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Summary Background Elevated proinflammatory cytokines are associated with greater COVID-19 severity. We aimed to assess safety and efficacy of sarilumab, an interleukin-6 receptor inhibitor, in patients with severe (requiring supplemental oxygen by nasal cannula or face mask) or critical (requiring greater supplemental oxygen, mechanical ventilation, or extracorporeal support) COVID-19. Methods We did a 60-day, randomised, double-blind, placebo-controlled, multinational phase 3 trial at 45 hospitals in Argentina, Brazil, Canada, Chile, France, Germany, Israel, Italy, Japan, Russia, and Spain. We included adults (≥18 years) admitted to hospital with laboratory-confirmed SARS-CoV-2 infection and pneumonia, who required oxygen supplementation or intensive care. Patients were randomly assigned (2:2:1 with permuted blocks of five) to receive intravenous sarilumab 400 mg, sarilumab 200 mg, or placebo. Patients, care providers, outcome assessors, and investigators remained masked to assigned intervention throughout the course of the study. The primary endpoint was time to clinical improvement of two or more points (seven point scale ranging from 1 [death] to 7 [discharged from hospital]) in the modified intention-to-treat population. The key secondary endpoint was proportion of patients alive at day 29. Safety outcomes included adverse events and laboratory assessments. This study is registered with ClinicalTrials.gov, NCT04327388; EudraCT, 2020-001162-12; and WHO, U1111-1249-6021. Findings Between March 28 and July 3, 2020, of 431 patients who were screened, 420 patients were randomly assigned and 416 received placebo (n=84 [20%]), sarilumab 200 mg (n=159 [38%]), or sarilumab 400 mg (n=173 [42%]). At day 29, no significant differences were seen in median time to an improvement of two or more points between placebo (12·0 days [95% CI 9·0 to 15·0]) and sarilumab 200 mg (10·0 days [9·0 to 12·0]; hazard ratio [HR] 1·03 [95% CI 0·75 to 1·40]; log-rank p=0·96) or sarilumab 400 mg (10·0 days [9·0 to 13·0]; HR 1·14 [95% CI 0·84 to 1·54]; log-rank p=0·34), or in proportions of patients alive (77 [92%] of 84 patients in the placebo group; 143 [90%] of 159 patients in the sarilumab 200 mg group; difference −1·7 [−9·3 to 5·8]; p=0·63 vs placebo; and 159 [92%] of 173 patients in the sarilumab 400 mg group; difference 0·2 [−6·9 to 7·4]; p=0·85 vs placebo). At day 29, there were numerical, non-significant survival differences between sarilumab 400 mg (88%) and placebo (79%; difference +8·9% [95% CI −7·7 to 25·5]; p=0·25) for patients who had critical disease. No unexpected safety signals were seen. The rates of treatment-emergent adverse events were 65% (55 of 84) in the placebo group, 65% (103 of 159) in the sarilumab 200 mg group, and 70% (121 of 173) in the sarilumab 400 mg group, and of those leading to death 11% (nine of 84) were in the placebo group, 11% (17 of 159) were in the sarilumab 200 mg group, and 10% (18 of 173) were in the sarilumab 400 mg group. Interpretation This trial did not show efficacy of sarilumab in patients admitted to hospital with COVID-19 and receiving supplemental oxygen. Adequately powered trials of targeted immunomodulatory therapies assessing survival as a primary endpoint are suggested in patients with critical COVID-19. Funding Sanofi and Regeneron Pharmaceuticals.

A fast FBG sensor interrogator based on a SOI ring resonator (RR) filter is presented. The measurement of the Bragg wavelength shift is based on the detection of the signals at the output ports of the RR. Ring resonance wavelength is tuned and fixed by an integrated heater and the ring acts as a passband filter for the reflected FBG spectrum.

We present the experimental results of thermally tunable double microring resonator devices for integrated wavelength division multiplexing applications. The devices demonstrated a free-spectral range up to 2.4 THz (19.2 nm) around 1550 nm and a channel rejection higher than 35 dB. Using Ti/TiN metal heaters, a power consumption of 20 mW per FSR per ring is achieved, which outperformed analogous devices fabricated using the standard silicon process. A thermal tuning efficiency of 0.95 nm/mW is accomplished, and a symmetric tuning is obtained with less than 1% of electrical compensation.

