# Automatic Initialization Methods for Photonic Components on a Silicon-Based Optical Switch
## 6 Conclusions  
This work detailed the theoretical grounds of the GBNM algorithm, and its practical use to align/restore integrated optical components as MRR switching nodes and interleavers. This optimization method dramatically reduced the steps to get the best out of devices where the spectral response depended on two or more independently tunable parameters. With the GBNM, it was not necessary to perform as many analyses as needed for an evolutionary algorithm to converge. Indeed, the global search bases on multiple local restarts of the NM method and could be terminated at will. This ensured a high probability to locate the global optimum of the target function within the search domain. In fact, it reduced the possible errors by averaging the local searches. Moreover, it represented the strategies to avoid stagnation or entrapment of the searches into degeneracy basins, through oriented/constrained search restarts.  
Our implementation of the GBNM has proven to be ready for massive optimization tasks, as it allowed the failure-free alignment of all active elements within the IRIS switch. The optimization engine has been exploited in a double-edged way--on one side maximizing the performances of each single optical component, on the other side, minimizing the spurious effects introduced by the fabrication process on the other. In addition, this method could be easily extended to tunable optical circuits with an arbitrary number of input parameters (for example multi MRR switching nodes).  
In the end, the optimization method proposed here could enable an efficient optical switch, as it provided an automatic light-path setup and its full reconfigurability/restoration on the fly, without the need of any external intervention.  
Conceptualization, S.T.; Data curation, C.C. and M.A.M.; Formal analysis, S.T.; Funding acquisition, L.P.; Investigation, S.T.; Methodology, S.T.; Project administration, L.P.; Software, S.T.; Validation, C.C.; Visualization, C.C.; Writing--original draft, S.T.; Writing--review & editing, C.C. and L.P.  
This work was funded by the European Union's Seventh Framework Program FP7/2007-2013 grant number 619194.  
Figure 9: Out-of-chip transmission spectrum of one wavelength channel of the IRIS device. (**a**), the intensity of the signal transmitted over the shortest optical path is compared with the intensity of the signal transmitted over the longest path. (**b**), the optimization of the channel isolation is shown when the unwanted secondary peaks (black curve) were removed by the automatic misalignment of all the other switching nodes along the optical path.  
**Acknowledgments:** The IRIS switch was fabricated by the LETI-Grenoble (photonic chip and chip-to-chip bonding), by ST-Microlectronics (electronic chip), and was packaged by UPV-Spain. The authors would like to thank all the members of the IRIS consortium.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.