorption cell for laser interferometry
Lazar, Josef ; Hrabina, Jan
The research included investigation of spectral properties of molecular iodine absorption cell intended for ultra-precise laser interferometer referencing to primary standard of length. The cell was based on fused silica glass material which allowed us to reach ultra-pure absorption environment without negative foreign-gas distortion effects (collisional quenching, frequency stability degradation).
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SMV-2012-04: Investigation of optical frequency refences for lasers stabilization in visible spectral range
Lazar, Josef ; Hrabina, Jan
The main aim of this work was oriented towards design and realization of optical frequency references for stabilization of frequency-doubled Nd:YAG lasers with 532 nm wavelength. Research included investigation of absorption references (cells filled with absorption media) technology. The realized cells will serve as references for precise frequency stabilization of laser sources intended for primary metrology of length. Evaluation measurement of realized cells performed by laser induced fluorescence method resulted in reached Stern-Volmer coefficients K0<1 Pa which means the most avaiable purity of absorption media with expected frequency offset of realized laser standard below 1 kHz. Expected reachable relative frequency stability is at level of 3e-14 for integration time of 100 s.
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