We present a polarization-independent fiber Bragg grating (FBG) interrogator based on a rapidly-tunable Sagnac interferometer using a dual-polarization lithium-niobate phase modulator. A bandwidth of 100 kHz along a range beyond a full free-spectral-range is demonstrated.

Control systems for automotive applications have rapidly evolved introducing intelligence to address the increasing demand for pollution and oil consumption reduction. Fiber Bragg Grating (FBG) sensors are used in this work for monitoring Gasoline Direct Injectors (GDI) in order to optimize the engine performance and reduce the emissions. Several fast-acting solenoid injectors have been instrumented with FBG sensors and mounted in a test bench at the testing department of CPT Italy S.r.l to simulate the injector's behavior during the actuation phase. The FBG sensors, installed on the stem of the GDI, provide dynamic measurement of the strain variation during the injection process, pointing out the unwanted effects of the reopening, leading to injector tip wetting and consequent increased polluting emissions. The acquired data allows one to fully understand the GDI process and to optimize the injector design in order to reduce emissions, as required by recent European directives for the emission standards.

Silicon photonics is becoming a consolidated technology, mainly in the telecom/datacom sector, but with a great potential in the chemical and biomedical sensor market too, mainly due to its CMOS compatibility, which allows massfabrication of huge numbers of miniaturized devices at a very low cost per chip. Integrated photonic sensors, typically based on resonators, interferometers, or periodic structures, are easy to multiplex as the light is confined in optical waveguides. In this work, we present a silicon-photonic sensor capable of measuring refractive index and chemical binding of biomolecules on the surface, using a low-cost phase interrogation scheme. The sensor consists of a pair of balanced Mach-Zehnder interferometers with interaction lengths of 2.5 mm and 22 mm, wound to a sensing area of only 500 μm x500 μm. The phase interrogation is performed with a fixed laser and an active phase demodulation approach based on a phase generated carrier (PGC) technique using a phase demodulator integrated within the chip. No laser tuning is required, and the technique can extract the univocal phase value with no sensitivity fading. The detection only requires a photo-receiver per interferometer, analog-to-digital conversion, and simple processing performed in real-time. We present repeatable and linear refractive index measurements, with a detection limit down to 4.7·10-7 RIU. We also present sensing results on a chemically-functionalized sample, where anti-BSA to BSA (bovine serum albumin) binding curves are clearly visible for concentrations down to 5 ppm. Considering the advantages of silicon photonics, this device has great potential over several applications in the chemical/biochemical sensing industry.

Ionizing radiations affect installed electronics, limit equipment lifetimes and eventually alter materials both in space applications as well as high energy accelerators and physics experiments. In order to monitor radiation levels and predict equipment and material lifetimes, an accurate radiation dosimetry is highly important and very challenging often due to two main reasons: (i) large areas and (ii) extended dose range of interest.

Recently, Distributed Acoustic Sensing (DAS) using Phase-Sensitive Optical Time Domain Reflectometry (φ-OTDR) has been widely investigated for its interesting applications in many strategic areas. In this contribution, we discuss some φ-OTDR sensing schemes for distributed perturbation measurement using direct detection. We also propose and experimentally demonstrate a high-speed DAS based on φ-OTDR using a conventional modulation scheme and a simple direct detection receiver. We show that suitable design of the amplification and modulation of pulses reduces coherent and ASE noises detrimental to φ-OTDR sensors, and confirm the effectiveness of the technique with measurements of high-frequency vibrations with minimal post-processing involving no averaging of acquired traces.

We present a design study and experimental results of first and second-order filters as switch elements for integrated switch matrices. A double racetrack-based filter using Bezier bends is investigated, showing a spectral response within specifications and a free spectral range higher than 2.4THz.

