Cost-Effective Spectrally-Efficient Optical Transceiver Architectures for Metropolitan and Regional Links

The work presented herein explores cost-effective optical transceiver architectures for access, metropolitan and regional links. The primary requirement in such links is cost-effectiveness and secondly, spectral efficiency. The bandwidth/data demand is driven by data-intensive Internet applications, such as cloud-based services and video-on-demand, and is rapidly increasing in access and metro links. Therefore, cost-effective optical transceiver architectures offering high information spectral densities (ISDs > 1(b/s)/Hz) need to be implemented over metropolitan distances. Then, a key question for each link length and application is whether coherent- or direct (non-coherent) detection technology offers the best cost and performance trade-off. The performance and complexity limits of both technologies have been studied. Single polarization direct detection transceivers have been reviewed, focusing on their achievable ISDs and reach. It is concluded that subcarrier modulation (SCM) technique combined with single sideband (SSB) and high-order quadrature amplitude modulation (QAM) signaling, enabled by digital signal processing (DSP) based optical transceivers, must be implemented in order to exceed an ISD of 1 (b/s)/Hz in direct-detection links. The complexity can be shifted from the optical to the electrical domain using such transceivers, and hence, the cost can be minimized. In this regard, a detailed performance comparison of two spectrally-efficient direct detection SCM techniques, namely Nyquist-SCM and OFDM, is presented by means of simulations. It is found out that Nyquist-SCM format offers the transmission distances more than double that of OFDM due to its higher resilience to signal-signal beating interference. Following this, dispersion-precompensated SSB 4- and 16-QAM Nyquist-SCM signal formats were experimentally demonstrated using in-phase and quadrature (IQ)-modulators at net optical ISDs of 1.2 and 2 (b/s)/Hz over 800 km and 323 km of standard single-mode fibre (SSMF), respectively. These demonstrations represent record net optical ISDs over such distances among the reported single polarization wavelength division multiplexed (WDM) systems. Furthermore, since the cost-effectiveness is crucial, the optical complexity of Nyquist-SCM transmitters can be significantly reduced by using low-cost modulators and high-linewidth lasers. A comprehensive theoretical study on SSB signal generation using IQ- and dual-drive Mach-Zehnder modulators (DD-MZMs) was carried out to assess their performance for WDM direct detection links. This was followed by an experimental demonstration of WDM transmission over 242 km of SSMF with a net optical ISD of 1.5 (b/s)/Hz, the highest achieved ISD using a DD-MZM-based transmitter. Following the assessment of direct detection technology using various transmitter designs, cost-effective simplified coherent receiver architectures for access and metro networks have been investigated. The optical complexity of the conventional (polarization- and phase-diverse) coherent receiver is significantly simplified, i.e., consisting of a single 3 dB coupler and balanced photodetector, utilizing heterodyne reception and Alamouti polarization-time block coding. Although the achievable net optical ISD is halved compared to a conventional coherent receiver due to Alamouti coding, its receiver sensitivity provides significant gain over a direct detection receiver at M-ary QAM formats where M ≥16

Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 1

Papers from the technical sessions of the Technology 2001 Conference and Exposition are presented. The technical sessions featured discussions of advanced manufacturing, artificial intelligence, biotechnology, computer graphics and simulation, communications, data and information management, electronics, electro-optics, environmental technology, life sciences, materials science, medical advances, robotics, software engineering, and test and measurement

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 45)

A subject index is provided for over 5600 patents and patent applications for the period May 1969 through June 1994. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

NASA patent abstracts bibliography: A continuing bibliography. Section 2: Indexes (supplement 46)

A subject index is provided for over 5600 patents and patent applications for the period May 1969 through December 1994. Additional indexes list personal authors, corporate authors, contract numbers, NASA case numbers, U.S. patent class numbers, U.S. patent numbers, and NASA accession numbers

Dynamic nuclear polarization in biomolecular solid state NMR : methods and applications in peptides and membrane proteins

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.Includes bibliographical references.Solid state NMR can probe structure and dynamics on length scales from the atomic to the supramolecular. However, low sensitivity limits its application in macromolecules. NMR sensitivity can be improved by dynamic nuclear polarization (DNP), in which electron polarization is transferred to nuclei. We present applications of magic angle spinning NMR that demonstrate its utility for the determination of structure at atomic resolution. We then present new techniques and instrumentation for DNP that permit these methods to be applied to larger systems such as membrane proteins. These applications rest on several advances in instrumentation: millimeter-wave sources and conduits of power to the sample; low-temperature MAS probes incorporating millimeter-wave transmission; cryogenics and pneumatic control systems. We describe a 380 MHz DNP spectrometer incorporating a 250 GHz gyrotron oscillator and present the theory and operation of a 460 GHz gyrotron at the second harmonic of electron cyclotron resonance. We have applied DNP to study trapped photo cycle intermediates of the archael membrane protein bacteriorhodopsin, a light-driven transmembrane ion pump.(cont.) We have observed the K photointermediate for the first time by NMR and found unexpected conformational heterogeneity in the L intermediate. With multidimensional correlation spectroscopy, we have assigned active site resonances in conformational mixtures of photointermediates of [U-13C,'SN]-bR with high sensitivity. By using non-linear sampling of indirect dimensions, we have observed transient product of K accumulation. We present frequency-selective experiments for amino acid-selective assignments and the measurement of heteronuclear distances and torsion angles in [U-13C, N]-bR and discuss the relevance of these results to its photocycle. In addition, we describe several applications of solid state NMR, including a study of dynamic and structural phase transitions in peptides and proteins near the canonical glass transition temperature. We present resonance width experiments that can be used to measure homonuclear and heteronuclear dipolar couplings in uniformly labeled solids.(cont.) Finally, we discuss applications to amyloid fibrils, which are protein aggregates that are implicated in diseases of protein misfolding. We report the atomic resolution structure of the disease-associated L 111M mutant of TTR105-115 in an amyloid fibril, and information about the supramolecular structure of fibrils from WT TTRos05115.by Vikram Singh Bajaj.Ph.D

Bibliography of Lewis Research Center Technical Publications announced in 1991

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific engineering work performed and managed by the Lewis Research Center in 1991. All the publications were announced in the 1991 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses