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oai:www.repository.cam.ac.uk:1810/3914342025-10-25T02:02:04Zcom_1810_213729com_1810_256065col_1810_219485

Multi-layer, Low-crosstalk Integrated Optical Switches https://doi.org/10.17863/CAM.122571 Sun, Bohao Penty, Richard The rapid growth of cloud computing and data-intensive applications necessitates optical switching technologies with ultra-low crosstalk, high bandwidth, and nanosecond-scale reconfigurability. This work presents a comprehensive study of 3D Si-SiN-SiN tri-layer optical switches employing switch-and-select (S&S) architectures for strictly non-blocking connectivity. The 3D crossing-free waveguide shuffle eliminates in-plane intersections, significantly reducing crosstalk (as low as -51.9 dB) and insertion loss (as low as 2.1 dB) while enabling scalable, high-density photonic integration. Two distinct implementations: a thermo-optic microring resonator (MRR)-based 8×8 switch and an electro-optic microdisk switch are demonstrated, both leveraging the tri-layer platform to achieve >70 GHz bandwidth and sub-microsecond to nanosecond switching speeds. The thermo-optic device achieves crosstalk suppression of −33.2 to −50.8 dB and on-chip losses of 2.1–10.5 dB with micro-second scale switching time, while the electro-optic variant reduces switching times to 5.9 ns (rise) and 2.8 ns (fall) with crosstalk ratios as low as −51.9 dB. A dedicated control framework enables automated calibration and simultaneous multicasting/switching operations, validated through fronthaul experiments using 64-QAM LTE signals with >40 dB RF dynamic range and <1.8% error vector magnitude (EVM). Future work will focus on lossless optical switching systems through advanced material engineering (e.g., low-loss SiN waveguides with optimized adiabatic tapers) and hybrid modulation schemes combining electro-optic and thermo-optic tuning. Additionally, we aim to integrate fault-tolerant control algorithms and machine learning-driven optimization to further minimize insertion loss (<1 dB) and enable dynamic reconfiguration for terabit-scale data centre networks. By addressing scalability and energy efficiency challenges, this work paves the way for next-generation optical interconnects in cloud radio access networks (C-RAN) and ultra-low-latency computing architectures. University of Cambridge 2025-06-27 Thesis Doctoral Doctor of Philosophy (PhD) eng https://www.repository.cam.ac.uk/handle/1810/391434 https://www.repository.cam.ac.uk/bitstreams/207ed16f-e8b9-4965-9520-acb3a77f2ce5/download 31cb77b96fbe1c9e1a286321a11cbc40 https://www.repository.cam.ac.uk/bitstreams/c8162511-a969-40a4-9115-06e5dbd3ab20/download 87eda9de84448d1f82354d60eee3eb5f https://creativecommons.org/licenses/by/4.0/ optical communication optical switches Photonic Integrated Circuits photonics