Torsional stress relaxation in tight-buffered optical fibers

The presence of torsional stress in optical fibers, introduced during splice storage, can adversely affect splice performance and reliability. The relaxation behavior of 900-mu m 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. (C) 1996 Society of Photo-Optical Instrumentation Engineers.