Transition of optical fiber delay coefficient under the action of fiber coating at low temperature

This paper shares a conjecture that in a specific low temperature region, the fiber delay coefficient with temperature exists a transition process. In the specific low temperature region, the soft and hard state of the optical fiber coating changes with temperature, which affects the strain effect of the coating on fiber core. At normal temperature, the soft inner coating layer has no strain on fiber core, while at ultra-low temperature, the inner plastic coating becomes frozen and hard. The frozen coating exerts strain on fiber core, resulting in additional length change and the increase of fiber delay coefficient. According to the theoretical analysis and experimental data, this paper briefly introduces the sources and main influencing factors of optical fiber delay, emphatically analyzes the influence of optical fiber coating on fiber delay coefficient in a specific low temperature region, and gives the possible explanation of the action of coating on fiber delay coefficient.