Radiation Testing of a Fiber Optics Data Link

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Abstract
A fiber optics data link modeled after general designs discussed in satellite systems studies has been designed, built, and radiation tested. Radiation effects were considered in the link design with emphasis on permanent degradation and transient outage time performance. A design goal of 1-msec transient outage time was established. The testing was for a simulated prompt-ionization environment and a simulated trapped-electron environment, which are of principal concern in evaluating the performance of a link. In prompt-ionization testing, an outage time of 300 μsec or less, set by the detector amplifier IC recovery, exists up to a dose of 104 rad(Si). Above this dose, the recovery of absorption in the fibers rapidly becomes longer and increases link recovery time to 1 sec or more at a dose of 105 rad(Si). Thus, the fiber optics link met the design goal for doses up to 104 rad(Si). In the steady-state electron testing, it was predicted from data extrapolation that the link could survive five years or perhaps more in the natural space environment in synchronous orbit. The limit was set by the fiber absorption produced. This survival time could be increased to in excess of 20 years by relatively simple electronic changes. Thus, a fiber optics link is also viable in a natural space environment. In a pumped-up, trapped-electron environment, the high initial fluxes exist for only short periods and then decay. Link survival depends on the actual flux behavior.