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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.

The operating principle of an optical high-resolution reflectometer running in the frequency domain (OFDR reflectometer) is examined. A mathematical model for measuring the parameters of fiber-optic systems using an OFDR reflectometer is presented. The accuracy characteristics of OFDR reflectometers are analyzed and the instrument accuracy is estimated quantitatively. Methods for calibrating OFDR reflectometers based on a distance scale are proposed and equipment for these methods is discussed.

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.

The results of international comparisons in the field of fiber-optic communication and information transmission systems, in particular, for the average power of optical radiation (COOMET PR-S6 and APMP PR-S2 projects) and chromatic dispersion in an optical fiber (EURAMET PR-S3 project), are considered. Data on comparisons as regards the length of the optical fiber (APMP PR-S8), polarization mode dispersion (COOMET PR-S9 project), and wavelength for fiber optics (COOMET PR-S8 project), all of which are now being performed, are presented.

The state and problems involved in achieving the uniformity of measurements in the field of fiber-optic information transmission systems and their components are considered. Possible approaches to the solution of these problems and the basic methods and techniques that have been developed in Russia up to this point are analyzed.