TIA TIA-455-28C

ANSI APPROVED

Failure stress distributions can be used to predict fiber reliabilityat a variety of alternativeconditions. TSB-61 shows mathematically how this can be done. Tocomplete a given reliabilityprojection, the tests used to characterize a distribution must becontrolled for the following:

• Population of fiber, e.g., coating, manufacturing period,diameter

• Gage length, i.e., length of section that is tested

• Stress rates

• Testing environment

• Preconditioning or aging treatments

• Sample size

This method measures the strength and the stress corrosion parametersof optical fiber at specifiedconstant strain rates. It is a destructive test, and is not asubstitute for prooftesting.

This method is used for those typical optical fibers for which themedian fracture stress isgreater than 3.1 GPa (450 kpsi) in 0.5 m gage lengths at the highestspecified strain rate of 25%/min. For fibers with lower median fracture stress, the conditionsherein have not demonstratedsufficient precision.

This method tests the fatigue behavior of fibers by varying the strainrate. The test is applicableto fibers and strain rates for which the relationship of log offailure stress vs. log of stressrate is essentially linear. Other approaches are feasible fornon-linear results.

Typical testing is conducted on 0.5-m gage lengths with sample numbersranging from 15 to 30. Therealm of probability that is characterized with a typical test doesnot approach the level neededfor installed cable when failure rates as low as 10⁻⁵break/km are required. To assessprobabilities at this low level, use ITM-1. This FOTP is useful,however, in comparing the effectsof different environmental treatments, or to measure either strengthor the stress corrosionparameter.

The test environment and any preconditioning or aging is critical tothe outcome of this test.There is no agreed upon model for extrapolating the results for oneenvironment to anotherenvironment. For failure stress at a given stress rate, however, asthe relative humidityincreases, failure stress decreases. Both increases and decreases inthe measured stress corrosionparameter and strength distribution parameters have been observed asthe result of preconditioningat elevated temperature and humidity for even a day or two.

Edition:

C

Published:

05/01/1995

Number of Pages:

34