Chapter 32 Fiber Based Time and Frequency Synchronization System

摘要

We build up a time and frequency synchronization system via the 80 km urban fiber link between Tsinghua University and the National Institute of Metrology in Changping city. Using the system, we demonstrate simultaneous time and RF signal distribution via optical fibers. The measured frequency dissemination stability of a 9.1 GHz RF signal is 7 × 10~(-15)/s, 5 × 10~(-19)/day, and the measured time synchronization accuracy is 50 ps. Relevant results were published on the Scientific Reports of Nature Publishing Group. To further build up a regional time and frequency network, integrated-designed modules are needed. Its long term continuous running stability and commonality should be tested. In this paper, we introduce the design of the frequency dissemination modules. After 135 days' continuously running, we get the million-second frequency dissemination stability of 8 × 10~(-19)/10~6 s. We also introduce our multiple-access download module, which improves the frequency dissemination scheme from the traditional point to point protocol to be a tree structure protocol, and greatly improves its applicability. Using it, the stability of the receiving frequency signal at arbitrary accessing point is almost 4 orders of magnitude better than that using directly accessing method. All of these modules will be applied to build up the regional time and frequency network.