This procedure is appropriate for coated and uncoated fibers, but is not appropriate for jacketed or "tight buffered" fibers. It measures the strength and the stress corrosion parameters of optical fiber at specified constant strain rates. The ITM is useful in comparing the effects of different environmental treatments. It is a destructive test, and is not a substitute for prooftesting.

This method tests the fatigue behavior of fibers by varying the strain rate. The test is applicable to fibers and strain rates for which the relationship of log of failure stress vs. log of stress rate is essentially linear. Other approaches are feasible for non-linear results.

The test environment and any preconditioning or aging is critical to the outcome of this test. There is no agreed upon model for extrapolating the results for one environment to another environment. For failure stress at a given stress rate, however, as the relative humidity increases, failure stress decreases. Both increases and decreases in the measured stress corrosion parameter and strength distribution parameters have been observed as the result of preconditioning at elevated temperature and humidity for even a day or two. Agreement between the results of ITM-13 and the results of FOTP-28 is a matter for study, and the results of this ITM are not to be used directly to predict fiber reliability.