Multifunctional, tunable and wideband all-fiber filter based on θ shaped microfiber resonator

A compact Θ shaped microfiber resonator for multifunctional, tunable and wideband filter is proposed. The filtering performance of reflection and transmission spectra depending on coupling coefficients and cavity length is theoretically investigated and experimentally demonstrated. © 2015 OSA.

Noise characterization and transmission evaluation of unrepeated Raman amplified DP-16QAM link

Impairments characterization and performance evaluation of Raman amplified unrepeated DP-16QAM transmissions are conducted. Experimental results indicate that small gain in forward direction enhance the system signal-to-noise ratio for longer reach without introducing noticeable penalty.

Reflection and reflexivity in reviewing and evaluating CDIO:an empirical approach to evaluation

Facilitated by an Engineer and a Social Scientist, both of whom have expertise in Engineering Education Research and Evaluation (EERE), this interactive workshop is divided into three main sections, each one focusing on a different area of evaluation. It will build on research conducted at Aston University School of Engineering and Applied Science to explore and critique the value of introducing CDIO across the first year undergraduate curriculum. Participants will be invited to consider the pedagogical and engineering related challenges of evaluating the academic and practical value of CDIO as a strategy for learning and teaching in the discipline. An empirical approach to evaluation developed by the researchers to provide empirically grounded evidence of the pedagogical and vocational value of CDIO will form the theoretical and conceptual basis of the workshop. This approach is distinctive in that it encapsulates both engineering and social science methods of evaluation. It is also contemporaneous in nature, with the researchers acting as a ‘fly on the wall’ capturing data as the programme unfolds. Through facilitated discussion and participation, the workshop will provide colleagues with the opportunity to develop a cross-disciplinary, empirically grounded research proposal specifically for the purposes of critically evaluating CDIO. It is anticipated that during the workshop, colleagues will work together in small groups. Suitable pedagogical approaches and tools will be suggested and a purposefully developed Engineering Education Research Guide, written by the workshop facilitators, will be given to all participants to inform and support the Workshop approach.

PMD tolerance of 288 Gbit/s Coherent WDM and transmission over unrepeatered 124 km of field-installed single mode optical fiber

Low-cost, high-capacity optical transmission systems are required for metropolitan area networks. Direct-detected multi-carrier systems are attractive candidates, but polarization mode dispersion (PMD) is one of the major impairments that limits their performance. In this paper, we report the first experimental analysis of the PMD tolerance of a 288Gbit/s NRZ-OOK Coherent Wavelength Division Multiplexing system. The results show that this impairment is determined primarily by the subcarrier baud rate. We confirm the robustness of the system to PMD by demonstrating error-free performance over an unrepeatered 124km field-installed single-mode fiber with a negligible penalty of 0.3dB compared to the back-to-back measurements. (C) 2010 Optical Society of America

Tailoring the temperature and strain coefficients of Type I and Type IA dual grating sensors:the impact of hydrogenation conditions

We report experimental findings for tailoring the temperature and strain coefficients of Type I and Type IA fibre Bragg gratings by influencing the photosensitivity presensitization of the host optical fibre. It is shown that by controlling the level of hydrogen saturation, via hot and cold hydrogenation, it is possible to produce gratings with lower thermal coefficients. Furthermore, there is a larger difference between the Type I and Type IA thermal coefficients and a significant improvement in the matrix condition number, which impacts the ability to recover accurate temperature and strain data using the Type 1-1A dual grating sensor. © 2006 IOP Publishing Ltd.

Fiber grating type dependence of temperature and strain coefficients and application to simultaneous temperature and strain measurement

Although fiber Bragg gratings (FBGs) have been widely used as advanced optical sensors, the cross-sensitivity between temperature and strain has complicated independent measurement procedures for these two measurands. We report here, for the first time to our knowledge, the results of a systematic investigation of the dependence of both temperature and strain sensitivities on the grating type, including the well-known Type I, Type IIA, and a new type which we have designated Type IA, using both hydrogen-free and hydrogenated B/Ge codoped fibers. We have identified distinct sensitivity characteristics for each grating type, and we have utilised them to implement a novel dual-grating, dual-parameter sensor device with performance superior to that of previously reported grating-based structures.

A matter of professionalism? Reflection and reflexivity in continuing engineering education and practice

The argument that this paper sets out to critique is that in order to promote professionalism in Engineering Education and Practice, graduate level engineering programmes need to introduce the concepts of reflection and reflexivity into the curriculum right from the onset. By focusing upon the delivery of a newly developed „Work Based‟ Master’s level programme in Professional Engineering, this paper provides an overview of the first part of an empirical study which sets out to investigate the challenges associated with embedding reflection and reflexivity into Engineering Education. The paper concludes by noting that whilst student engineers may struggle with the concepts of reflection and reflexivity, with support and encouragement such difficulties can be overcome. Moreover, by encouraging students to reflect upon their Professional Practice, the programme not only enables students to consider how they may apply what they have learnt to their Professional Practice, but also encourages them to think about how they can link their experiences as Professional Engineers to what and how they learn both whilst on the programme but also as lifelong learners.

