{"id":{"repo_id":"cau-kiel","oai_identifier":"oai:macau.uni-kiel.de:macau_mods_00008562"},"canonical_url":"https://search.dev.ndltd.org/etd/cau-kiel/oai:macau.uni-kiel.de:macau_mods_00008562","repository":{"repo_id":"cau-kiel","name":"Christian-Albrechts Universität Kiel","base_url":"https://macau.uni-kiel.de/servlets/OAIDataProvider"},"display":{"title":"Multi-Channel Nonlinear Frequency Division Multiplexed Optical Transmission Systems","abstract":"Fiber-optic communication systems form the backbone of today's global digital infrastructure. Driven by the continuous growth of data traffic, these systems face major challenges in meeting the ever-increasing demand for higher data rates. This work focuses on long-haul systems that achieve high capacity by compensating for fiber losses using optical amplifiers and employing wavelength division multiplexing (WDM). To further increase the achievable data rates, higher optical power is required, for example, to enable the use of more complex modulation formats. However, increasing the optical power leads to a stronger impact of the nonlinear effects of the fiber and limits the system's performance. A promising approach to overcome this limitation is the use of the nonlinear Fourier Transform (NFT), whose spectrum propagates linearly along the nonlinear fiber. Although the NFT has been intensively studied in recent years, most of the work has focused on single-channel transmissions. A major challenge is the scaling of NFT-based systems to wide spectra, such as the entire C-band. When the channels are multiplexed linearly, inter-channel crosstalk occurs, which is not considered in the calculation of the NFT of the individual channels. To avoid this effect, guard bands are usually inserted between channels which reduces the spectral efficiency, since these spectral regions cannot be used for data transmission. This work presents a novel concept for implementing WDM transmission systems based on the NFT that eliminates the need for guard bands. The proposed concept creates a spectral overlap region between channels in which the modulated data of neighboring channels is identical. By applying linear trapezoidal-shaped filtering before multiplexing the channels, a seamless spectrum is created that mitigates inter-channel crosstalk. The concept is highly scalable, and an extension that allows add-drop multiplexing further enhances the system's flexibility. The proposed concept is evaluated through simulations using a single-polarization system with four channels, which achieves a spectral efficiency of 4 b/s/Hz over a transmission distance of 800 km. In addition, concrete photonic integrated circuit-based realizations are proposed for the practical implementation of the concept.","abstract_html":"Fiber-optic communication systems form the backbone of today's global digital infrastructure. Driven by the continuous growth of data traffic, these systems face major challenges in meeting the ever-increasing demand for higher data rates. This work focuses on long-haul systems that achieve high capacity by compensating for fiber losses using optical amplifiers and employing wavelength division multiplexing (WDM). To further increase the achievable data rates, higher optical power is required, for example, to enable the use of more complex modulation formats. However, increasing the optical power leads to a stronger impact of the nonlinear effects of the fiber and limits the system's performance. A promising approach to overcome this limitation is the use of the nonlinear Fourier Transform (NFT), whose spectrum propagates linearly along the nonlinear fiber. Although the NFT has been intensively studied in recent years, most of the work has focused on single-channel transmissions. A major challenge is the scaling of NFT-based systems to wide spectra, such as the entire C-band. When the channels are multiplexed linearly, inter-channel crosstalk occurs, which is not considered in the calculation of the NFT of the individual channels. To avoid this effect, guard bands are usually inserted between channels which reduces the spectral efficiency, since these spectral regions cannot be used for data transmission. This work presents a novel concept for implementing WDM transmission systems based on the NFT that eliminates the need for guard bands. The proposed concept creates a spectral overlap region between channels in which the modulated data of neighboring channels is identical. By applying linear trapezoidal-shaped filtering before multiplexing the channels, a seamless spectrum is created that mitigates inter-channel crosstalk. The concept is highly scalable, and an extension that allows add-drop multiplexing further enhances the system's flexibility. The proposed concept is evaluated through simulations using a single-polarization system with four channels, which achieves a spectral efficiency of 4 b/s/Hz over a transmission distance of 800 km. In addition, concrete photonic integrated circuit-based realizations are proposed for the practical implementation of the concept.","abstract_has_math":false,"creators":["Schulz, Olaf"],"institution":"Christian-Albrechts-Universität zu Kiel","degree_name":null,"degree_level":"thesis.doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Pachnicke, Stephan","Wahls, Sander"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-06-12","date_published":"2026-06-12","updated_at":"2026-07-24T01:35:26Z","subjects":["Optical Communications","Nonlinear Schrödinger Equation","Wavelength Division Multiplexing","Nonlinear Fourier Transform","Nonlinear Frequency Division Multiplexing"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://macau.uni-kiel.de/receive/macau_mods_00008562","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Pachnicke, Stephan","Wahls, Sander"]},{"key":"dc:creator","label":"Author","values":["Schulz, Olaf"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:publisher","label":"Institution","values":["Universitätsbibliothek