Bidirectional Pumping Research Articles

Transmission performance improvement using random DFB laser based Raman amplification and bidirectional second-order pumping.

We demonstrate that a distributed Raman amplification scheme based on random distributed feedback (DFB) fiber laser enables bidirectional second-order Raman pumping without increasing relative intensity noise (RIN) of the signal. This extends the reach of 10 × 116 Gb/s DP-QPSK WDM transmission up to 7915 km, compared with conventional Raman amplification schemes. Moreover, this scheme gives the longest maximum transmission distance among all the Raman amplification schemes presented in this paper, whilst maintaining relatively uniform and symmetric signal power distribution, and is also adjustable in order to be highly compatible with different nonlinearity compensation techniques, including mid-link optical phase conjugation (OPC) and nonlinear Fourier transform (NFT).

Reduction of stimulated brillouin scattering threshold using bidirectional pumping with pump recycling scheme

Reduction of stimulated brillouin scattering threshold using bidirectional pumping with pump recycling scheme

双向多泵浦光纤拉曼放大器偏振相关增益研究

双向多泵浦光纤拉曼放大器偏振相关增益研究

双向多泵浦光纤拉曼放大器偏振相关增益研究

双向多泵浦光纤拉曼放大器偏振相关增益研究

Bismuth-doped fibre amplifier operating between 1600 and 1800 nm

We report the first bismuth-doped fibre amplifier operating between 1600 and , which utilises bidirectional pumping (co-propagating and counter-propagating pump beams) by laser diodes at a wavelength of . The largest gain coefficient of the amplifier is , at a wavelength of . It has a noise figure of gain bandwidth of and gain efficiency of .

Truly random bit generation based on a novel random Brillouin fiber laser.

We propose a novel dual-emission random Brillouin fiber laser (RBFL) with bidirectional pumping operation. Numerical simulations and experimental verification of the chaotic temporal and statistical properties of the RBFL are conducted, revealing intrinsic unpredictable intensity fluctuations and two completely uncorrelated laser outputs. A random bit generator based on quantum noise sources in the random Fabry-Perot resonator of the RBFL is realized at a bit rate of 5 Mbps with verified randomness.

Comparison between threshold and sensitivity of stimulated Brillouin scattering at different pumping configurations in high-power double-clad fiber lasers

Theoretical analysis of stimulated Brillouin scattering (SBS) in high power ytterbium-doped double-clad (YDDC) fiber lasers is presented by solving the steady-state rate equations with regard to SBS at different pumping configurations. The behavior of Brillouin Stokes power growth along the fiber is investigated and the SBS threshold power is quantitatively compared at forward, backward and bi-directional pumping configurations. It is shown that the backward pumping configuration has higher SBS threshold power than two others. Also. The effect of cavity parameters such as cavity length, front mirror reflectivity, dopant concentration and laser linewidth at different pumping configuration have been studied. It can be seen although the backward puming has higher SBS threshold but its sensitivity to cavity parameters is higher than other pumping configuration which is a negative impact for cavity designing.

160 W 800 fs Yb:YAG single crystal fiber amplifier without CPA

We demonstrate a compact and simple two-stage Yb:YAG single crystal fiber amplifier which delivers 160 W average power, 800 fs pulses without chirped pulse amplification. This is the highest average power of femtosecond laser based on SCF. Additionally, we demonstrate the highest small signal gain of 32.5 dB from the SCF in the first stage and the highest extraction efficiency of 42% in the second stage. The excellent performance of the second stage was obtained using the bidirectional pumping scheme, which is applied to SCF for the first time.

Evaluation of 100G DP-QPSK long-haul transmission performance using second order co-pumped Raman laser based amplification.

