Search

Background: Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by abnormal autoantibody production, inflammation, and organ damage. Most SLE treatment strategies aim to induce remission or reduce disease activity while avoiding flares. Baricitinib has been used effectively to manage various inflammatory diseases, and some randomized controlled trials (RCT) have shown that it is beneficial in treating SLE. The current study aims to assess the efficacy of baricitinib in treating SLE patients. Materials and Methods: Various databases such as PubMed, Scopus, and Science Direct were searched to obtain eligible studies for the present meta‐analysis. Data such as baseline characteristics of patients, doses of the baricitinib, follow‐up duration, and treatment outcome in the form of SLE responder index‐4 (SRI‐4) and lupus low disease activity state (LLDAS) were extracted. Combined odds ratio, 95% confidence interval, and probability values were calculated to study the efficacy of baricitinib in treating SLE patients. A p‐value less than.05 was taken as significant. Comprehensive meta‐analysis v3 was used for all analyses. Results: Three articles were found eligible for the present meta‐analysis comprising 614 patients with placebo, 614 SLE patients receiving 4 mg, and 621 patients with 2 mg of baricitinib. Meta‐analysis revealed a beneficial effect of 4 mg baricitinib in SLE patients compared to placebo, as measured by an increase in the SRI‐4 (p =.006, OR = 1.370) and LLDAS (p =.083, OR = 1.252) rates. In contrast to the placebo group, however, patients receiving 2 mg of baricitinib exhibited no significant improvement. The trial sequential analysis revealed the need for additional RCTs to determine the role of baricitinib in treating SLE patients. Conclusion: In treating SLE patients, administrating a higher dose of baricitinib (4 mg) may be effective. However, additional RCTs in different populations with larger sample sizes are required to validate our findings. [ABSTRACT FROM AUTHOR]

Novel fundamental notions helping in the interpretation of the complex dynamics of nonlinear systems are essential to our understanding and ability to exploit them. In this work we predict and demonstrate experimentally a fundamental property of Kerr-nonlinear media, which we name mode rejection and takes place when two intense counter-propagating beams interact in a multimode waveguide. In stark contrast to mode attraction phenomena, mode rejection leads to the selective suppression of a spatial mode in the forward beam, which is controlled via the counter-propagating backward beam. Starting from this observation we generalise the ideas of attraction and rejection in nonlinear multimode systems of arbitrary dimension, which paves the way towards a more general idea of all-optical mode control. These ideas represent universal tools to explore novel dynamics and applications in a variety of optical and non-optical nonlinear systems. Coherent beam combination in polarisation-maintaining multicore fibres is demonstrated as example.The authors introduce and demonstrate experimentally a novel fundamental property of nonlinear multimode optical systems, named mode rejection. This paves the way towards a more general idea of all-optical mode control and its related applications. [ABSTRACT FROM AUTHOR]

Cyanobacteria are photosynthetic prokaryotes and are reservoir of bioactive compounds having substantial antimicrobial and antioxidant activity. They serve as a rich source of structurally novel and biologically active metabolites, holding great potential for various pharmaceutical applications. The aim of this study is to investigate in vitro antimicrobial and antioxidant activities of the extracts of Nostoc punctiforme, a filamentous heterocystous cyanobacterium predominant in the rice fields of Lakhanpur (Bargarh District), Odisha. The heterocystous cyanobacteria was collected from rice field and identified by means of morphological and molecular approach (Nostoc punctiforme Jbr02). Subsequently, in vitro antimicrobial and antioxidant activity was assayed using acetone, methanol, and benzene extract. The cyanobacterial extracts established important antimicrobial actions against bacterial and fungal pathogens with significant MIC values from 62.5 to 500 µg/ml. The methanolic extract displayed better inhibitory activities against both V. Cholerae and P. verrucosun with the MIC value 62.5µg/ml while no such activity was recorded in benzene extract against B. subtilis, A. niger and F. oxysporum pathogens. The antioxidant study, depicted that the methanolic extract showed relatively higher antiradical activity of IC50 542±0.012 µg/ml among the three solvents. The Ferric reducing assay result was also maximum in methanolic extract (0.478±0.78) as compared to benzene and acetone extract. These findings infer that Nostoc punctiforme has potential antimicrobial and antioxidant activity, unveiling its potential as a valuable source of bioactive compounds. Thus, N. punctiforme in specific and cyanobacteria in general are one of the most promising candidates for commercial applications. [ABSTRACT FROM AUTHOR]

