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The neonate transitions from placenta-derived oxygen, to supply from the pulmonary system, moments after birth. This requires a series of structural developments to divert more blood through the right heart and onto the lungs, with the tissue quickly remodelling to the changing ventricular workload. In some cases, however, the heart structure does not fully develop causing poor circulation and inefficient oxygenation, which is associated with an increase in mortality and morbidity. This study focuses on developing an enhanced knowledge of the 1-day old heart, quantifying the region-specific microstructural parameters of the tissue. This will enable more accurate mathematical and computational simulations of the young heart. Hearts were dissected from 12, 1-day-old deceased Yorkshire piglets (mass: 2.1–2.4 kg, length: 0.38–0.51 m), acquired from a breeding farm. Evans blue dye was used to label the heart equator and to demarcate the left and right ventricle free walls. Two hearts were used for three-dimensional diffusion-tensor magnetic resonance imaging, to quantify the fractional anisotropy (FA). The remaining hearts were used for two-photon excited fluorescence and second-harmonic generation microscopy, to quantify the cardiomyocyte and collagen fibril structures within the anterior and posterior aspects of the right and left ventricles. FA varied significantly across both ventricles, with the greatest in the equatorial region, followed by the base and apex. The FA in each right ventricular region was statistically greater than that in the left. Cardiomyocyte and collagen fibre rotation was greatest in the anterior wall of both ventricles, with less dispersion when compared to the posterior walls. In defining these key parameters, this study provides a valuable insight into the 1-day-old heart that will provide a valuable platform for further investigation the normal and abnormal heart using mathematical and computational models. Electronic supplementary material The online version of this article (10.1007/s10439-018-2089-4) contains supplementary material, which is available to authorized users.

This work explains in detail the role of the dispersion contribution provided by a single-mode optical fibre (SMF) in the pulse propagation problem modelled by the nonlinear Schrödinger equation. Firstly, the basics of chromatic dispersion in fibre are presented, including a modified Sellmeier equation for representing the dispersion contribution of the fibre core material (in an illustrative case of fused silica doped with germanium dioxide) that is modified by the waveguide dispersion contribution. At the same time, the contribution of the second-, third- and fourth-order dispersion parameters are illustrated for a SMF. Finally, a numerical analysis of the propagation problem is presented in order to understand the dispersion effects for a sech2 pulse profile, as well as the interplay of its contribution with the nonlinear Kerr effect, which is also involved in the pulse propagation. For a better understanding of the numerical methods applied to develop the propagation problem, we include a guide detailing the stages to follow in the numerical approach, considering how to select the initial parameters as well as the iterative steps of the numerical method.

Even if a number of methods have been proposed for resolving crossing fibres from diffusion-weighted (DW) MRI, other complex fibre geometries have drawn minimal attention. In this study, we focus on fibre orientation dispersion induced by within-voxel fanning. We use a multi-compartment, model-based approach to estimate fibre dispersion. A Bingham distribution is employed to represent a continuum of fibre orientations, centred around a main orientation. We evaluate the accuracy of the model for different simulated fanning geometries, under different acquisition protocols and we illustrate the high SNR and angular resolution needs. We apply the proposed model on high-quality, postmortem macaque data and present whole-brain maps of fibre dispersion. © 2012 IEEE.

The study presents theoretical and experimental investigations on radio over fibre links concerning the effect of fibre dispersion. An approach is presented to overcome the radio-frequency suppression effect in optical links based on the joint effect of semiconductor optical amplifier chirp, chromatic dispersion and non-linearities of optical fibre. The results show that the frequency notches caused by the dispersion induced carrier suppression effect may be sharply alleviated and the performance of the transmitted signal can be improved.

Wood fibres suspended in air were studied whilst flowing through a throttle. Measurements of volume fraction and velocity were compared with results from a two-fluid model simulation. Results from earlier work have shown that the lift forces acting on the individual fibres are of importance for the dispersion of volume fraction. Since the orientation of the individual fibres cannot be determined, a dispersion force was utilised to model the dispersing effect of the lift forces. The addition of a lift dispersion model significantly improved the agreement between measurement and model data.

