Advanced raman amplification techniques for high capacity and broadband coherent optical transmission systems

This thesis presents a detailed study of different advanced Raman fibre laser (RFL) based amplification schemes and the development of novel broadband distributed and discrete Raman amplifiers in order to improve the transmission performance of modern high capacity, long-haul coherent optical systems. The numerical modelling of different Raman amplifier techniques including power distribution of signal, pump and noise components, RIN transfer from pump to signal, broadband gain optimization and so on have been described in details.The RIN and noise performances of RFL based distributed Raman amplifiers (DRAs) with different span lengths, forward pump powers and input reflection levels have been characterized experimentally. It has been shown through coherent transmission experiment that, in order to improve pump power efficiency, a low level of input reflection up to ~10% can be allowed without increasing the Q factor penalty > 1dB due to additional signal RIN penalty.A novel broadband (>10nm) first order Raman pump is developed for use as a forward pump in long-haul transmission experiment. Significant signal RIN mitigation up to 10dB compared with conventional low RIN, narrowband sources was obtained for bidirectional DRA schemes. Long-haul coherent transmission experiments with 10×120Gb/s DP-QPSK system were carried out in are circulating loop setup using the proposed broadband pump in bidirectional and backward only pumping configurations. The maximum transmission reach up to ~8330km was reported with first order broadband pumped bidirectional DRA, with transmission reach extensions of 1250km and1667km compared with conventional backward only and first order semiconductor pumped bidirectional pumping scheme respectively.Finally, a novel design of bidirectional broadband distributed DRA is proposed to reduce the noise figure tilt and improve the WDM transmission performances. Furthermore, broadband discrete Raman amplifier schemes in dual stage configuration are also shown for high gain, high output power, low noise and low nonlinear performance

Failure Factors of Platform Start-ups: A Systematic Literature Review

Purpose: The quantity of platform start-ups is rising consistently. Nonetheless, it has been discovered that a large number of the new businesses crash and burn toward the starting stages and the greater part of them fall flat in under five years. The reasons for such failure are still to be uncovered in a systematic way. While there are adequate investigations that have independently propounded different reasons, this study aims to examine these reasons together by proposing a theoretical structure that will recognize the elements impacting the failure of platform start-ups. Methodology: An extensive systematic literature review was led to uncover and examine the different elements answerable for the failure of such platforms. A sum of 113 scholarly and non-scholastic sources were inspected and broke down to distinguish the basic elements. Findings/Contribution: For platform failure, three classes have been revealed including organizational, business model innovation, and environmental. In addition, 29 basic elements have been identified and classified into six categories while concentrating on similar ramifications. Utilizing the recognized components, the authors have proposed a map. This map uncovers that different elements are liable for platform failure. Media platform start-ups can be profited to a great extent from this study

Seismic response and design of subassemblies for multi-storey prestressed timber buildings.

Timber has experienced renewed interests as a sustainable building material in recent times. Although traditionally it has been the prime choice for residential construction in New Zealand and some other parts of the world, its use can be increased significantly in the future through a wider range of applications, particularly when adopting engineered wood material, Research has been started on the development of innovative solutions for multi-storey non-residential timber buildings in recent years and this study is part of that initiative. Application of timber in commercial and office spaces posed some challenges with requirements of large column-free spaces. The current construction practice with timber is not properly suited for structures with the aforementioned required characteristics and new type of structures has to be developed for this type of applications. Any new structural system has to have adequate capacity for carry the gravity and lateral loads due to occupancy and the environmental effects. Along with wind loading, one of the major sources of lateral loads is earthquakes. New Zealand, being located in a seismically active region, has significant risk of earthquake hazard specially in the central region of the country and any structure has be designed for the seismic loading appropriate for the locality. There have been some significant developments in precast concrete in terms of solutions for earthquake resistant structures in the last decade. The “Hybrid” concept combining post-tensioning and energy dissipating elements with structural members has been introduced in the late 1990s by the precast concrete industry to achieve moment-resistant connections based on dry jointed ductile connections. Recent research at the University of Canterbury has shown that the concept can be adopted for timber for similar applications. Hybrid timber frames using post-tensioned beams and dissipaters have the potential to allow longer spans and smaller cross sections than other forms of solid timber frames. Buildings with post-tensioned frames and walls can have larger column-free spaces which is a particular advantage for non-residential applications. While other researchers are focusing on whole structural systems, this research concentrated on the analysis and design of individual members and connections between members or between member and foundation. This thesis extends existing knowledge on the seismic behaviour and response of post-tensioned single walls, columns under uni-direction loads and small scale beam-column joint connections into the response and design of post-tensioned coupled walls, columns under bi-directional loading and full-scale beam-column joints, as well as to generate further insight into practical applications of the design concept for subassemblies. Extensive experimental investigation of walls, column and beam-column joints provided valuable confirmation of the satisfactory performance of these systems. In general, they all exhibited almost complete re-centering capacity and significant energy dissipation, without resulting into structural damage. The different configurations tested also demonstrated the flexibility in design and possibilities for applications in practical structures. Based on the experimental results, numerical models were developed and refined from previous literature in precast concrete jointed ductile connections to predict the behaviour of post-tensioned timber subassemblies. The calibrated models also suggest the values of relevant parameters for applications in further analysis and design. Section analyses involving those parameters are performed to develop procedures to calculate moment capacities of the subassemblies. The typical features and geometric configurations the different types of subassemblies are similar with the only major difference in the connection interfaces. With adoption of appropriate values representing the corresponding connection interface and incorporation of the details of geometry and configurations, moment capacities of all the subassemblies can be calculated with the same scheme. That is found to be true for both post-tensioned-only and hybrid specimens and also applied for both uni-directional and bi-directional loading. The common section analysis and moment capacity calculation procedure is applied in the general design approach for subassemblies