In this paper, wepresent a comparative study on temperature-dependent spectroscopic characteristics and L-band amplifier performance for aluminum-rich erbium-doped fiber (EDF) and in-house fabricated phosphorus co-doped EDF. Different pumping configurations were studied to conclude that the pump wavelength of 980 nm with unequal forward/backward pump powers exhibited better temperature stability. Phosphorus EDF provided 19.4±1.4 dB gain and 4.6±0.2 dB noise figure (NF) from 1575–1615 nm at room temperature (RT), for a multi-channel input signal of −25 dBm in each channel, whereas the aluminum-rich EDF provided 20.3±5.1 dB gain and 5.3±0.8 dB NF. Using a single-channel input signal of −25 dBm at 1625 nm, phosphorus EDF maintained >10 dB gain with a 9.6 dB and 12 dB gain increment than aluminum-rich EDF at RT and −60 °C, respectively. The temperature-dependent gain (TDG) coefficient from 1575–1615 nm was in the range −0.006 to −0.044 dB/°C for phosphorus EDF and 0.011 to −0.023 dB/°C for aluminum-rich EDF, over the temperature range −60 to +80 °C. We propose a hybrid L-band amplifier concatenating aluminum-rich EDF with phosphorus EDF, to suppress the temperature dependence of phosphorus EDF and improve the gain bandwidth restriction of aluminum-rich EDF. The hybrid EDF exhibited multi-channel 20.9±3.9 dB gain and 3.7±0.6 dB NF from 1575–1615 nm at RT. The TDG coefficient of the hybrid EDF remained almost constant from 1585–1615 nm, contributing to a temperature-insensitive gain flatness. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a bidirectional Vanilla recurrent neural network (Vanilla-RNN) based equalization scheme for O-band coarse wavelength division multiplexed (CWDM) transmission. Based on a 4 × 50-Gb/s intensity modulation and direct detection (IM/DD) system, we demonstrate the significantly better bit error rate (BER) performance of the Vanilla-RNN scheme over the conventional decision feedback equalizer (DFE) for both Nyquist on-off keying (OOK) and Nyquist 4-ary pulse amplitude modulation (PAM4) formats. It is shown that the Vanilla-RNN equalizer is capable of compensating for both linear and nonlinear impairments induced by the transceiver and the single-mode fiber (SMF). As a result, up to 100-km and 75-km SMF transmission can be achieved for OOK and PAM4 transmission, respectively. Furthermore, through the comparison with other equalization schemes, including the linear equalizer, 3rd-order Volterra equalizer, and Volterra+DFE, it is demonstrated that the Vanilla-RNN equalizer achieves the best BER performance. In the meantime, it also exhibits lower implementation complexity when compared to Volterra-based schemes. Our results show that the Vanilla-RNN scheme is a viable solution for realizing simple and effective equalization. This work serves as an exploration and offers useful insights for future implementations of reach-extended O-band CWDM IM/DD systems. [ABSTRACT FROM AUTHOR]

A tunable dual-wavelength Brillouin-bismuth fiber laser with a triple-Brillouin frequency spacing of ∼37.8 GHz was demonstrated by employing modular structures. The modular designs can be divided into two main cavities, whereby cavity 1 consisted of a 2-km single-mode fiber (SMF) and a loop mirror that was able to generate a single-spaced Brillouin shift, while cavity 2 comprised of 10-km dispersion compensating fiber (DCF) that was able to produce a double-spaced Brillouin shift. Based on this design, a stable dual-wavelength lasing was established with a low peak power fluctuation of 0.13 dB and 0.6 dB for the Brillouin pump (BP) and third Brillouin Stokes line (BS3), respectively. By varying the center wavelength of the Brillouin pump, the dual-wavelength laser can be tuned across a 40 nm span, ranging from 1300 nm to 1340 nm. The frequency spacing of the Brillouin-bismuth fiber laser can also be easily switched between ∼12.6 GHz, ∼25.2 GHz, and ∼37.8 GHz by utilizing these modular structures. The proposed dual-wavelength laser has a promising potential for application as a low phase noise source for microwave generation. [ABSTRACT FROM AUTHOR]