We present the measurement of chromatic dispersion around 1550 nm of a number of optical fibres with a pulse delay technique utilising an electroabsorption modulator and an autocorrelator for high temporal accuracy. In total, 10 fibres with various lengths and dispersion characteristics have been characterised, demonstrating the flexibility of the method. Mismatches between manufacturer-quoted and measured dispersion values ranged from 0.8% to 9% and it is believed that higher accuracies can be achieved by perfecting the data processing procedure. This technique may find application in research laboratories for quick and reliable fibre dispersion characterisation.

There have been numerous reports on the distortions suffered by gaussian-shaped pulses transmitted through dispersive optical fibres. Such distortions are in the form of pulse broadening due to second-order fibre dispersion and the breakdown of the transmitted pulses into multiple pulses due to third-order dispersion. In this paper, the distortions suffered by square-shaped pulses transmitted through dispersive optical fibres are investigated. It is shown that square-shaped pulses suffer the same kinds of distortions as gaussian-shaped pulses.

The bandwidth of coherent supercontinuum generated in optical fibres is strongly determined by the all-normal dispersion characteristic of the fibre. We investigate all-normal dispersion limitations in all-solid oxide-based soft glass photonic crystal fibres with various relative inclusion sizes and lattice constants. The influence of material dispersion on fibre dispersion characteristics for a selected pair of glasses is also examined. A relation between the material dispersion of the glasses and the fibre dispersion has been described. We determined the parameters which limit the maximum range of flattened all-normal dispersion profile achievable for the considered pair of heavy-metal-oxide soft glasses.

In recent years much research has focussed on the development of high capacity optical transmission systems for terrestrial and undersea application. The development of optical amplifier repeaters has led to the situation where multigigabit transmission is required over very large distances. In this situation the effects of fibre dispersion pose a serious limitation to performance. This paper considers the effects of fibre dispersion and discusses the technique of non-linear propagation which has been proposed to overcome the problem. The main design equations for a soli-ton system are presented and discussed.

In this paper, we investigate the transmission of a WiMAX 54Mbit/s signal with 3.5GHz carrier frequency using radio over fibre (RoF) for a fibre length of 410km. A Fibre Bragg Grating (FBG) and Dispersion Compensating Fibre (DCF) are used to control chromatic dispersion, signal distortion and to compensate for the accumulated dispersion in the fibre. In our study, the WiMAX signal is first simulated with a single mode fibre (SMF) for distances over 200km. We then combine the SMF and dispersion compensating fibre (DCF), with negative dispersion (−80ps/km/nm at 1552nm), in order to extend the distance to 288 km. Finally, we merge the SMF, DCF and FBG, with negative fibre dispersion (−140ps/nm), such that the transmission distance can be extended to 410km. Simulation results show that the combination of SMF, DCF and FBG has increased the transmission distance in the fibre by more than 100% (from 180km to 410km) using the same power optic amplifier (EDFAs) as for SMF (65 dB).

Performance of SPM based all-optical regenerator is evaluated for 40-Gb/s data. Results indicate that as the ratio between the product of fibre dispersion and length to the nonlinear phase-shift keeps constant, overall system performance improvements are similar.

Radio-over-fibre systems can efficiently deliver broadband wireless services in access and in-building networks. RoF signal transport and routing techniques are presented which are robust against fibre dispersion and provide capacity-on-demand for high-capacity multi-tone radio signals.

A numerical method is proposed to accurately discriminate the influence of each intrachannel nonlinear effect. In contrast to other studies, we obtain that i-FWM is the most penalizing effect in all our investigated 43 Gb/s cases. (2 pages)

The impact of fibre chromatic dispersion on 40 Gbit/s on-off keying and differential phase-shift keying transmission is compared by means of numerical simulation. The optimum fibre type is identified for various duty-cycles. While NZDSF is the optimum choice for OOK-formats, SSMF is preferable for RZ-DPSK. (2 pages)

The effectivity of the presented simulation model of an analog CATV link taking into account nonlinear effects present in an optical fibre has been confirmed through comparison with the results of the theoretical analysis. The model can be used to investigate the method of compensation utilizing prechirping in the transmitter, as well as other parasitic phenomena, as for example phase shift between modulating signals or non-flat EDFA spectral characteristic. The possibility of nonlinear compensation of a fibre working with large powers of order tens of mW, and distance exceeding 100 km was presented.

