Thermal Memory Effect in Polymer Optical Fibers

The basic properties of a thermal memory effect of polymer optical fibers (POFs) are experimentally investigated. We measure the thermally induced loss as a function of time at several high temperatures, and find that the loss becomes almost constant after heating for ~200 s. The loss remains unchanged even after the heated section is cooled to room temperature. We subsequently measure the optical time-domain reflectometry traces under three different conditions: 1) before a POF section is heated; 2) shortly after the POF section is heated at high temperature; and 3) after the heated section is cooled to room temperature. The traces measured under 2) and 3) are moderately identical, which indicates that the thermal memory effect can be exploited in developing excess-heat detecting system in future.