Alternate-mark-inversion (AMI) has been used in the past to improve the transmission performance of binary intensity modulation formats. In this work, we improved the tolerance of O-band 4-level pulse amplitude modulation (PAM4) transmission to channel impairments through the adoption of an AMI scheme. Improvements in receiver sensitivity were shown in both semiconductor optical amplifier (SOA) and bismuth-doped fibre amplifier (BDFA) equipped links. We confirmed the capability of 4-level AMI to extend the reach in the O-band, which was achieved through the mitigation of nonlinear and dispersive effects. We experimentally demonstrated a 4.28-dB Q-factor improvement for transmission over 60 km of SMF-28e. To offer an insight to the mechanisms leading to the improved tolerance to transmission impairments, we presented numerical simulations that illustrate the underlying method of action of AMI4. [ABSTRACT FROM AUTHOR]

In this article, we experimentally demonstrate an all-fiber optical amplifier using Bi-doped phosphosilicate fiber (BPSF) operating in both the O-band and the E-band, providing >20 dB gain from 1345 to 1460 nm for an input signal power of −23 dBm. A maximum gain of 31 dB with a noise figure (NF) of 4.8 dB was achieved at 1420 nm for −23 dBm input signal, whereas for an input signal power of −10 dBm it was 26 dB with a NF of 5.3 dB. The in-band OSNR of the proposed Bi-doped fiber amplifier (BDFA) was >22 dB from 1345 to 1460 nm for a −23 dBm input signal. The gain coefficient was found to be 0.04 dB/mW for a −23 dBm input signal. Also, the temperature dependent gain and NF performance of the BDFA within −40 to +60 °C were characterized. The temperature-dependent-gain (TDG) coefficient for a −23 dBm input signal was found to be −0.015 dB/°C at a signal wavelength of 1420 nm where the BDFA gain is maximum, while for an input signal power of −10 dBm it was −0.01 dB/°C at 1420 nm. The TDG coefficient of the proposed BDFA from 1350–1460 nm was in the range from −0.079 to −0.008 dB/°C. The BDFA gain and NF performance were also measured and compared using BPSFs with different unsaturable loss (UL) characteristics. [ABSTRACT FROM AUTHOR]

Multiwavelength fiber lasers operating in the 1.3 μm wavelength region are of great interest as they complement existing systems in the conventional optical communication band of 1.55 μm. In this work, a multiwavelength Brillouin fiber laser with single- and double-Brillouin frequency spacings operating in 1.3 μm is proposed and demonstrated using a dispersion compensating fiber (DCF) as the Brillouin gain medium. A bismuth-doped fiber serves as the laser gain medium. At the maximum pump power of 1021 mW and with the Brillouin pump set at 11 dBm, up to 7 Brillouin Stokes lines with a wavelength spacing of 0.074 nm are obtained in the single-spaced configuration. In the case of the double-spaced configuration, 14 Stokes lines are generated with a wavelength spacing of 0.15 nm between the even Stokes lines. By tuning the central wavelength of the Brillouin pump, both laser configurations are wavelength-tunable with a range of 93 nm and 19 nm for the single-spaced and double-spaced Brillouin lasers respectively. This is, to the best of the author's knowledge, the first demonstration of a multiwavelength/Brillouin laser using a bismuth-doped fiber as the laser gain medium. [ABSTRACT FROM AUTHOR]

Here we present a fully fiberized Bi-doped ring laser incorporating a fiber Bragg grating (FBG) operating at a wavelength of 1340nm, which provides 172mW of continuous-wave output power with a slope efficiency of 35%. In addition, we demonstrate a wavelength-tunable version of the laser, which can be tuned from 1320nm to 1370nm by employing a home-made mechanically tunable FBG. Within the whole 50nm tuning band the laser maintains the output power of more than 100mW and the slope efficiency of more than 25%. A maximum output power of ~165mW is achieved over the wavelength range of 1330-1340nm. The linewidth of tunable laser is 0.04nm. [ABSTRACT FROM AUTHOR]

We propose a novel approach of exploiting the LP02 mode in ultra-high NA confined-doped M-type fibers to ensure effective single-mode operation, thereby breaking the trade-off between mode-area scaling and ultra-high NA. This novel approach opens the door to highly rare-earth doped fibers suitable for power scaling applications. Therefore enabling, simultaneously scaling of power and slope efficiency of fiber lasers. [ABSTRACT FROM AUTHOR]

