The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The objective of this thesis was to develop novel technologies for measuring the physical characteristics of high-speed pulse trains, for use in performance monitoring applications. This thesis describes the development of three separate techniques that perform measurements in either the time domain, frequency domain or the phase space of the optical signal. The first section investigates phase-sensitive pulse measurement techniques. A high- resolution SHG-FROG apparatus was custom-designed to measure 40GHz RZ pulse trains, from which an operational characterisation of a Mach-Zehnder modulator (MZM) was realised. A numerical model of a nonlinear pulse compressor was developed to compress 40GHz RZ pulses from 8.5ps down to 3.4ps. These pulses were time-division multiplexed to 80GHz, and phase-retrievals of the 80GHz pulse trains were measured. A comparison between the techniques of SHG-FROG and linear spectrogram has been undertaken for 10GHz pulse sources, exposing SHG-FROG's weaknesses at this particular repetition rate. The second section investigates a simple, time-averaged, nonlinear detection technique. Two-photon absorption in a GaAs/InGaAs quantum-well laser diode was used to measure the duty cycle (and by extension, the pulse duration) of a range of pulse sources. This technique was further developed to measure the extinction ratio of NRZ pulse trains. Additionally, the pulse duration of a mode-locked laser source was measured using the nonlinear absorption in a 1-m length of As2Se3 Chalcogenide glass fiber. This demonstrates that the nonlinear properties of this glass may well find application in future instrumentation. The third section investigates the development of an ultra-high resolution swept heterodyne spectrometer. This spectrometer was used to spectrally-distinguish repetitive 8-bit NRZ patterns at 2.5Gbit/s. It was also used to measure the chirp parameter of an X-cut LiNbO3 MZM, revealing a chirp parameter of απ/2 < 0.1 across a modulation band- width of 250-2500MHz. Additionally, the distinctive CW spectrum of a DFB laser diode was measured. Analysis of the measured CW spectrum yielded a linewidth enhancement factor of α≃ 1.8 and also the relative intensity noise of the DFB laser diode.

The capacity of optical communications networks continues to grow unabated. Applications for streaming video, social networking and cloud computing, are driving exponential growth of the traffic carried over the world’s ICT networks, which has been sustained thus far through the proliferation of datacenters and efficient, effective use of existing optical fibre. To meet increasing capacity demands requires increasingly sophisticated modulation formats and spectral management to achieve effective use of the available spectrum provided by an optical fibre. Moreover, the technology developed for optical communications is finding broader application to other sectors such as data centres, 5&6 G wireless; lidar and radar. Ultimately, some essential signal processing functions must occur at speeds beyond purely electronic means even when accounting for anticipated technological development. The option is to perform signal processing in the optical domain. Optical signal processors are fundamentally analog and linear in nature. To provide high performance, an analogue processor must be well controlled in a way analogous to the numerous and sophisticated controllers employed by the process industry. Consequently, a further extension of control to deeper levels within the physical layer reaching the optical layer will be necessary. For example, current reconfigurable optical add-drop multiplexers are coloured and directional and the wavelength division multiplexing channel grid, transponders modulation format, and the routing are all fixed. Through optimization of the interface between the physical components, sensors, and processors elastic optical network technology can be achieved by employing colour-, direction-, contention-, grid-less, filter-, gap-less reconfigurable optical add-drop multiplexers, flexible channels centre frequencies and width, flexible sub-carriers in super-channels, flexible modulation formats and forward error control coding transponders, and impairment-aware wavelength routing and spectral assignment. The aim of this thesis is to advance the state-of-the-art in photonic circuits and subsystems via proposing new architecture; study of the feasibility of photonic integration and, proof of concept implementations using available resources. The goal is to introduce new architectural concepts that make effective use of physical components and/or optical processors with reduced energy consumption, reduced footprint and offer speed beyond all-electronic implementations. The thesis presents four case studies based on one or more published papers and supplementary material that advance the goal of the thesis. The first study presents a coherent electro-optic circuit architecture that generates N spatially distinct phase-correlated harmonically related carriers using a generalized Mach-Zehnder Interferometer with its N×1 combiner replaced by an N×N optical Discrete Fourier Transform. The architecture subsumes all Mach-Zehnder Interferometer-based architectures in the prior art given an appropriate selection of output port(s) and dimension N, although the principal application envisaged is phase-correlated subcarrier generation for next-generation optical transmission systems. The theoretical prediction is then verified experimentally using laboratory available photonic integrated circuit fabricated for other applications. Later on, a novel extension of the circuit architecture is introduced by replacing the optical Discrete Fourier Transform network using the combination of a properly chosen phase shifter and single MMI coupler. The second study proposes two novel architectures for an on-chip ultra-high-resolution panoramic spectrometer and presents their design, analysis, integration feasibility, and verification by simulation. The target application is to monitor the power of a wavelength division multiplexed signals in both fixed and flex grid over entire C-band with minimum scan time and better than 1 GHz frequency accuracy. The two architectures combine in synchrony a scanning comb filter stage and channelized coarse filter. The fine filtering is obtained using a ring resonator while the coarse filtering is obtained using an arrayed waveguide grating with appropriate configuration. The fully coherent first architecture is optimised for compactness but relies on a repeatable fabrication processes to match the optical path lengths between a Mach-Zehnder interferometer and a multiple input arrayed waveguide grating. The second architecture is less compact than the first but is robust to fabrication tolerances as it does not require the path length matching. The third study proposes a new circuit architecture for single sideband modulation or frequency conversion which employs a cascade Mach-Zehnder modulator architecture departing from the orthodox dual parallel solution. The theoretical analysis shows that the circuit has 3-dB optical and 3-dB electrical advantage over the orthodox solution. The 3-dB electrical advantage increases the linear operating range of Mach-Zehnder modulator before RF amplifier saturation. An experimental verification of the proposed architecture is provided using an available photonic integrated circuit. The proposed circuit can also perform complex modulation. An alternative implementation based on polarization modulators is also described. The fourth study presents the theoretical modelling of a photonic generation of broadband radio frequency phase shifter. The proposed phase shifter can generate any phase without bound: the complex transmission of the phase shifter follows a trajectory that rotates on a unit circle and may encircle the origin any number of times in either direction, which has great utility in the tuning of RF-photonic systems. The proposed concept is then verified experimentally using off the shelf low frequency electronic components.