We present, for the first time, a detailed investigation of the impact of second order co-propagating Raman pumping on long-haul 100G WDM DP-QPSK coherent transmission of up to 7082 km using Raman fibre laser based configurations. Signal power and noise distributions along the fibre for each pumping scheme were characterised both numerically and experimentally. Based on these pumping schemes, the Q factor penalties versus co-pump power ratios were experimentally measured and quantified. A significant Q factor penalty of up to 4.15 dB was observed after 1666 km using symmetric bidirectional pumping, compared with counter-pumping only. Our results show that whilst using co-pumping minimises the intra-cavity signal power variation and amplification noise, the Q factor penalty with co-pumping was too great for any advantage to be seen. The relative intensity noise (RIN) characteristics of the induced fibre laser and the output signal, and the intra-cavity RF spectra of the fibre laser are also presented. We attribute the Q factor degradation to RIN induced penalty due to RIN being transferred from the first order fibre laser and second order co-pump to the signal. More importantly, there were two different fibre lasing regimes contributing to the amplification. It was random distributed feedback lasing when using counter-pumping only and conventional Fabry-Perot cavity lasing when using all bidirectional pumping schemes. This also results in significantly different performances due to different laser cavity lengths for these two classes of laser.

Automatic In-Syringe Dispersive Microsolid Phase Extraction Using Magnetic Metal-Organic Frameworks.

A novel automatic strategy for the use of micro- and nanomaterials as sorbents for dispersive microsolid phase extraction (D-μ-SPE) based on the lab-in-syringe concept is reported. Using the developed technique, the implementation of magnetic metal-organic framework (MOF) materials for automatic solid-phase extraction has been achieved for the first time. A hybrid material based on submicrometric MOF crystals containing Fe3O4 nanoparticles was prepared and retained in the surface of a miniature magnetic bar. The magnetic bar was placed inside the syringe of an automatic bidirectional syringe pump, enabling dispersion and subsequent magnetic retrieval of the MOF hybrid material by automatic activation/deactivation of magnetic stirring. Using malachite green (MG) as a model adsorption analyte, a limit of detection of 0.012 mg/L and a linear working range of 0.04-2 mg/L were obtained for a sample volume equal to the syringe volume (5 mL). MG preconcentration was linear up to a volume of 40 mL, obtaining an enrichment factor of 120. The analysis throughput is 18 h(-1), and up to 3000 extractions/g of material can be performed. Recoveries ranging between 95 and 107% were obtained for the analysis of MG in different types of water and trout fish samples. The developed automatic D-μ-SPE technique is a safe alternative for the use of small-sized materials for sample preparation and is readily implementable to other magnetic materials independent of their size and shape and can be easily hyphenated to the majority of detectors and separation techniques.

Direct Evidence of Egestion and Salivation of Xylella fastidiosa Suggests Sharpshooters Can Be "Flying Syringes".

Xylella fastidiosa is unique among insect-transmitted plant pathogens because it is propagative but noncirculative, adhering to and multiplying on the cuticular lining of the anterior foregut. Any inoculation mechanism for X. fastidiosa must explain how bacterial cells exit the vector's stylets via the food canal and directly enter the plant. A combined egestion-salivation mechanism has been proposed to explain these unique features. Egestion is the putative outward flow of fluid from the foregut via hypothesized bidirectional pumping of the cibarium. The present study traced green fluorescent protein-expressing X. fastidiosa or fluorescent nanoparticles acquired from artificial diets by glassy-winged sharpshooters, Homalodisca vitripennis, as they were egested into simultaneously secreted saliva. X. fastidiosa or nanoparticles were shown to mix with gelling saliva to form fluorescent deposits and salivary sheaths on artificial diets, providing the first direct, conclusive evidence of egestion by any hemipteran insect. Therefore, the present results strongly support an egestion-salivation mechanism of X. fastidiosa inoculation. Results also support that a column of fluid is transiently held in the foregut without being swallowed. Evidence also supports (but does not definitively prove) that bacteria were suspended in the column of fluid during the vector's transit from diet to diet, and were egested with the held fluid. Thus, we hypothesize that sharpshooters could be true "flying syringes," especially when inoculation occurs very soon after uptake of bacteria, suggesting the new paradigm of a nonpersistent X. fastidiosa transmission mechanism.