Embedded channel waveguides formed on a z-cut erbium-doped lithium niobate (Er:LiNbO3) substrate by a high-energy ion implantation technique are first described. A detailed theoretical design of a waveguide laser for continuous wave operation is then discussed, taking into account realistic input parameters and measured data. To simulate waveguide modes and to predict laser outputs from our fabricated waveguide sample, a numerical tool is developed in FORTRAN based on the full vectorial finite element method. Using the developed tools, the waveguide dimension is optimized, ensuring single-mode operation at both pump (980 nm) and laser (1531 nm) wavelengths. Finally, laser outputs as a function of various waveguide parameters are analyzed. The proposed analysis allows the effective optimization of the ion-implanted waveguide laser in Er:LiNbO3.

We numerically investigate the potential of Al2O3:Er3+ active slot waveguides for realizing small-form factor lasers on silicon on insulator at 2.8 μm. Based on recent technological improvements in the reliable and low-cost fabrication of alumina doped with high Er3 + concentration and exploiting the extremely high field intensity achievable in optimized active slot waveguides, we point out the possibility of realizing silicon-compatible emitters at 2.8 μ m, optically pumped at 1480 nm with a few milliwatts threshold pump power. A strong potential impact can be envisaged for chemical sensing, biosensing and lab-on-a-chip applications.

We present a finite element based model for Si-nc sensitized Er3+ doped waveguide amplifiers (EDWA), longitudinally pumped by a novel pumping scheme using broad-area visible lasers, which accurately describes the effect of the Si-nc to Er3+ coupling ratio on the amplifier performance. We show that by pumping the active material resonantly with the Er3+ absorption spectrum, the Si-nc sensitization is extremely beneficial even at relatively low fractions of Er3+ ions coupled to the nanoclusters. On the other hand, when the pump light is only directly absorbed by the Si-nc, more than 80% of the Er3+ ions should be coupled to the Si-nc in order to achieve significant net gain. In particular, numerical results based on realistic material parameters, point out that resonant multimode pumping at 660 nm provides significant benefits in terms of gain enhancement, with respect to standard EDWAs, even at low fractions of Er3+ ions coupled to the Si-nc (less than 50%). This feature suggests that further material optimization could lead to the realization of compact and cost-effective integrated amplifiers and lasers.

This paper presents PCFDT, which is an accurate and friendly photonic crystal fiber design tool based on full-vectorial finite element method. Photonic crystal fibers based on circular and non-circular microstructured holes, and on different propagation mechanisms have been analyzed. Comparisons with other numerical methods and experimental results have shown excellent agreement. The design tool validation includes experimental results of hybrid photonic crystal fibers, proposed by us, which made possible for the first time light be simultaneously confined and manipulated by two propagation mechanism, total internal reflection and photonic bandgap effect.

Resume Buts de l’etude Faut-il disposer d’une circulation extracorporelle (CEC) pour traiter en urgence des lesions de l’aorte thoracique descendante ? Materiels et methodes Entre janvier 2004 et mai 2006, parmi 16 patients, 13 (81 %) ont ete traites en urgence (neuf hommes ; âge moyen : 75,4 ans, de 30 a 94 ans), pour rupture traumatique de l’aorte ( n = 3 ; 23 %), dissection aortique aigue type B ( n = 4 ; 31 %), anevrisme thoracique douloureux ou rompu ( n = 4 ; 31 %), fistule aorto-œsophagienne ( n = 1 ; 7,5 %) et hematome intramural ( n = 1; 7,5 %). L’angioscanner systematique a montre dans cinq cas (38 %) un hemomediastin et/ou hemothorax ; l’echocardiographie transœsophagienne (ETO) et l’arteriographie ont ete realisees respectivement chez deux (15 %) et un patients. Chez deux patients (15 %), un drainage du LCR a ete mis en place. Resultats Le taux de succes technique etait de 92,3 %. Un deces (7,5 %) est survenu a j8 et une paraplegie differee (7,5 %). Durant un suivi moyen de 10,2 mois (deux a 24 mois), aucune rupture et deux (15 %) endofuites type I ont ete traitees. Deux deces sont survenus a distance sans rapport direct avec la pathologie aortique thoracique. Chez aucun patient, une CEC n’a ete necessaire. Conclusion La non-disponibilite de la CEC ne semble pas compromettre la prise en charge de ce type de pathologie mais une maitrise des techniques endovasculaires est indispensable.

