Graded-index polymer optical fiber with high temperature stability

The long-term thermal stability of the attenuation of graded-index plastic optical fibers (GI POFs) is strongly dependent on whether the glass transition temperature (Tg) of the cladding layer is higher than the environmental temperature. When fibers are exposed to higher temperatures than both the core and cladding Tg values, the core-cladding boundary fluctuates spatially and scatters light. However, our study indicates that the core layer is not necessarily required to be in a glassy state to maintain a flat, smooth interface if the cladding layer is in a glassy state. The attenuation increment of a GI POF with a high-Tg (115 °C) cladding under dry heat conditions at 105 °C was only 0.28 dB/10m over 6 000 h, even though the core was between glassy and rubbery states.