Numerical modelling of devices and advanced transmission schemes embracing Raman effect

This thesis presents a theoretical investigation on applications of Raman effect in optical fibre communication as well as the design and optimisation of various Raman based devices and transmission schemes. The techniques used are mainly based on numerical modelling. The results presented in this thesis are divided into three main parts. First, novel designs of Raman fibre lasers (RFLs) based on Phosphosilicate core fibre are analysed and optimised for efficiency by using a discrete power balance model. The designs include a two stage RFL based on Phosphosilicate core fibre for telecommunication applications, a composite RFL for the 1.6 μm spectral window, and a multiple output wavelength RFL aimed to be used as a compact pump source for fiat gain Raman amplifiers. The use of Phosphosilicate core fibre is proven to effectively reduce the design complexity and hence leads to a better efficiency, stability and potentially lower cost. Second, the generalised Raman amplified gain model approach based on the power balance analysis and direct numerical simulation is developed. The approach can be used to effectively simulate optical transmission systems with distributed Raman amplification. Last, the potential employment of a hybrid amplification scheme, which is a combination between a distributed Raman amplifier and Erbium doped amplifier, is investigated by using the generalised Raman amplified gain model. The analysis focuses on the use of the scheme to upgrade a standard fibre network to 40 Gb/s system.

Good practice guide in learning and teaching

This is the second edition of our Aston Business School (ABS) Good Practice Guide and the enthusiasm of the contributors appears undiminished. I am again reminded that I work with a group of very committed, dedicated and professional colleagues. Once again this publication is produced to celebrate and promote good teaching across the School and to offer encouragement to those imaginative and innovative staff who continue to wish to challenge students to learn to maximum effect. It is hoped that others will pick up some good ideas from the articles contained in this volume. Contributors to this Guide were not chosen because they are the best teachers in the School, although they are undoubtedly all amongst my colleagues who are exponents of enthusiastic and inspiring approaches to learning. The Quality Unit approached these individuals because they declared on their Annual Module Reflection Forms that they were doing something interesting and worthwhile which they thought others might find useful. Amongst those reading the Guide I am sure that there are many other individuals who are trying to operate similar examples of good practice in their teaching, learning and assessment methods. I hope that this publication will provoke these people into providing comments and articles of their own and that these will form the basis of next year’s Guide. It may also provoke some people to try these methods in their own teaching. The themes of the articles this year can be divided into two groups. The first theme is the quest to help students to help themselves to learn via student-run tutorials, surprise tests and mock examinations linked with individual tutorials. The second theme is making learning come to life in exciting practical ways by, for example, hands-on workshops and simulations, story telling, rhetorical questioning and discussion groups. A common theme is one of enthusiasm, reflection and commitment on behalf of the lecturers concerned. None of the approaches discussed in this publication are low effort activities on the part of the facilitator, but this effort is regarded as worthwhile as a means of creating greater student engagement. As Biggs (2003)[1] says, in his similarly inspiring way, students learn more the less passive they are in their learning. (Ref). The articles in this publication bear witness of this and much more. Since last year Aston Business School has launched its Research Centre in Higher Education Learning and Management (HELM) which is another initiative to promote excellent learning and teaching. Even before this institution has become fully operational, at least one of the articles in this publication has seen the light of day in the research arena and at least two others are ripe for dissemination to a wider audience via journal publication. More news of our successes in this activity will appear in next year’s edition. May I thank the contributors for taking time out of their busy schedules to write the articles this summer, and to Julie Green who runs the ABS Quality Unit, for putting our diverse approaches into a coherent and publishable form and for chasing us when we have needed it! I would also like to thank Ann Morton and her colleagues in the Centre for Staff Development who have supported this publication. During the last year the Centre has further stimulated the learning and teaching life of the School (and the wider University) via their Learning and Teaching Week and sponsorship of Teaching Quality Enhancement Fund (TQEF) projects. Pedagogic excellence is in better health at Aston than ever before – long may this be because this is what life in HE should be about.

Unequal OTDM channels in a 2R regenerated, dispersion managed transmission system

The dynamics of switching and transmission of an optical signal comprising individual OTDM channels of unequal amplitudes in a dispersion-managed link with in-line non-linear fibre loop mirrors is investigated for the first time.

Exploitation of fibre characteristics in temperature sensing and radio-over-fibre applications