Objective: Laser technology in urology is currently used for both stone lithotripsy and prostate enucleation. Thulium fiber laser (TFL) is a novel laser, with initial studies showing potential benefits over other lasers both in terms of its effectiveness and safety profile. Material and methods: In the first part of this review, a descriptive analysis of the theoretical concepts behind TFL was performed. This part focused on the physics and laser parameters as applied to the clinical practice. These were interpreted in the context of other lasers, namely, the Holmium:YAG laser to highlight the theoretical advantages as well as potential pitfalls offered by the TFL. In the second part of the review, a narrative synthesis of in-vitro studies regarding TFL and its modifications is performed assessing stonerelated parameters, namely, ablation rate, operative time retropulsion, and safety. Results: TFL achieved high ablation rates in most studies and performed better than Holmium:YAG laser across a range of different settings and ablation modes when the two lasers were compared. Moreover, its ability to use low pulse energy ensures minimal stone retropulsion with the retropulsion threshold estimated to be 2-4 times higher than that of Holmium:YAG laser. From a safety viewpoint, TFL poses no additional risks than other lasers, although it does potentially lead to slightly higher temperatures in the surrounding tissues during lithotripsy. Conclusion: The unique properties of TFL have made it an attractive alternative to conventional laser techniques currently used in urology. Clinical studies are required before its application can become more widespread. [ABSTRACT FROM AUTHOR]

A planarized optical fibre designed for two-dimensional bend monitoring and external refractive index sensing is presented. The approach uses two single-mode waveguides each containing a set of spectrally multiplexed Bragg gratings. To achieve sensitivity to bending and external refractive index, the cladding material of the fibre is partially removed through physical machining. This acts to offset the neutral axis, increasing bend sensitivity, and exposes the evanescent field of the guided mode, permitting external refractive index monitoring. Through collective monitoring of the Bragg grating array, real time, multiparameter sensing is attainable, allowing new capability for intelligent monitoring. [ABSTRACT FROM AUTHOR]

In this article, we report high-speed multi-band direct-detection (DD) transmission over a hollow-core nested antiresonant nodeless fiber (NANF). Thanks to the ultrawide bandwidth of the NANF, we demonstrate dual-band transmission across the O- and C-bands over a ∼1-km length of a hollow-core fiber for the first time. Eight wavelength-division multiplexed (WDM) channels were transmitted using 100-Gb/s/λ Nyquist 4-ary pulse-amplitude modulation (PAM4) signals, which to the best of our knowledge, is the highest aggregate capacity ever transmitted in a DD hollow-core fiber-based transmission system. Optical pre-amplification was adopted for signal reception in both bands, achieved using an in-house built bismuth-doped optical fibre amplifier (BDFA) and a commercial erbium-doped fiber amplifier (EDFA) in the O- and C-band, respectively. We further demonstrate beyond 100-Gb/s/λ adaptively-loaded discrete multitone (DMT) transmission over the S+C+L-bands using the same NANF, without the use of optical amplification. Our experiments show that apart from fiber loss, the use of the NANF did not introduce any additional transmission penalties. The demonstrated results validate the ultrawide bandwidth and excellent modal purity of the fabricated NANF, which allow beyond 100-Gb/s/λ penalty-free transmission over multiple bands, highlighting the potential of this fiber technology for high-speed short- to intermediate-reach applications. [ABSTRACT FROM AUTHOR]

In this article, we experimentally demonstrate dual O+C-band direct-detection wavelength division multiplexed (WDM) transmission over 50 km of standard single-mode fibre, wherein 4 × 40-Gb/s Nyquist on-off keying (OOK) modulation is used in the O-band whilst 4 × 40-Gb/s single-sideband (SSB) subcarrier modulation (SCM) with Kramers–Kronig (KK) detection is used in the C-band. A bismuth-doped fibre amplifier (BDFA) is used as the pre-amplifier in the O-band to extend the reach of the direct-detection system. It is demonstrated that the O-band exhibits superior receiver sensitivity relative to the C-band and its transmission performance is limited by the chromatic dispersion (CD), especially when longer reaches and wavelengths in the longer edge of the band are explored. In contrast, due to the adoption of the SSB format, the C-band shows enhanced tolerance to CD effects. In this case, some receiver sensitivity is sacrificed to accommodate the adoption of the KK detection which is used to eliminate the signal-to-signal beating interference of the SSB-SCM format. The inferior receiver sensitivity in the C-band is caused by (1) the higher CSPR requirement of the KK detection and (2) the restriction of small-signal modulation for the dual-drive Mach–Zehnder modulator to generate optical SSB signals. The results indicate the feasibility to further extend the reach of O-band transmission systems, which enables the possibility to realise dual O+C-band WDM transmission in intermediate- to long-haul optical networks. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to examine the classic characteristics of highly cited articles (HCAs) of top-ranked library and information science (LIS) journals and get acquainted with the high-quality works in specific areas of LIS for distinguishing what gets cited and who the prolific authors are. Design/methodology/approach: The HCAs published across the top four LIS journals were downloaded, coded and a database was developed with basic metadata elements for analysis using bibliometric indicators. Lotka's Inverse Square Law of Scientific Productivity was applied to assess the author's productivity of HCA. The content analysis method was also used to find out the emerging areas of research that have sought high citations. Findings: Inferences were drawn for the proposed five number of research questions pertaining to individual productivity, collaboration patterns country and institutional productivity, impactful areas of research. The Netherland found to be the potential player among all the affiliating countries of authors and Loet Leydesdorff tops the list among the prolific authors. It is observed that Lotka's Classical Law also fits the HCA data set in LIS. "Research impact measurement and research collaboration," "Social networking" and "Research metrics and citation-based studies" are found to be the emerging areas of LIS research. Practical implications: Researchers may find a way what gets cited in specific areas of LIS literature and why along with who are the prolific authors. Originality/value: This study is important from the perspective of the growing research field of the LIS discipline to identify the papers that have influenced others papers as per citation count, spot the active and more impactful topics in LIS research. [ABSTRACT FROM AUTHOR]