Compact Tm-doped fibre laser pumped by a 1600 nm Er-doped fibre laser designed for environmental gas sensing

In this work, the compact all-fibre linear Erbium (Er)-doped fibre lasers, operating at wavelengths of 1584nm and 1600nm have been described and optimized, with an aim to achieve better pumping conditions for a Thulium (Tm)-doped fibre laser. Optimization of the system has been carried out involving the studies on the different lengths of the Er-doped fibre and the different grating pairs used to achieve 173.5mW of laser power at 1600nm under bidirectional pumping at 980nm. The designed Er-doped fibre laser at 1600nm has been utilized successfully to pump longer wavelength Tm-doped fibre laser. The obtained laser power (output of Tm-doped fibre laser) of 35.5mW at 1874nm and 10.6mW at 1995nm is effective for environmental gas sensing, as these wavelengths align well with the absorption spectra of greenhouse gases such as CO2. The laser offers high power (tens of milliWatts), good directionality and a compact overall packaging with the diode pumping, making them ideally suited to ‘in-the-field’ use.

Influences of pumping schemes on the properties of dissipative soliton in fiber lasers

Based on the extended scalar nonlinear Schrödinger equation, the influences of pumping schemes on the properties of dissipative soliton are investigated theoretically in passively mode-locked ytterbium-doped fiber laser with positive dispersion cavity. Results show that, under the conditions of the same initial total gain, the dissipative solitons obtained in the backward pumping fiber laser have the narrowest spectral width, shortest pulse duration and highest pulse peak power for the forward, backward and bidirectional pumping schemes, moreover, the linear fitting degree of pulse chirp is lowest. With the same gain saturation energy, the pulse energies of the dissipative solitons are equal for three pumping schemes, but the differences of output spectra and temporal waveforms increase as the gain saturation energy increases.

A Design Solution for Efficient and Compact Electro-hydraulic Actuators

This paper presents and describes an innovative design solution for a compact Electro-Hydraulic Actuator (EHA). Although the current trend in many mobile applications is towards the use of Electro Mechanical Solutions (EMAS) instead of Hydraulic Actuation Systems (HAS), HEAs can actually represent the best technological compromise. In fact, EHAs can combine the power to weight ratio advantage of hydraulic technology with the versatility and ease of installation and control of electric technology. Compared to EMAS, which are often equipped with low efficient load holding mechanisms, EHAs can also offer superior energy efficiency. Moreover, the EHAs do not suffer of jamming problems, which make them a strong candidate to be employed in harsh environments. Applications of EHAs like the one proposed in this work include aircrafts, cargo and vehicle doors, hatches and landing gears. The system studied in this research is based on miniature bi-directional gear pump (from 0.13 cc/rev), specifically designed to maximize performance in terms of efficiency, noise emissions and durability for the reference application. This pump is used in a system layout architecture that includes built-in valves to allow a power on demand strategy control of a differential linear actuator. In particular, a novel pressure compensation system was formulated to minimize power losses associated with the internal lubricating gaps in the whole field of operation. The paper details the numerical modelling of the system, showing also results which describe its main features of operation. Advantages in terms of energy consumption, with respect to a more common configuration of EHA are also discussed.

Bidirectional microfluidic pumping using an array of magnetic Janus microspheres rotating around magnetic disks.

We demonstrate a novel, flexible and programmable method to pump liquid through microchannels in lab-on-a-chip systems without the use of an external pump. The pumping principle is based on the rotation of ferromagnetic Janus microspheres around permalloy disks, driven by an external rotating magnetic field. By placing the disks close to the edge of the microchannel, a pumping rate of at least 0.3 nL min(-1) was measured using tracking microspheres. Geometric programming of the pumping direction is possible by positioning the magnetic disk close to the side wall. A second degree of freedom in the pumping direction is offered by the rotational direction of the external magnetic field. This method is especially suited for flow-controlled recirculation of chemical and biological species in microchannels - for example, medium recirculation in culture chambers - opening the way towards novel, portable, on-chip applications without the need for external fluidic or electrical connections.

Comparative Study of the Birefringence in Photonic Crystal Fiber Lasers

In this paper, we study the birefringence in photonic crystal fiber lasers PCFs and in conventional fiber lasers in the bi-directional pump scheme in the linear cavity laser. We show that the value of birefringence in photonic crystal fibers is smaller than that of conventional fiber lasers [1].

Accurate modeling of cladding pumped, star-shaped, Yb-doped fiber amplifiers

Based on an iterative numerical approach, we model continuous wave (CW), high power, cladding-pumped Yb-doped fiber amplifiers with bi-directional pumping of the star-shaped cladding. Accurate prediction of over 1kW output power is demonstrated, and the calculation results are in good agreement with experiments. Absorption and emission cross sections for the used doped fiber are determined experimentally in advance. Using the model at such high powers, it is shown that the Giles model parameter of the effective overlap integral in the star-shaped cladding may vary coupling the light from diodes with different numerical apertures, which is believed caused by the increasing amount of pump light launched into higher order modes.

