Reducing the Measurement Error of Signal Propagation Delays Using an Optical Reflectometer with Picosecond Resolution

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.