Technical digest, Symposium on Optical Fibert Measurements, 1980 : digest of a symposium /

"October 1980."

Adaptive phase measurements for narrowband squeezed beams

We have previously [Phys. Rev. A 65, 043803 (2002)] analyzed adaptive measurements for estimating the continuously varying phase of a coherent beam, and a broadband squeezed beam. A real squeezed beam must have finite photon flux N and hence can be significantly squeezed only over a limited frequency range. In this paper we analyze adaptive phase measurements of this type for a realistic model of a squeezed beam. We show that, provided it is possible to suitably choose the parameters of the beam, a mean-square phase uncertainty scaling as (N/kappa)(-5/8) is possible, where kappa is the linewidth of the beam resulting from the fluctuating phase. This is an improvement over the (N/kappa)(-1/2) scaling found previously for coherent beams. In the experimentally realistic case where there is a limit on the maximum squeezing possible, the variance will be reduced below that for coherent beams, though the scaling is unchanged.

Optical phase conjugation for dispersion and nonlinearity compensation in a 1600km, 42 Gb/s quasi-lossless system

We experimentally investigate a long-distance, high-bit-rate transmission system which combines optical-phase-conjugation with quasi-lossless amplification. Comparison with a conventional system configuration demonstrates the possibility of obtaining both dispersion compensation and improved nonlinear tolerance using proposed scheme.

All-optical phase and amplitude regenerator for next-generation telecommunications systems

Fibre-optic communications systems have traditionally carried data using binary (on-off) encoding of the light amplitude. However, next-generation systems will use both the amplitude and phase of the optical carrier to achieve higher spectral efficiencies and thus higher overall data capacities(1,2). Although this approach requires highly complex transmitters and receivers, the increased capacity and many further practical benefits that accrue from a full knowledge of the amplitude and phase of the optical field(3) more than outweigh this additional hardware complexity and can greatly simplify optical network design. However, use of the complex optical field gives rise to a new dominant limitation to system performance-nonlinear phase noise(4,5). Developing a device to remove this noise is therefore of great technical importance. Here, we report the development of the first practical ('black-box') all-optical regenerator capable of removing both phase and amplitude noise from binary phase-encoded optical communications signals.

Optical phase conjugation for dispersion and nonlinearity compensation in a 1600km, 42 Gb/s quasi-lossless system

We experimentally investigate a long-distance, high-bit-rate transmission system which combines optical-phase-conjugation with quasi-lossless amplification. Comparison with a conventional system configuration demonstrates the possibility of obtaining both dispersion compensation and improved nonlinear tolerance using proposed scheme.

Exceeding the nonlinear-shannon limit using Raman laser based amplification and optical phase conjugation

We demonstrate that a combination of Raman laser based amplification and optical phase conjugation enables transmission beyond the nonlinear-Shannon limit. We show nonlinear compensation of 7x114Gbit/s DP-QPSK channels, increasing system reach by 30%. © 2013 Optical Society of America.

1THz-bandwidth polarization-diverse optical phase conjugation of 10x114Gb/s DP-QPSK WDM signals

Polarization diverse optical phase conjugation of a 1THz spectral-band 1.14Tb/s DP-QPSK WDM multiplex is demonstrated for the first time, showing a worst case Q2 penalty of 0.9dB over all conjugate wavelengths, polarizations and OSNR. © 2014 OSA.

1.14Tb/s DP-QPSK WDM polarization-diverse optical phase conjugation

Optical phase conjugation (OPC) of a polarization-multiplexed comb of 10x114Gb/s DP-QPSK signals has been demonstrated for the first time, occupying a spectral bandwidth of >1THz (~9nm). The nonlinear element employed for the OPC was highly nonlinear fiber (HNLF) optimized for the suppression of stimulated Brillouin scattering (SBS) and configured in a bi-directional loop offering polarization diversity. Pump power (each way about the loop) and input signal power to the OPC subsystem were optimized at 29.7dBm and + 3dBm respectively producing a Q2 penalty of ≤0.9dB over all conjugate wavelengths, polarizations and output OSNR (up to 20dB).

Capacity limits of systems employing multiple optical phase conjugators

We extend the theory of parametric noise amplification to the case of transmission systems employing multiple optical phase conjugators, demonstrating that the excess noise due to this process may be reduced in direct proportion to the number of phase conjugation devices employed. We further identify that the optimum noise suppression is achieved for an odd number of phase conjugators, and that the noise may be further suppressed by up to 3dB by partial digital back propagation (or fractional spans at the ends of the links).

