We report on laboratory experiments on single-mode optical fibers for use in measuring earth strain. We have monitored the long-term stability of 25-m long tensioned fibers and found their rates of fractional change in optical path lengths to be no more than 2 x 10(-6)/yr. The optical temperature coefficients for several fibers whose physical lengths were held constant were found to be within 4% of 1.17 x 10(-5) apparent strain/ degrees C. The strain sensitivity (the ratio of observed optical path change to physical path change) was determined to be within 1% of 1.16 for all the fibers tested. Initial field tests indicate that fibers are suitable for earth strain measurements of moderate precision.
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Zumberge et al. (1988) studied this question.