The wavelength-division-multiplexed passive optical network (WDM-PON) offers many advantages such as large bandwidth per user, easy management, high network security and low insertion loss enabling long-reach and/or high split-ratio. However, with the rapid development and growing interest for deployment of WDM-PON, the PON systems are becoming increasingly vulnerable to various failures. Therefore, network supervision becomes extremely important to guarantee an appropriate level of network reliability performance. The aim of PON supervision is to provide automated test and diagnostic capability without compromising the available bandwidth for services. An essential function is to detect any kind of deterioration in the network that can cause suspended services and to remotely localize these faults in order to avoid the high cost arising from troubleshooting. In this thesis, we evaluate several existing WDM PON supervision methods, based on which two simple and cost-effective new solutions are proposed to localize fiber failures in WDM PON systems. In the first solution, a conventional optical time domain reflectometry (OTDR) and a switch unit are employed, while in the second method, a novel architecture based on N×N arrayed waveguide grating (AWG) is proposed. Both methods are able to localize failures in feeder fiber and drop fibers without e.g. using expensive tunable OTDRs. A patent has been filed based on the second solution. The first proposed method is validated by simulations using VPI Transmission Maker. According to the results, this supervision method is able to give accurate measurement of many different types of failures that may happen in a fiber link. Furthermore, VPI is examined in terms of its future applicability in modeling complete PON supervision methods based on OTDR.

著者名別形の記述を修正（2022-04-21） / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第16850号 / 工博第3571号 / 新制||工||1540(附属図書館) / 29525 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 河合 潤, 教授 酒井 明, 教授 大塚 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13015号 / 論工博第4140号 / 新制||工||1650(附属図書館) / 32943 / (主査)教授 斧 髙一, 教授 木村 健二, 教授 立花 明知 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Patman is a fluorescent membrane probe related to Laurdan. The structural distinctions between the two probes are the lengths of the aliphatic tails (eleven carbons in Laurdan and fifteen in Patman) and the presence of a trimethylammonium group on Patman that produces a positively-charged head. Preliminary studies exploring Patman as a probe to detect membrane properties during apoptosis revealed that the fluorescence intensity of two edges of the emission spectrum (435 and 500 nm) stabilizes at different rates as the probe binds to the cell membrane. To test whether these differences represent dissimilarities in probe binding to ordered and disordered domains, experiments were conducted to monitor Patman equilibration with bilayers composed of various mixtures of saturated and unsaturated phosphatidylcholines at temperatures above, at, and below the main thermotropic phase transition. In general, Patman equilibrated more rapidly with bilayers in the liquid-disordered phase than in the solid-ordered phase. With solid phase membranes, the fluorescence stabilized faster at 500 nm than at 435 nm. Similar, yet more subtle, results occurred in the lipid disordered phase. In contrast, the situation was reversed at the phase transition temperature; equilibration was faster at 435 nm than at 500 nm. To determine whether these results reflected specific properties of Patman, the experiments were repeated with Laurdan, and several distinctions were observed. First, equilibration with solid phase lipids was faster than for Patman and not different from equilibration with the fluid phase. Second, differences in rates between the two wavelengths were less than with Patman for solid phase membranes but greater than with Patman for melted bilayers. Third, at the phase transition temperature, the difference in equilibration rates was the opposite of the result obtained with Patman. Computer simulations were used to assist with interpretation of these results. The data suggest that both probes bind superficially to the membrane before incorporating among the lipid molecules. Once within the membrane, Patman localizes to at least two distinct depths within the bilayer. Probe molecules in the shallow, more hydrated position favor 500 nm emission and those occupying a deeper, dehydrated position emit primarily at 435 nm. Laurdan's equilibration additionally represents movement of the probe between leaflets and multiple bilayers.

