355 research outputs found
Principles of Neuromorphic Photonics
In an age overrun with information, the ability to process reams of data has
become crucial. The demand for data will continue to grow as smart gadgets
multiply and become increasingly integrated into our daily lives.
Next-generation industries in artificial intelligence services and
high-performance computing are so far supported by microelectronic platforms.
These data-intensive enterprises rely on continual improvements in hardware.
Their prospects are running up against a stark reality: conventional
one-size-fits-all solutions offered by digital electronics can no longer
satisfy this need, as Moore's law (exponential hardware scaling),
interconnection density, and the von Neumann architecture reach their limits.
With its superior speed and reconfigurability, analog photonics can provide
some relief to these problems; however, complex applications of analog
photonics have remained largely unexplored due to the absence of a robust
photonic integration industry. Recently, the landscape for
commercially-manufacturable photonic chips has been changing rapidly and now
promises to achieve economies of scale previously enjoyed solely by
microelectronics.
The scientific community has set out to build bridges between the domains of
photonic device physics and neural networks, giving rise to the field of
\emph{neuromorphic photonics}. This article reviews the recent progress in
integrated neuromorphic photonics. We provide an overview of neuromorphic
computing, discuss the associated technology (microelectronic and photonic)
platforms and compare their metric performance. We discuss photonic neural
network approaches and challenges for integrated neuromorphic photonic
processors while providing an in-depth description of photonic neurons and a
candidate interconnection architecture. We conclude with a future outlook of
neuro-inspired photonic processing.Comment: 28 pages, 19 figure
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Fully-photonic digital radio over fibre for future super-broadband access network applications
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityIn this thesis a Fully-Photonic DRoF (FP-DRoF) system is proposed for deploying of future super-broadband access networks. Digital Radio over Fibre (DRoF) is more independent of the fibre network impairments and the length of fibre than the ARoF link. In order for fully optical deployment of the signal conversion techniques in the FP-DRoF architecture, two key components an Analogue-to-Digital Converter (ADC) and a Digital-to-Analogue Converter (DAC)) for data conversion are designed and their performance are investigated whereas the physical functionality is evaluated. The system simulation results of the proposed pipelined Photonic ADC (PADC) show that the PADC has 10 GHz bandwidth around 60 GHz of sampling rate. Furthermore, by
changing the bandwidth of the optical bandpass filter, switching to another band of sampling frequency provides optimised performance condition of the PADC. The PADC has low changes on the Effective Number of Bit (ENOB) response versus analogue RF input from 1 GHz up to 22 GHz for 60 GHz sampling frequency. The proposed 8-Bit pipelined PADC performance in terms of ENOB is evaluated at 60 Gigasample/s which is about 4.1. Recently, different methods have been reported by researchers to implement Photonic DACs
(PDACs), but their aim was to convert digital electrical signals to the corresponding analogue signal by assisting the optical techniques. In this thesis, a Binary Weighted PDAC (BW-PDAC) is proposed. In this BW-PDAC, optical digital signals are fully optically converted to an analogue signal. The spurious free dynamic range at the output of the PDAC in a back-to-back deployment of the PADC and the PDAC was 26.6 dBc. For further improvement in the system performance, a 3R (Retiming, Reshaping and Reamplifying) regeneration system is proposed in this thesis. Simulation results show that for an ultrashort RZ pulse with a 5% duty cycle at 65 Gbit/s using the proposed 3R regeneration system on a link reduces rms timing jitter by 90% while the regenerated pulse eye opening height is improved by 65%. Finally, in this thesis the proposed FP-DRoF functionality is evaluated whereas its performance is investigated through a dedicated and shared fibre links. The simulation results show (in the case of low level signal to noise ratio, in comparison with ARoF through
a dedicated fibre link) that the FP-DRoF has better BER performance than the ARoF in the order of 10-20. Furthermore, in order to realize a BER about 10-25 for the ARoF, the power penalty is about 4 dBm higher than the FP-DRoF link. The simulation results demonstrate that by considering 0.2 dB/km attenuation of a standard single mode fibre, the dedicated fibre length for the FP-DRoF link can be increased to about 20 km more than the ARoF link. Moreover, for performance assessment of the proposed FP-DRoF in a shared fibre link, the BER of the FP-DRoF link is about 10-10 magnitude less than the ARoF link for -19 dBm launched power into the fibre and the power penalty of the ARoF system is 10 dBm more than the FP-DRoF link. It is significant to increase the fibre link’s length of the FP-DRoF access network using common infrastructure. In addition, the simulation results are demonstrated that the FP-DRoF with non-uniform Wavelength Division Multiplexing (WDM) is more robust against four wave mixing impairment than the conventional WDM technique with uniform wavelength allocation and has better performance in terms of BER. It is clearly verified that the lunched power penalty at CS for DRoF link with uniform WDM techniques is about 2 dB higher than non-uniform WDM technique. Furthermore, uniform WDM method requires more bandwidth than non-uniform scheme which depends on the total number of channels and channels spacing
INTEGRATED SINGLE-PHOTON SENSING AND PROCESSING PLATFORM IN STANDARD CMOS
Practical implementation of large SPAD-based sensor arrays in the standard CMOS process has been fraught with challenges due to the many performance trade-offs existing at both the device and the system level [1]. At the device level the performance challenge stems from the suboptimal optical characteristics associated with the standard CMOS fabrication process. The challenge at the system level is the development of monolithic readout architecture capable of supporting the large volume of dynamic traffic, associated with multiple single-photon pixels, without limiting the dynamic range and throughput of the sensor.