No description available.

Philosophiae Doctor - PhD / The limited supply of fossil hydrocarbon resources and the negative impact of CO2 emission on the global environment dictate the increasing usage of renewable energy sources. Concentrating solar power (CSP) systems are the most likely candidate for providing the majority of the renewable energy. For efficient photo-thermal conversion, these systems require spectrally selective solar absorber surfaces with high solar absorbance in the solar spectrum region and low thermal emittance in the infrared region. In this thesis, a spectrally selective AlxOy/Pt/AlxOy multilayer solar absorber was designed and deposited onto copper substrate using electron beam evaporation at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit the multilayer solar absorber coatings. The optical constants measured using spectroscopic ellipsometry, showed that both AlxOy layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance ~ 0.94±0.01 and low thermal emittance ~ 0.06 ± 0.01 at 82oC.The structural and optical properties of the coatings were investigated. It was found that the stratification of the coatings consists of a semitransparent middle Pt layer sandwiched between two layers of AlxOy. The top and bottom AlxOy layers were nonstoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of AlxOy. The surface roughness of the stack was found to be comparable to the inter-particle distance. To study the thermal stability of the multilayer solar absorber coatings, the samples were annealed at different temperatures for different duration in air. The results showed changes in morphology, structure, composition, and optical properties depend on both temperature and duration of annealing. The XRD pattern showed that the intensity of Pt decreased with increasing annealing temperature and therefore, disappeared at high temperature. With increasing annealing temperature, an increase in the size of Pt particles was observed from SEM. The AlxOy/Pt/AlxOy multilayer solar absorber coatings deposited onto Cu substrate were found to be thermally stable up to 500oC in air for 2 h with good spectral selectivity of 0.951/0.09. At 600oC and 700oC, the spectral selectivity decreased to 0.92/0.10 and 0.846/0.11 respectively, which is attributed to the diffusion of Cu and formation of CuO and Cu2O phases. Long term thermal stability study showed that the coatings were thermally stable in air up to 450oC for 24 h. To elucidate the degradation mechanism beyond 500oC, HI-ERDA has been used to study depth-dependent atomic concentration profiles. These measurements revealed outward diffusion of the copper substrate towards the surface and therefore, the decrease in the constituents of the coating. Hence, to prevent copper from diffusing towards the coatings, a thin Tantalum (Ta) layer was deposited between the base AlxOy layer and the copper substrate.The effect of a thin Ta layer on the thermal stability of AlxOy/Pt/AlxOy multilayer solar absorber coatings was investigated. The Cu/Ta/AlxOy/Pt/AlxOy multilayer solar absorber coatings were found to be thermally stable up to 700oC in air for 2 h with good spectral selectivity of 0.937/0.10. At 800oC, the spectral selectivity decreased to 0.870/0.12, which is attributed to the diffusion of Cu and formation of CuO phase. The formation of CuO phase was confirmed by XRD, EDS and Raman spectroscopy. Long term thermal stability study showed that the coatings were thermally stable in air up to 550oC for 24 h. Therefore, the Cu/Ta/AlxOy/Pt/AlxOy spectrally selective solar absorber coatings can be used for high temperature solar-thermal applications.

The manufacturing of optical components, such as lenses or mirrors, consists of numeroussteps that are essential to the performance of the fnished optical system, such as the specifcation ofthe optical surface. For a longer period, the main focus has been in identifying and restricting thenegative effects of the low and high spatial frequency content of the surface. However, as technologyand optical equipment has become more advanced, the effects of the mid-spatial frequencies havebeen studied more, and continue to be a topic of research. As of now, there is still a need for methodsthat accurately predict and analyse the regime of mid-spatial frequencies, such that they can becontrolled during the specifcation phase, successfully limiting the need of post-processing steps.This work introduces a software tool, specifcally designed to approach this problem, which wasto be developed in Python as a contribution to the existing Optical Scripting Library at OHB. Byspecifying an optical component in terms of a Power Spectral Density function, together with thecontributions from different spatial frequency domains and the application of a ripple patterns, thissoftware tool can generate pseudo-random optical surfaces, which maintains the input specifcations.Furthermore, a Dynamic Link Library fle was developed, sharing the same functionality as thePython implementation, allowing for simulations using Zemax OpticStudio. Using the software tool,it was found that the relative error between input and output measurements were approximately0.78%, in terms of the Power Spectral Density Function. In addition, the result of analysing one of thetwo test cases indicate that the software tool is effective in predicting the infuence of mid-spatialfrequency errors, fulflling a previously measured predicition. The second test case proved that thesoftware tool can be used for mimicing surfaces of real measurements, holding the same specifcations.