Optic-fiber gravity frequency transfer network

Abstract

<p>According to<strong> </strong>Einstein’s general relativity theory (GRT), a clock at a position with higher potential runs faster than a clock at a position with lower potential. Hence, inversely, one can determine the gravity potential (geopotential) and orthometric height based on precise clocks. If a clock with an accuracy of 10<sup>-18</sup> is used, the geopotential difference between two points can be determined with an accuracy of centimeters level.<strong> </strong>With the rapid development of science and technology, optical clocks achieve 10<sup>-18</sup> stability, which opens up opportunity for scientists to practically determine geopotential as well as orthometric height using optical clocks. One of the challenges of classical geodesic in the long time has been the unification of local hight systems. To complete this task is very difficult because each country has a regional high system. This problem can be solved if using a clock network, which overcomes the weaknesses of the spirit leveling method. Here we provide a formulation to establish a model of a network using optical clocks linked together by optical fibers for the purpose of determining the geopotential and establishing a unified world hight system at centimeter accuracy level. This study is supported by National Natural Science Foundation of China (NSFC) (grant Nos. 41721003, 42030105, 41631072, 41874023, 41804012), and Space Station Project (2020)228.</p><p><strong>Key words:</strong><strong> </strong>GRT, optical clocks network, frequency transfer, geopotential, orthometric height</p>