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Problems requiring high-precision comparisons and synchronization of time scales (TS) of remote time and frequency standards are analyzed. The prospects of using fiber-optic communication lines to solve these problems are considered. Data on maximum operating distances and accuracy characteristics of TS comparison systems using fiber-optic communication lines are given. It is shown that the range of existing systems is not sufficient for solving a number of relevant problems. A method for amplifying optical signals in an optical fiber using the stimulated Raman scattering (SRS) effect is proposed. The application of the Raman amplifier in telecommunication systems is considered. A method is suggested for using SRS to amplify the optical signals of TS comparison systems. A scheme is proposed for a system of one- and two-way TS comparisons of distant objects using signal amplification based on the SRS effect realized using two-way counter-pumping. The operational principle of the system is described along with the procedure for determining the divergence in the TS of remote objects. The results of estimating the error and range of systems of one- and two-way comparisons of time scales using the Raman amplifier are presented. It is shown that the implementation of Raman amplification in the equipment of such systems will allow their range to be increased by more than three times without reducing system accuracy. [ABSTRACT FROM AUTHOR]

We present the results of investigations of an installation aimed at the transmission of highly stable 1 PPS time signals from the hydrogen time and frequency standard over a 150 km optical fiber communication line with the use of active electronic compensation of time delays. The error (mean-square deviation) of transmission of time signals does not exceed 80 psec on the daily interval of averaging. The installation enables us to guarantee the synchronization of the time scales of remote time and frequency standards included in the primary and secondary standards of time and frequency units. [ABSTRACT FROM AUTHOR]

The features of a multichannel modem that has been developed for transmission of frequency and time reference signals on a fiber-optic communication line with phase instability compensation are examined. Its capabilities for transmitting signals of reference frequencies of active hydrogen masers (such as the Ch1-1003M), we well as a 1 PPS signal with an error of synchronization no greater than 250 psec over 100 km without the use of optical amplifiers are assessed. The results of experimental verification of the metrological characteristics of the modem are given. [ABSTRACT FROM AUTHOR]

The results are presented for the study of an installation for transmission of a highly stable frequency signal with relative instability no greater than 4·10-17 on a fiber-optic communications line over a distance of 150 km. The installation uses external modulation of laser radiation and active electronic compensation of phase noise. The installation makes it possible to provide synchronization or time scale comparison of mutually separated time and frequency standards that are a component of the highest-category time and frequency standards. [ABSTRACT FROM AUTHOR]

A prototype of a system of unilateral and bilateral comparisons of the time scales of distant objects by means of a fiber-optic communication line is described. Results of tests of the prototype and experimental investigations are presented. Errors in the comparison of the time scales and the maximal range of operation of the system are determined. [ABSTRACT FROM AUTHOR]