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Projects
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Photonic Signal Processing
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan, A/Prof Xiaoke Yi |
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Description
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This project aims to develop new photonic signal processing structures that can manipulate broadband signals. An important aspect of the work is to explore techniques to make the processors adaptive and tunable so that the characteristics can be controlled for information processing. Optical signal processing is expected to effectively handle high-speed, broadband signals in advanced optical communications systems and information processing. This can provide direct interfacing of fibre processing with high-speed systems.
Photonic signal processors can overcome limitations imposed by conventional electrical signal processors at sampling speeds above 1 GHz. In addition photonic processors are compatible with fire-optic transmission systems and can process signals in the optical domain directly. Research is aimed at deriving new structures that can perform high speed processing tasks on the signals that are contained within the fibre.
Applications both in the frequency domain and time domain include microwave filtering, interference suppressors, channel selectors, fast signal correlation, matched filtering and programmable delay lines.
The structures being researched are based on discrete time signal processors using Bragg grating sampling elements and multiple wavelength techniques. The objectives are to investigate new structures that can realise high-resolution optical filters for microwave signals. An additional objective is to investigate techniques to make these processors widely tunable and adaptive, to enable high-resolution microwave optical signal processing with high time-bandwidth operation.
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Dispersion managed solitons
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Staff
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Internal Research Member
A/Prof Javid Atai |
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Description
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The aim of this project is to study the propagation of optical pulses in dispersion managed links particularly in the presence of optical filtering. One of the goals this project is to find better ways of suppressing Gordon-Haus jitter.
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Staff
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Internal Research Member
Prof Robert Minasian |
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Description
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This project aims to study a new concept for synthesising a large number of different wavelengths from a single laser. Such sources are essential for gigahertz photonic signal processing functions and dense wavelength division multiplexed systems. The objective is to generate a large number of wavelengths at precise frequencies, and also have the ability of tuning the microwave frequency spacing between the wavelengths. The lightwave synthesiser output aims to provide a comb of precisely defined optical frequencies locked to a highly stable master laser, together with accurate frequency channel spacing that can be arbitrarily chosen over a wide range of frequencies.
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Nonlinear pulse propagation in periodic media
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Staff
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Internal Research Member
A/Prof Javid Atai |
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Support
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Boris Malomed
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Description
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In this project we have studied the stability of Bragg grating solitons in media where the sign of nonlinearity is periodically changing ("nonlinearity management"). We have found that the stability diagram in this model is a universal one inthat it is not dependent on the soliton's power
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Optically-controlled Phased Arrays
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan |
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Description
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This project aims to derive new architectures of optical phased arrays that realise high capacity phased array antennas that can generate high-resolution steerable beams and which can operate with wide bandwidth. Future radar and communication systems will require phased array antennas that can achieve true-time delay beam-forming and which can synthesises a large number of beams. The important advantages of wideband and squint-free operation motivate the use of optical beamforming techniques.
The aim is to investigate new photonic-based beamforming architecture that can realise a true-time delay beam steering in wide-band phased array antennas. This is based on fibre Bragg grating true time delay elements and multiple wavelength WDM techniques. This exploits the wavelength selectivity of gratings to realise a highly parallel delay processing function, which perform the complex signal delay processing equalisation on a large number of array elements simultaneously within the fibre. Our new architecture uses wavelength mapping to the array elements and partitioning concepts. Another objective is to investigate new direction finding techniques using photonics-based techniques that solve the accuracy and wideband operation requirements of these systems. The aim is to open the way to the realization of high-functionality arrays for high-resolution multiple-beam antennas with wideband operation.
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WDM photonic downconverter
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan |
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Description
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Photonic mixing has several advantages over the conventional approach of direct detection of the optical carrier followed by electronic mixing. This includes a higher conversion efficiency and dynamic range. In addition, photonic mixing has inherent high isolation due to the optical interaction process in mixing, immunity of EMI and crosstalk, and the ability of operating over very wide bandwidths.
This project aims to derive new techniques that provide linearisation as well as wideband mixing capability. The objective is to use WDM techniques to simultaneously frequency convert multiple carriers. Another objective is to increase the dynamic range characteristics. Investigations involve optimum optoelectronic device structures for increasing the spurious free dynamic range, and for reducing the noise figure. The aim is to obtain new topologies that overcome existing limitations of mixers, and to increase the dynamic range, which is a fundamental requirement of receiver systems.
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Solitons in dual-core optical waveguides
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Staff
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Internal Research Member
A/Prof Javid Atai |
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Support
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Boris Malomed
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Description
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In this project stability and interactions of spatial solitons in a model of two linearly coupled nonlinear optical waveguides with a phase-velocity difference between them are investigated. By means of systematic numerical simulations, conjectures about stability of different branches of solitons in this system are verified. Additionally, a stable branch into which unstable solitons evolve is identified. It is also shown that the outcome of interaction depends on the initial separation and asymmetry parameter.
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan, A/Prof Xiaoke Yi |
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Description
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There is currently investigation of possible applications of photonics applicable to the development of radar and microwave signal conditioning systems. This includes optimum optical modulation formats and structures for programmable photonic delay lines. The project also aims to develop new photonic-based tunable filters to provide signal conditioning in receivers. Future receiver systems will utilise the benefits of fibre optics and it is useful to implement as much signal conditioning as possible in the fibre. The objective of this project is to investigate new structures for signal conditioning of RF signals using optical fibre and widely tunable filters implemented in the fibre.
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Optical Fibre Transmission and Interference Mitigation Filters
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan, A/Prof Xiaoke Yi |
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Description
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Two critical aspects of research relating to next-generation antenna arrays relate to the transmission of broadband (>1GHz) signals over the array network and the removal of interfering signals. The objective of this project is to investigate new fibre-based filter structures that can suppress interference and which are compatible with fibre-optic transmission systems.
