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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
Attosecond Precision Multi-km Laser-Microwave Network
Synchronous laser-microwave networks delivering attosecond timing precision
are highly desirable in many advanced applications, such as geodesy,
very-long-baseline interferometry, high-precision navigation and
multi-telescope arrays. In particular, rapidly expanding photon science
facilities like X-ray free-electron lasers and intense laser beamlines require
system-wide attosecond-level synchronization of dozens of optical and microwave
signals up to kilometer distances. Once equipped with such precision, these
facilities will initiate radically new science by shedding light on molecular
and atomic processes happening on the attosecond timescale, such as
intramolecular charge transfer, Auger processes and their impact on X-ray
imaging. Here, we present for the first time a complete synchronous
laser-microwave network with attosecond precision, which is achieved through
new metrological devices and careful balancing of fiber nonlinearities and
fundamental noise contributions. We demonstrate timing stabilization of a
4.7-km fiber network and remote optical-optical synchronization across a 3.5-km
fiber link with an overall timing jitter of 580 and 680 attoseconds RMS,
respectively, for over 40 hours. Ultimately we realize a complete
laser-microwave network with 950-attosecond timing jitter for 18 hours. This
work can enable next-generation attosecond photon-science facilities to
revolutionize many research fields from structural biology to material science
and chemistry to fundamental physics.Comment: 42 pages, 13 figure
Damping in a Superconducting Mechanical Resonator
We study a mechanical resonator made of aluminum near the normal to super
conductivity phase transition. A sharp drop in the rate of mechanical damping
is observed below the critical temperature. The experimental results are
compared with predictions based on the Bardeen Cooper Schrieffer theory of
superconductivity and a fair agreement is obtained
Long-term Stabilization of Fiber Laser Using Phase-locking Technique with Ultra-low Phase Noise and Phase Drift
We review the conventional phase-locking technique in the long-term
stabilization of the mode-locked fiber laser and investigate the phase noise
limitation of the conventional technique. To break the limitation, we propose
an improved phase-locking technique with an optic-microwave phase detector in
achieving the ultra-low phase noise and phase drift. The mechanism and the
theoretical model of the novel phase-locking technique are also discussed. The
long-term stabilization experiments demonstrate that the improved technique can
achieve the long-term stabilization for the MLFL with ultra-low phase noise and
phase drift. The excellent locking performance of the improved phase-locking
technique implies that this technique can be used to stabilize the mode-locked
fiber laser with the highly stable H-master or optical clock without stability
loss
Photo-detectors integrated with resonant tunneling diodes
We report on photo-detectors consisting of an optical waveguide that incorporates
a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical
communications C band we achieve maximum sensitivities of around 0.29 A/W which is
dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage
characteristic that has a negative differential resistance (NDR) region. The resonant
tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or
oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is
apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and
microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive
characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical
carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have
applications in generation and optical control of GHz low-phase noise oscillators, clock
recovery systems, and fiber optic enabled radio frequency communication systems.info:eu-repo/semantics/publishedVersio
Photo-detectors integrated with resonant tunneling diodes
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.FCT under the project WOWi [PTDC/EEA-TEL/100755/2008]; programme POCTI/FEDER [REEQ/1272/EEI/2005]; FCT Portugal [SFRH/BPD/84466/2012]info:eu-repo/semantics/publishedVersio
Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links
Los sistemas de radio sobre fibra(Radio Over fibre ROF) ofrecen el ancho de banda y flexibilidad necesario para la generación y distribución de del señales inalámbricas del futuro en una arquitectura de red óptica, que reduce el coste de las redes centralizando el procesado y simplificando la ubicación de la antena (estación de base EB). El uso de sistemas de comunicaciones ópticas como una media de transporte de señales inalámbricas en enlaces RoF reduce el cuello de botella entre los estándares de acceso inalámbrico y cableado en un dominio convergente óptico. Las redes de acceso ópticas están evolucionando con capacidades de hasta 10 Gb/s con el estándard 10GEPON, dejando un cuello de botella entre tecnologías de acceso inalámbrico y óptico. . Eso ha motivado gran esfuerzo de investigación en la generación y distribución de señales inalámbricas de alta capacidad (> 10 Gb/s) basada en RoF.