In this paper, we present the optical elements needed for the fabrication of a wavelength selective silicon photonic integrated switching matrix. We focus on the device proposed in the European project IRIS, which is a wavelength division multiplexing (WDM) transponder aggregator. It implements a colourless, directionless, and contentionless reconfigurable optical add/drop multiplexer (ROADM) node for metro transport networks. The building blocks are described as well as the system specifications and the system architecture.

We present an overview of the key aspects for the design of scalable silicon photonic switch matrices. We first discuss different possible configurations, and then we present the proposed architecture for a multiport transponder aggregator within the European project IRIS. We also analyze all the necessary photonic building blocks for this application; we will show design considerations as well as experimental demonstrations of many of them, discussing all the possible issues that must be considered for the system to work within specifications.

We present experimental results of thermally tunable double ring resonators with doped silicon and silicide heaters and different geometries. We study the effects of fabrication inaccuracies which affect the symmetry of the heating, and we show how spectra are recovered when asymmetry is electrically compensated.

We experimentally demonstrate the feasibility of Fiber Bragg Grating sensors interrogation using integrated unbalanced Mach-Zehnder Interferometers (MZI) and phase sensitive detection in silicon-on-insulator (SOI) platform. The Phase- Generated Carrier (PGC) demodulation technique is used to detect phase changes, avoiding signal fading. Signal processing allows us to extract the wavelength shift from the signal patterns, allowing accurate dynamic FBG interrogation. High resolution and low cost chips with multiple interrogators and photodetectors on board can be realized by exploiting the advantages of large scale fabrication capabilities of well-established silicon based industrial infrastructures. Simultaneous dynamic reading of a large number of FBG sensors can lead to large volume market applications of the technology in several strategic industrial fields. The performance of the proposed integrated FBG interrogator is validated by comparing with a commercial FBG readout based on a spectrometer and used as a reference.

We compare standard fiber Raman laser and new high-power- and low relative-intensity-noise (RIN)-copumping technologies for long-span unrepeated wavelength-division-multiplexing (WDM) transmission systems. We show that, by using enhanced forward-error-correction techniques and by optimizing the transmission-system parameters in terms of signal power per channel, dispersion map, and copropagating on- off Raman gain, both copumping technologies allow successful transmission of 8 10-Gb/s WDM channels over more than 70 dB of standard single-mode fiber. However, transmission experiments point out that only the newly proposed high-power and low-RIN lasers can guarantee realistic system margins and can potentially provide further span-reach enhancement when used in optimized higher order copumping configurations.

In this paper, we experimentally demonstrate a hybrid distributed acoustic and temperature sensor (DATS) based on Raman and coherent Rayleigh scattering processes in a standard singlemode fiber. A single commercial off-the-shelf DFB laser and a common receiver block are used to implement a highly integrated hybrid sensor system with key industrial applications. Distributed acoustic sensing and Raman temperature measurement are simultaneously performed by exploiting cyclic Simplex pulse coding in a phase-sensitive OTDR and in Raman DTS using direct detection. Suitable control and modulation of the DFB laser ensures inter-pulse incoherence and intra-pulse coherence, enabling accurate long-distance measurement of vibrations and temperature with minimal post-processing.

The first results of distributed optical fiber radiation sensing measurements based on radiation induced attenuation (RIA) at the new mixed-field irradiation facility CHARM are presented.

Benefits provided by higher order bidirectional Raman pumping schemes in 10-Gb/s unrepeated wavelength-division-multiplexing transmission systems are experimentally quantified in terms of BER performances at 10 Gb/s. By keeping under control double-Rayleigh-scattering-noise-induced transmission penalties, which can degrade system performance at very high ON-OFF Raman gain, as well as nonlinear propagation effects such as Brillouin scattering, self- and cross-phase modulations, four-wave-mixing, and Raman-induced crosstalks, we show a total unrepeated system reach enhancement up to 3.5 dB with respect to first-order bidirectional pumping. As confirmed by theory, the maximum reach enhancement is mainly limited by pump-to-signal relative intensity noise transfer induced by higher order copumping.