Due to trade-offs in both functionality and performance, no general solution currently exists for an integrated single-photon sensor in standard CMOS single photon sensing and multi-photon resolution. The research described herein is directed towards the development of a versatile high performance integrated SPAD sensor in the standard CMOS process.
Towards this purpose a SPAD device with elongated junction geometry and a perimeter field gate that features a large detection area and a highly reduced dark noise has been presented and characterized. Additionally, a novel front-end system for optimizing the dynamic range and after-pulsing noise of the pixel has been developed. The pixel is also equipped with an output interface with an adjustable pulse width response. In order to further enhance the effective dynamic range of the pixel a theoretical model for accurate dead time related loss compensation has been developed and verified.
This thesis also introduces a new paradigm for electrical generation and encoding of the SPAD array response that supports fully digital operation at the pixel level while enabling dynamic discrete time amplitude encoding of the array response. Thus offering a first ever system solution to simultaneously exploit both the dynamic nature and the digital profile of the SPAD response. The array interface, comprising of multiple digital inputs capacitively coupled onto a shared quasi-floating sense node, in conjunction with the integrated digital decoding and readout electronics represents the first ever solid state single-photon sensor capable of both photon counting and photon number resolution. The viability of the readout architecture is demonstrated through simulations and preliminary proof of concept measurements
Power Control In Optical CDMA
Optical CDMA (OCDMA) is the multiplexing technique over the fiber optics medium to increase the number of users and this is a step towards all optical Passive Optical Networks (PON). Optical OFDM, WDM and Optical TDM have also been studied in this thesis which are also candidates to all optical passive optical networks. One of the main features of Optical CDMA over other multiplexing techniques is that it has smooth capacity. The capacity of OCDMA is constrained by the interference level. Hence, when some users are offline or requesting less data rates, then the capacity will be increased in the network. Same feature could be obtained in other multiplexing techniques, but they will need much more complicated online organizers. However, in OCDMA it is critical to adjust the transmission power to the right
value; otherwise, near-far problem may greatly reduce the network capacity and performance.
