This paper shows the results of temperature measurements on an overhead power transmission line segment under controlled conditions using Fiber Bragg Grating (FBG) sensors. An optical fiber with three FBG sensors enclosed in copper was characterized in temperature and then attached along an overhead transmission line to perform the measurements. It was found that variations due to wind and environment temperature can be as high as 30°C and that those variations increase as current and conductor temperature increases and sometimes exceeding the maximum allowable.