Current developments in high performance satellite data links rely on fiber optic systems to take advantage of light weight, electromagnetic isolation, low power, and high bandwidth. Indications are that fiber data links operate with little degradation or interference in the earth's trapped radiation belts. To quantify this, we report analyses of experimental investigations in which operating fiber bus components are subjected to proton bombardment at varying proton energy, proton flux, angle of incidence, data rate, and signal levels. Parameterization of bit error rate (BER) effects in terms of these variables offers insights into the physical mechanisms involved and suggests both circuit modification and device selection criteria to maximize link performance. We outline a method to predict BER in orbit and offer this as a basis for evaluating proposed hardening solutions. The method combines predicted trapped particle orbital environmental data, including spacecraft shielding effects, with the measured system response.