A systematic study of the methodology that determines the probability of the DGD overcomes a settled maximum value was presented. The methodology was discussed in a theoretical way; the values were based on a database received from optical fibers manufacturers/cablers. A comparison was conducted taking in consideration these same cables already installed in two backbones. The result of this systematic comparison was presented, as a statistic of the DGD value exceeds certain maximum value established by the standard ITU-T for systems from 10 to 40Gbps. Based on these results, the identification of mistakes that ascends the beginning of manufacture process of the optical fiber cables was important. The restriction of the sensibility of measurement devices leads to a overestimation of the probability of the DGD exceeds a given maximum value and the concept of the guideline TIA/EIA TSB107, that defines the methodology of acquisition of these results. These critical results could lead to a mistake choosing the optical system transmission and cause loss profit as well as time delay in a project. There were proposed three recommendations in order to guide the methodology for a trustful preview of the obtained results from TIA/EIA method 2, offering more comfort for optical high capacity system design.