Effects of Accelerated Aging on Fiber Damage Thresholds

摘要

Laser-induced damage mechanisms that can occur during high-intensity fiber transmission have been under study for a number of years. The authors' particular interest in laser initiation of explosives has led them to examine damage processes associated with the transmission of Q-switched, Nd:YAG pulses at 1.06 mu(m) through step-index, multimode, fused silica fiber. Laser breakdown at the fiber entrance face is often the first process to limit fiber transmission, but catastrophic damage can also occur at either fiber end face, within the initial 'entry' segment of the fiber, and at other internal sites along the fiber path. Past studies have examined how these various damage mechanisms depend upon fiber end-faced preparation, fiber fixturing and routing, laser characteristics, and laser-to-fiber injection optics. In some applications of interest, however, a fiber transmission system may spend years in storage before it is used. Consequently, an important additional issue for these applications is whether or not there are aging processes that can result in lower damage thresholds over time. Fiber end-face contamination would certainly lower breakdown and damage thresholds at these surfaces, but careful design of hermetic seals in connectors and other end-face fixtures can minimize this possibility. A more subtle possibility would be a process for the slow growth of internal defects that could lead to lower thresholds for internal damage.