Research of Track-Type Full Feeding Combine Harvester Walking Design Scheme Based on Hydraulic Close System

Hydraulic technology is one of the key techniques of modern transmission and control. Closed type hydraulic power transmission system is weight ratio, fast action, easy to realize the advantages of flexible stepless speed regulation, flexible power transmission. In this paper, the closed hydraulic system of double bidirectional variable hydraulic pump and the bidirectional quantitative motor, the drive system for crawler type machinery, advantages, in the walking system design process can reasonable calculation and power matching, reasonable selection of power components, the universal value of engineering application.

NUMERICAL AND EXPERIMENTAL STUDY ON WAVE-CURRENT INTERACTIONS OVER A SUBMERGED BAR

Wave-current interactions are simulated by a fully-nonlinear numerical wave tank (NWT). The model is developed based on the time-domain higher-order boundary element method (HOBEM). The mixed Eulerian-Lagrangian scheme is adopted to track the transient free surface with the fourth-order Runga-Kutta method for refreshing wave profile and velocity potential at the next time step. The meshes are regridded at each time step to avoid numerical instabilities caused by mesh motions. An image Green function is utilized to increase the speed of computation. Using the developed NWT, nonlinear wave-current interactions (1) without body; (2) with a submerged vertical bar for various wave and current conditions have been simulated. The physical experiment on evolution of waves in uniform current is carried out in a wave flume at Dalian University of Technology. The flume is 69.0m long, 3.0m wide and 1.8m deep. The experimental setup is shown in Fig.1. The flume is equipped with a hydraulically driven, irregular wave generator at one end, and a wave absorber at the other. The still-water depth (h) used in this study was 0.6m, and then a vertical submerged bar was installed along the bottom of flume. It was 0.4m height and 0.5m width. In order to record the wave transformation and propagation clearly, five wave gauges were installed. The incident wave amplitude is varied from 0.025m to 0.054m, and incident wave periods are 1s and 2s, respectively. Currents are introduced by a bidirectional centrifugal pump. Following currents flow in the same direction as wave propagation, and its velocity was set for positive, and the opposite situation represented opposing currents. An acoustic Doppler velocimeter (ADV) was used to measure the current velocity and the mean velocity U0=0.2m/s was chosen. The numerical results and experimental data are compared well with each other. The effects of currents and submerged bar on wave profile, higher-harmonic waves and reflection coefficient are further studied, respectively.

Dual-band wavelength tunable nonlinear polarization rotation mode-locked Erbium-doped fiber lasers induced by birefringence variation and gain curvature alteration.

With the combining effects of the fiber birefringence induced round-trip phase variation and the gain profile reshaping induced spectral filtering in the Erbium-doped fiber laser (EDFL) cavity, the mechanism corresponding to the central wavelength tunability of the EDFL passively mode-locked by nonlinear polarization rotation is explored. Bending the intracavity fiber induces the refractive index difference between orthogonal axes, which enables the dual-band central wavelength shift of 2.9 nm at 1570 nm region and up to 10.2 nm at 1600 nm region. The difference between the wavelength shifts at two bands is attributed to the gain dispersion decided by the gain spectral curvature of the EDFA, and the spacing between two switchable bands is provided by the birefringence induced variation on phase delay which causes transmittance variation. In addition, the central wavelength shift can also be controlled by varying the pumping geometry. At 1570 nm regime, an offset of up to 5.9 nm between the central wavelengths obtained under solely forward or backward pumping condition is observed, whereas the bidirectional pumping scheme effectively compensates the gain spectral reshaping effects to minimize the central wavelength shift. In contrast, the wavelength offset shrinks to only 1.1 nm when mode-locking at 1600 nm under single-sided pumping, as the gain profile strongly depends on the spatial distribution of the excited erbium ions under different pumping schemes. Except the birefringence variation and the gain spectral filtering phenomena, the gain-saturation mechanism induced refractive index change and its influence to the dual-band central wavelength tunability are also observed and analyzed.