{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/391434"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/391434","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Multi-layer, Low-crosstalk Integrated Optical Switches","abstract":"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.","abstract_html":"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&amp;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 &gt;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 &gt;40 dB RF dynamic range and &lt;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 (&lt;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.","abstract_has_math":false,"creators":["Sun, Bohao"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Penty, Richard"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-06-27","date_published":"2025-06-27","updated_at":"2026-07-22T22:24:30Z","subjects":["optical communication","optical switches","Photonic Integrated Circuits","photonics"],"languages":["eng"],"rights":[],"rights_urls":["https://www.repository.cam.ac.uk/bitstreams/c8162511-a969-40a4-9115-06e5dbd3ab20/download","https://creativecommons.org/licenses/by/4.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.122571","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Penty, Richard"]},{"key":"dc:creator","label":"Author","values":["Sun, Bohao"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2025-06-27"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/391434"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["optical communication","optical switches","Photonic Integrated Circuits","photonics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://www.repository.cam.ac.uk/bitstreams/c8162511-a969-40a4-9115-06e5dbd3ab20/download","https://creativecommons.org/licenses/by/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.122571"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://www.repository.cam.ac.uk/bitstreams/207ed16f-e8b9-4965-9520-acb3a77f2ce5/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The rapid growth of cloud computing and data-intensive applications necessitates optical switching technologies with ultra-low crosstalk, high bandwidth, and nanosecond-scale reconfigurability. 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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. 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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. 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