Digital Coherent Receivers and Advanced Optical Modulation Formats in 100 and 200 Gb/s DWDM Systems

Recent advances in coherent optical receivers is reviewed. Digital-Signal-Processing (DSP) based phase and polarization management techniques make coherent detection robust and feasible. With coherent detection, the complex field of the received optical signal is fully recovered, allowing compensation of linear and nonlinear optical impairments including chromatic dispersion (CD) and polarization-mode dispersion (PMD) using digital filters. Coherent detection and advanced optical modulation formats have become a key ingredient to the design of modern dense wavelength-division multiplexed (DWDM) optical broadband networks. In this paper, firstly we present the different subsystems of a digital coherent optical receiver, and secondly, we will compare the performance of some multi-level and multi-dimensional modulation formats in some physical impairments and in high spectral-efficiency (SE) and high-capacity DWDM transmissions, simulating the DSP with Matlab and the optical network performance with OptiSystem software.

Pulse-Shape Analysis of PDM-QPSK Modulation Formats for 100 and 200 Gb/s DWDM transmissions

Advanced optical modulation format polarization-division multiplexed quadrature phase shift keying (PDM-QPSK) has become a key ingredient in the design of 100 and 200-Gb/s dense wavelength-division multiplexed (DWDM) networks. The performance of this format varies according to the shape of the pulses employed by the optical carrier: non-return to zero (NRZ), return to zero (RZ) or carrier-suppressed return to zero (CSRZ). In this paper we analyze the tolerance of PDM-QPSK to linear and nonlinear optical impairments: amplified spontaneous emission (ASE) noise, crosstalk, distortion by optical filtering, chromatic dispersion (CD), polarization mode dispersion (PMD) and fiber Kerr nonlinearities. RZ formats with a low duty cycle value reduce pulse-to-pulse interaction obtaining a higher tolerance to CD, PMD and intrachannel nonlinearities.

Identification of two flavivirus-like genomes in the GB hepatitis agent.

A subtractive PCR methodology known as representational difference analysis was used to clone specific nucleotide sequences present in the infectious plasma from a tamarin infected with the GB hepatitis agent. Eleven unique clones were identified, seven of which were examined extensively. All seven clones appeared to be derived from sequences exogenous to the genomes of humans, tamarins, Saccharomyces cerevisiae, and Escherichia coli. In addition, sequences from these clones were not detected in plasma or liver tissue of tamarins prior to their inoculation with the GB agent. These sequences were detected by reverse transcription-PCR in acute-phase plasma of tamarins inoculated with the GB agent. Probes derived from two of the seven clones detected an RNA species of > or = 8.3 kb in the liver of a GB-agent-infected tamarin by Northern blot hybridization. Sequence analysis indicated that five of the seven clones encode polypeptides that possess limited amino acid identity with the nonstructural proteins of hepatitis C virus. Extension of the sequences found in the seven clones revealed that plasma from an infected tamarin contained two RNA molecules > 9 kb long. Limited sequence identity with various isolates of hepatitis C virus and the relative positions of putative RNA helicases and RNA-dependent RNA polymerases in the predicted protein products of these molecules suggested that the GB agent contains two unique flavivirus-like genomes.

Farewell to Cucullain : (Londonderry air) : for violin and piano /

Mode of access: Internet.

Lives of Lord Castlereagh and Sir Charles Stewart, the second and third Marquesses of Londonderry; with annals of contemporary events in which they bore a part ...

Mode of access: Internet.

Memoirs and correspondence of Viscount Castlereagh, second marquess of Londonderry /

Second series published by W. Shoberl; 3d series, by J. Murray. Third series has added t.p.

Documentos pertenecientes a las Observaciones sobre la historia de la guerra de España que escribieron los señores Clarke, Southey, Londonderry y Napier, publicadas en Londres, el año 1829 /

En portadilla: "Defensa del honor de la nación española contra las injustas acusaciones que le hace la rivalidad extranjera"

The bargain: a historical novel on the defense of Londonderry.

Mode of access: Internet.

A record of the Searight family, (also written Seawright). Established in America by William Seawright, who came from near Londonderry ... to Lancaster County, Pennsylvania, about 1740; with an account of his descendants as far as can be ascertained.

Photocopy.

The doctrine of predestination, truly and fairly stated : confirmed from clear Scripture evidence, and defended against all the material arguments and objections advanced against it, to which is prefixed, a short and faithful narrative of a remarkable revival of religion, in the congregation of New-Londonderry, and other parts of Pennsylvania, as the same was sent in a letter to the Rev. Mr. Prince of Boston /

Mode of access: Internet.