Birefringence effects in multi-core fiber: coupled local-mode theory.

In this paper, we evaluate experimentally and model theoretically the intra- and inter-core crosstalk between the polarized core modes in single-mode multi-core fiber media including temporal and longitudinal birefringent effects. Specifically, extensive experimental results on a four-core fiber indicate that the temporal fluctuation of fiber birefringence modifies the intra- and inter-core crosstalk behavior in both linear and nonlinear optical power regimes. To gain theoretical insight into the experimental results, we introduce an accurate multi-core fiber model based on local modes and perturbation theory, which is derived from the Maxwell equations including both longitudinal and temporal birefringent effects. Numerical calculations based on the developed theory are found to be in good agreement with the experimental data.

Experimental evaluation of nonlinear crosstalk in multi-core fiber.

In this paper we evaluate experimentally and model theoretically the nonlinear crosstalk random process in multi-core fiber. The experimental results indicate that mode coupling in multi-core fibers is reduced in presence of fiber Kerr nonlinearities. An analytical study of the inter-core crosstalk probability density function in nonlinear regime is performed, where the theoretical distribution, derived from the nonlinear coupled-mode equation, is experimentally validated in homogeneous four-core fiber. The herein presented analysis includes the evaluation of the inter-core crosstalk probability density function, mean and variance evolution considering the optical power launched into the fiber.

On-the-field performance of quintuple-play long-reach OFDM-based WDM-PON optical access networks.

In this paper the on-the-field performance of a WDM-PON optical access providing quintuple-play services using orthogonal frequency division multiplexing (OFDM) modulation is evaluated in a real fiber-to-the-home (FTTH) network deployed by Towercom operator in Bratislava (Slovakia). A bundle of quintuple-play services comprising full-standard OFDM-based signals (LTE, WiMAX, UWB and DVB-T) and an ad-hoc OFDM-GbE signal is transmitted in coexistence per single user. Both downstream and upstream transmission performances are evaluated in different on-the-field long-reach optical link distance configurations. Four wavelength multi-user transmission of quintuple-play OFDM services is demonstrated exceeding 60.8 km reach in standard single mode fiber.

Transmission of OFDM wired-wireless quintuple-play services along WDM LR-PONs using centralized broadband impairment compensation.

The simultaneous transmission of four orthogonal frequency-division multiplexing (OFDM)-based signals used to provide quintuple-play services along wavelength division multiplexing (WDM) long-reach passive optical networks (LR-PONs) is demonstrated experimentally. Particularly, the transmission performance of custom signal bearing Gigabit Ethernet data, Worldwide Interoperability for Microwave Access, Long Term Evolution and Ultra Wideband (sub-bands 2 and 3) signals is evaluated for different LR-PONs reaches, considering single-wavelength and WDM transmission, and using a centralized impairment compensation technique at the central office that is transparent to the services provided.It is shown that error vector magnitude-compliant levels are obtained for all the OFDM-based signals in WDM LR-PONs reaching 100 km and that negligible inter-channel crosstalk is obtained for a channel spacing of 100 GHz regardless the OFDM-based signal considered. The successful multi-format OFDM transmission along the 100 km-long WDM LR-PON is achieved in the absence of optical dispersion compensation or single sideband modulation, and it is enabled by the performance improvement provided by the centralized impairment compensation realized.

480 Mbit/s UWB bi-directional radio over fiber CWDM PON using ultra-low cost and power VCSELs.

Radio-over-fiber (RoF) schemes offer the possibility of permitting direct access to native format services for the domestic user. A low power requirement and cost effectiveness are crucial to both the service provider and the end user. Here, we present an ultra-low cost and power RoF scheme using direct modulation of commercially-available 1344 nm and 1547 nm VCSELs by band-group 1 UWB wireless signals (ECMA-368) at near broadcast power levels. As a result, greatly simplified electrical-optical-electrical conversion is accomplished. A successful demonstration over a transmission distance of 20.1 km is described using a SSMF, CWDM optical network. EVMs of better than -18.3 dB were achieved.

Dual-drive LiNbO3 interferometric Mach-Zehnder architecture with extended linear regime for high peak-to-average OFDM-based communication systems.