Optical-phase conjugation nonlinearity compensation in Flexi-Grid optical networks

Optical-phase conjugation nonlinearity compensation (OPC-NLC) in optical networks is evaluated using a built-in tool including self-channel and crosstalk channel interference effects. Though significant improvements are observed, a further refined launch power policy is required to fully take advantage of OPC-NLC capability.

4 Tb/s transmission reach enhancement using 10 × 400 Gb/s super-channels and polarization insensitive dual band optical phase conjugation

In this paper, we experimentally demonstrate the benefit of polarization insensitive dual-band optical phase conjugation for up to ten 400 Gb/s optical super-channels using a Raman amplified transmission link with a realistic span length of 75 km. We demonstrate that the resultant increase in transmission distance may be predicted analytically if the detrimental impacts of power asymmetry and polarization mode dispersion are taken into account.

Signal power asymmetry optimisation for optical phase conjugation using random DFB laser Raman amplification

We numerically optimise in-span signal power asymmetry in advanced Raman amplification schemes, reaching 3% over 62 km SMF, and evaluate its impact on the performance of systems using mid-link OPC using 7 × 15 16QAM Nyquist-spaced WDM-PDM. © 2015 OSA.

Signal power asymmetry optimisation for optical phase conjugation using Raman amplification

We numerically optimise in-span signal power asymmetry in different advanced Raman amplification schemes, achieving a 3% asymmetry over 62 km SMF using random DFB Raman laser amplifier. We then evaluate the impact of such asymmetry on the performance of systems using mid-link OPC by simulating transmission of 7 x 15 Gbaud 16QAM Nyquist-spaced WDM-PDM signals. (C) 2015 Optical Society of America

Pore water and solid-phase measurements on sediment cores from the Black Sea

The surface sediments in the Black Sea are underlain by extensive deposits of iron (Fe) oxide-rich lake sediments that were deposited prior to the inflow of marine Mediterranean Sea waters ca. 9000 years ago. The subsequent downward diffusion of marine sulfate into the methane-bearing lake sediments has led to a multitude of diagenetic reactions in the sulfate-methane transition zone (SMTZ), including anaerobic oxidation of methane (AOM) with sulfate. While the sedimentary cycles of sulfur (S), methane and Fe in the SMTZ have been extensively studied, relatively little is known about the diagenetic alterations of the sediment record occurring below the SMTZ. Here we combine detailed geochemical analyses of the sediment and pore water with multicomponent diagenetic modeling to study the diagenetic alterations below the SMTZ at two sites in the western Black Sea. We focus on the dynamics of Fe, S and phosphorus (P) and demonstrate that diagenesis has strongly overprinted the sedimentary burial records of these elements. Our results show that sulfate-mediated AOM substantially enhances the downward diffusive flux of sulfide into the deep limnic deposits. During this downward sulfidization, Fe oxides, Fe carbonates and Fe phosphates (e.g. vivianite) are converted to sulfide phases, leading to an enrichment in solid phase S and the release of phosphate to the pore water. Below the sulfidization front, high concentrations of dissolved ferrous Fe (Fe2+) lead to sequestration of downward diffusing phosphate as authigenic vivianite, resulting in a transient accumulation of total P directly below the sulfidization front. Our model results further demonstrate that downward migrating sulfide becomes partly re-oxidized to sulfate due to reactions with oxidized Fe minerals, fueling a cryptic S cycle and thus stimulating slow rates of sulfate-driven AOM (~ 1-100 pmol/cm**3/d) in the sulfate-depleted limnic deposits. However, this process is unlikely to explain the observed release of dissolved Fe2+ below the SMTZ. Instead, we suggest that besides organoclastic Fe oxide reduction, AOM coupled to the reduction of Fe oxides may also provide a possible mechanism for the high concentrations of Fe2+ in the pore water at depth. Our results reveal that methane plays a key role in the diagenetic alterations of Fe, S and P records in Black Sea sediments. The downward sulfidization into the limnic deposits is enhanced through sulfate-driven AOM with sulfate and AOM with Fe oxides may provide a deep source of dissolved Fe2+ that drives the sequestration of P in vivianite below the sulfidization front.

4 Tb/s transmission reach enhancement using 10 × 400 Gb/s super-channels and polarization insensitive dual band optical phase conjugation

In this paper, we experimentally demonstrate the benefit of polarization insensitive dual-band optical phase conjugation for up to ten 400 Gb/s optical super-channels using a Raman amplified transmission link with a realistic span length of 75 km. We demonstrate that the resultant increase in transmission distance may be predicted analytically if the detrimental impacts of power asymmetry and polarization mode dispersion are taken into account.