Short-wavelength transmission-loss suppression in fibre Bragg gratings

Fibre Bragg Gratings (FBGs) are known to suffer from short-wavelength, transmission losses due to resonant coupling into backward-propagating cladding modes. Figure 1 shows a typical transmission spectrum of a 10cm standard FBG. The cladding mode losses increase with grating reflectivity and could eventually impose severe limitations in the use of FBGs. The problem can be quite acute in the case that FBG wavelength-multiplexing is required. So far, several attempts have been made to eliminate the short-wavelength, transmission losses and improve grating performance. In all cases, the resonant coupling of the forward-propagating core mode to the backward-propagating cladding modes is minimised by reducing the coupling strength. In this paper, we report on a novel method for reducing cladding-mode transmission losses in standard FBGs. We show that short-wavelength, transmission losses can be practically eliminated by damping the resonant excitation of the cladding modes. The damping is achieved by properly introducing a substantial propagation loss into the cladding modes. For maximum effect, the core mode should experience no extra propagation losses. By applying a thin lossy layer on the fibre cladding surface, a reduction of cladding-mode-losses of about 12dB was achieved

Experimental demonstration of gridless spectrum and time optical switching

An experimental demonstration of gridless spectrum and time switching is presented. We propose and demonstrate a bit-rate and modulation-format independent optical cross-connect architecture, based on gridless spectrum selective switch, 20-ms 3D-MEMS and 10-ns PLZT optical switches, that supports arbitrary spectrum allocation and transparent time multiplexing. The architecture is implemented in a four-node field-fiber-linked testbed to transport continuous RZ and NRZ data channels at 12.5, 42.7 and 170.8 Gb/s, and selectively groom sub-wavelength RZ channels at 42.7 Gb/s. We also showed that the architecture is dynamic and can be reconfigured to meet the routing requirements of the network traffic. Results show error-free operation with an end-to-end power penalty between 0.8 dB and 5 dB for all continuous and sub-wavelength channels

Birefringence upper limit analysis of low birefringence fibers employed in the Faraday effect current sensors

The theoretical model of the Faraday rotation in the low birefringence optical fiber is proposed to serve as a convenient tool for the determination of the birefringence upper limit allowed to retain current sensor sensitivity. The measurement technique offers a fast and efficient determination of the ultra-low linear birefringence when other techniques are not sensitive enough or they are difficult to implement. A temperature dependence of the Faraday rotation and its causes are investigated

Field trial of a 15 Tb/s adaptive and gridless OXC supporting elastic 1000-fold all-optical bandwidth granularity

An adaptive gridless OXC is implemented using a 3D-MEMS optical backplane plus optical modules (sub-systems) that provide elastic spectrum and time switching functionality. The OXC adapts its architecture on demand to fulfill the switching requirements of incoming traffic. The system is implemented in a seven-node network linked by installed fiber and is shown to provide suitable architectures on demand for three scenarios with increasing traffic and switching complexity. In the most complex scenario, signals of mixed bit-rates and modulation formats are successfully switched with flexible per-channel allocation of spectrum, time and space, achieving over 1000-fold bandwidth granularity and 1.5 Tb/s throughput with good end-to-end performance

Limited Depressive and Anxiety Symptoms Late in Pregnancy Are Not Related to Neonatal Outcomes

Background: Prior studies have reported inconsistent findings regarding the link between antenatal depressive and anxiety symptomatology, with neonatal outcomes. Objectives: The aim of the present study was to assess the possible association of prenatal depressive and anxiety symptoms, in the third trimester of pregnancy, with perinatal outcomes (birth weight of the newborn, Apgar score and the newborn’s admission in neonatal intensive care unit) in a sample of pregnant women, in Greece. Patients and Methods: A total of 117 women from Athens, during the 32nd to 35th week of pregnancy, participated in the study. Demographic and obstetric history data, as well as neonatal outcomes, were recorded. Three self-administered psychometric scales (Beck depression inventory (BDI), Edinburg postnatal depression scale (EPDS) and beck anxiety inventory (BAI)) were used to evaluate in detail the prenatal depressive and anxiety symptoms. Descriptive statistics, Spearman’s Rho coefficients, Mann-Whitney U and Kruskal-Wallis testes were applied to analyze the data. Results: On the basis of BDI, 81.1% of the sample showed minimal, 15.4% mild, 2.6% moderate and 0.9% severe depressive symptoms, respectively. Furthermore, 80.3% of the participants, scored on EPDS below the cut-off point for a likely diagnosis of depression. According to BAI scale, 43.6% showed minimal, 42.7% women mild, 10.3% moderate and 3.4% severe anxiety symptoms. No statistically significant correlations were found between depressive and anxiety symptoms and neonatal outcomes (birth weight, Apgar score and admission in neonatal intensive care unit). Conclusions: Limited levels of prenatal depressive and anxiety symptoms do not seem to be associated with neonatal outcomes. In clinical practice, pregnant women, who suffer from low levels of prenatal depressive and anxiety symptoms, may be reassured, in respect of the adverse outcomes of these mood symptoms on the neonate

Design and transmission analysis of trench-assisted multi-core fibre in standard cladding diameter

6-core and 8-core trench-assisted heterogeneous fibres in standard cladding diameter are designed using artificial intelligence-based techniques including a cut-off wavelength regressor. The designs proposed here, for the first time, suppress crosstalk at 1550 nm of 8-core fibre to as low as −55 dB/km covering the whole S+C+L band while keeping coating loss below 0.001 dB/km. We compare them to reveal the influence of the additional cores in the 125 µm cladding diameter scenario. We report on the transmission characteristics and performance of the MCFs in terms of capacity and spatial spectral efficiency, including the influence of bandwidth, effective mode area, distance and crosstalk, for a range of transmission distances. The artificial intelligence-based method and insights given can be used to significantly speed up and tailor designs for a variety of telecom and datacom applications

Near-infrared Fourier transform room-temperature photoluminescence of erbium complexes

A modified Fourier transform (FT) Raman bench spectrometer designed for the detection of weak light emission in the 800–1700 nm wavelength region has been used to demonstrate the advantages of FT spectroscopy for measuring near-infrared photoluminescence spectra of lanthanide complexes with a good resolution and very good sensitivity. This apparatus has been tested with an ultraviolet laser source (325 nm) on three standard erbium complexes. The 4I13/24I15/2 emission of tris-(acetylacetonato) (1,10 phenanthroline) erbium [Er(acac)3(phen)], tris-(4,4,4,-trifluoro-1-(2 thenoyl)-1,3-butenedione) (1,10 phenanthroline) erbium [Er(TTFA)3(phen)] and tris(8-hydroxyquinolinato) erbium [Erq3] has thus been recorded in solution and in the solid state and compared with literature. ©2003 American Institute of Physics

321W average power, 1GHz, 20ps 1060nm pulsed fiber MOPA source

Pulses from a gain-switched laser diode were amplified in a fiber MOPA system to produce in excess of 320W of average power in 20ps pulses at 1GHz repetition rate at 1060nm