Enhanced Transmission Performance Using Backward-Propagated Broadband ASE Pump

We propose a novel first order incoherent broadband ASE pump which can be used as a seed pump in dual order backward-pumped distributed Raman amplification. Using this broadband ASE pump mitigates the RIN transfer from the backward-propagated second order pump to the signal, and extends the reach of 10×120 Gb/s DP-QPSK WDM transmission to 7915 km, giving a minimum of 12% (833 km) increase, compared with using low RIN semiconductor laser diode and random distributed feedback (DFB) fiber laser

On the Mitigation of RIN Transfer and Transmission Performance Improvement in Bidirectional Distributed Raman Amplifiers

We develop a novel broadband first order Raman pump for use as a forward pump in transmission experiments. Our results show significant signal relative intensity noise (RIN) reduction, to a level comparable to backward only pumping. The corresponding optical signal to noise ratio can be improved in dual and first order forward pumped 83.32km bidirectional distributed Raman amplifiers by using the proposed broadband pump as a first order pump. A detailed experimental characterization of RIN, signal power evolution and performance of a 10-120Gb/s DP-QPSK coherent WDM transmission system are presented. We report ~10dB RIN reduction and 0.7dB Q factor improvement which allows a 1250km transmission distance increase compared with conventional low RIN and narrowband 1st order pump sources. We also demonstrate that, bidirectional pumping with only broadband 1st order forward pumping at 50mW shows the lowest RIN transfer from pump to signal. This extends the transmission reach up to 8332km with maximum distances increased by 1250km and 1667km compared with conventional backward only and 1st order semiconductor forward pumped bidirectional pumping respectively

RIN Transfer Mitigation Technique Using Broadband Incoherent Pump in Distributed Raman Amplified Transmission Systems

The paper reviews the recent advances on RIN transfer mitigation techniques used in distributed Raman amplified long-haul coherent transmission systems. The use of a broadband first order pump in substantial pump to signal RIN transfer mitigation has been demonstrated experimentally in both bidirectional and backward only pumping schemes. The generation process of a novel broadband, low RIN and incoherent pump is also reported in detail. In a 10×120 Gb/s DP-QPSK WDM transmission system, our proposed pumping schemes shows maximum transmission reach up to 8332 km and significant reach extensions compared with conventional low RIN and narrowband Raman pump sources

Effective, Practical PON Monitoring Beyond the Splitter

Monitoring beyond the splitter in a PON is costly due to the need for additional hardware. A non-standard monitoring wavelength can reduce cost and increase the visibility of customers to 97% on a C+ GPO

RIN and transmission performance improvement using second order and broadband first order forward Raman pumping

Low RIN bidirectionally pumped Raman amplification is studied. We investigate the importance of the 1st order forward pump generation technique and optimize the forward pump characteristics to achieve RIN comparable with backward only pumping and increased transmission reach

Mitigating RIN-penalty to enhance the transmission performance in distributed Raman amplification system

The paper reviews three different technologies to mitigate the relative intensity noise (RIN) penalty in distributed Raman amplification system. We demonstrate the performance improvement in long-haul repeatered transmission systems, thanks to the signal RIN reduction