En esta tesis se ha investigado el uso de técnicas fotónicas para la generación , distribución y demodulación de señales inalámbricas moduladas vectorialmente. Esta tesis está principalmente dedicada a la generación de señales inalámbricas espectralmente eficientes como la modulación de fase en cuadratura (QPSK) o modulación de amplitud cuadratura de multinivel (M-QAM). El trabajo presentado en esta tesis está clasificado en dos partes: la primera de ellas trata de las técnicas fotónicas que utilizan señales eléctricas coherente para la generación y demodulación de señales inalámbricas, mientras la segunda parte trata de usar señales ópticas incoherentes.
En la primera parte de la tesis, están presentadas diferentes arquitecturas de sistemas y están analizadas numéricamente, y demostradas experimentalmente. Un nuevo concepto denominado "modulación vectorial fotónica" (PVM) es propuesto para la generación de señales inalámbricas con una modulación M-QAM. Basado en esta técnica se presenta la generación de señales de capacidad 10Gb/s con una modulación de QPSK y 16-QAM.Sambaraju -, R. (2010). Photonic Modulation and Demodulation techniques for Multi-Gb/s Millimetre wave Wireless Links [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8857Palanci
Theory and optimisation of double conversion heterodyne photoparametric amplifier
An optical wireless transmission technique represents an attractive choice for many
indoor and outdoors applications within fixed and mobile networks. It has the advantage of
providing a wide bandwidth that is unregulated worldwide, with availability to use it in a
very dense fashion, and potentially very low cost. Due to the high attenuation suffered by
Infrared radiation through the air, operating low power transmission sources, and generally
adverse signal to the noise environment found by ambient background light, where the
optical signal is typically at it is minimum power level when detected. A high sensitivity
and high selectivity receiver will be imperative for such applications as subcarrier
multiplex systems, millimetre-wave radio over fibre and other wireless optical system
applications.
The thesis details the research, design, and optimisation of a novel, low-noise frontend
optical receiver concept using a photoparametric amplifier (PPA) technique, in which
the detected optical baseband signal is electrically amplified and up-converted to upperside
frequency, based on the nonlinear characteristic of the pin photodiode junction; the
desired signal passes through a further signal processing stage, and the original baseband
signal is recovered again, using the concept of the superheterodyne principle. The designed
DCHPPA receiver acts in a parallel manner to a conventional double superheterodyne
detector system, but without the noise penalty normally incurred in the first stage. The PPA
is used instead of a resistive/transistor based mixer at the first stage. DCHPPAs have the
properties to provide very high gain, with high selectivity, combined with a very low noise
operation.
The research is conducted from three aspects: theoretical analysis, modelling and
simulation, and practical implementation and result analysis. The three approaches
followed the same trend shown, and the results correspond closely with each other.
Theoretically, a new non-degenerate PPA mode of operation is discussed, in which the
applied dc bias to the pin photodetector is replaced by the applied ac pump signal. This is
shown to be advantageous in terms of the desirable characteristics for PPA operation,
leading to improved conversion efficiency and the potential for low noise operation. PPA
was shown to behave more optimally with load resistance which was much lower than
normally used in the common optical wireless receiver-amplifiers. A new PPA gain theory
was derived and optimised accordance with the original gain theory, PPA input/output
admittance power was analysed for optimum power transfer. More accurate DCHPPA
circuit configurations were modelled and simulated using nonlinear simulator tools (AWR)
which help to understand and optimise system performance, particularly device parameters
and characteristics. The full DCHPPA system was implemented practically, and tested in
VHF and UHF as a sequel to the simulation configuration, which subsequently exhibited a
34.9dB baseband signal over the modulated optical signal; by employing a chain gain
DCHPPA cascaded configuration, 56.3 dB baseband signal gain was achieved. The PPA
noise was also measured and analysed, which satisfied the tough front-end optical system
requirements
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