5,174 research outputs found
The OPERA experiment Target Tracker
The main task of the Target Tracker detector of the long baseline neutrino
oscillation OPERA experiment is to locate in which of the target elementary
constituents, the lead/emulsion bricks, the neutrino interactions have occurred
and also to give calorimetric information about each event. The technology used
consists in walls of two planes of plastic scintillator strips, one per
transverse direction. Wavelength shifting fibres collect the light signal
emitted by the scintillator strips and guide it to both ends where it is read
by multi-anode photomultiplier tubes. All the elements used in the construction
of this detector and its main characteristics are described.Comment: 25 pages, submitted to Nuclear Instrument and Method
The design and commissioning of the MICE upstream time-of-flight system
In the MICE experiment at RAL the upstream time-of-flight detectors are used
for particle identification in the incoming muon beam, for the experiment
trigger and for a precise timing (sigma_t ~ 50 ps) with respect to the
accelerating RF cavities working at 201 MHz. The construction of the upstream
section of the MICE time-of-flight system and the tests done to characterize
its individual components are shown. Detector timing resolutions ~50-60 ps were
achieved. Test beam performance and preliminary results obtained with beam at
RAL are reported.Comment: accepted on Nuclear Instruments and Methods
DESIGN OF SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY
openPresentation on the state of the art of optical coherence tomography (OCT) and design of a tomograph based on a swept-type laser source centered at 1305 nm
The Cosmic Infrared Background Experiment (CIBER): A Sounding Rocket Payload to Study the Near Infrared Extragalactic Background Light
The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earth's atmosphere. The instrument package comprises two imaging telescopes designed to characterize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the Zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, and electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBER's flight profile and configurations. CIBER is designed to be recoverable and has flown twice, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the second flight, and the scientific data from this flight are currently being analyzed
Digital electronic predistortion for optical communications
The distortion of optical signals has long been an issue limiting the performance of
communication systems. With the increase of transmission speeds the effects of distortion
are becoming more prominent. Because of this, the use of methods known from digital
signal processing (DSP) are being introduced to compensate for them.
Applying DSP to improve optical signals has been limited by a discrepancy in digital signal
processing speeds and optical transmission speeds. However high speed Field
Programmable Gate Arrays (FPGA) which are sufficiently fast have now become available
making DSP experiments without costly ASIC implementation possible for optical
transmission experiments.
This thesis focuses on Look Up Table (LUT) based digital Electronic Predistortion (EPD) for
optical transmission. Because it is only one out of many possible implementations of EPD,
it has to be placed in context with other EPD techniques and other distortion combating
techniques in general, especially since it is possible to combine the different techniques.
Building an actual transmitter means that compromises and decisions have to be made in
the design and implementation of an EPD based system. These are based on balancing the
desire to achieve optimal performance with technological and economic limitations. This
is partly done using optical simulations to asses the performance.
This thesis describes a novel experimental transmitter that has been built as part of this
research applying LUT based EPD to an optical signal. The experimental transmitter
consists of a digital design (using a hardware description language) for a pair of FPGAs and
an analogue optical/electronic setup including two standard DAC integrated circuits. The
DSP in the transmitter compensated for both chromatic dispersion and self phase
modulation.
We achieved transmission of 10.7 Gb/s non-return-to-zero (NRZ) signals with a +4 dBm
launch power over 450 km keeping the required optical-signal-to-noise-ratio (OSNR) for a
bit-error-rate of 2x10^{-3} below 11 dB. In doing so we showed experimentally, for the first
time, that nonlinear effects can be compensated with this approach and that the
combination of FPGA-DAC is a viable approach for an experimental setup
Convergence of millimeter-wave and photonic interconnect systems for very-high-throughput digital communication applications
In the past, radio-frequency signals were commonly used for low-speed wireless electronic systems, and optical signals were used for multi-gigabit wired communication systems. However, as the emergence of new millimeter-wave technology introduces multi-gigabit transmission over a wireless radio-frequency channel, the borderline between radio-frequency and optical systems becomes blurred. As a result, there come ample opportunities to design and develop next-generation broadband systems to combine the advantages of these two technologies to overcome inherent limitations of various broadband end-to-end interconnect systems in signal generation, recovery, synchronization, and so on. For the transmission distances of a few centimeters to thousands of kilometers, the convergence of radio-frequency electronics and optics to build radio-over-fiber systems ushers in a new era of research for the upcoming very-high-throughput broadband services.
Radio-over-fiber systems are believed to be the most promising solution to the backhaul transmission of the millimeter-wave wireless access networks, especially for the license-free, very-high-throughput 60-GHz band. Adopting radio-over-fiber systems in access or in-building networks can greatly extend the 60-GHz signal reach by using ultra-low loss optical fibers. However, such high frequency is difficult to generate in a straightforward way. In this dissertation, the novel techniques of homodyne and heterodyne optical-carrier suppressions for radio-over-fiber systems are investigated and various system architectures are designed to overcome these limitations of 60-GHz wireless access networks, bringing the popularization of multi-gigabit wireless networks to become closer to the reality.
In addition to the advantages for the access networks, extremely high spectral efficiency, which is the most important parameter for long-haul networks, can be achieved by radio-over-fiber signal generation. As a result, the transmission performance of spectrally efficient radio-over-fiber signaling, including orthogonal frequency division multiplexing and orthogonal wavelength division multiplexing, is broadly and deeply investigated. On the other hand, radio-over-fiber is also used for the frequency synchronization that can resolve the performance limitation of wireless interconnect systems. A novel wireless interconnects assisted by radio-over-fiber subsystems is proposed in this dissertation.
In conclusion, multiple advantageous facets of radio-over-fiber systems can be found in various levels of end-to-end interconnect systems. The rapid development of radio-over-fiber systems will quickly change the conventional appearance of modern communications.PhDCommittee Chair: Gee-Kung Chang; Committee Member: Bernard Kippelen; Committee Member: Shyh-Chiang Shen; Committee Member: Thomas K. Gaylord; Committee Member: Umakishore Ramachandra
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