Performance analysis of 20 Gbit/s RZ-DPSK non-slope matched transoceanic submarine links

This paper studies the performance of a typical non-slope matched transoceanic submarine link using 20Gb/s channel rate and RZ-DPSK modulation with different duty cycles. Through comparison with direct error counting, we have also demonstrated the limitations of the available numerical approaches to the BER estimation for return-to-zero differential phase-shift keying (RZ-DPSK). The numerical results have been confirmed by experiments, and indicate that 20 Gb/s RZ-DPSK transmission is a feasible technique for the upgrade of existing submarine links.

An examination of the Prandtl mechanism in large dimension slope failures

An alternative explanation for the modes of failure of large scale failures of open pit walls to those of classical slope stability theory is proposed that makes use of the concept of a transition zone, which is described by a modified Prandtls prism.

Bit-error rate performance of 20 Gbit/s WDM RZ-DPSK non-slope matched submarine transmission systems

Applying direct error counting, we assess the performance of 20 Gbit/s wavelength-division multiplexing return-to-zero differential phase-shift keying (RZ-DPSK) transmission at 0.4 bit/(s Hz) spectral efficiency for application on installed non-zero dispersion-shifted fibre based transoceanic submarine systems. The impact of the pulse duty cycle on the system performance is investigated and the reliability of the existing theoretical approaches to the BER estimation for the RZ-DPSK format is discussed.

Performance analysis of 20 Gb/s RZ-DPSK non-slope matched transoceanic submarine links

Direct computation of the bit-error rate (BER) and laboratory experiments are used to assess the performance of a non-slope matched transoceanic submarine transmission link operating at 20Gb/s channel rate and employing return-to-zero differential-phase shift keying (RZ-DPSK) signal modulation. Using this system as an example, we compare the accuracies of the existing theoretical approaches to the BER estimation for the RZ-DPSK format.

Tuneable compensator of dispersion and slope using non-uniformly strained chirped fibre grating

Summary form only given. A novel method for tuning the second and the third order dispersion using a simple multi-point bending device has been demonstrated. A simple model has been developed that allows to calculate the exact bending profile required for compensation for the given values of dispersion and dispersion slope.

Performance analysis of 20 Gbit/s RZ-DPSK non-slope matched transoceanic submarine links

This paper studies the performance of a typical non-slope matched transoceanic submarine link using 20Gb/s channel rate and RZ-DPSK modulation with different duty cycles. Through comparison with direct error counting, we have also demonstrated the limitations of the available numerical approaches to the BER estimation for return-to-zero differential phase-shift keying (RZ-DPSK). The numerical results have been confirmed by experiments, and indicate that 20 Gb/s RZ-DPSK transmission is a feasible technique for the upgrade of existing submarine links.

Efficient optimisation of per-channel pre-compensation in WDM 20-Gbit/s RZ-DPSK transmission in non-slope matched submarine links

We propose a computationally efficient method to the per-channel dispersion optimisation applied to 50 GHz-spaced N × 20-Gbit/s wavelength division multiplexing return-to-zero differential phase shift keying transmission in non-zero dispersion-shifted fibre based submarine systems. Crown Copyright © 2010.

Tunable pure dispersion slope compensators realized with novel complex gratings

We present a novel tunable dispersion compensator that can provide pure slope compensation. In experiments, we achieve dispersion slope tuning range of +/-650ps/nm2with >0.9nm usable bandwidth.

Tunable dispersion slope compensator using novel tailored Gires-Tournois etalons

We present a novel concept of tailored GTE structure and show that such devices are very useful for the realization of DSC with almost arbitrary dispersion profile and also with tunability in dispersion slope.

Tailored Gires-Tournois etalons as tunable dispersion slope compensators

We present a novel concept of a tailored Gires-Tournois etalon structure and show that such a device is useful for the fabrication of a dispersion-slope compensator with an almost arbitrary dispersion profile and also with tunability in the dispersion slope. © 2004 Optical Society of America.