Extension in the reach of 1.3 μm optical communication systems has traditionally been restricted by the availability of suitable low-noise fiber amplifiers. Addressing this challenge, we present the first repeatered wavelength division multiplexing (WDM) experiments using a bismuth-doped exhibits 8.4 THz (50 nm) of gain bandwidth in the O-band. WDM signals arranged either with coarse or dense wavelength spacings are transmitted over lengths of single-mode fibre (SMF)-28e ranging between 100 and 140 km. [ABSTRACT FROM AUTHOR]

We review the performances of few-mode in-line fiber amplifiers for mode division multiplexed transmission systems. We have experimentally demonstrated that differential modal gain (DMG) of <2 dB can be achieved amongst the guided modes using ring shaped erbium doping profile. The amplifier provides >20 dB small signal gain for all the guided modes with a gain flatness of ≤4.0 dB over the full C-band. Numerical modelling suggests that the DMG can be reduced to <1 dB by adopting complex doping profiles with the complexity rises as the number of guided modes increases. We have also reported the experimental demonstration of a few mode amplifier at the emerging telecommunication window of 2 μm supporting 3 spatial modes. [ABSTRACT FROM AUTHOR]

We describe novel fiber Raman lasers pumped directly by spectrally combined high power multimode laser diodes at ~975 nm and emitting at ~1019 nm. With a commercial multimode graded-index fiber, we reached 20 W of laser output power with a record slope efficiency of 80%. With an in-house double-clad fiber, the beam quality improved to M² = 1.9, albeit with lower output power and slope efficiency due to higher fiber loss. We believe this is the first publication of a fiber Raman laser cladding-pumped directly by diodes. [ABSTRACT FROM AUTHOR]

Withania somnifera root extract has been used traditionally in ayurvedic system of medicine as a memory enhancer. Present study explores the ameliorative effect of withanolide A, a major component of withania root extract and its molecular mechanism against hypoxia induced memory impairment. Withanolide A was administered to male Sprague Dawley rats before a period of 21 days pre-exposure and during 07 days of exposure to a simulated altitude of 25,000 ft. Glutathione level and glutathione dependent free radicals scavenging enzyme system, ATP, NADPH level, γ-glutamylcysteinyl ligase (GCLC) activity and oxidative stress markers were assessed in the hippocampus. Expression of apoptotic marker caspase 3 in hippocampus was investigated by immunohistochemistry. Transcriptional alteration and expression of GCLC and Nuclear factor (erythroid-derived 2)–related factor 2 (Nrf2) were investigated by real time PCR and immunoblotting respectively. Exposure to hypobaric hypoxia decreased reduced glutathione (GSH) level and impaired reduced gluatathione dependent free radical scavenging system in hippocampus resulting in elevated oxidative stress. Supplementation of withanolide A during hypoxic exposure increased GSH level, augmented GSH dependent free radicals scavenging system and decreased the number of caspase and hoescht positive cells in hippocampus. While withanolide A reversed hypoxia mediated neurodegeneration, administration of buthionine sulfoximine along with withanolide A blunted its neuroprotective effects. Exogenous administration of corticosterone suppressed Nrf2 and GCLC expression whereas inhibition of corticosterone synthesis upregulated Nrf2 as well as GCLC. Thus present study infers that withanolide A reduces neurodegeneration by restoring hypoxia induced glutathione depletion in hippocampus. Further, Withanolide A increases glutathione biosynthesis in neuronal cells by upregulating GCLC level through Nrf2 pathway in a corticosterone dependenet manner. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate an inline few-mode erbium doped fiber amplifier supporting six spatial modes with reconfigurable differential gain control and excellent gain flatness obtained through mode-selective bidirectional pumping of a custom fiber with a radially profiled erbium dopant distribution. A signal gain of >20 dB was obtained for all the guided modes with a differential modal gain <;2 dB and good gain flatness across the C-band. [ABSTRACT FROM PUBLISHER]

