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The possibility of determining the difference in gravitational potentials and orthometric heights in the Earth's field based on measurements of the phase difference of laser radiation in an optical fiber is proposed and investigated in this study. Such a phase difference is attributed to the effect of the gravitational delay of light waves. A block diagram of a measuring complex designed to measure the phase difference of light waves caused by this effect is proposed. The measurements use two coherent light waves from a single laser, each propagating along a separate fiber-optic communication line. The composition of each fiber-optic communication line includes the same coils of a long optical fiber, spaced apart in height. The analysis of the factors influencing the phase relations of waves propagating along two communication lines of the measuring complex is performed. The phase effects of the delay, caused by the influence of the true gravitational field of the Earth, and the influence of the fields of inertial forces and gyroscopic effects due to the Earth's rotation are determined. Methods for suppressing interfering effects are proposed. The achievable errors in measuring the differences in gravitational potentials and corresponding orthometric heights are estimated. With a fiber length in coils of 100 km and a height difference of 100 m, the errors are 0.2 m2/s2 and 2 cm, respectively. The measuring complex under study is called a laser gravipotentiometer. It is an optical analog of the well-known radio-frequency quantum-level unit, but it does not require ultrastable frequency and time standards. The research results of the proposed measuring complex are relevant for the development and improvement of measuring instruments for the parameters of the Earth's gravitational field and a means of the high-precision synchronization of time scales of remote standards. [ABSTRACT FROM AUTHOR]

Problems that arise in the course of attempting to determine and monitor an optical fiber, the medium of transmission of fiber-optic communication systems, are considered. One of the controllable parameters is the cut-off wavelength of a single-mode optical fiber. The cut-off wavelength defines the minimal wavelength of optical radiation at which an optical fiber supports only a single propagated mode, i.e., it functions in a single-mode regime. The problem of determining the cut-off wavelength of an optical fiber used in fiber-optic communication systems is critical, since in a multi-mode regime of operation of an optical fiber its throughput decreases as a consequence of inter-mode dispersion. Methods of measuring the cut-off wavelength of an optical fiber are considered. A model of a new high-precision apparatus for measurement of the cut-off wavelength of an optical fiber is proposed. The measurements are performed on the basis of the reference bending method described in GOST R MEK 60793-1-44-2013. The precision characteristics of the newly developed apparatus are analyzed and a quantitative assessment of the measurement error is obtained. [ABSTRACT FROM AUTHOR]

In this paper, to solve the problems requiring high-precision measurements of signal propagation delays in optical fiber communication lines, the design features of a pulsed optical reflectometer with picosecond resolution designed for measuring the propagation delays of a signal are considered. The error of such a reflectometer is shown to include additive and multiplicative components. A method for determining the additive component of the optical reflectometer error based on measurements of signal delays introduced by individual optical fiber coils and the total delay introduced by serially connected coils is proposed. The measurement requirements are formulated, and the results of the error estimation of the proposed method are presented. To exclude the multiplicative component of the reflectometer error, a method for determining corrections to the reflectometer readings is proposed. The method is based on measuring the propagation delays of the signal in the optical fiber coils, first using reference equipment (installation for measuring the propagation delay of the signal), and then using an optical reflectometer. Then, the differences in the obtained measurement results are calculated. The scheme of installation for measurements of a signal propagation delay in an optical fiber coil is presented, and the operation principle of the installation is described. Moreover, the results of the estimation of the error in determining the corrections to the reflectometer readings by the proposed method are presented. It is shown that excluding the additive and multiplicative components of the error will reduce the error of optical reflectometers to values less than ±100 ps. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]