A dual-drive LiNbO(3) architecture modulator with chirp management is proposed and developed offering SFDR > 25 dB in a 1.4 V bias excursion compared to only 0.5 V bias excursion in a conventional Mach-Zehnder electro-optical modulator (MZ-EOM). The architecture effectively extends the linear regime and enables the optical transmission of wireless systems employing orthogonal division multiplexing (OFDM) modulation such as ultra-wide band (UWB) which require high linearity over a broad frequency range due to their high peak-to-average power ratio (PARP). Radio-over-fiber UWB transmission in a passive optical network is experimentally demonstrated employing this technique, exhibiting an enhancement of 2.2 dB in EVM after 57 km SSMF when the dual-drive developed modulator is employed.

[Evolution of psychomotor development in pre-school children born prematurely]. / Evolución del desarrollo psicomotor en preescolares con antecedentes de prematuridad.

INTRODUCTION: The rate of premature births has significantly increased, and it is important to determine its effects. The objective of this study is to determine the psychomotor development profile of a group of children born prematurely, at the age of 4, 5 and 6, and to compare them with a group of full-term birth children, in order to detect any differences. PATIENTS AND METHODS: The sample consisted of 98 participants, evenly distributed into two groups, premature and full-term born children. A prospective longitudinal observational analytical study, with a design of cases and controls, was carried out. For some analyses, the separation into early pre-term, moderate pre-term, and late pre-term was considered. The evaluations were performed using the McCarthy Scale of Aptitudes and Psychomotor skills for children. RESULTS: The data shows achievements within the middle intervals. However, there are more difficulties in development at 4 years in the group of premature children, according to gestational age. Early pre-term (gestational age less than 32 weeks) showed significantly lower scores compared to moderate and late pre-term, mainly at 6 years, and with those born at term, at 4 and 6 years. CONCLUSIONS: Development difficulties are greater at a lower gestational age, and may affect the Primary Education stage. The need to monitor all premature children in the preschool stage is suggested, as well as to evaluate more specific skills and continue with the care from specialist teams.

Evolution of psychomotor development in pre-school children born prematurely.

INTRODUCTION: The rate of premature births has significantly increased, and it is important to determine its effects. The objective of this study is to determine the psychomotor development profile of a group of children born prematurely, at the age of 4, 5 and 6, and to compare them with a group of full-term birth children, in order to detect any differences. PATIENTS AND METHODS: The sample consisted of 98 participants, evenly distributed into two groups, premature and full-term born children. A prospective longitudinal observational analytical study, with a design of cases and controls, was carried out. For some analyses, the separation into early pre-term, moderate pre-term, and late pre-term was considered. The evaluations were performed using the McCarthy Scale of Aptitudes and Psychomotor skills for children. RESULTS: The data show achievements within the middle intervals. However, there are more difficulties in development at 4 years in the group of premature children, according to gestational age. Early pre-term (gestational age less than 32 weeks) showed significantly lower scores compared to moderate and late pre-term, mainly at 6 years, and with those born at term, at 4 and 6 years. CONCLUSIONS: Development difficulties are greater at a lower gestational age, and may affect the Primary Education stage. The need to monitor all premature children in the preschool stage is suggested, as well as to evaluate more specific skills and continue with the care from specialist teams.

Neuronal and Astrocytic Differentiation from Sanfilippo C Syndrome iPSCs for Disease Modeling and Drug Development.

Sanfilippo syndrome type C (mucopolysaccharidosis IIIC) is an early-onset neurodegenerative lysosomal storage disorder, which is currently untreatable. The vast majority of studies focusing on disease mechanisms of Sanfilippo syndrome were performed on non-neural cells or mouse models, which present obvious limitations. Induced pluripotent stem cells (iPSCs) are an efficient way to model human diseases in vitro. Recently developed transcription factor-based differentiation protocols allow fast and efficient conversion of iPSCs into the cell type of interest. By applying these protocols, we have generated new neuronal and astrocytic models of Sanfilippo syndrome using our previously established disease iPSC lines. Moreover, our neuronal model exhibits disease-specific molecular phenotypes, such as increase in lysosomes and heparan sulfate. Lastly, we tested an experimental, siRNA-based treatment previously shown to be successful in patients' fibroblasts and demonstrated its lack of efficacy in neurons. Our findings highlight the need to use relevant human cellular models to test therapeutic interventions and shows the applicability of our neuronal and astrocytic models of Sanfilippo syndrome for future studies on disease mechanisms and drug development.