Calculating the change in frequency of a laser as it passes through a ring of charge.

How would one calculate the change in frequency of a laser as it approaches and passes through the center of a ring of electrical charges? A 1/r^2 term arises in the Reissner-Nordstrom (RN) metric, which is attributed to the addition of charge as compared to the Schwarzschild metric (spherically, symmetric, non-rotating, but uncharged). A controversy exists as other researches (P. Mannheim, M. Ozer) have found the responsible term to instead be 1/r. The consequences would be enormous as the latter would match the contribution of mass, reigniting the possibility of a unification of gravity and electromagnetism. Mainstream RN advocates rely on celestial observations in defense of their contention, but can a tight fit be placed on the amount of charge a celestial contains? That is what draws one back to seeking an in-the -lab experimental test, which in turn, leads one back to the opening question of this discussion, as a theoretical predictions for both the 1/r vs. 1/r^2 cases could be checked with that obtained from the experiment.