title: Techniques for low coherence pulsed Doppler lidar

authors: Dorrington, Adrian A.

abstract: Wind shear and clear air turbulence are atmospheric phenomena that pose a hazard to aircraft and their passengers. In the past, these phenomena have caused injuries and the occasional death. The ability of a lidar system to make wind speed measurements and detect wind shear and turbulence has been known for some time. However, lidar systems are still not commercially viable as early warning systems in aircraft and at airports. The main reason is the expense and bulk of the single frequency injection locked lasers currently used. These are required to ensure coherence is maintained between the reference and measurement beams over long pathlength differences. 

In order to reduce the cost and size of lidar systems, we have developed new lidar design philosophies based on using components that are cheaper and smaller. Two different techniques are presented in this thesis, one to eliminate the requirement for a highly coherent laser source, and the other provides a method to generate a frequency offset that is an alternative to the currently favoured acousto-optic modulator. 

The first approach presented is a design in which a sample of the transmitted pulse is stored in a fibre optic ring resonator of pathlength longer than the pulse. Each time the pulse circulates the storage loop a fraction is split off and used as the reference beam. Because this reference beam has travelled an equivalent distance to the measurements beam, the coherence requirements are relaxed significantly allowing the use of a much cheaper and smaller low coherence source. 

In the second method presented, a frequency offset is generated without the use of the currently favoured and relatively expensive acousto-optic modulator. This method utilises a quadrature beam combiner and radio frequency quadrature modulator techniques. Configured as a single sideband (SSB) modulator, two balanced mixers produce double sideband signals in which one sideband is π out-of-phase. When combined, one sideband cancels leaving a single sideband output containing the baseband Doppler signal shifted up the RF spectrum by a predetermined offset. This is implemented in both electronic and semi-optical configurations. 

Concept validation experiments have been performed for both techniques. Using the reference beam storage loop, the velocity of a rotating mirror was measured at several simulated ranges. Successful optical mixing between the stored reference and the delayed measurement beams has been demonstrated. Utilising the SSB offset generation method, the velocity of a piezo mounted mirror has also been successfully measured, after an offset was applied with the new techniques. The results obtained show that both concepts are viable, and that these techniques could be applied in a new lidar design philosophy resulting in significant benefits with respect to complexity, cost, size, weight, and power consumption.

text: Techniques for low coherence pulsed Doppler lidar Wind shear and clear air turbulence are atmospheric phenomena that pose a hazard to aircraft and their passengers. In the past, these phenomena have caused injuries and the occasional death. The ability of a lidar system to make wind speed measurements and detect wind shear and turbulence has been known for some time. However, lidar systems are still not commercially viable as early warning systems in aircraft and at airports. The main reason is the expense and bulk of the single frequency injection locked lasers currently used. These are required to ensure coherence is maintained between the reference and measurement beams over long pathlength differences. 

In order to reduce the cost and size of lidar systems, we have developed new lidar design philosophies based on using components that are cheaper and smaller. Two different techniques are presented in this thesis, one to eliminate the requirement for a highly coherent laser source, and the other provides a method to generate a frequency offset that is an alternative to the currently favoured acousto-optic modulator. 

The first approach presented is a design in which a sample of the transmitted pulse is stored in a fibre optic ring resonator of pathlength longer than the pulse. Each time the pulse circulates the storage loop a fraction is split off and used as the reference beam. Because this reference beam has travelled an equivalent distance to the measurements beam, the coherence requirements are relaxed significantly allowing the use of a much cheaper and smaller low coherence source. 

In the second method presented, a frequency offset is generated without the use of the currently favoured and relatively expensive acousto-optic modulator. This method utilises a quadrature beam combiner and radio frequency quadrature modulator techniques. Configured as a single sideband (SSB) modulator, two balanced mixers produce double sideband signals in which one sideband is π out-of-phase. When combined, one sideband cancels leaving a single sideband output containing the baseband Doppler signal shifted up the RF spectrum by a predetermined offset. This is implemented in both electronic and semi-optical configurations. 

