High-precision frequency synthesizer for geophysical and biotechnical measurements using laser meter

Abstract

Abstract The paper describes a frequency synthesizer for expanding applications and improving the accuracy of a laser device for measuring ultra-small displacements. Such devices are used to measure Earth’s crust deformations. The specified device allows measuring the increment of lengths based on 25 m in two mutually orthogonal directions. Year-round use of such device in an observatory tunnel inside a mountain, such as, for example, in the Talaya Observatory near Lake Baikal, allows for detailed recording of Earth’s crust deformations by studying the long-term and relatively short-term components of these vibrations. The main use of these results consists in registering a nonstandard change in the deformations, which can serve as a precursor of earthquakes, which causes the highest relevance of these studies. The device contains two lasers tied to each other in frequency with a frequency difference defined from the outside. The binding is carried out by a phase locked loop system, and a reference sample oscillator forms the external frequency. For some applications, the highest accuracy of the frequency tuning of the reference oscillator is required, which is achieved only by using a frequency synthesizer specially designed for this purpose. The paper describes the main circuit solutions for this synthesizer and the results of its use as part of the specified high-precision laser gauge of displacements and deformations of Earth’s crust.