The development of sensing devices is one of the instrumentation fields that has grown rapidly in the last decade. Corresponding to the swift advance in the development of microelectronic sensors, optical fibre sensors are widely investigated because of their advantageous properties over the electronics sensors such as their wavelength multiplexing capability and high sensitivity to temperature, pressure, strain, vibration and acoustic emission. Moreover, optical fibre sensors are more attractive than the electronics sensors as they can perform distributed sensing, in terms of covering a reasonably large area using a single piece of fibre. Apart from being a responsive element in the sensing field, optical fibre possesses good assets in generating, distributing, processing and transmitting signals in the future broadband information network. These assets include wide bandwidth, high capacity and low loss that grant mobility and flexibility for wireless access systems. Among these core technologies, the fibre optic signal processing and transmission of optical and radio frequency signals have been the subjects of study in this thesis. Based on the intrinsic properties of single-mode optical fibre, this thesis aims to exploit the fibre characteristics such as thermal sensitivity, birefringence, dispersion and nonlinearity, in the applications of temperature sensing and radio-over-fibre systems. By exploiting the fibre thermal sensitivity, a fully distributed temperature sensing system consisting of an apodised chirped fibre Bragg grating has been implemented. The proposed system has proven to be efficient in characterising grating and providing the information of temperature variation, location and width of the heat source applied in the area under test.To exploit the fibre birefringence, a fibre delay line filter using a single high-birefringence optical fibre structure has been presented. The proposed filter can be reconfigured and programmed by adjusting the input azimuth of launched light, as well as the strength and direction of the applied coupling, to meet the requirements of signal processing for different purposes in microwave photonic and optical filtering applications. To exploit the fibre dispersion and nonlinearity, experimental investigations have been carried out to study their joint effect in high power double-sideband and single-sideband modulated links with the presence of fibre loss. The experimental results have been theoretically verified based on the in-house implementation of the split-step Fourier method applied to the generalised nonlinear Schrödinger equation. Further simulation study on the inter-modulation distortion in two-tone signal transmission has also been presented so as to show the effect of nonlinearity of one channel on the other. In addition to the experimental work, numerical simulations have also been carried out in all the proposed systems, to ensure that all the aspects concerned are comprehensively investigated.

Nonlinearly regenerated long haul data transmission

This thesis experimentally examines the use of different techniques for optical fibre transmission over ultra long haul distances. Its format firstly examines the use of dispersion management as a means of achieving long haul communications. Secondly, examining the use concatenated NOLMs for DM autosoliton ultra long haul propagation, by comparing their performance with a generic system without NOLMs. Thirdly, timing jitter in concatenated NOLM system is examined and compared to the generic system and lastly issues of OTDM amplitude non-uniformity from channel to channel in a saturable absorber, specifically a NOLM, are raised. Transmission at a rate of 40Gbit/s is studied in an all-Raman amplified standard fibre link with amplifier spacing of the order of 80km. We demonstrate in this thesis that the detrimental effects associated with high power Raman amplification can be minimized by dispersion map optimization. As a result, a transmission distance of 1600 km (2000km including dispersion compensating fibre) has been achieved in standard single mode fibre. The use of concatenated NOLMs to provide a stable propagation regime has been proposed theoretically. In this thesis, the observation experimentally of autosoliton propagation is shown for the first time in a dispersion managed optical transmission system. The system is based on a strong dispersion map with large amplifier spacing. Operation at transmission rates of 10, 40 and 80Gbit/s is demonstrated. With an insertion of a stabilizing element to the NOLM, the transmission of a 10 and 20Gbit/s data stream was extended and demonstrated experimentally. Error-free propagation over 100 and 20 thousand kilometres has been achieved at 10 and 20Gbit/s respectively, with terrestrial amplifier spacing. The monitor of timing jitter is of importance to all optical systems. Evolution of timing jitter in a DM autosoliton system has been studied in this thesis and analyzed at bit ranges from 10Gbit/s to 80Gbit/s. Non-linear guiding by in-line regenerators considerably changes the dynamics of jitter accumulation. As transmission systems require higher data rates, the use of OTDM will become more prolific. The dynamics of switching and transmission of an optical signal comprising individual OTDM channels of unequal amplitudes in a dispersion-managed link with in-line non-linear fibre loop mirrors is investigated.

Simultaneous measurement of strain and temperature using the first- and second-order diffraction wavelengths of Bragg gratings

A method of discriminating between temperature and strain effects in fibre sensing using a conventionally written, in-fibre Bragg grating is presented. The technique uses wavelength information from the first and second diffraction orders of the grating element to determine the wavelength dependent strain and temperature coefficients, from which independent temperature and strain measurements can be made. The authors present results that validate this matrix inversion technique and quantify the strain and temperature errors which can arise for a given uncertainty in the measurement of the reflected wavelength.

Cues and knowledge structures used by mental-health professionals when making risk assessments

Background: Research into mental-health risks has tended to focus on epidemiological approaches and to consider pieces of evidence in isolation. Less is known about the particular factors and their patterns of occurrence that influence clinicians’ risk judgements in practice. Aims: To identify the cues used by clinicians to make risk judgements and to explore how these combine within clinicians’ psychological representations of suicide, self-harm, self-neglect, and harm to others. Method: Content analysis was applied to semi-structured interviews conducted with 46 practitioners from various mental-health disciplines, using mind maps to represent the hierarchical relationships of data and concepts. Results: Strong consensus between experts meant their knowledge could be integrated into a single hierarchical structure for each risk. This revealed contrasting emphases between data and concepts underpinning risks, including: reflection and forethought for suicide; motivation for self-harm; situation and context for harm to others; and current presentation for self-neglect. Conclusions: Analysis of experts’ risk-assessment knowledge identified influential cues and their relationships to risks. It can inform development of valid risk-screening decision support systems that combine actuarial evidence with clinical expertise.