Digital curves in 3D space and a linear-time length estimationalgorithm

We consider simple digital curves in a 3D orthogonal grid as special polyhedrally bounded sets. These digital curves model digitized curves or arcs in three-dimensional Euclidean space. The length of such a simple digital curve is defined to be the length of the minimum-length polygonal curve fully contained and complete in the tube of this digital curve. So far, no algorithm was known for the calculation of such a shortest polygonal curve. The paper provides an iterative algorithmic solution for approximating the minimum-length polygon of a given simple digital space-curve. The theoretical foundations of this algorithm are presented as well as experimental results     

Adaptive PMD compensation by electrical and optical techniques

Adaptive polarization-mode dispersion (PMD) compensation in 10 and 40 Gb/s transmission systems might become necessary if the link PMD causes strong signal distortions, which results in an unacceptable high system outage. The application of PMD compensation has the potential to lead to a drastic improvement of system robustness. Optical and electrical compensators will be reported, their operation principle explained, and their benefits will be quantified. The discussion is focused on the most important structures for practical system application including adaptive feedback loops. Experimental investigations proof compensator concepts which performance conforms with simulations. The electronical feed forward equalizer and the decision feedback equalizer are assessed in comparison to the optical simple and the two-stage compensator and the differences in performance are discussed for statistical PMD limited systems.     

System outage probability due to first- and second-order PMD

A theoretical approach is proposed that allows one to quantify the impact of fiber polarization mode dispersion (PMD) on optical binary transmission taking into account not only first-order polarization mode dispersion, but also signal distortion induced by second-order PMD. Using this approach the impact of the spectral signal width on PMD-induced system outage probability could be studied for the first time. An analysis of 10-Gb/s transmission exhibits that, as long as the mean PMD remains below the commonly accepted limit (about 10 ps) for negligible outage, a linear chirp of up to 30 GHz does not lead to an additional increase of the system outage. This result confirms that low bandwidth modulation schemes (external modulator, low chirp laser) do not suffer from additional outage degradation due to second-order PMD     

Electronic Dispersion Compensation

The performance of different electronic equalization and processing schemes for 40- and 10-Gb/s optical transmission over single-mode fiber (SMF) are discussed, from the point of their ability to compensate chromatic dispersion (CD) and polarization mode dispersion (PMD). In addition, the impact of fiber nonlinearity and modulation format on equalization is also investigated. The main objective of this paper is to present an overview and a comparison of the performances rather than a detailed explanation of the principles of the different equalization schemes. The equalizers which will be covered are analog equalizer (feedforward and decision feedback type), maximum likelihood sequence estimator (MLSE), electronic precompensation, coherent/intradyne detection with digital signal processing (DSP) equalization, DSP-based optical orthogonal frequency division multiplexing (OFDM), and turbo equalization.     

PMD-Induced Outage Probability in an Optical Communication System With Fast Polarization Scramblers and Time-Varying PMD Sections

Polarization-mode-dispersion (PMD) tolerance of an optical communication system with distributed fast polarization scramblers (PS's) and time-varying PMD sections in terms of outage probability (OP) is investigated. We show that with a moderate number of PS's (up to 14), the PMD mitigation technique using distributed fast PS's and a typical forward-error correction increases the PMD tolerance by up to ~50% at an OP of 10^-5. We provide a scaling rule to link the PMD tolerance in the system with fixed PMD sections to that with time-varying PMD sections. The implication of the Hinge model is briefly discussed.     

Operation of digital optical transmission system with minimaldegradation due to polarisation mode dispersion

The probability of BER degradation above 10^-9 is evaluated theoretically as the quality parameter for examining the robustness of an optical transmission system incorporating an EDFA to fibre polarisation mode distortion (PMD). Provided that there is an existing power margin, a significantly reduced sensitivity to PMD is achieved by detuning the decision level of the optical receiver from the optimum for zero PMD     

NMR investigations on molecular transport in ZSM-5 type zeolites containing structural defects

NMR spectroscopy is used to study the transport properties in ZSM-5 type zeolites containing structural irregularities. Using methane as a probe molecule, the structural distortions in polycrystalline aggregates are found to lead to an enhanced molecular mobility. After coking, molecular mobility is more reduced than in the monocrystalline specimen. This finding is explained by a preferential coke deposition in the secondary pore system. A variation of the concentration of non-acidic OH groups (silanol groups) indicating non-intact Si---O---Si bonds as structural defects of the pentasil structure, leads to characteristic changes in the sorption and diffusion properties of water. Bronsted acid sites are probed by methane self-diffusion measurements after chemisorption of ammonia and pyridine.     

Output power characteristics of erbium-doped fiber ring lasers

The output power of an erbium-doped fiber ring laser has been measured as a function of pump power, emission wavelength, doped-fiber length, and reflectivity of the output coupler. A theoretical model for the calculation of the output power is introduced that is based on a previously derived gain equation for erbium-doped fiber amplifiers. The calculated values are in good agreement with the experimental data, confirming the applicability of the theory to a reliable modeling of the output power of erbium fiber ring lasers     

Calculation of the noise figure of erbium-doped fiber amplifiersusing small signal attenuations and saturation powers

A theory allowing the noise figure of an erbium-doped fiber amplifier to be computed with a reduced set of fiber parameters is evaluated. The approach is accurate when the amplified spontaneous emission has no significant influence on the gain. Then four parameters, saturation power and absorption coefficient for pump and signal wavelength, are sufficient for 980-nm pumped fiber amplifier. This theory is used to investigate the noise characteristics of a 980-nm pumped booster amplifier within the whole gain spectrum