In the first section of this paper, the author reports the measurment of a tensile strain distribution on field-installed OPGW (optical fiber composited over-head ground wire) using the method of Brillouin optical fiber time domain analysis (BOTDA). The strain differences between strung sections and non-strung sections of OPGW are clealy differenciated and observed. The obtained differences are about 0.1% in the winter and about 0.2% in the summer. Those values are less than the allowable strain on the OPGW. An analysis of a relationship between measured strain and temperature is also described. It is found that the temperature dependency of strain data agrees quite well with a thermal expansion coefficient of OPGW.
In the second section, it is introduced a new strain measurement technique named “Ring Amplification Method”, which enables measurements of rapidly varying strains such as the one caused by galloping. A principle and a measurable distance by this method are studied, and it is clarified that this method is applicable to a measurement on a long-extended fiber up to 40km. Furthermore, the ability of measuring the time-varying strain and its distribution has been demonstrated in the basic experiments.