SOA enhanced optical line terminal for future optical access network
| dc.contributor.advisor | Townsend, Paul D. | |
| dc.contributor.advisor | Antony, Cleitus | |
| dc.contributor.author | Jamali, Fariba | en |
| dc.contributor.funder | Research Ireland | |
| dc.contributor.funder | Engineering and Physical Sciences Research Council | |
| dc.date.accessioned | 2026-05-21T13:20:16Z | |
| dc.date.available | 2026-05-21T13:20:16Z | |
| dc.date.issued | 2026-02-28 | |
| dc.date.submitted | 2026-02-28 | |
| dc.description.abstract | Future passive optical networks (PONs) aim to deliver data rates of 100 Gb/s per wavelength using intensity-modulation direct detection (IM/DD) and up to 400 Gb/s per wavelength using coherent technology. Achieving these targets requires overcoming the large dynamic range of burst-mode upstream packets, typically around 20.5 dB, caused by differential loss between optical network units (ONUs). Conventional burst-mode receivers rely on transimpedance amplifiers (BM-TIAs) that adjust electrical gain for each burst, but their limited linearity and bandwidth restrict scalability to higher speeds. As IM/DD systems approach and exceed 100 Gb/s per wavelength, they also struggle to meet the 29 dB optical power budget defined by the International Telecommunication Union (ITU-T) G.9804 standard. Coherent transmission is therefore seen as a promising solution for extending PON capacity, offering superior receiver sensitivity, higher spectral efficiency, and inherent chromatic dispersion tolerance. This thesis investigates Semiconductor Optical Amplifier (SOA)-based optical burst power equalisation as a promising approach to dynamic range management across both IM/DD and coherent PON architectures. By regulating optical gain before photodetection, SOA-based equalisation mitigates gain saturation effects, suppresses nonlinear distortions, and reduces the need for complex digital signal processing. Two novel techniques are developed and experimentally demonstrated: (A) variable bias and (B) control light injection. Both methods achieve a 24 dB dynamic range in 100 Gb/s 4-level pulse amplitude modulation (PAM4) burst-mode transmission with bit error rates below the soft-decision forward error correction threshold using a simplified low-gain receiver. The optical-domain equalisation concept is further extended to coherent PONs employing dual-polarisation 16-quadrature amplitude modulation (DP-16QAM). In this case, a low-power local oscillator (LO) configuration is implemented to demonstrate compatibility with potential comb-source-based architectures. This design relaxes the wavelength alignment requirement between the ONU and the LO, addressing one of the main challenges in coherent PONs where ONU wavelengths can drift by a few nanometers. SOA gain control enhances linearity and enables high-fidelity burst detection without requiring fast BM-TIAs. These findings show that SOA-based equalisation eliminates the need for high-gain BM-TIAs, thereby preventing bandwidth, gain, and dynamic range limitations associated with the TIA in both coherent and IM/DD systems. Furthermore, the results demonstrate that complex digital signal processing is unnecessary to achieve high dynamic range using an SOA preamplifier, and that simple linear equalisation is sufficient to compensate for low-cost 25G-class receiver bandwidth limitations and moderate fibre dispersion in IM/DD systems. To explore manufacturable integration, a transfer-printed SOA preamplifier is demonstrated for the first time in a 100 Gb/s PON context, confirming its potential for scalable, and low-cost receiver designs. Overall, this work establishes SOA-based optical power equalisation as a key enabler for next-generation high-speed PONs. It provides a pathway to support 100 Gb/s IM/DD and 400 Gb/s coherent operation while maintaining high dynamic range, receiver sensitivity, and system simplicity, enabling fully integrated, energy-efficient, and cost-effective optical access networks. | en |
| dc.description.status | Not peer reviewed | en |
| dc.description.version | Accepted Version | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.citation | Jamali, F. 2026. SOA enhanced optical line terminal for future optical access network. PhD Thesis, University College Cork. | |
| dc.identifier.endpage | 143 | |
| dc.identifier.uri | https://hdl.handle.net/10468/18807 | |
| dc.language.iso | en | en |
| dc.publisher | University College Cork | en |
| dc.relation.project | info:eu-repo/grantAgreement/SFI/Research Centres Programme::Phase 2/12/RC/2276_P2/IE/IPIC_Phase 2/ | |
| dc.relation.project | info:eu-repo/grantAgreement/SFI/EPSRC Centres for Doctoral Training (CDT) Partnership/18/EPSRC-CDT/3585/IE/EPSRC-SFI CDT in Photonic Integration and Advanced Data Storage/ | |
| dc.relation.project | Engineering and Physical Sciences Research Council (Grant no. EP/S023321/1) | |
| dc.rights | © 2026, Fariba Jamali. | |
| dc.rights.uri | https://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject | PON | |
| dc.subject | SOA | |
| dc.subject | Optical equalisation | |
| dc.subject | Next generation | |
| dc.subject | Burst-mode | |
| dc.subject | CPON | |
| dc.subject | Integrated SOA | |
| dc.title | SOA enhanced optical line terminal for future optical access network | |
| dc.type | Doctoral thesis | en |
| dc.type.qualificationlevel | Doctoral | en |
| dc.type.qualificationname | PhD - Doctor of Philosophy | en |
