The growth of Second Harmonic Generation (SHG) in fibers has been observed to saturate with time as well as with length and can actually decrease after prolonged exposure to fundamental light. We have measured the length dependence of the SHG as a function of time during preparation, saturation and subsequent exposure to IR light. We have also measured the time dependence of erasure of the (chi) (2) grating with exposure to various amounts of green light. Based on these measurements we have been able to determine the parameters of the asymmetric photoionization model, specifically the current and two photon absorption rate. We have performed preliminary experiments using planar waveguides to measure the asymmetric photocurrent.