## 6 Conclusions  
Optical wireless networks-on-chip are investigated in this work by means of simulations carried out in some reference cases and according to a multi-level analysis, i.e., taking into account the main factors simultaneously affecting the performance of the on-chip, point-to-point communication. In particular, bit error-probability and communication range have been assessed in relation to the antenna radiation properties, the geometry and the constituting material of the chip, the mutual position of the interfering links and other system parameters like the data-rate, the noise power and the photo-diode responsivity at the receiver side.  
Results show that in all the considered cases communications seem primarily limited by noise, with interference representing an issue only if the interfering links are quite close each other. For instance, in presence of one/two interfering links equipped with plasmonic Vivaldi antennas (gain \(\sim\)10 dB), interference effect is basically negligible (compared to noise) as the links spacing is larger than few tens of \(\upmu\)m. The communication range compliant with a target data rate of 10 Gbit/s turns out to be lower than 100 \(\upmu\)m when the antennas are buried in a few \(\upmu\)m silica layer, whereas it is more than doubled if a 5 dB gain increase is achieved resorting to Vivaldi array configurations. Further extension of the coverage area up to some hundreds of \(\upmu\)m can be accomplished reducing the data-rate, as long as this may be acceptable. Otherwise, to keep the channel throughput to values fully competitive with other  
Figure 11: BEP map in the space (d,\(\Delta\)) for the scenario in Figure 6a with \(\text{R}_{\text{b}}=1\) Gbit/s and \(\text{R}_{\text{L}}=10\) k\(\Omega\), 5-elements Vivaldi antenna arrays and \(\text{t}=6\)\(\upmu\)m.  
Figure 12: BEP map in the space (d,\(\Delta\)) for the scenario in Figure 6b with 5-elements Vivaldi antenna arrays and \(\text{t}=6\)\(\upmu\)m.  
interconnect technologies, further efforts on the project of OWiNoC are required, e.g., aimed at the design of optical nano-antennas with larger gain.  
Regardless of its extension, uniformity of the coverage area is jeopardized by multipath propagation, which can result in spots where communications reliability is prevented by the heavy multipath loss. Reducing the thickness of the dielectric layer including the antennas can contrast this multipath effect, but it would also worsen the received power range dependence at the same time.  
In conclusion, as many factors simultaneously concur to the overall link performance in a somehow interlaced fashion, the optimization of each design parameter is likely to be possible only in the framework of a comprehensive, multi-level assessment.  
Conceptualization: F.F., M.B., G.C., V.T., G.B. and V.P. Methodology: F.F., M.B., G.C., V.T., G.B. and V.P. Software: F.F., M.B., G.C., V.T., G.B., M.Z., J.S.D. and B.A. Validation: F.F., G.B., V.T. and J.S.D. Investigation: F.F., M.B., G.C., V.T., G.B., M.Z., J.S.D., J.N., B.A. and V.P. Data curation: F.F., M.B., G.C., V.T., G.B., J.S.D. and B.A. Writing-original draft preparation, F.F., G.C., V.T., G.B., M.Z. and J.N. Writing--review and editing: F.F., M.B., G.C., V.T., G.B., J.S.D., J.N., B.A. and V.P. Supervision: [PERSON]. All authors have read and agreed to the published version of the manuscript. This research was funded by the Italian Ministry of Education, University and Research (MIUR) in the framework of the PRIN 2015 \"Wireless Networks through on-chip Optical Technology--WiNOT\" Project (20155 EA8 BC-PE7). The authors declare no conflict of interest.