Over the last decade, rapid growth of broadband services necessitated research aimed at increasing transmission capacity in fiber-optic communication systems. Wavelength division multiplexing (WDM) technology has been widely used in fiber-optic systems to fully utilize fiber transmission bandwidth. Among optical amplifiers for WDM transmission, semiconductor optical amplifier (SOA) is a promising candidate, thanks to its broad bandwidth, compact size, and low cost. In transmission systems using SOAs, due to their large noise figures, high signal launching powers are required to ensure reasonable optical signal-to-noise ratio of the received signals. Hence the SOAs are operated in the saturation region and the signals will suffer from SOA impairments including self-gain modulation, self-phase modulation, and inter channel crosstalk effects such as cross-gain modulation, cross-phase modulation, and four-wave mixing in WDM. One possibility to circumvent these nonlinear impairments is to use constant-intensity modulation format in the 1310 nm window where dispersion is also negligible. In this dissertation, differential phase-shift keying (DPSK) WDM transmission in the 1310 nm window using SOAs was first considered to increase the capacity of existing telecommunication network. A WDM transmission of 4 x 10 Gbit/s DPSK signals over 540 km standard single mode fiber (SSMF) using cascaded SOAs was demonstrated in a recirculating loop. In order to increase the transmission reach of such WDM systems, those SOA impairments must be compensated. To do so, an accurate model for quantum-dot (QD) SOA must be established. In this dissertation, the QD-SOA was modeled with the assumption of overall charge neutrality. Static gain was calculated. Optical modulation response and nonlinear phase noise were studied semi-analytically based on small-signal analysis. The quantitative studies show that an ultrafast gain recovery time of ~0.1 ps can be achieved when QD-SOAs are under high current injection, which leads to high saturation output power. However more nonlinear phase noise is induced when the QD-SOAs are used in the transmission systems operating at 10 Gbit/s or 40 Gbit/s. Electronic post-compensation for SOA impairments using coherent detection and digital signal processing (DSP) was investigated next in this dissertation. An on-off keying transmission over 100 km SSMF using three SOAs at 1.3 [micrometer] were demonstrated experimentally with direct detection and SOA impairment compensation. The data pattern effect of the signal was compensated effectively. Both optimum launching power and Q-factor were improved by 8 dB. For advanced modulation formats involving phase modulation or in transmission windows with large dispersion, coherent detection must be used and fiber impairments in WDM systems need to be compensated as well. The proposed fiber impairment compensation is based on digital backward propagation. The corresponding DSP implementation was described and the required calculations as well as system latency were derived. Finally joint SOA and fiber impairment compensations were experimentally demonstrated for an amplitude-phase-shift keying transmission.

No description available.

The IceCube Neutrino Observatory has sensitivity to MeV electron antineutrinos from core-collapse supernovae through an excess of the detection rate over the background. Wavelength-shifting sensors have the potential to greatly increase photon collection making it a promising candidate for improving the measurement of the supernova neutrino light curve in IceCube-Gen2. For high-energy neutrino reconstruction, the competing effect of increased photon collection and the broader time distribution necessitate detailed simulations to determine the impact. In this thesis, we investigate the sensitivity gain caused by wavelength shifters in a future IceCube-Gen2 detector regarding the detection of faint modulations of the supernova neutrino lightcurve. Furthermore, we lay the groundwork for a future high-energy reconstruction through the implementation and integration of wavelength-shifting sensors into the IceCube simulation framework.

High efficiency is an essential requirement for any system, where the energy can be saved with full retention of system performance. The power amplifier in modern mobile communications system consumes most of the supplied power through the dissipated power and the required cooling systems. However, as new services were added as features for the developed mobile generations, the required data rate has increased to fulfil the new requirements. In this case, the data should be sent with the allocated bandwidth, so complex modulation schemes are used to utilise the available bandwidth efficiently. Nevertheless, the modulated signal will have a Peak to Average Power Ratio (PAPR) which increases as the modulation complexity is increasing. In this case, the power amplifier should be backed off and designed to provide good linearity and efficiency over high PAPR. Among the efficiency enhancement techniques, the Doherty technique (Load modulation technique) is the simplest one, where no additional circuity nor signal processing is required. In this work, the theory of load modulation amplifiers is investigated through two asymmetrical Doherty Power Amplifiers (DPA) targeting 3.3-3.5 GHz were designed and fabricated using two transistors (25 W and 45 W). In addition, more compact load modulation amplifiers targeting sub 6-GHz bandwidth of 5G specifically 3.4-3.8 GHz is discussed including the theory of implementing these amplifiers, where different amplifier capabilities are explored. Each amplifier design was discussed in detail, in which the input and output matching networks were designed and tested in addition to the design of the stability circuit to make sure that the amplifier is stable and working according to the specified requirements. The fabricated circuits were evaluated practically using the available instrument test, whereas Microwave Office software was used for the simulation purpose, each amplifier was designed separately, where all the designed amplifiers were able to provide the targeted efficiency at different back-off power points. Besides, some additional factors that affect the designed load modulation amplifiers such as the effect of the harmonics at the back-off and mismatching the amplifier is discussed. / European Union’s Horizon 2020 research and innovation programme (SECRET)

No description available.

No description available.