We theoretically and experimentally investigate the performance of erbium-doped fiber amplifier (EDFA)-based WDM ring networks with free amplified spontaneous emission (ASE) light recirculation. We show that, with proper network and amplifier design, the lasing light generated by free ASE recirculation within the looped network provides an effective gain clamping technique, ensuring limited signal power excursions under WDM channels add-drop operations. Considering a ring network composed of eight fiber sections and eight EDFAs, maximum signal power overshoots below 2.5dB have been measured under 23/24 WDM channels drop. Optical signal-to-noise ratio (OSNR) analysis and bit-error rate (BER) measurement at 10 Gb/s confirm acceptable performances and negligible penalties due to polarization effects and relative intensity noise transfer from laser light to WDM signals. We also propose and demonstrate a new link control technique which overcomes the main limiting factors of such networks, respectively, related to OSNR degradation, stability and survivability to fiber and EDFA breakages.

We propose a new Raman pump module that effectively reduces four-wave-mixing (FWM) nonlinear interaction among longitudinal pump modes and wavelength-division-multiplexed (WDM) signals in co-pumped distributed Raman amplifiers based on nonzero dispersion-shifted fibers (NZ-DSFs). Theory and experiments confirm that the proposed pump module structure, based on polarization- and wavelength-multiplexed Fabry-Perot lasers, allows distributed amplification with high co-propagating on-off Raman gain, providing a key technology for all-Raman-based dense-WDM ultralong-haul transmission.

We describe hybrid distributed optical fiber sensor schemes for temperature, strain and vibration measurements. In particular, we first introduce the use of cyclic Simplex coding in hybrid Raman/BOTDA distributed sensors for fast long-distance strain and simultaneous temperature measurements over the same SMF, using a single narrowband source. The same advanced coding technique is also proposed to demonstrate a hybrid distributed acoustic and temperature sensor (DATS) based on Raman and coherent Rayleigh scattering processes in a standard SMF, using a single commercial off-the-shelf DFB laser and a common receiver block.

The symmetry of the silicon crystal cell under elementary deformation is theoretically investigated. A model exploiting a linear approximation is derived for predicting the behaviour of second-order dielectric susceptibility, providing excellent agreement with experimental results.

Cyclic pulse coding is proposed for fast implementation of long-range Brillouin optical time domain analysis and simultaneous static Raman based temperature measurement over 10 km of standard single mode fiber using a narrowband laser source only.

Small-signal amplification in short, Yb/sup 3+/-sensitized, Er/sup 3+/-doped alumina (Al/sub 2/O/sub 3/) channel optical waveguides with high Er/sup 3+/ concentrations is analyzed. Taking into account uniform up conversion, excited state absorption (ESA) from the Er/sup 3+/ metastable level (/sup 4/I/sub 13/2/), and Yb/sup 3+//spl rarr/Er/sup 3+/ energy transfer by cross relaxation, the obtainable gain improvements compared to Yb/sup 3+/-free Er/sup 3+/-doped Al/sub 2/O/sub 3/ optical waveguides are investigated. The amplifier model is based on propagation and population rate equations and is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that 5-cm long Yb/sup 3+//Er/sup 3+/ co-doped Al/sub 2/O/sub 3/ waveguides show 13-dB net signal gain for 100 mW pump power at /spl lambda//sub p/=980 nm.

We numerically investigate the potential of Al2O3:Er3+ active slot waveguides for realizing small-form factor lasers on silicon-on-insulator. Based on recent technological improvements in the reliable and low-cost fabrication of alumina doped with high Er3+ concentration, we point out the possibility of realizing silicon compatible emitters at 1.55 μm, optically pumped at 1480 nm with a few milliwatts threshold pump power.

