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Fiber-optic cables are being considered for use in environments where they will be exposed to a potentially damaging thermal radiation pulse. Recognizing the seriousness of this problem, the Harry Diamond Laboratories (HDL) initiated a program designed (a) to test cables in pulsed thermal environments, (b) to identify the damage modes and damage levels of these cables and (c) to develop hardening measures. Tests were performed at the White Sands Solar Facility (WSSF) by Baba, Share, and Wasilik1 on a limited number of fiber-optic cables; results indicated that cable damage--breaching of the cable jackets--occurred in the 30 to 80 cal/cm2 range. Based on these results, hardening techniques were developed; these techniques use thin aluminum and/or white Teflon tape either wrapped over the outer cable jacket or placed under transparent cable jackets. Since these initial tests, other commercial cable types have been tested; in addition, other nonmetallic hardening techniques, which use thin silicone rubber, glass cloth, PVC, or polyimide, have been investigated at thermal fluences up to 150 cal/cm with an associated maximum thermal flux around 80 cal/cm2s. The tests were performed at WSSF and at a Quartz Lamp Bank facility (QLB). All but the thickest cable jackets were found to be "thermally thin" for most of the pulse widths used in this investigation; thus, variations in flux, pulse shape, and pulse width generally had no appreciable effect on damage if the fluence and spectrum were constant. However, much larger fluences (by a factor of 2 to 3) were required at the QLB to produce damage equivalent to that observed at the WSSF. It was concluded that these large differences in damage fluences were due to the differences in spectra between the two sources.
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