Generation of 100 GHz trains of 500-700 fs pulses using dual-frequency beat conversion in a step-like dispersion profiled fibre is reported. The authors believe that this is the first time the generation and compression of soliton pulses using such a fibre has been demonstrated. The fabrication of such fibre assemblies does not require any special facilities and relies only on conventional optical fibre technology. They believe that the use of profiling the fibre dispersion by fibre segments instead of continuously dispersion-decreasing fibre is not only possible but preferable in many applications.

Digital signal processing combined with either pre-distortion at the transmitter or coherent detection at the receiver can eliminate penalties due to fibre dispersion. The nonlinearity of transmission fibre results in an optimal balance of pre-distortion and receiver equalisation.

Microwave photonic filtering is realised using a superstructured fibre Bragg grating. The time delay of the optical taps is precisely controlled by the grating characteristics and fibre dispersion. A bandpass response with a rejection level of >45 dB is achieved.

The dispersion slope of dispersion-shifted fibre has been successfully equalised by using a bend-induced positive dispersion slope in a singlemode fibre. We realised the bent fibre dispersion slope equaliser by using a 1.3 µm zero-dispersion pure silica core fibre (PSM). This equaliser provides a dispersion slope of –12.54 ps/nm2/km in the 1.5 µm region.

Optical millimetre-wave generation at 60 GHz using dual-mode semiconductor modelocked lasers is demonstrated. Dual-mode operation is achieved by mode selectivity of the chirped gratings. Suppression of signal distortion due to fibre dispersion is confirmed for generated millimetre waves.

Using direct measurement, the effect of macro-bending on the dispersion in dispersion compensating fibres was investigated. It was shown that even a relatively large bend radius of /spl sim/10 cm can modify the fibre dispersion in the range 1500-1600 nm.

It is shown by using numerical simulations that the carrier-suppressed-return-to-zero (CS-RZ) format has a wider dispersion tolerance relative to the conventional return-to-zero (RZ) format. Numerical simulations predict that the optimum fibre dispersion of the CS-RZ format should be zero and should stay near Ops/nm at a high fibre input power of 12 dBm in the L-band of a dispersion-shifted-fibre link. This robust dispersion characteristic against self-phase modulation was experimentally confirmed by a 40 Gbit/s 162 km transmission experiment.

Transmission of short pulses with suppressed third-order fibre dispersion effects is demonstrated by sinusoidal phase modulation of stretched optical pulses. Numerical simulation results show significantly less pulse distortion for transmission of 530 fs pulses over a 10 km fibre link achieved by applying 2.56 GHz phase modulation with a peak phase shift of 3π.

A simplified dispersion limit formula for IM/DD systems is derived to cover both positive and negative fibre dispersion coefficients. A simple method for calculating the dispersion limit of various singlemode fibres (conventional, dispersion-shifted or TrueWave, etc.) and for providing eye opening penalty evaluation of deployed systems is proposed.

Optical fibre transmission systems have developed rapidly from a “gleam in the eye” in 1966 to the 1st Generation Production Systems in 1980 and on to the 2nd or 3rd Generation Systems of today which offer huge performance already and promise far more. We will briefly trace this historical development and then concentrate on the single-mode fibre technology, both in terms of its present production form and of its future potential. Following from that, we will then suggest some networking implications of this radical new technology.

We present a novel measurement technique of nonlinearity coefficient of optical fibre, the nonlinearity coefficient is evaluated by fitting of a new fibre transfer function which takes into account the fibre dispersion and nonlinearity. We present a novel measurement technique of the nonlinearity coefficient of optical fibre using the fibre transfer function. A new fibre transfer function which takes into account the group velocity dispersion (GVD), nonlinearity and loss of optical fibre is used to obtain the fibre nonlinearity coefficient by fitting to experimental data.

By using dispersion-free single-mode fibres at 1.5 μm, where silica fibres have minimum loss, an optical transmission experiment was successfully carried out at 800 Mbit/s with 20 km repeater spacing. Error rate against receiving optical level characteristics showed that the optical power penalty caused by fibre dispersion is negligible after long line transmission at 1.5 μm.

It is shown with numerical examples that single-cladded, dispersion-shifted, single-mode fibres with arbitrary refractive-index profiles have spectral spot size and dispersion variations predictable from only two parameters. These are the Laplace spot-size value ?L and fibre dispersion value Mf specified at the wavelength ? = 1.55 ?m.