Transmission transparency and potential convergence of optical network solutions at the physical layer for bit rates from 2.5 Gb·s-1 to 256 Gb·s-1

In this paper, we investigate optical network recommendations GPON and XG-PON with triple-play services in terms of physical reach, number of subscribers, transceiver design, modulation format and implementation cost. Despite trends to increase the bit rate from 2.5 Gb s1 to 10 Gb s1 and beyond, TDMPONs cannot cope with bandwidth requirements of future networks. TDM and WDM techniques can be combined, resulting in improved scalability. Longer physical reach can be achieved by deploying active network elements within the transmission path. We investigate these options by considering their potential coexistence at the physical layer. Subsequently, we analyse the upgrade of optical channels to 100 Gb s1 and 256 Gb s1 by using advanced modulation formats, which combine polarization division multiplexing with coherent detection and digital signal processing. We show that PDMQPSK format is suitable for 100 Gb s1 systems and PDM-16QAM is more beneficial at 256 Gb s1. Simulations are performed in the OptSim software environment

Benefits and limits of modulation formats for optical communications

This paper is focused on benefits and limits of intensity and phase modulation formats used in optical communications. The simulation results are obtained using OptSim software environment, employing Time Domain Split Step method. Non-Return to Zero, Return to Zero, Chirped Return to Zero and Carrier-Suppressed Return to Zero formats are compared in terms of Bit Error Rate and spectral efficiency to find the limits for selected transmission network topologies. It is shown that phase modulation formats offer many advantages compared to intensity formats. Differential Phase-Shift Keying and mainly Differential Quadrature Phase-Shift Keying improve the Bit Error Rate and transmission reach, among others. A promising solution is the application of Polarization Division Multiplexing Quadrature Phase-Shift Keying, which primarily benefits in spectral efficiency, estimated reach, optical signal to noise ratio and chromatic dispersion tolerances

Structural tolerances of optical characteristics in various types of photonic lattices

A systematic study of various photonic crystal lattices and their optical characteristics is carried out in this paper. Sensitivity of both dispersion and effective mode area characteristics to deviations of particular structural parameters of the lattices are the main studied topics. The presented results can be exploited during the design of fibers and new devices utilizing the studied lattices, when strict requirements on optical characteristics of the fabricated devices are imposed. Performance benefits for the implementation of particular lattices types in photonic designs are shown

System Performance and Limits of Optical Modulation Formats in Dense Wavelength Division Multiplexing Systems

In this paper we investigate in OptSim software environment the system performance of intensity and phase modulation formats for different network scenarios and dense wavelength division multiplexing grids. OptSim employs the Time Domain Split Step method to implement the signal distribution equation in a fiber. We investigate intensity formats, such as Non Return to Zero, Return to Zero, Carrier- Suppressed Return to Zero and DuoBinary, and phase modulation formats like Differential Phase-Shift Keying and Differential Quadrature Phase-Shift Keying. The main goal is to compare these formats in terms of bit error rate, Q-factor, optical reach and grid limitations for transmission rates 10, 40 and 100 Gbps per channel and discuss the possibilities of increasing their spectral efficiency. We also focus on other advanced solutions such as the polarization division multiplexing combined with phase modulations, coherent detection and advanced digital signal processing which mainly benefits in spectral efficiency, optical signal to noise ratio and chromatic dispersion tolerances

Comparision of splitting properties of various 1x16 splitters

Optical Access Networks (OAN) mostly use optical splitters to distribute the services from Optical Line Terminal (OLT) on the provider's side to the subscribers in Optical Network Unit (ONU). Optical splitters are the key components in such access networks as for example GPON and XG-PON by ITU-T. In this paper we investigate the optical properties of 1x16 Y-branch splitter and 1x16 MMI splitters based on different widths of multimode interference section and different lengths of the output ports. These two splitters were designed, simulated and the obtained results of both were studied and compared with each other. Additionally, we show that the used standard waveguide core size (usually 6x6 µm2 to match the diameter of the single mode input/output fibers, i.e. to keep the coupling loses as low as possible) supports not only propagation of the single mode but of the first mode too, leading to an asymmetric splitting ratio (increasing non-uniformity of split power over all the output waveguides). Decreasing waveguide core size, it is possible to suppress presence of the first mode and this way to reduce non-uniformity

Abnormal development of monoaminergic neurons is implicated in mood fluctuations and bipolar disorder

Subtle mood fluctuations are normal emotional experiences, whereas drastic mood swings can be a manifestation of bipolar disorder (BPD). Despite their importance for normal and pathological behavior, the mechanisms underlying endogenous mood instability are largely unknown. During embryogenesis, the transcription factor Otx2 orchestrates the genetic networks directing the specification of dopaminergic (DA) and serotonergic (5-HT) neurons. Here we behaviorally phenotyped mouse mutants overexpressing Otx2 in the hindbrain, resulting in an increased number of DA neurons and a decreased number of 5-HT neurons in both developing and mature animals. Over the course of 1 month, control animals exhibited stable locomotor activity in their home cages, whereas mutants showed extended periods of elevated or decreased activity relative to their individual average. Additional behavioral paradigms, testing for manic-and depressive-like behavior, demonstrated that mutants showed an increase in intra-individual fluctuations in locomotor activity, habituation, risk-taking behavioral parameters, social interaction, and hedonic-like behavior. Olanzapine, lithium, and carbamazepine ameliorated the behavioral alterations of the mutants, as did the mixed serotonin receptor agonist quipazine and the specific 5-HT 2C receptor agonist CP-809101. Testing the relevance of the genetic networks specifying monoaminergic neurons for BPD in humans, we applied an interval-based enrichment analysis tool for genome-wide association studies. We observed that the genes specifying DA and 5-HT neurons exhibit a significant level of aggregated association with BPD but not with schizophrenia or major depressive disorder. The results of our translational study suggest that aberrant development of monoaminergic neurons leads to mood fluctuations and may be associated with BPD

Dispersion compensating photonic crystal fiber with enhanced properties achieved by modified core geometry

A novel dispersion compensating fiber based on photonic crystal fiber has been designed and studied in terms of optimal dispersion and operating bandwidth. The investigation of dispersion characteristics with respect to change in hole diameter and pitch has been provided. Further optimization of the designed fiber has been applied to the achieved fiber’s properties in order to achieve a potentially easy-to-fabricate dispersion compensating fiber