In this research, we consider the impact of spectrum fragmentation in optical single-/multi-path routing transmission on the efficiency of the elastic optical networks. O-OFDM multicarrier transmission is a promising technique that makes it possible to choose just an adequate portion of available spectrum to satisfy the requested capacity. This involves focusing on the work to reduce the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity. that serves the light path requests over multipath networks. We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAɡ and NLDAɡ that are proportional to the optical link/path bandwidth fragmentation status. Simulation results show that the minimum bandwidth granularity dynamic adaptation based on the optical path fragmentation status offers improved performance over fixed minimum bandwidth allocation granularity with respect to the bandwidth blocking probability, the throughput, the network bandwidth utilization and the number of path splitting.