All-optical signal processing techniques for phase-shift keyed (PSK) systems were developed theoretically and demonstrated experimentally. Nonlinear optical effects in fibers, in particular four-wave mixing (FWM) that occurs via the ultra-fast Kerr nonlinearity, offer a flexible framework within which numerous signal processing functions can be accomplished. This research has focused on the regenerative capabilities of various FWM configurations in the context of processing PSK signals. Phase-preserving amplitude regeneration, phase regeneration, and phase-regenerative wavelength conversion are analyzed and demonstrated experimentally. The single-pump phase-conjugation process was used to regenerate RZ-DPSK pulse amplitudes with different input noise distributions, and the impact on output phase characteristics was studied. Experiments revealed a limited range over which amplitude noise could effectively be suppressed without introduction of phase noise, particularly for signals with intensity pattern effects. Phase regeneration requires use of phase-sensitive amplification (PSA), which occurs in nonlinear interferometers when the pump and signal frequencies are degenerate (NI-PSA), or in fiber directly through single-stage (degenerate) or cascaded (non-degenerate) FWM processes. A PSA based on a Sagnac interferometer provided the first experimental demonstration of DPSK phase and amplitude regeneration. The phase-regenerative capabilities of the NI-PSA are limited in practice by intrinsic noise conversion (amplitude to phase noise) and to a lesser extent by the requirement to modulate the pump wave to suppress stimulated Brillouin scattering (SBS). These limitations are relaxed in novel materials with higher SBS thresholds and nonlinearities. Degenerate FWM provides PSA in a traveling-wave configuration that intrinsically suppresses the noise conversion affecting the NI-PSA, while providing stronger phase-matched gain. Experiments confirmed superior phase-regenerative behavior to the NI-PSA with simultaneous reduction of amplitude noise for NRZ-DPSK signals. Phase-regenerative wavelength conversion (PR-WC) provides the regenerative properties of PSA at a new wavelength, and was proposed and demonstrated for the first time in this research. The parallel implementation of two FWM processes, phase-conjugation and frequency conversion, provides two idlers which exhibit interesting and useful regenerative properties. These were investigated theoretically and experimentally. Ideal phase-regenerative behavior is predicted when the contributing FWM processes are equally phase-matched, which can be maintained over any interaction length or wavelength shift provided the pump powers are properly adjusted. Depleted-pump regime PR-WC provides simultaneous phase and amplitude regeneration. Experiments confirmed regenerative behavior for wavelength shifts of the idlers up to 5 nm. Two techniques for phase regeneration of 4-level PSK signals were developed and evaluated. The first is based on parallel operation of PSAs suitable for processing 2-level PSK signals, where phase projection and regeneration are combined to recover the input data. Analysis of this scheme outlined the conditions required for effective phase regeneration and for practical implementation using known PSAs. A novel process based on FWM (parallel phase-conjugation followed by PSA) was developed and analyzed, and demonstrated using numerical simulations. These studies provide a basis for further work in this area.

In a world characterized by constant changes and increasing diversity, controversialevents unfold in society on a daily basis. Given the School's role in educating democraticcitizens, it is imperative for educational institutions to adapt and incorporate current andcontroversial topics into their curriculum. This thesis explores the perspectives of socialstudies teachers on controversial issues in the classroom. Employing a phenomenologicalapproach and conducting in-depth interviews with social studies teachers, the studyanalyzes their subjective experiences, definitions of the subject, and approaches toteaching controversial topics. Therefore, our purpose and research questions are groundedin three themes, which are also pervasive throughout the work: Teacher management,teacher experience, and teacher definition of controversial issues in education.In summary, the results from our interview study reveal that teachers acknowledge theemotional impact associated with these issues, a finding supported by prior research. Thechallenge lies in the complexity of these topics and the ability to strike a balance betweenintellectual challenge and emotional understanding. The study highlights the difficultyteachers face in maintaining objectivity while navigating through their own values, andthe intricate interplay between subject content, emotions, and the teacher's ownperspective. It is evident that a conscious effort is required to create a classroomatmosphere that fosters open dialogues and respectful confrontations to promotedemocratic values, where diverse perspectives can be included.

Swedish municipalities increasingly prioritize blue-green infrastructure in response to the changing climate and precipitation. This study focuses on Norrköping, Huddinge, Nyköping, and Kalmar and how urban planning develops strategies for implementing blue-green infrastructure. Through document content analysis, the municipalities recognize the importance of blue-green infrastructure for stormwater management. However, challenges with implementation remain. Clashes with higher legal and economic interests impede progress. There are issues with responsibility allocation and operation. Most of the challenges can be ascribed to the absence of a comprehensive framework for sustainable stormwater management. Each municipality has developed unique practices to handle this, which have emerged through the interviews. The strategies break down to collaborative models involving multiple stakeholders. These findings advocate for a holistic approach suggest potential for a unified framework, and a path forward in sustainable urban planning.

This study aims to obtain a deeper understanding of upper secondary teachers’ didactical choiceswhen teaching about controversial or sensitive topics; and what the challenges and possibilities arewithin a subject. Controversial and sensitive topics are a part of our everyday life. This study wantstherefore to contribute to the understanding of what can be regarded as controversial or sensitive intoday’s classrooms. To do this we carried out qualitative interviews with semi-structured questionswhich allowed openness in possible follow-up questions. Five civics teachers were interviewed, theirviews recorded, and transcribed. An inductive approach was initially taken when analysing thetranscripts. The three didactical questions what, why, and how, were used as a guide when coding thetranscription. In addition, the data was conceptualised, and themes were identified. These themeswere then used as markers for the result and discussion. The teachers' statements aligned with whatprevious research told us. All teachers interviewed identified at least one controversy, and stated theyfelt positively about their use in schools to aid students in learning. These included recently emergingtopics such as the conflict between Israel and Palestine, national party politics, LGBTQI+, andvictimology. The topics could be used as a tool to give perspective to the information flow in societyand social media surrounding the students. Discussions were also deemed as important whenhandling matters that could cause the class distress. The teachers often used their own or others’ pastexperiences with a subject when handling a topic, often with the students' possible connection andbackground in mind. Even though they found the student’s relation to the subject to be the toughestchallenge and not the topic itself. The teachers' beliefs were that nuancing the subject and discussionsabout controversial and sensitive topics are vital in civic education. / <p>Godkänd 2024-01-19</p>

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.