Transient Response of Optical Fibers Exposed to Pulsed Radiations

Bremsstrahlung and electron-beam radiation experiments have been performed to measure transient radiation darkening and recovery at room temperature in seven commercial optical glass fibers. Several of these fibers were also tested at temperatures approaching the temperature of dry ice, 216 K. Fiber responses measured during and immediately after the radiation pulse have been reduced to delta function response parameters using curve fitting techniques. Most fibers examined demonstrated a complex recovery history that suggests the presence of multiple anneal mechanisms with significantly different characteristic times. At room temperature, peak darkening coefficients ranged from 10-3 to 10-5 dB/m-R; typical recovery rates ranged from 104 to 107 s-1. At temperatures between 216 and 247 K, most fibers demonstrated increased darkening and markedly slowed recovery rates, althotugh exceptions to this result were observed.