Kiel"]},{"key":"dc:type","label":"Dc Type","values":["PhDThesis"]},{"key":"thesis:degree_level","label":"Degree Level","values":["thesis.doctoral"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Christian-Albrechts-Universität zu Kiel"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Optical Communications","Nonlinear Schrödinger Equation","Wavelength Division Multiplexing","Nonlinear Fourier Transform","Nonlinear Frequency Division Multiplexing"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Fiber-optic communication systems form the backbone of today's global digital infrastructure. Driven by the continuous growth of data traffic, these systems face major challenges in meeting the ever-increasing demand for higher data rates. This work focuses on long-haul systems that achieve high capacity by compensating for fiber losses using optical amplifiers and employing wavelength division multiplexing (WDM). To further increase the achievable data rates, higher optical power is required, for example, to enable the use of more complex modulation formats. However, increasing the optical power leads to a stronger impact of the nonlinear effects of the fiber and limits the system's performance. A promising approach to overcome this limitation is the use of the nonlinear Fourier Transform (NFT), whose spectrum propagates linearly along the nonlinear fiber. Although the NFT has been intensively studied in recent years, most of the work has focused on single-channel transmissions. A major challenge is the scaling of NFT-based systems to wide spectra, such as the entire C-band. When the channels are multiplexed linearly, inter-channel crosstalk occurs, which is not considered in the calculation of the NFT of the individual channels. To avoid this effect, guard bands are usually inserted between channels which reduces the spectral efficiency, since these spectral regions cannot be used for data transmission. This work presents a novel concept for implementing WDM transmission systems based on the NFT that eliminates the need for guard bands. The proposed concept creates a spectral overlap region between channels in which the modulated data of neighboring channels is identical. By applying linear trapezoidal-shaped filtering before multiplexing the channels, a seamless spectrum is created that mitigates inter-channel crosstalk. The concept is highly scalable, and an extension that allows add-drop multiplexing further enhances the system's flexibility. The proposed concept is evaluated through simulations using a single-polarization system with four channels, which achieves a spectral efficiency of 4 b/s/Hz over a transmission distance of 800 km. In addition, concrete photonic integrated circuit-based realizations are proposed for the practical implementation of the concept."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Multi-Channel Nonlinear Frequency Division Multiplexed Optical Transmission Systems"]}]}],"canonical_facts":{"dc:contributor":["Pachnicke, Stephan","Wahls, Sander"],"dc:creator":["Schulz, Olaf"],"dc:description.abstract":["Fiber-optic communication systems form the backbone of today's global digital infrastructure. Driven by the continuous growth of data traffic, these systems face major challenges in meeting the ever-increasing demand for higher data rates. This work focuses on long-haul systems that achieve high capacity by compensating for fiber losses using optical amplifiers and employing wavelength division multiplexing (WDM). To further increase the achievable data rates, higher optical power is required, for example, to enable the use of more complex modulation formats. However, increasing the optical power leads to a stronger impact of the nonlinear effects of the fiber and limits the system's performance. A promising approach to overcome this limitation is the use of the nonlinear Fourier Transform (NFT), whose spectrum propagates linearly along the nonlinear fiber. Although the NFT has been intensively studied in recent years, most of the work has focused on single-channel transmissions. A major challenge is the scaling of NFT-based systems to wide spectra, such as the entire C-band. When the channels are multiplexed linearly, inter-channel crosstalk occurs, which is not considered in the calculation of the NFT of the individual channels. To avoid this effect, guard bands are usually inserted between channels which reduces the spectral efficiency, since these spectral regions cannot be used for data transmission. This work presents a novel concept for implementing WDM transmission systems based on the NFT that eliminates the need for guard bands. The proposed concept creates a spectral overlap region between channels in which the modulated data of neighboring channels is identical. By applying linear trapezoidal-shaped filtering before multiplexing the channels, a seamless spectrum is created that mitigates inter-channel crosstalk. The concept is highly scalable, and an extension that allows add-drop multiplexing further enhances the system's flexibility. The proposed concept is evaluated through simulations using a single-polarization system with four channels, which achieves a spectral efficiency of 4 b/s/Hz over a transmission distance of 800 km. In addition, concrete photonic integrated circuit-based realizations are proposed for the practical implementation of the concept."],"dc:format.medium":["application/pdf"],"dc:publisher":["Universitätsbibliothek Kiel"],"dc:subject":["Optical Communications","Nonlinear Schrödinger Equation","Wavelength Division Multiplexing","Nonlinear Fourier Transform","Nonlinear Frequency Division Multiplexing"],"dc:title":["Multi-Channel Nonlinear Frequency Division Multiplexed Optical Transmission Systems"],"dc:type":["PhDThesis"],"thesis:degree_level":["thesis.doctoral"],"thesis:institution_name":["Christian-Albrechts-Universität zu Kiel"]},"updated_at":"2026-07-24T01:35:26Z"}