Ice coating is a serious threat to the safe operation of the optical fiber composite overhead ground wire (OPGW). However

the effective monitor range and sensing model for ice coating thickness using Brillouin optical time domain reflectometry (BOTDR) remain undefined. This paper proposes a BOTDR-based methodology for monitoring the minimum critical sensing thickness of natural ice coating on OPGW. Under thin ice coating conditions

the Brillouin frequency shift is assumed to be solely temperature-dependent. As ice thickness increases

the error in temperature monitored by Brillouin frequency shift measurements grows. The ice thickness at which the temperature monitored by Brillouin frequency shift exceeds its judgment interval is defined as the minimum critical sensing thickness. A BOTDR monitoring system was deployed at Key Laboratory of Ice Prevention & Disaster Reducing of China Southern Power Grid for validation. The results demonstrate that

BOTDR is capable of detecting the minimum critical sensing thickness of OPGW under natural ice coating conditions

and the minimum critical sensing thickness in the test is 11.61 mm.When the ice coating is thinner than the minimum critical sensing thickness

the temperature monitored by Brillouin frequency shift of BOTDR can only monitor the temperature

the maximum difference between the temperature monitored by Brillouin frequency shift and the temperature monitored by the micrometeorological terminal is 1.5 ℃

within the temperature accuracy of ±2 ℃ of the BOTDR used for testing in this paper

and the BOTDR can not sense the light ice coating thinner than the minimum critical sensing thickness. When the ice coating is thicker than the minimum critical sensing thickness

the BOTDR Brillouin frequency shift of the tension-dependent Brillouin frequency shift is strongly linearly correlated with the OPGW ice coating tension with a correlation coefficient of 0.99. The research of this paper provides a theoretical basis for accurate monitoring of ice coating on long-distance OPGW lines based on BOTDR technology.