The presence of torsional stress in optical fibers, introduced
during splice storage, can adversely affect splice performance and reliability.
The relaxation behavior of 900-mm buffer-coated optical fibers
following a torsional strain is examined in this study using a transient
rheological technique. Samples of different configurations were examined,
including completely coated fibers, coated fibers with one end
stripped so as to mimic an actual splicing application, and the coating
alone with the fibers removed. All samples displayed a power-law stress
relaxation with the power-law exponent n dependent on the fiber configuration.
The behavior of the coated fiber and that of the coating alone
were similar, indicating that the torsional stress relaxation was dictated
by the coating itself. Samples with coating stripped from one end showed
a lower stress level and a smaller exponent suggestive of a different
relaxation mode, which can be interpreted in terms of the stress distribution
at the glass coating interface. All samples, regardless of fiber
configuration, exhibited very slow stress relaxation, indicating that considerable
stress will be present in the fibers in a splice for a long period
of time. The effect of the torsional stress on fiber lifetime is discussed
using a simplified model.