Resulting plots of the balanced intensity differences of the two lowest modes were shown in Fig. 8.3. Finding the bound modes for each waveguide parameter choice, with , typically took between 3 and 20 minutes of computing time on a desktop workstation8.5. This was dominated by the sparse eigenvalue diagonalization time. The convergence time of the eigenvalues for the same could vary by an order of magnitude, and was largely dependent on how close to cut-off the guide was: closer to cut-off took longer. Little attempt was made to optimize this.
Future improvements to the method, which would increase the accuracy or the convergence rate , include using higher order elements (if done carefully, this could correctly represent physical and components at dielectric steps), and explicit modelling of the field singularities at guide corners using specialized elements.