To avoid over-engineered and expensive systems, it is important that the design takes account of variations in optical fiber characteristics due to the presence of many fiber pieces and splices in optical fiber networks. We present a design method for optical fiber networks that employ distributed Raman amplification (DRA), that considers variations in both optical losses at signal and pump wavelengths, Raman gain characteristics and splice losses. Our method can be applied to the design of both newly developed systems and installed systems. We show design examples based on our method and reveal the practicability of our method.