In this thesis Power control concepts are analyzed in optical
CDMA star networks. It is applied so that the QoS of the network get enhanced and all users after the power control have their desired signal to interference (SIR) value. Moreover, larger number of users can be accommodated in the network. Centralized power control algorithm is considered for this thesis. In centralized algorithm noiseless case and noisy case have been studied. In this thesis several simulations have been performed which shows the QoS difference before and after power control. The simulation
results are validated also by the theoretical computation.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format
Novel linear and nonlinear optical signal processing for ultra-high bandwidth communications
The thesis is articulated around the theme of ultra-wide bandwidth single channel signals. It focuses on the two main topics of transmission and processing of information by techniques compatible with high baudrates. The processing schemes introduced combine new linear and nonlinear optical platforms such as Fourier-domain programmable optical processors and chalcogenide chip waveguides, as well as the concept of neural network. Transmission of data is considered in the context of medium distance links of Optical Time Division Multiplexed (OTDM) data subject to environmental fluctuations. We experimentally demonstrate simultaneous compensation of differential group delay and multiple orders of dispersion at symbol rates of 640 Gbaud and 1.28 Tbaud. Signal processing at high bandwidth is envisaged both in the case of elementary post-transmission analog error mitigation and in the broader field of optical computing for high level operations (“optical processor”). A key innovation is the introduction of a novel four-wave mixing scheme implementing a dot-product operation between wavelength multiplexed channels. In particular, it is demonstrated for low-latency hash-key based all-optical error detection in links encoded with advanced modulation formats. Finally, the work presents groundbreaking concepts for compact implementation of an optical neural network as a programmable multi-purpose processor. The experimental architecture can implement neural networks with several nodes on a single optical nonlinear transfer function implementing functions such as analog-to-digital conversion. The particularity of the thesis is the new approaches to optical signal processing that potentially enable high level operations using simple optical hardware and limited cascading of components
A High-speed Reconfigurable Free Space Optical Communication System Utilizing Software Defined Radio Environment
Free space optical (FSO) communication allows for high-speed data transmissions while also being extremely cost-effective by using visible or infrared wavelengths to transmit and receive data wirelessly through the free space channel. However, FSO links are highly susceptible to the effects of the atmosphere, particularly turbulence, smoke, and fog. On the other hand, FSO itself does not provide enough flexibility to address the issue of such blockage and obstruction caused by objects and atmospheric conditions. This research investigates, proposes, and evaluates a software defined multiple input multiple output (MIMO) FSO system to ensure link availability and reliability under weather conditions as part of the last mile access in the 5th generation, 6th generation, and beyond. Software defined radio (SDR) technology is adopted in order to provide a certain degree of flexibility to the optical wireless communications system. The scope of this research focuses on the design, validation, implementation, and evaluation of a novel adaptive switching algorithm i.e., activating additional transmitters of a MIMO FSO system using a software defined ecosystem. The main issues are the compactness of the experimental design; the limitation of software-oriented signal generation; robustness; reliability; and the quality of service. As part of the system design, the thresholding method, a decision-making process via the feedback link, and a spatial diversity technique is adopted to carry out the adaptive switching. The adaptive switching is performed via a feedback link in which the atmospheric loss and scintillation index are calculated for fog and turbulence respectively. The initial design is implemented in SDR/ GNURadio for a real-time emulation of the proposed system to enhance the system flexibility of a traditional MIMO FSO system. A bit-by-bit comparison is performed with the GNURadio signal processing block and BERT for a real-time BER estimation. However, based on the initial results, the switching mechanism can only overcome the effect of turbulence at a certain level. A new design to mainly mitigate the varying fog conditions is proposed based on the SDR-based adaptive switching for a gigabit ethernet (GbE) MIMO FSO system and tested in a 5 m dedicated atmospheric chamber. The proposed system is implemented using off-the-shelf components such as a media converter, small form pluggable transceivers, optical switch, and power meter to estimate the channel state information. A new Schmitt trigger-based thresholding method is also introduced. The proposed software defined GbE MIMO FSO with an adaptive switching algorithm is fabricated, implemented, and investigated. The results are also compared with the real-time simulated data. Since the purpose of this Ph.D. is to explain and demonstrate the proof of concept for the proposed SDR-MIMO FSO system, the emphasis has been on the design, evaluation, and minimal performance requirements rather than maximizing the data rate. The outcome of the thesis will be a huge degree of flexibility and mitigation property MIMO FSO can offer with the help of SDR. It will be shown that the designed system has the capability to provide data transmission with 99.999% availability with a packet error rate and data rate of 7.2 ×10−2 and ~120 Mbps respectively, under extremely harsh fog conditions with visibility V of < 11 m
Optical sampling and metrology using a soliton-effect compression pulse source
A low jitter optical pulse source for applications including optical sampling and optical
metrology was modelled and then experimentally implemented using photonic
components. Dispersion and non-linear fibre effects were utilised to compress a periodic
optical waveform to generate pulses of the order of 10 picoseconds duration, via
soliton-effect compression. Attractive features of this pulse source include electronically
tuneable repetition rates greater than 1.5 GHz, ultra-short pulse duration (10-15 ps), and
low timing jitter as measured by both harmonic analysis and single-sideband (SSB)
phase noise measurements. The experimental implementation of the modelled
compression scheme is discussed, including the successful removal of stimulated
Brillouin scattering (SBS) through linewidth broadening by injection dithering or phase
modulation. Timing jitter analysis identifies many unwanted artefacts generated by the
SBS suppression methods, hence an experimental arrangement is devised (and was
subsequently patented) which ensures that there are no phase modulation spikes present
on the SSB phase noise spectrum over the offset range of interest for optical sampling
applications, 10Hz-Nyquist. It is believed that this is the first detailed timing jitter study
of a soliton-effect compression scheme. The soliton-effect compression pulses are then
used to perform what is believed to be the first demonstration of optical sampling using
this type of pulse source.
