Dynamic pixel selection in free-space photon-counting optical communication systems for the exploitation of excess channel capacity

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 111-112).Atmospheric turbulence in free-space optical communications turns signal demodulation and decoding into a multimode problem as wavefronts of the transmitting laser beams are warped spatially past the desired form of a diffraction-limited spot at the receiver end of a free-space optical receiver. Adaptive optics, a traditional solution to this problem, is computationally expensive and adds complexity to receiver architecture by requiring tools like wavefront sensors and deformable mirrors. Due to the enabling technology of Geiger-mode avalanche photodiode (GM-APD) arrays, a simple algorithm that only requires information from the GM-APD array to implement the technique of dynamic pixel selection can be realized entirely in software or firmware. Dynamic pixel selection exploits the temporal and spatial information attached to each received photon by filtering out noisy or otherwise undesirable portions of the array in order to exploit any excess channel capacity in the link to allow on-the-fly adjustments of data rates. Preliminary results, specific to the MIT Lincoln Laboratory photon-counting, free-space optical communication system, which utilizes an 8 x 8 GM-APD receiver array, operates at a 1.06pm wavelength with 16-PPM signaling, and supports data rates up to 10 Mbps over 1-5km long paths, will be discussed.by Nivedita Chandrasekaran.M.Eng

The telecommunications and data acquisition

Radio astronomy and radio interferometry at microwave frequencies are discussed. Other topics concerning the Deep Space Network include program planning, planetary and interplanetary mission support, tracking and ground based navigation, communications, and station control and system technology

A note on the R sub 0-parameter for discrete memoryless channels

An explicit class of discrete memoryless channels (q-ary erasure channels) is exhibited. Practical and explicit coded systems of rate R with R/R sub o as large as desired can be designed for this class

The Telecommunications and Data Aquisition Report

Tracking and ground-based navigation techniques are discussed in relation to DSN advanced systems. Network data processing and productivity are studied to improve management planning methods. Project activities for upgrading DSN facilities are presented

Particle physics experiments at JLC

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Photonic Technology for Precision Metrology

Photonics has had a decisive influence on recent scientific and technological achievements. It includes aspects of photon generation and photon–matter interaction. Although it finds many applications in the whole optical range of the wavelengths, most solutions operate in the visible and infrared range. Since the invention of the laser, a source of highly coherent optical radiation, optical measurements have become the perfect tool for highly precise and accurate measurements. Such measurements have the additional advantages of requiring no contact and a fast rate suitable for in-process metrology. However, their extreme precision is ultimately limited by, e.g., the noise of both lasers and photodetectors. The Special Issue of the Applied Science is devoted to the cutting-edge uses of optical sources, detectors, and optoelectronics systems in numerous fields of science and technology (e.g., industry, environment, healthcare, telecommunication, security, and space). The aim is to provide detail on state-of-the-art photonic technology for precision metrology and identify future developmental directions. This issue focuses on metrology principles and measurement instrumentation in optical technology to solve challenging engineering problems

A precision measurement of the rate of muon capture on the deuteron

Because quantum chromodynamics (QCD) is non-perturbative at low energies, strong in- teractions at the ∼ GeV scale are very challenging to understand. Theoretical progress has been made recently using QCD-based effective field theories (EFT). The short-distance physics of the effective theory is absorbed into a limited number of low energy constants (LECs), which are determined by direct experimental measurement. The MuSun experi- ment is measuring the rate Λd for muon capture on the deuteron, which is the simplest weak interaction in a two nucleon system. Λd will be used, in turn, to better determine a funda- mental LEC known as dR in the EFT. An improvement in the precision of this LEC will improve our understanding of several other processes in the two-nucleon sector: pp fusion, the main source of energy in the sun and other main-sequence stars and neutrino-deuteron scattering, as observed in the SNO experiment. The MuSun experiment determines Λd via a precision measurement of the negative muon lifetime in deuterium. The time difference between an incoming muon, which stops in deuterium, and the subsequent decay electron characterizes the muon disappearance rate. That disappearance rate is the sum of the ordinary muon decay rate and the nuclear capture rate. The ultimate goal of the MuSun experiment is to determine the nuclear capture rate (Λd) to a precision of 1.5 %, an order of magnitude improvement over previous efforts. The principal experimental development required to achieve this goal is a cryogenic (T ∼30K) time projection chamber, which not only serves as the deuterium gas target, but also provides an unambiguous measurement of muon stopping position - muons that stop in high Z materials outside the fiducial deuterium volume produce a very large systematic error. The low temperature helps minimize several other systematic errors. The MuSun experiment is taking place at the Paul Scherrer Institut in Villigen, Switzer- land. Over the past 5 years, the MuSun collaboration has staged 4 major experimental production runs. In this thesis, I present a measurement of the muon capture rate on deu- terium, as determined from data taken in the summer of 2013. The estimated statistical and systematic error is about 7.5%