Concept validation experiments have been performed for both techniques. Using the reference beam storage loop, the velocity of a rotating mirror was measured at several simulated ranges. Successful optical mixing between the stored reference and the delayed measurement beams has been demonstrated. Utilising the SSB offset generation method, the velocity of a piezo mounted mirror has also been successfully measured, after an offset was applied with the new techniques. The results obtained show that both concepts are viable, and that these techniques could be applied in a new lidar design philosophy resulting in significant benefits with respect to complexity, cost, size, weight, and power consumption.

year: 2000

title: Robocop - The depersonalisation of police officers and their emotions: A diary study of emotional labor and burnout in front line British police officers

authors: Lennie, Sarah-Jane

subjects: Emotional labor

abstract: Policing has long been recognized as an emotionally distressing and stressful occupation, and recent years have seen a marked increase in psychological illness within the police service of Britain. Research into the emotional labor of police officers and its psychological consequences is limited and has predominately engaged quantitative methodologies. This paper takes a mixed methods approach, exploring emotional labor and the relationship with burnout within a large police force in the north of England. The use of audio diary provides in-depth exploration of feeling and display rules operating within the police service. Narrative analysis of thirty-eight audio diary entries and a focus group is integrated with results from the Maslach and Jackson Burnout Inventory. Findings indicated depersonalisation as a requirement of feeling and display rules, a strategy also used as a form of coping, as well as experienced as an aspect of burnout. Emotional suppression went beyond interactions with members of the public, continuing into peer and family relationships, with many officers never expressing their true emotions. This presents an important opportunity for the police service of England and Wales to better understand and respond to the emotional pressures and coping mechanisms that officer's experience within their lives.

text: Robocop - The depersonalisation of police officers and their emotions: A diary study of emotional labor and burnout in front line British police officers Policing has long been recognized as an emotionally distressing and stressful occupation, and recent years have seen a marked increase in psychological illness within the police service of Britain. Research into the emotional labor of police officers and its psychological consequences is limited and has predominately engaged quantitative methodologies. This paper takes a mixed methods approach, exploring emotional labor and the relationship with burnout within a large police force in the north of England. The use of audio diary provides in-depth exploration of feeling and display rules operating within the police service. Narrative analysis of thirty-eight audio diary entries and a focus group is integrated with results from the Maslach and Jackson Burnout Inventory. Findings indicated depersonalisation as a requirement of feeling and display rules, a strategy also used as a form of coping, as well as experienced as an aspect of burnout. Emotional suppression went beyond interactions with members of the public, continuing into peer and family relationships, with many officers never expressing their true emotions. This presents an important opportunity for the police service of England and Wales to better understand and respond to the emotional pressures and coping mechanisms that officer's experience within their lives.

year: 2019

title: The science-society relationship in Aotearoa: practicing responsible innovation in the New Zealand research and innovation system

authors: Finlay-Smits, Susanna

subjects: Responsible innovation

abstract: Reports on Aotearoa New Zealand’s research, science, and innovation (RSI) system suggest the sector could improve its social responsibility and create more social value. However, researchers and innovators within the sector find this challenging. Through qualitative interviews and a national survey of RSI system participants, this study explores the current perceptions, practices enacted, and support given around responsible research and innovation practices. Findings indicate that researchers and innovators have diverse understandings of what responsible research and innovation entails, viewing anticipation and reflexivity-aligned practices as the most important aspects of responsible research and innovation. Participants feel most supported by research organisations and funding bodies to enact such aspects of responsible practice. However, they perceive a discrepancy, across all dimensions explored, between what researchers and innovators should do, and what they actually do in terms of enacting responsible practices. Thus, significant room for improvement is identified, particularly regarding practices that align with researchers’ and innovators’ obligations under Te Tiriti o Waitangi, and requirements under Vision Mātauranga.

text: The science-society relationship in Aotearoa: practicing responsible innovation in the New Zealand research and innovation system Reports on Aotearoa New Zealand’s research, science, and innovation (RSI) system suggest the sector could improve its social responsibility and create more social value. However, researchers and innovators within the sector find this challenging. Through qualitative interviews and a national survey of RSI system participants, this study explores the current perceptions, practices enacted, and support given around responsible research and innovation practices. Findings indicate that researchers and innovators have diverse understandings of what responsible research and innovation entails, viewing anticipation and reflexivity-aligned practices as the most important aspects of responsible research and innovation. Participants feel most supported by research organisations and funding bodies to enact such aspects of responsible practice. However, they perceive a discrepancy, across all dimensions explored, between what researchers and innovators should do, and what they actually do in terms of enacting responsible practices. Thus, significant room for improvement is identified, particularly regarding practices that align with researchers’ and innovators’ obligations under Te Tiriti o Waitangi, and requirements under Vision Mātauranga.

year: 2023-05-17