Abstract: Variations in bending loss for relatively small radii bends along a length of optical fiber (26) are determined by using an optical time domain reflectometer (20) to measure the backscattering power as a function of distance along the fiber in one direction along the length of fiber by launching light energy into one end of the fiber. Then the backscattering power is measured as a function of distance along the fiber in the opposite direction from an opposite end by launching light energy into an opposite end of the fiber. Mathematical representations of backscattering forward and reverse signals for corresponding points along the length of the fiber are added to provide a quantity which is related to mode field diameter of the fiber. Variations in the mode field diameter are indicative of variations in the bending loss along the length of fiber. By measuring the bending loss at the end points of the length of fiber, the absolute bending loss along the length of fiber can be estimated from the above quantity.