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Wavelength division multiplexing in a stabilized Ginzburg-Landau system
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Staff
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Internal Research Member
A/Prof Javid Atai |
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Support
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B.A. Malomed, D.J. Frantzeskakis, K. Hizanidis
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Description
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We have studied the stability and interactions of chirped solitary pulses in a system of nonlinearly coupled cubic Ginzburg-Landau (CGL) equations with a group-velocity mismatch between them, where each CGL equation is stabilized by linearly coupling it to an additional linear dissipative equation. In the context of nonlinear fiber optics, the model describes transmission and collisions of pulses at different wavelengths in a dual-core fiber, in which the active core is furnished with bandwidth-limited gain, while the other, passive (lossy) one is necessary for stabilization of the solitary pulses. It is demonstrated that the model may readily support fully stable pulses whose collisions are quasielastic, provided that the group-velocity difference between the two channels exceeds a critical value. In the case of quasielastic collisions, the temporal shift of pulses, predicted by the analytical approach, is in semi-quantitative agreement with direct numerical results in the case of anomalous dispersion. We also consider a simultaneous collision between pulses in three channels. It is found that this collision remains quasielastic, and the pulses remain completely stable.
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Novel optical discrete time processor filters
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan |
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Description
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Fibre-optic delay lines are finding an increasing number of applications in the fields of communications and photonic signal processing. There is a need for generating small time delay steps of the order of ps-steps as a function of wavelength, for example in wavelength multiplexed optical beamforming networks for microwave phased arrays and photonic signal processors. We have obtained a new approach for generating extremely small time delay steps that uses multiple overwritten gratings with different Bragg wavelengths in the same length of fibre. This has demonstrated very small delay steps, potentially below 1 ps, for the generation of the delay increments that are required in high-resolution processors.
This project also aims to sove several fundamental challenges, including coherence limitations, and methods for generating negative taps. Another objective is to investigate topologies for photonic signal processors that overcome the limitations of a periodic frequency response to enable the realisation of photonic signal processors with wide passband.
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Photonics-based Arbitrary Waveform Generators
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Staff
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Internal Research Member
Prof Robert Minasian |
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Description
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The synthesis of high-speed arbitrary waveforms using photonics has attracted significant interest because of its importance in a range of applications such as radar, signal processing, and communications. This stems from the potential ability of photonics techniques to overcome the inherent limitations of electronics-based approaches in generating high frequency waveforms and achieving the very high sampling frequencies required and the limited speed and linearity of electronic device technology such as digital-to-analog converters.
This project investigates new photonic methods for generating high-speed arbitrary RF waveforms. It is based on the generation of short sample pulses using photonics, the generation of high sampling rates using short delay steps in fibre grating reflectors in conjunction with a novel delay line structure, and the generation of arbitrary high-speed waveforms using sample weighting and filtering. The technique employs a simple fiber optic structure, and is capable of synthesizing wideband waveforms with high resolution.
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New Optical Sources for Photonic Signal Processing
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Staff
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Internal Research Member
Prof Robert Minasian |
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Description
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Photonic signal processing offers the potential of high-speed processing of signals directly in the optical domain to realise fiber systems with built-in signal conditioning. In order to avoid optical interference effects and obtain robust transfer functions, nearly all photonic signal processors operate in the incoherent regime. This requires that the coherence time of the optical source is shorter than the minimum time delay in the processor. Hence, for high-speed processors that operate at multi-GHz fundamental frequencies, this requires an optical source with a relatively large linewidth appropriate to the processor frequency.
However, optical sources with suitable linewidth are not readily available. Intrinsic laser linewidth is usually too small and can cause coherent interference effects in the processor. On the other hand, broadband sources such as ASE and SLD sources that have extremely wide spectral bandwidths, as needed for sensor applications, are unsuitable because of their low power density. Hence, spectrum-slicing approaches from such broadband sources are usually limited by the low source power generated.
This project investigates new structures that can generate optical sources of optimum linewidth for photonic signal processor applications, and which can simultaneously achieve a high power. The structures are based on a two-stage double-pass topology. A significant feature of this novel optical source is that it can achieve extremely high conversion efficiency without the presence of lasing effect and it can realise a source with appropriate linewidth for photonic signal processing.
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THz Imaging and Phased Array Techniques
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Staff
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Internal Research Member
Prof Robert Minasian |
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Support
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Trevor Bird (CSIRO)
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Description
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Terahertz waves lie in the electromagnetic spectrum between infrared light and microwaves. The term terahertz is generally accepted as referring to the submillimetre wave energy with wavelengths between 1000mm and 100mm (frequencies between 300GHz and 3THz). Today, the terahertz region remains one of the least utilised regions of the electromagnetic spectrum, with potential applications in imaging, medicine, radio astronomy and short-range radar and communications. This research project will explore the use of sensor arrays for performing terahertz imaging. It is a collaborative research project between the CSIRO’s Electromagnetics and Antennas group and The University of Sydney’s Fibre-Optics & Photonics Group. This research has potential applications relating to medical imaging, security, communications and spectroscopy.
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Staff
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Internal Research Members
Prof Robert Minasian, Dr Erwin Chan, A/Prof Xiaoke Yi |
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Description
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Two critical aspects of research relating to next-generation antenna arrays relate to the transmission of broadband (>1GHz) signals over the array network and the removal of interfering signals. The objective of this project is to investigate new fibre-based filter structures that can suppress interference and which are compatible with fibre-optic transmission systems.
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