Er/sup 3+/-doped tellurite and Er/sup 3+/-doped alumina optical waveguide amplifiers are analyzed both as single amplifiers and as elements of 16-channel wavelength-division multiplexing (WDM) systems; their performances are compared with that from Er/sup 3+/-doped Al/P silica waveguide amplifiers. The amplifier model is based on propagation and population-rate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis predicts that Er/sup 3+/-doped tellurite waveguides exhibit improved gain characteristics compared with alumina and Al/P silica waveguides. Using Er/sup 3+/-doped tellurite waveguide amplifiers, it is suggested that 16 WDM channels may be transmitted to a maximum distance of 4250 km. By using in-line notch gain equalizing filters, the maximum transmission distance can be increased to 5250 km.

In this work, we propose the use of optical pulse coding techniques for simultaneous strain and temperature sensing based on spontaneous Brillouin scattering. Optical pulse coding provides a significant receiver signal-to-noise ratio enhancement, allowing for accurate Brillouin intensity and frequency shift measurements at low peak power levels. Due to the cross-sensitivity of these two parameters on both temperature and strain, optical pulse coding improves the temperature and strain resolution and sensing range with respect to Brillouin sensors operating with conventional single-pulses at the same peak power level. The proposed technique provides a high-performance cost-effective solution avoiding the use of high peak power levels.

Er3+-doped Al2O3 optical waveguides are analyzed both as single amplifiers and as elements of a 16-channel wavelength division multiplexing transmission system; their performance is compared with that from Er3+-doped SiO2 optical waveguide amplifiers. The amplifier model, based on propagation and population-rate equa tions, includes both uniform and pair-induced up-conversion mechanisms and is solved numerically by combining finite elements and the Runge-Kutta algorithm. The analysis showed that Er3+-doped Al2O3 waveguides exhibit much higher signal gains than Er3+-doped SiO2 waveguides and also that the use of Er3+-doped Al2O3 waveguides reduces the deleterious gain peaking effect, increasing the maximum transmission distance.

In this paper a two-dimensional (2-D) dynamic model, based on a tensor formulation and solved numerically by combining finite elements and finite differences, is proposed and used for analyzing nematic liquid crystal (LC) test cells with interdigital electrodes. We compare theoretical and experimental results concerning the switching behavior, response mechanism, and viewing angle characteristics of nematic LC pixel structures which use the in-plane-switching (IPS) mode. The good agreement observed between theory and experiment in terms of electro-optical properties validates our modeling and demonstrates its potential for design optimization. We show that the proposed LC test cells, using the in-plane-switching mode, ensure switching-ON and -OFF response times of 22 and 28 ms, respectively, and excellent viewing angle characteristics.

We experimentally investigate dynamic bit-error rate (BER) performance impairments induced by add-drop operations in semiconductor-optical amplifer (SOA)-based wavelength-division-multiplexing (WDM) metro-ring networks. Link control techniques in short-medium span networks provide effective performance improvement and significant BER transient reduction during add-drop operation, with respect to SOA linear operating condition (low input signal power). This behavior is confirmed by dynamic BER measurements and optical signal-to-noise penalty analysis.

A new, simplified analytical model for the calculation of the signal-to-noise ratio (SNR) in multiwavelength erbium-doped fibre amplifier (EDFA) cascades is presented. Comparisons with numerical results give excellent agreement, confirming the validity of this model and its significance for optimising system parameters.

We present a longitudinal multimode pumping scheme which allows Yb-sensitized Er-doped silica waveguide amplifiers to be effectively pumped by high-power and low-cost broad-area lasers. The proposed configuration is based on evanescent pump light coupling from a multimode low-loss waveguide to a Er-Yb codoped active core. Theoretical predictions, based on propagation and population-rate equations for the coupled Er-Yb system, show that longitudinal multimode pumping by high-power broad-area lasers at around 980 nm can provide up to 4-dB gain per centimeter, suggesting possible integration of low-cost amplifiers with important applications in wavelength-division-multiplexing metro and access optical networks.

