Degree of polarization degradation due to cross-phase modulation and its impact on polarization-mode dispersion compensators

A novel analytical model is proposed to predict the cross-phase modulation (XPM)-induced depolarization in a two-channel transmission system, in which the Stokes' vector of each channel rotates around a space-invariant pivot by a time-varying angle which depends on the total instantaneous optical power in the fiber, on the angle between pump and probe input Stokes' vectors, and on the walk-off between channels. The model leads to a simple formula of the probe degree of polarization (DOP) which is validated both by simulation and experiment. The model helps identify the key physical factors that determine the XPM-induced performance degradation of DOP-based first-order polarization-mode dispersion compensators, and experiments that quantify such degradation are presented.     

Experimental investigation of stimulated Raman scatteringlimitation on WDM transmission over various types of fiberinfrastructures

We measure the impact of stimulated Raman scattering on the power distribution of a 32-channel multiplex after 100-km transmission over various fiber types. The Raman gain coefficient is then estimated in each configuration     

Nonlinearity Limitations When Mixing 40-Gb/s Coherent PDM-QPSK Channels With Preexisting 10-Gb/s NRZ Channels

We investigate the penalties onto a 40-Gb/s polarization-division-multiplexing (PDM)-quadrature phase-shift keying caused by PDM, wavelength-division multiplexing and 10-Gb/s nonreturn-to-zero neighbor channels. Besides, we optimize the carrier phase estimation process and introduce bandgaps in the multiplex in order to contain limitations caused by cross nonlinear effects.     

Dependence of self-phase modulation impairments on residualdispersion in 10-Gb/s-based terrestrial transmissions using standardfiber

We carry out, by computer simulation, an extensive investigation of the impact of residual dispersion on power margins induced by self-phase modulation in typical 5×100 km-long terrestrial transmission systems at 10 Gb/s, using standard single-mode fiber and modular dispersion compensation. We show that the most performing compensation technique is postcompensation, with positive residual dispersion, and that precompensation must be avoided in case of dual-stage amplification. We also propose a design rule to perform optimal dispersion compensation in multichannel transmissions     

Parametric gain in the strongly nonlinear regime and its impact on 10-Gb/s NRZ systems with forward-error correction

In this paper, we show that the nonlinear parametric gain (PG) interaction between signal and noise is a nonnegligible factor in the design and analysis of long-haul dispersion-managed optical 10-Gb/s on-off keying nonreturn to zero transmission systems operated at small signal-to-noise ratios (OSNRs) such as those employing forward-error correction (FEC) coding. In such a regime, we show that the in-phase noise spectrum exhibits a large gain close to the carrier frequency, which is due to the higher order noise terms accounting for the noise-noise beating during propagation that is usually neglected in the nonlinear Schro/spl uml/dinger equation. With a novel stochastic analysis that keeps such higher order terms, we are able to analytically quantify the maximum tolerable signal power after which PG unacceptably degrades system performance. We verify such an analytical power threshold by both simulation and experiment. We finally quantify the needed extra OSNR, or equivalently FEC coding gain, required when taking PG into account.     

WDM transmission at 6-Tbit/s capacity over transatlantic distance, using 42.7-Gb/s differential phase-shift keying without pulse carver

We report the transmission of a record 6 Tbit/s capacity over 6120 km distance, involving channels modulated at 42.7-Gb/s bit-rate with differential phase-shift keying (DPSK). The performance is found similar to DPSK with subsequent pulse carving, namely RZ-DPSK.     

Experimental evaluation of TeraLight/sup TM/ resistance to cross-nonlinear effects for channel spacings down to 50 GHz

An investigation is presented into the impact of cross-nonlinear effects over TeraLight/sup TM/ fibre through an analysis of a 400 km-long 32/spl times/10 Gbit/s WDM transmission with channel spacing of 100 and 50 GHz, span loss of 28 dB and optimised dispersion management.     

Upgrading WDM Submarine Systems to 40-Gbit/s Channel Bitrate

The introduction of wavelength division multiplexing (WDM) has triggered a tremendous capacity growth in submarine systems, both by the increase of the number of WDM channels and by the increase of the channel bitrate. Starting from 2.5 Gbit/s in the mid-1990s, the bitrate was upgraded to 10 Gbit/s by the end of the century in commercial products. The next generation of submarine systems will likely be based on a 40-Gbit/s bitrate. However, transmissions at a 40-Gbit/s rate are more challenging than transmissions at 10 Gbit/s. The goal of this paper is to provide an overview of the technologies which could be required or used in next-generation submarine systems. In the first part of this paper, an overview of the history of submarine links is provided. Then the technologies used in current N /spl times/ 10 Gbit/s systems are described. Eventually, the challenges to overcome are discussed, whether they concern the type of fiber, the type of optical amplifier, or the nature of the modulation format.     

Pseudomembranous colitis caused by antibiotics

To study the effectiveness of a trend at the Mayo Clinic toward modifying the standard radical mastectomy, the 5-year survival of 873 women treated surgically for breast cancer from 1965 through 1968 was evaluated. The observed survival of 534 patients treated by the standard radical mastectomy was 85% when nodes were negative and 56% when nodes were positive. For 339 patients treated by the modified radical mastectomy, the observed survival was 80% and 48% when axillary nodes were negative and positive, respectively. In order to accomplish a more significant analysis of cancer risk and results of the two operative procedures, a relatively homogeneous group of 541 patients was established from the total group. In this homogeneous group, the observed survival of 336 patients treated by the standard radical mastectomy was 86% when nodes were negative and 66% when nodes were positive. For 205 patients treated by the modified radical mastectomy, the observed survival was 84% and 66% when axillary nodes were negative and positive, respectively. When patients were further analyzed and compared according to the extent of axillary-node involvement, age at the time of treatment, grade, size, location, and histopathologic type of tumor, and the use of postoperative irradiation, survival was essentially the same, irrespective of the type of mastectomy performed.