Bit-error rate performance of 20 Gbit/s WDM RZ-DPSK non-slope matched submarine transmission systems

Applying direct error counting, we assess the performance of 20 Gbit/s wavelength-division multiplexing return-to-zero differential phase-shift keying (RZ-DPSK) transmission at 0.4 bit/(s Hz) spectral efficiency for application on installed non-zero dispersion-shifted fibre based transoceanic submarine systems. The impact of the pulse duty cycle on the system performance is investigated and the reliability of the existing theoretical approaches to the BER estimation for the RZ-DPSK format is discussed.

Performance analysis of 20Gb/s RZ-DPSK non-slope matched transoceanic submarine links

Direct computation of the bit-error rate (BER) and laboratory experiments are used to assess the performance of a non-slope matched transoceanic submarine transmission link operating at 20Gb/s channel rate and employing return-to-zero differential-phase shift keying (RZ-DPSK) signal modulation. Using this system as an example, we compare the accuracies of the existing theoretical approaches to the BER estimation for the RZ-DPSK format. © 2007 Optical Society of America.

Current observations near the continental slope off Portugal

Some current meter data obtained from a mooring at 2450 m water depth near the continental slope off Portugal are presented. The mean currents at five levels with observations are northward. Mean speeds in the core of the Mediterranean Water exceed speeds at shallower levels by 2 to 3 cm/sec, indicating advection connected to this specific water mass. The current variability is dominated by semi-diurnal tidal components. Normal mode analysis reveals a predominant mode of order 2, representing 48% of the total kinetic tidal energy. Results for the barotropic tidal component are in good agreement with earlier predictions for this area. The motion at higher frequencies w in the internal gravity wave band can be well described by a w**-2 power law for the energy density spectrum. This result is consistent with earlier observations in other parts of the ocean.

Geochemistry of sediments from the continental slope of the Ross Sea, Antarctica

A sediment core, collected from the western part of the continental slope of the Ross Sea at 2380 m water depth, records events of the last two climatic cycles (250 kyr). A 230Thex-based chronology was obtained and boundaries of the isotope stages were set assuming that biological productivity was enhanced during periods of less ice cover. Then, 230Thex0, organic carbon, biogenic silica and biogenic Ba distributions were compared to the glacial-interglacial stage boundaries and corresponding ages of the delta18O record of Martinson et al. [Martinson et al., 1987, doi:10.1016/0033-5894(87)90046-9]. Sediment accumulation rates ranged between 1.2 cm kyr**-1 in the isotope stage 6 and 3.8 cm kyr**-1 during the Holocene. Variations in the concentrations and fluxes of organic carbon, biogenic Ba, biogenic silica and Mn gave information on palaeoclimate changes. Processes of sediment redistribution in the Ross Sea margin were enlightened from a comparison of the measured and expected fluxes of 230Thex. Calculation of the focusing-corrected accumulation rates of biogenic Ba enabled us to evaluate the export palaeoproductivity. Corrected accumulation rates of biogenic components and calculated palaeoproductivities were low, compared to the Antarctic Polar Front in the Atlantic sector, throughout the last two climatic cycles. Glacial-interglacial changes of sea ice cover and ventilation of the Ross Sea were probably major causes of variations in biogenic particle flux and distribution of redox-sensitive elements within the sediment column.

Submarine slope failures in gassy soils

Submarine slope stability has become an important concern and a subject of research with increasing demand for offshore developments and technological advancement for harsh and challenging environments. The consequences of submarine slope failure adjacent to oil and gas facilities would have a large financial, safety and regulatory impact. This current research work investigates potential failure of submarine gassy slopes triggered by tidal variations. Due to tidal variations, failure of an unsaturated slope may occur under specific combinations of increasing degree of saturation and soil permeability, and decreasing tidal period. Novel physical model tests in a geotechnical centrifuge were undertaken to examine submarine slope failure mechanisms containing gassy sediments. The model preparation techniques, measurement systems and results are presented. The response observed in the model test is discussed and further developments proposed. The buried PPT’s response of the submarine slope are comparable in terms of attenuation and phase lag with Nagaswaran (1983) and with field measurements of Atigh and Byrne (2004) in terms of phase lag.