National Repository of Grey Literature 17 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Comparison of frequency stability of laser wavelength standards over photonic networks
Pravdová, Lenka ; Hrabina, Jan ; Čížek, Martin ; Lazar, Josef ; Číp, Ondřej
In our work we present a metrological ampaign in which the stability of the 1540 nm normal laser located at the CESNET workplace in Prague was compared with the wavelength of the supercoherent laser transmitted from the ÚPT workplace in Brno via the 306 km phase-coherent transfer line Brno - Prague. The assembled acetylene standard was transferred to the CESNET workplace and a unit receiving coherent wave from the supercoherent laser stabilized by the optical frequency comb and the H-maser at the ISI workplace in Brno was put into operation. The optical frequency mixer with a photodetector recorded a frequency response between the acetylene optical frequency normal and the supercoherent laser distributed over the photonic network whose stability is given by the H-maser in the 15th order. We have verified that the laser normal meets the requirements of the BIMP Recommendation for the Practical Implementation of the Meter Standard.
Utilization of hydrogen cyanide as an absorption media for laser spectroscopy
Hošek, Martin ; Řeřucha, Šimon ; Pravdová, Lenka ; Čížek, Martin ; Hrabina, Jan ; Číp, Ondřej
The main goal of our investigation is the use of hydrogen cyanide (concretely isotope H13C14N) as absorption medium for realisation of etalon of optical frequency. The advantage of HCN over typically used acetylene (isotopes 13C2H2 and 12C2H2) is the better availability and also the wider absorption spectrum in the 1550 nm wavelength band (telecommunication band). The hyperfine transitions in HCN were investigated in the 90‘, but because of technological limitations the measured data are not as precise as the data for C2H2. We aim on use of more developed methods (saturated absorption spectroscopy, optical frequency lock, beat-note against the optical frequency comb) for the measurement of more precise data of absorption lines of HCN. Our other goals will be to obtain the data enough precise to allow the use of them in Mise en pratique.
Stable optical frequency transfer between ISI and CESNET workplaces
Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Jelínek, Michal ; Hrabina, Jan ; Řeřucha, Šimon ; Mikel, Břetislav ; Lazar, Josef ; Číp, Ondřej ; Smotlacha, V. ; Havliš, O. ; Vojtěch, J.
The contribution reports on the current state of a 306km long experimental line for transfering stable optical frequency from a telecommunication band laser standard between ISI CAS (Brno) and CESNET (Prague). The bidirectional link uses a telecommunication fiber with a dedicated DWDM window of 1540-1546 nm.1540-1546 nm. In the Czech rep. this technology can be utilized currently in two fields: remote comparisons of optical frequency standards and remote callibration of instruments (optical spectral analyzers) in industrial applications that do not allow transporting the device to a specialized laboratory. The stability of the optical frequency transfer was evaluated. A long-term measurement of transport delay was conducted. \n
Phase and group refractive indices of air calculation by fitting\nof phase difference measured using a combination of laser and\nlow-coherence interferometry
Pikálek, Tomáš ; Šarbort, Martin ; Číp, Ondřej ; Pham, Minh Tuan ; Lešundák, Adam ; Pravdová, Lenka ; Buchta, Zdeněk
The air refractive index is an important parameter in interferometric length measurements, since it substantially\naffects the measurement accuracy. We present a refractive index of air measurement method based on monitoring\nthe phase difference between the ambient air and vacuum inside a permanently evacuated double-spaced cell. The cell is placed in one arm of the Michelson interferometer equipped with two light sources—red LED and HeNe laser, while the low-coherence and laser interference signals are measured separately. Both phase and group refractive indices of air can be calculated from the measured signals. The method was experimentally verified by\ncomparing the obtained refractive index values with two different techniques.
Laser standard for precise length and time metrology
Pravdová, Lenka ; Hrabina, Jan ; Čížek, Martin ; Číp, Ondřej
We present the development and the achieved parameters of the telecom C-band optical frequency laser standard. Compact and robust laser system based on ultra-narrow linewidth fiber laser achieves relative frequency stabilities from 9e-13/1s down to 8e-14/256s levels and can serve as stable frequency source for applications of dissipation of precise time and frequency, wavelength calibrations in optical telecommunication or laser interferometry measurement systems.
