All-Raman amplified transmission at 40 Gbit/s in standard single mode fibre

We investigate a 40 Gbit/s all-Raman amplified standard single mode fibre (SMF) transmission system with the mid-range amplifier spacing of 80-90 km. The impact of span configuration on double Rayleigh back scattering (DRBS) was studied. Four different span configurations were compared experimentally. A transmission distance of 1666 km in SMF has been achieved without forward error correcting (FEC) for the first time. The results demonstrate that the detrimental effects associated with high pump power Raman amplification in standard fibre can be minimised by dispersion map optimisation. © 2003 IEEE.

16,000 km, 10 Gbits-1 soliton transmission over standard fibre by reduction of interactions through optimum amplifier positioning

We show that by optimizing the amplifier position in a two-stage dispersion map, the (dispersion-managed) soliton-soliton interaction can be reduced, enabling transmission of 10-Gbits-1 solitons over standard fiber over 16,000 km

10Gbit/s dispersion managed soliton transmission over 16,500km in standard fibre by reduction of soliton interactions

We show experimentally and numerically that in high-speed strongly dispersion-managed standard fiber soliton systems nonlinear interactions limit the propagation distance. We present results that show that the effect of these interactions can be significantly reduced by appropriate location of the amplifier within the dispersion map. Using this technique, we have been able to extend the propagation distance of 10-Gbit/s 231–1pseudorandom binary sequence soliton data to 16, 500km over standard fiber by use of dispersion compensation. To our knowledge this distance is the farthest transmission over standard fiber without active control ever reported, and it was achieved with the amplifier placed after the dispersion-compensating fiber in a recirculating loop.

Autosoliton propagation at 80 Gbit/s using concatenated nonlinear loop switches in standard fibre

Experimental observation of autosoliton propagation in a nonlinear switch-guided, dispersion-managed system operating at 80 Gbit/s is reported for the first time. The system is based on a strong dispersion map and supports autosoliton propagation over 3000 km.

10Gbit/s dispersion managed soliton transmission over 16,500km in standard fibre by reduction of soliton interactions

We show experimentally and numerically that in high-speed strongly dispersion-managed standard fiber soliton systems nonlinear interactions limit the propagation distance. We present results that show that the effect of these interactions can be significantly reduced by appropriate location of the amplifier within the dispersion map. Using this technique, we have been able to extend the propagation distance of 10-Gbit/s 231–1pseudorandom binary sequence soliton data to 16, 500km over standard fiber by use of dispersion compensation. To our knowledge this distance is the farthest transmission over standard fiber without active control ever reported, and it was achieved with the amplifier placed after the dispersion-compensating fiber in a recirculating loop.

16,000 km, 10 Gbits-1 soliton transmission over standard fibre by reduction of interactions through optimum amplifier positioning

We show that by optimizing the amplifier position in a two-stage dispersion map, the (dispersion-managed) soliton-soliton interaction can be reduced, enabling transmission of 10-Gbits-1 solitons over standard fiber over 16,000 km

Autosoliton propagation at 80Gbit/s in standard fibre using in-line nonlinear loop switches

Experimental observation of autosoliton propagation in a nonlinear switch-guided, dispersion-managed system operating at 80Gbit/s is reported for the first time. The system is based on a strong dispersion map and supports autosoliton propagation over 3,000km.

Does the Swedish Interactive Threshold Algorithm (SITA) accurately map visual field loss attributed to vigabatrin?

Background: Vigabatrin (VGB) is an anti-epileptic medication which has been linked to peripheral constriction of the visual field. Documenting the natural history associated with continued VGB exposure is important when making decisions about the risk and benefits associated with the treatment. Due to its speed the Swedish Interactive Threshold Algorithm (SITA) has become the algorithm of choice when carrying out Full Threshold automated static perimetry. SITA uses prior distributions of normal and glaucomatous visual field behaviour to estimate threshold sensitivity. As the abnormal model is based on glaucomatous behaviour this algorithm has not been validated for VGB recipients. We aim to assess the clinical utility of the SITA algorithm for accurately mapping VGB attributed field loss. Methods: The sample comprised one randomly selected eye of 16 patients diagnosed with epilepsy, exposed to VGB therapy. A clinical diagnosis of VGB attributed visual field loss was documented in 44% of the group. The mean age was 39.3 years∈±∈14.5 years and the mean deviation was -4.76 dB ±4.34 dB. Each patient was examined with the Full Threshold, SITA Standard and SITA Fast algorithm. Results: SITA Standard was on average approximately twice as fast (7.6 minutes) and SITA Fast approximately 3 times as fast (4.7 minutes) as examinations completed using the Full Threshold algorithm (15.8 minutes). In the clinical environment, the visual field outcome with both SITA algorithms was equivalent to visual field examination using the Full Threshold algorithm in terms of visual inspection of the grey scale plots, defect area and defect severity. Conclusions: Our research shows that both SITA algorithms are able to accurately map visual field loss attributed to VGB. As patients diagnosed with epilepsy are often vulnerable to fatigue, the time saving offered by SITA Fast means that this algorithm has a significant advantage for use with VGB recipients.

Simple approximate MAP inference for Dirichlet processes mixtures

The Dirichlet process mixture model (DPMM) is a ubiquitous, flexible Bayesian nonparametric statistical model. However, full probabilistic inference in this model is analytically intractable, so that computationally intensive techniques such as Gibbs sampling are required. As a result, DPMM-based methods, which have considerable potential, are restricted to applications in which computational resources and time for inference is plentiful. For example, they would not be practical for digital signal processing on embedded hardware, where computational resources are at a serious premium. Here, we develop a simplified yet statistically rigorous approximate maximum a-posteriori (MAP) inference algorithm for DPMMs. This algorithm is as simple as DP-means clustering, solves the MAP problem as well as Gibbs sampling, while requiring only a fraction of the computational effort. (For freely available code that implements the MAP-DP algorithm for Gaussian mixtures see http://www.maxlittle.net/.) Unlike related small variance asymptotics (SVA), our method is non-degenerate and so inherits the “rich get richer” property of the Dirichlet process. It also retains a non-degenerate closed-form likelihood which enables out-of-sample calculations and the use of standard tools such as cross-validation. We illustrate the benefits of our algorithm on a range of examples and contrast it to variational, SVA and sampling approaches from both a computational complexity perspective as well as in terms of clustering performance. We demonstrate the wide applicabiity of our approach by presenting an approximate MAP inference method for the infinite hidden Markov model whose performance contrasts favorably with a recently proposed hybrid SVA approach. Similarly, we show how our algorithm can applied to a semiparametric mixed-effects regression model where the random effects distribution is modelled using an infinite mixture model, as used in longitudinal progression modelling in population health science. Finally, we propose directions for future research on approximate MAP inference in Bayesian nonparametrics.