The pulse source was also optimised for use in a novel optical metrology (range
finding) system, which is being developed and patented under European Space Agency
funding as an enabling technology for formation flying satellite missions. This new
approach to optical metrology, known as Scanning Interferometric Pulse Overlap
Detection (SIPOD), is based on scanning the optical pulse repetition rate to find the
specific frequencies which allow the return pulses from the outlying satellite, i.e. the
measurement arm, to overlap exactly with a reference pulse set on the hub satellite. By
superimposing a low frequency phase modulation onto the optical pulse train, it is
possible to detect the pulse overlap condition using conventional heterodyne detection.
By rapidly scanning the pulse repetition rate to find two frequencies which provide the
overlapping pulse condition, high precision optical pulses can be used to provide high
resolution unambiguous range information, using only relatively simple electronic detection circuitry. SIPOD’s maximum longitudinal range measurement is limited only
by the coherence length of the laser, which can be many tens of kilometres. Range
measurements have been made to better than 10 microns resolution over extended
duration trial periods, at measurement update rates of up to 470 Hz. This system is
currently scheduled to fly on ESA’s PROBA-3 mission in 2012 to measure the intersatellite
spacing for a two satellite coronagraph instrument.
In summary, this thesis is believed to present three novel areas of research: the first
detailed jitter characterisation of a soliton-effect compression source, the first optical
sampling using such a compression source, and a novel optical metrology range finding
system, known as SIPOD, which utilises the tuneable repetition rate and highly stable
nature of the compression source pulses
LASER Tech Briefs, Spring 1994
Topics in this Laser Tech Brief include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Mechanics, Fabrication Technology, and books and reports
New advances in vehicular technology and automotive engineering
An automobile was seen as a simple accessory of luxury in the early years of the past
century. Therefore, it was an expensive asset which none of the common citizen could
afford. It was necessary to pass a long period and waiting for Henry Ford to establish
the first plants with the series fabrication. This new industrial paradigm makes easy to
the common American to acquire an automobile, either for running away or for
working purposes. Since that date, the automotive research grown exponentially to the
levels observed in the actuality. Now, the automobiles are indispensable goods; saying
with other words, the automobile is a first necessity article in a wide number of
aspects of living: for workers to allow them to move from their homes into their
workplaces, for transportation of students, for allowing the domestic women in their
home tasks, for ambulances to carry people with decease to the hospitals, for
transportation of materials, and so on, the list don’t ends. The new goal pursued by the
automotive industry is to provide electric vehicles at low cost and with high reliability.
This commitment is justified by the oil’s peak extraction on 50s of this century and also
by the necessity to reduce the emissions of CO2 to the atmosphere, as well as to reduce
the needs of this even more valuable natural resource. In order to achieve this task and
to improve the regular cars based on oil, the automotive industry is even more
concerned on doing applied research on technology and on fundamental research of
new materials. The most important idea to retain from the previous introduction is to
clarify the minds of the potential readers for the direct and indirect penetration of the
vehicles and the vehicular industry in the today’s life. In this sequence of ideas, this
book tries not only to fill a gap by presenting fresh subjects related to the vehicular
technology and to the automotive engineering but to provide guidelines for future
research.
This book account with valuable contributions from worldwide experts of
automotive’s field. The amount and type of contributions were judiciously selected to
cover a broad range of research. The reader can found the most recent and
cutting-edge sources of information divided in four major groups: electronics (power,
communications, optics, batteries, alternators and sensors), mechanics (suspension
control, torque converters, deformation analysis, structural monitoring), materials (nanotechnology, nanocomposites, lubrificants, biodegradable, composites, structural
monitoring) and manufacturing (supply chains).
We are sure that you will enjoy this book and will profit with the technical and
scientific contents. To finish, we are thankful to all of those who contributed to this
book and who made it possible.info:eu-repo/semantics/publishedVersio
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