Frequency stabilized semiconductor laser source for high-resolution interferometry
Řeřucha, Šimon ; Hucl, Václav ; Holá, Miroslava ; Čížek, Martin ; Pham, Minh Tuan ; Pravdová, Lenka ; Lazar, Josef ; Číp, Ondřej
We have assembled an experimental iodine stabilized Distributed Bragg Reflector (DBR) diode based laser system lasing at a wavelength that is in a close proximity to the wavelength of a stabilized He-Ne lasers traditionally used for metrological applications (λ=632.9 nm in vacuum). The aim was to verify whether such a system could be used as an alternative to the He-Ne laser while yielding wider optical frequency tuning range, higher output power and high frequency modulation capability. We have measured the basic characteristics of the laser source and then we have compared the performance of the laser system with that of a traditional frequency stabilized He-Ne laser with a series of experimental arrangements similar to those usually found in laser interferometry and displacement metrology applications. The results indicate that DBR diode laser system provides a good laser source for applications in dimensional (nano)metrology since it provides more output power and advanced tunability options than stabilized He-Ne lasers while maintaining fundamental requirements such as the frequency stability, coherence length and also a defined traceability.\n\n
Optical low dispersion rezonator as length sensor using optical frequency comb
Pravdová, Lenka ; Hucl, Václav ; Lešundák, Adam ; Lazar, Josef ; Číp, Ondřej
Ultra-high precis measurements are domain of lasers interferometers. An optical resonator measuring method using broad spectrum of radiation of an optical frequency comb was designed and experimentally verified at our workplace. The measuring of a quantity – a distance of resonator mirrors – is provided by its conversion to the value of repetition frequency of the pulse laser with mode-locked optical frequency comb. In this paper the comparison of the absolute scale of the optical resonator with an incremental interferometer scale is introduced. The incremental interferometer is implemented for verification of the optical resonator scale. The double beam incremental interferometer is operating at the wavelength of 633 nm and the measuring mirror with piezo actuator is used as one of its reflectors. It turns out that the major error signal is the reflection of the periodic nonlinearity of the incremental resonator scale. The relative resolution of our method reaches values up to 10-9 while maintaining measuring scale.
A pair of phase-synchronized semiconductor lasers for length metrology
Hucl, Václav ; Holá, Miroslava ; Čížek, Martin ; Řeřucha, Šimon ; Pham, Minh Tuan ; Pravdová, Lenka ; Lazar, Josef ; Číp, Ondřej
Semiconductor lasers are increasingly widespread in areas that have been so far dominated by He-Ne lasers. One of such areas is the length metrology, where He-Ne laser operating at 633nm wavelength is still a traditional source of coherent light for laser interferometers distance measuring. The advantages of semiconductor lasers compared with He-Ne laser are greater optical power and a significantly wider range of wavelength tuning without mode jumps. Another advantage is the possibility of frequency modulation of wavelength of the laser diode by directly changing the injection current. The benefits predetermine these laser diodes for the realization of dual-frequency laser sources for heterodyne interferometry. In this case, using a phase-locked loop technique the optical frequency of a laser diode is locked to the optical frequency of another laser diode with a certain frequency offset in the MHz order. In our contribution we present utilization of DBR laser diodes in implementing a dual-frequency laser source for laser interferometry with heterodyne detection.\n
Phase coherent transfer of stable optical frequency for sensory networks
Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Řeřucha, Šimon ; Hrabina, Jan ; Mikel, Břetislav ; Lazar, Josef ; Číp, Ondřej
Using long-haul optical fiber links for phase coherent transfers of stable optical frequencies has been developed by metrological laboratories for at least a decade. Present boom of optical fiber sensors puts a demand on transferring this technology from laboratories to industrial practice. A remote calibration of fiber Bragg grating tensometers can be an example. In our contribution we present a 306 km long fiber link between laboratories of ISI in Brno and CESNET in Prague. The line uses a telecom fiber with a dedicated DWDM window at 1540-1546 nm. The setup implements a phase coherent transfer of a laser standard working with 1540.5nm wavelength and a bi-directional transfer of 1PPS timestamps from radiofrequency standards at the both ends of the line. A long-term measurement of transport delay fluctuations and relative stability of the line are discussed.
SMV-2015-38: Theoretical study of laser source for precise optical frequencies distribution
Hrabina, Jan ; Pravdová, Lenka ; Čížek, Martin ; Pham, Minh Tuan ; Hucl, Václav ; Řeřucha, Šimon ; Číp, Ondřej
The contractual project was oriented to theoretical study of design of ultra-stable laser source for precise optical frequencies long-range distribution through standard telecom optical fiber links. The research included theoretical investigation of possible optical setup arrangements with selection of optimal spectroscopy methods for the laser source frequency stabilization, special care was taken about ultra-high coherence of the laser needed for long-range distribution of the transmitted signals (hundreds of kilometers long links). The stabilization method was selected with respect to metrological traceability of the intended applications. The proposed optical system was compared to up-to-date available laser sources working at other wavelengths and crucial spectral and frequency stability parameters were summarized and compared. Proposed laser spectroscopy method and optical setup was experimentaly evaluated at laboratory environmental conditions and resulted stability/spectral parameters were summarized.

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2 Pravdová, Lucie
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