We experimentally study the performance of wavelength-division-multiplexing (WDM) metro/access ring networks, based on semiconductor optical amplifiers (SOAs), considering several gain control techniques. We show that gain control through link-control (LC) channel or amplified spontaneous emission (ASE) power recirculation, effectively used in erbium-doped fiber amplifier-based WDM ring networks, introduces serious penalties due to intensity noise transfer, and cannot be used in short-span SOA-based WDM rings. On the other hand, we observe a net benefit using LC channel and ASE extraction for short span rings and a limited WDM channel number, compared with linear operating conditions. An effective optical signal-to-noise ratio improvement of 2.1 dB has been achieved with LC channel extraction with respect to linear operation, for a 4 x 13.5 dB span ring with eight WDM channels. For spans longer than 15 dB, system performance in gain-controlled rings is found to be similar to noncontrolled ones.

Challenging samples were processed using alternative quantification and STR PCR methods that include internal performance controls. These internal controls can be used to monitor potential inhibition or degradation of a sample. We compared the different workflows with regard to the predictive value the internal controls provided.

In this letter, a coded, Raman-based distributed temperature sensor system using 255-bit Simplex coded optical time domain reflectometry (OTDR) and optimized sensing link composed of cascaded fibers with different Raman coefficients, is proposed. This system is compared to a system with an uncoded OTDR on standard single-mode fiber, demonstrating significant enhancement in the interrogation distance (19.5 km from coding gain, and 9.6 km from link optimization). Total sensing range of 37 km at 17-m/3-K spatial/temperature resolution were achieved, while employing conventional low power (80 mW) laser diodes

We propose a novel high-power (up to 1.9 W) and low relative intensity noise (RIN) laser structure for effective first- and higher order distributed Raman copumping. RIN characterization and bit-error-rate measurements at 10 Gb/s point out RIN-penalty free transmission up to 25 dB of on-off copropagating Raman gain. This new copumping technology can provide sensible span reach enhancement in long-span unrepeated WDM transmission systems in a simple and effective way

We report on an advanced optical fiber sensing implementation enabling submeter resolution over long distance exploiting Brillouin optical time-domain analysis with differential pulse-width pair. Long sensing distances have been attained thanks to the combined use of distributed Raman amplification of optical signals together with optical pulse coding. We experimentally demonstrate strain-temperature sensing capabilities with a spatial resolution better than 50 cm throughout 93 km standard single-mode fiber, attaining accuracy in terms of measured strain and temperature smaller than 1.7 C and 34 ??, respectively. © 2014 Springer International Publishing Switzerland.

We propose a second-order counterpumped Raman ring fiber oscillator for high gain and low noise discrete Raman amplification with enhanced robustness to wavelength-division-multiplexing channels add-drop operations. Bit-error-rate measurement at 10 Gb/s shows negligible penalties up to 20-dB net gain.

A two-dimensional finite-element code is presented for the steady-state analysis of liquid crystal structures in nonuniform electric fields. It is based on a free-energy formulation which includes all three elastic constants and can deal with pure nematic, twisted nematic, and cholesteric liquid crystal materials. The enhanced capabilities of our code allow the design of composite structures made of both dielectric and liquid crystal materials and with arbitrary configuration of electrodes. Unwanted effects, such as the formation of disclination lines in the director orientation, can be accurately predicted. The method has been applied for analyzing pure nematic liquid crystal microlenses with variable focal length and twisted nematic liquid crystal cells for display applications. Numerical results show that a careful choice of the device structures can avoid the formation of defects and improve their performance.

The continuous wave operations of highly-efficient Er/sup 3+//Yb/sup 3+/ co-doped fiber lasers pumped at 980 nm are numerically analyzed. The model, based on propagation-rate equations, includes uniform upconversion from the /sup 4/I/sub 13/2/ and /sup 4/I/sub 11/2/ erbium levels and a pair-induced energy transfer process from Yb/sup 3+/ to Er/sup 3+/; it allows the description of both single-mode and multimode laser operations. Numerical results show that slope efficiencies close to the quantum limit, with threshold pump powers of few mW, can be achieved in short single-frequency fiber lasers using grating Bragg reflectors. Moreover, we demonstrate the possibility of performing equispaced multiwavelength laser emissions in high-concentration Fabry-Perot fiber microlasers.