Modeling and Performance Enhancement of Hybrid Fiber Network-PON/DPPM-DWDM-FSO Communications under Atmospheric Turbulence Conditions

A Wavelength Division Multiplexing (WDM) access network using high-speed free-space optical (FSO) communication based on the passive optical networks (PONs) for the distribution link is proposed. In such network architecture, the FSO link can extend the system to areas where an optical fiber link is not feasible, and or provide limited mobility for indoor coverage. The performance of Hybrid Fiber/FSO (HFFSO) network based on digital pulse position modulation (DPPM), for both the indoor and outdoor environments of the optical access network, are compared with the performance of such a network that is based on conventional On-Off Keying Non-Return-to-Zero (OOK-NRZ) modulation using results obtained through computational and analytical modeling. The WDM channels suffer from inter-channel crosstalk, while the HFFSO communication performance in a clear atmosphere is limited by atmospherically induced scintillation. The impairments, plus the amplified spontaneous emission noise from optical amplification, combining in a potentially problematic way, particularly in the upstream direction, which is investigated here. The results obtained indicate that in a clear atmosphere with a sufficiently high signal to crosstalk ratio the proposed system can achieve a human-safe and high-capacity access network. Dense Wavelength Division Multiplexing (DWDM) has dramatically increased the capacity of optical transmission systems. Its inherent advantages have made it the current favorite multiplexing technology for an optical network, also used on fiber optic backbones and long-distance transmission. The crosstalk due to inter-band crosstalk for Ultra-Dense WDM systems causes higher noise and degrades the network performance and analyzed the performance of DWDM-PON link that is corrupted crosstalk for Optical Cross-Connect (OXC). Then the analysis of BER with crosstalk was done. Using the equation for crosstalk number of channels was plotted using Matlab. An analysis is carried out to find the amount of crosstalk considering a WDM-FSO over OOK-NRZ and DPPM based OXC. The bit error rate performance degradation due to crosstalk is evaluated for the OXC parameter and number of wavelength per fiber.

Study of the echoes of the Arabic story in Nigerian Arabic literature: Ilorin as a case study

The story is an art of prose literature. Arab writers and others have done valuable works of fiction, showing the extent of their artistic ability; however, this art has witnessed in the modern era developed and developed to add to it another form known - in Western literature - poetry story; which has no era - before - in literature Old Arab, and the poems appeared stories woven on the Western vein. After looking at the story in Arabic literature, this article looks at some of the echoes of the Arab story in Arabic literature, with an emphasis on what the thinkers of the city of Eulen produced as a living model reflecting the many stories that were presented at the Arab literature table in Nigeria. For a commendable effort by the writers of Nigeria to expand the Arabic language and create a clear atmosphere for artistic creativity and conscience.

Do modelled or satellite-based estimates of surface solar irradiance accurately describe its temporal variability?

This study investigates the characteristic time-scales of variability found in long-term time-series of daily means of estimates of surface solar irradiance (SSI). The study is performed at various levels to better understand the causes of variability in the SSI. First, the variability of the solar irradiance at the top of the atmosphere is scrutinized. Then, estimates of the SSI in cloud-free conditions as provided by the McClear model are dealt with, in order to reveal the influence of the clear atmosphere (aerosols, water vapour, etc.). Lastly, the role of clouds on variability is inferred by the analysis of in-situ measurements. A description of how the atmosphere affects SSI variability is thus obtained on a time-scale basis. The analysis is also performed with estimates of the SSI provided by the satellite-derived HelioClim-3 database and by two numerical weather re-analyses: ERA-Interim and MERRA2. It is found that HelioClim-3 estimates render an accurate picture of the variability found in ground measurements, not only globally, but also with respect to individual characteristic time-scales. On the contrary, the variability found in re-analyses correlates poorly with all scales of ground measurements variability.