Semiconductor Optical Amplifier (SOA)–Based Amplification of Intensity-Modulated Optical Pulses — Deterministic Timing Jitter and Pulse Peak Power Equalization Analysis

During the last few years, large-scale efforts towards realizing high-photonic integration densities have put SOAs in the spotlight once again. Hence, the need to develop a complete framework for SOA-induced signal distortion to accurately evaluate a system’s performance has now become evident. To cope with this demand, we present a detailed theoretical and experimental investigation of the deterministic timing jitter and the pulse peak power equalization of SOA-amplified intensity-modulated optical pulses. The deterministic timing jitter model relies on the pulse mean arrival time estimation and its analytic formula reveals an approximate linear relationship between the deterministic timing jitter and the logarithmic values of intensity modulation when the SOA gain recovery time is faster than the pulse period. The theoretical analysis also arrives at an analytic expression for the intensity modulation reduction (IMR), which clearly elucidates the pulse peak power equalization mechanism of SOA. The IMR analysis shows that the output intensity modulation depth is linearly related to the respective input modulation depth of the optical pulses when the gain recovery time is faster than the pulse period. This novel theoretical platform provides a qualitative and quantitative insight into the SOA performance in case of intensity-modulated optical pulses

Wake dynamics of external flow past a curved circular cylinder with the free stream aligned with the plane of curvature

Accepted versio

Modulation and Equalization Techniques for mmWave ARoF

Fifth generation (5G) is the emerging mobile communications platform that aims to meet the market requirements in terms of enhanced broadband connectivity based on harnessing small cell and mmWave technology. These two in synergy will provide high capacity gain not only through the hyperdense deployment of small cell but also through accessing large swathes of untapped spectrum at mmWave frequencies. The envisaged architecture entails an integrated optical wireless network architecture, where optical technology will complement radio in order to handle the new demands on capacity over the backhaul and fronthaul network, leading to the notion of analog radio over fiber (ARoF). The goal of this chapter is to provide novel approaches to optimize the performances of mmWave ARoF systems that includes developing enabling technology from a digital to signal processing (DSP) and device perspective

Is All Seagrass Habitat Equal? Seasonal, Spatial, and Interspecific Variation in Productivity Dynamics Within Mediterranean Seagrass Habitat

Seagrass meadows’ ability to capture carbon through sequestering autochthonous carbon via photosynthesis means they could represent a potential nature-based solution to rising carbon emissions. In multispecies seagrass communities, and due to species introduction or predicted range shifts, it is important to know which species deliver different carbon sequestration gains to inform conservation actions. Large benthic chamber experiments (volume = 262L) assessed the seasonal and spatial variation in metabolism dynamics of the endemic and dominant Mediterranean seagrass, P. oceanica whilst small benthic chamber experiments (volume = 7L) compared the dynamics between, P. oceanica the native C. nodosa and non-native H. stipulacea. Within shallow P. oceanica edge habitat lower Net Apparent Productivity (NAP) occurs in autumn ((Formula presented.) = 1.3, SD ± 2.95 O2 mmol m-2 d-1) compared to summer ((Formula presented.) = 9.9, SD ± 2.75 O2 mmol m-2 d-1 corresponding with periods of light limiting and light saturating conditions, but it remains overall autotrophic annually (2.3 C mol m-2 yr-1). However, spatial heterogeneity exists, the center areas of P. oceanica were more productive (NAP (Formula presented.) =19.7, SD± 3.83 O2 mmol m-2 d-1) compared to edge habitat with spatial changes in productivity relating to plant surface area (96%), shoot density (81%), blade length (72%) and seagrass percentage cover (64%). Under comparative conditions in a sparse multispecies area of the meadow the species demonstrated different capacities for carbon fixation. H. stipulacea was carbon positive and P. oceanica fluctuated between positive and negative carbon balance suggesting both can maintain a balance between carbon fixation and carbon utilised for metabolic activity. In contrast the C. nodosa here would be expected to deteriorate as it was utilising carbon more than it was fixing (NAPN2 ((Formula presented.) = -0.0012, SD ± 0.0007 O2 mmol cm-2 d-1). This study demonstrates that not all seagrass habitat is equal. If seagrass meadows are to play a part in mitigating CO2 emissions, variability in primary productivity within seagrass meadows needs to be accounted for to produce accurate total fixed carbon estimates, and subsequently autochthonous carbon sequestration estimates. This means seagrass meadow species composition and the condition of these meadows must be better understood

Bacterial Community Legacy Effects Following the Agia Zoni II Oil-Spill, Greece

In September 2017 the Agia Zoni II sank in the Saronic Gulf, Greece, releasing approximately 500 tonnes of heavy fuel oil, contaminating the Salamina and Athens coastlines. Effects of the spill, and remediation efforts, on sediment microbial communities were quantified over the following 7 months. Five days post-spill, the concentration of measured hydrocarbons within surface sediments of contaminated beaches was 1,093–3,773 μg g–1 dry sediment (91% alkanes and 9% polycyclic aromatic hydrocarbons), but measured hydrocarbons decreased rapidly after extensive clean-up operations. Bacterial genera known to contain oil-degrading species increased in abundance, including Alcanivorax, Cycloclasticus, Oleibacter, Oleiphilus, and Thalassolituus, and the species Marinobacter hydrocarbonoclasticus from approximately 0.02 to >32% (collectively) of the total bacterial community. Abundance of genera with known hydrocarbon-degraders then decreased 1 month after clean-up. However, a legacy effect was observed within the bacterial community, whereby Alcanivorax and Cycloclasticus persisted for several months after the oil spill in formerly contaminated sites. This study is the first to evaluate the effect of the Agia Zoni II oil-spill on microbial communities in an oligotrophic sea, where in situ oil-spill studies are rare. The results aid the advancement of post-spill monitoring models, which can predict the capability of environments to naturally attenuate oil