In this letter, pump power depreciation due to photodarkening effects in an ytterbium doped fiber (YDF) is investigated. Photodarkening is monitored by measuring the transmitted power at visible and pump wavelengths simultaneously, which renders direct quantitative measurement of pump power reduction rather than excess background loss. Our observation of substantial reduction in the pump power and the shortened fluorescence decay time in the photodarkened fiber indicates that the photodarkening influences pump efficiency. The effect of the photodarkening in a device level is also investigated by observing the performance of the YDF amplifier implementing the same YDF. The pump power depreciation of this fiber amplifier is quantitatively investigated by numerical simulation. The results suggest that operating at a saturated regime helps to subdue the photodarkening, with explanation in terms of population inversion density provided. The level of power depreciation is calculated to be 15%-30%, which matches our experimental observation. [ABSTRACT FROM PUBLISHER]

We report signal amplification and output signal-to-noise ratio (SNR) for simultaneous four-channel amplification at C-band in the new type of erbium-doped fiber (EDF) having core glass compositions of zirconia-yttria-alumino-phospho-silicate (EDF-I). Performance of EDF-I is compared with two mostly used EDFs having core glass compositions of alumino-silicate (EDF-II) and germino-alumino-silicate (EDF-III). EDF-I produces the best result of maximum gain difference < 2 dB with output SNR of > 22 dB at input signal level of -30 dB\cdotm/channel amplification. [ABSTRACT FROM PUBLISHER]

We report a highly versatile chemical-in-crucible preform fabrication technique suitable for gas-phase deposition of doped optical fibers. Aluminosilicate and ytterbium-doped phosphosilicate fibers are presented demonstrating the technique and its potential for realizing complex fiber designs that are suitable for the next generation of high-power fiber devices. The results show aluminum-doped fiber with numerical aperture of 0.28 and ytterbium-doped fiber with a measured slope efficiency of 84% with respect to pump launch power. [ABSTRACT FROM PUBLISHER]

We theoretically detail and explain how to control unwanted excess gain for higher order modes in cladding-pumped large-core ytterbium-doped fiber amplifiers operating on the fundamental mode by using a small inner cladding and pumping close to the emission wavelength in a so-called tandem-pump configuration. Such excess gain can otherwise limit the core size. We study this experimentally by comparing the level of amplified spontaneous emission at the edge of the core in a conventional diode-pumped and tandem-pumped large-core ytterbium-doped multimode fiber. We also discuss the potential benefits of tandem pumping in reducing fiber photodarkening. [ABSTRACT FROM PUBLISHER]

A tunable highpower cladding-pumped neodymium- doped aluminosilicate fiber laser is demonstrated. The maximum power reached was 2.4 W with a slope efficiency of 41 % and a threshold pump power of 1.68 W, both with respect to launched pump power, when cladding pumped by two 808-nm diode pump sources at both fiber ends. The dependence of the tuning range on the fiber length is investigated. The tuning range changed from 922 to 942 nm for a 25-m-long fiber to 908-938 nm with a 14-m-long fiber, because of reabsorption effects. The output llnewidth was 0.26 nm in a diffraction-limited beam. Operation on the challenging 0.9-μm three-level transition in neodymium-doped double-dad fiber laser was facilitated by a W-type core refractive index profile. This filtered out the unwanted and competing strong transition at 1.06 μm while guidance of 0.9 μm remained intact. [ABSTRACT FROM AUTHOR]

A cladding-pumped multi-element fiber (MEF) comprising 4-Er/Yb-doped signal fibers and single multimode pump fiber has been used to demonstrate a wideband amplifier. The MEF amplifier has been characterized for different pump powers and signal fiber lengths. A maximum gain of 37 dB and corresponding noise figure of 7.3 dB have been obtained with an input signal of −23 dBm in the $C$ -band. The signal fibers were cascaded to provide >17-dB gain over a 80-nm bandwidth covering a wavelength range of 1536–1615 nm. [ABSTRACT FROM PUBLISHER]