Pump Power Ratio Research Articles

F143 矩形フィン形素子を用いたマイクロ熱電発電システムに関する準三次元熱・電気連成解析(OS-12 マイクロ・ナノスケール熱流動現象IV)

Total performance prediction was carried out for a micro thermoelectric power generator employing rectangular-fin elements and regenerative combustion, which utilizes the combustion gas to preheat the working gas. In the analysis, an array of rectangular-fin elements and hot- and cold-side gases were modeled as a fluid-saturated porous medium bounded by a solid wall. After the validation of the porous medium model, quasi three-dimensional simulations considering the heat and electric current flow in the flow direction were carried out. As a result, for element thickness t=0.5mm, it was found that the overall conversion efficiency from total heat input into electrical energy exceeds 3% as a target, at the electrical power to pumping power ratio more than three and volumetric power density more than 30mW/cm^3.

Investigation and optimization of bidirectionally dual-order pumped distributed Raman amplifiers

A theoretical investigation of bidirectionally dual-order pumped distributed Raman amplifiers is presented in detail, and comparisons with other Raman amplification schemes, i.e., bidirectional first-order pumping and Raman-plus-erbium-doped fiber hybrid amplification, are carried out, for the first time to the authors' knowledge, at identical nonlinear phase shifts. The results show that symmetric bidirectional dual-order pumping can achieve the best optical signal-to-noise ratio performance by appropriate choice of the second-order pump wavelength and second-to-first-order pump power ratio for both short- and long-span conditions, which will be helpful for designing long-haul transmission systems.

Thermodynamic optimization of laminar viscous flow under convective heat-transfer through an isothermal walled duct

The main objective of this paper is to explore the existence of thermodynamic irreversibility due to laminar fluid flow with heat transfer under fully-developed conditions through a duct of circular cross-section. The evaluation of thermodynamic trade-offs caused by simultaneous heat transfer under a finite temperature-difference and fluid friction has been examined in terms of dimensionless entropy generation as a performance criterion. The temperature dependence of viscosity is taken into consideration in the analysis. Expressions involving relevant variables for entropy generation and pumping power for constant viscosity and temperature-dependent viscosity have been derived. The dimensionless entropy-generation defined on the basis of total heat-transfer rate attains a minimum along the duct length and the ratio of pumping power to total heat-transfer rate increases considerably along the duct length when the fluid is heated. The dimensionless entropy-generation increases as the dimensionless ratio of inlet wall to fluid temperatures ( α) increases, but the pumping power ratio decreases as α increases. The results correspond to the constant viscosity assumption and temperature-dependent viscosity cases are compared and it was found that the constant viscosity assumption may yield a significant amount of deviation in entropy-generation and pumping power from those for the temperature-dependent viscosity case, especially for more viscous fluids.

Power-equalized parallel-type pump-shared fiber lasers based on parameter-adjustment

A parallel-type, pump-shared (PTPS) scheme linear-cavity laser array (LCLA) is proposed and numerically studied. Power-equalization of multiwavelength fiber lasers can be achieved by varying the pumping power ratio, length of the erbium-doped fiber or reflectivity of grating reflector for the individual channels. Before and after power-equalization, the maximum power variation among seven equal-spaced channels, ranging from 1530 to 1560 nm, is 5.8 and 0.2 dB, respectively.

Diffractive effects in singly resonant continuous-wave parametric oscillators

This paper presents a detailed numerical study of the effect of focusing on the conversion efficiency of low-loss singly-resonant parametric oscillators with collinear focusing of pump and signal. Results are given for the maximal pump depletion and for pump power levels required for various amounts of depletion, as functions of pump and signal confocal parameters, for kI/kP=0.33 and 0.50. It is found that the ratio of pump depletion to maximal depletion as a function of the ratio of pump power to threshold power agrees with the plane-wave prediction to within 5%, for a wide range of focusing conditions. The observed trends are explained as resulting from intensity and phase dependent mechanisms.

Numerical analysis of Yb3+-sensitised, Er3+-doped, fibre-ring laser

The performance of a Yb/sup 3+/-sensitised Er/sup 3+/-doped, continuous-wave, fibre-ring laser is analysed using a comprehensive numerical model. The model is based on iterative solution propagation-rate equations and takes account realistic refractive-index profile and Er/sup 3+//Yb/sup 3+/-doping distribution function, uniform upconversion from the /sup 4/I/sub 13/2/ erbium level and propagation of amplified spontaneous emission in the pump wavelength range. The dependence of output power on active fibre length, input pump power and output coupling ratio has been investigated. The analysis has shown that the laser can be tuned in the range 1525 nm - 1610 nm. The calculated ring-laser characteristics have been found in quantitative agreement with the experimentally obtained data.

Temporal modulation instabilities of counterpropagating waves in a finite dispersive Kerr medium I Theoretical model and analysis

This paper presents a comprehensive analytical study of temporal modulation instabilities in a finite, nonlinear, dispersive medium in which two counterpropagating pump beams interact through a Kerr-type nonlinearity. The analysis includes self- and cross-phase modulations, group-velocity dispersion, four-wave mixing, and reflections occurring at the two facets of the dispersive Kerr medium. The use of a new method based on a small-parameter analysis has resulted in a physically transparent model in terms of a doubly resonant optical parametric oscillator that allows characterization of the complicated nonlinear system in a familiar language. The effects of boundary reflections are shown to be very important. In the low-frequency limit, in which dispersive effects are negligible, our results reduce to those obtained previously. At high frequencies, dispersive effects lead to new instabilities both in the normal- and anomalous-dispersion regions of the dispersive Kerr medium. The anomalous-dispersion case is discussed in detail after including weak boundary reflections. The growth rate and the threshold for the absolute instability are obtained in an analytical form for arbitrary pump–power ratios. Our analytic results are in agreement with previous numerical work done by neglecting boundary reflections and assuming equal powers for the counterpropagating pump beams.

Design Considerations for Er3+-doped Planar Optical Amplifiers in Silica on Silicon

Large-signal numerical model for erbium-doped integrated optical amplifier has been used to optimize the parameters of waveguide core for maximum gain in dependence on pump power and waveguide aspect ratio. The model developed for the analysis of Er-doped fiber amplifier has been modified. The azimuthal effective-index method is used to determine the field distribution of the fundamental mode of an optical waveguide with rectangular core cross section and step refractive-index profile. It has been found that the optimum core height increases with increasing pump power and decreasing core aspect ratio.

Novel 0.98/1.55 μm dichroic coupler based on lithium niobate

Abstract A novel 0.98/1.55 μm dichroic coupler with high-extinction ratio and low insertion loss has been designed and implemented on LiNbO3 for Erbium-doped fiber amplifier applications. The design of dichroic coupler is based on a modified directional coupler structure with a single bend in each channel. Beam propagation method is used to analyze the coupler performance to get the optimal parameters for device design, such as channel width, titanium thickness, channel gap, and interaction length. Samples with the signal coupling ratio as high as 100% and pumping power ratio as high as 95% have been obtained.

Highly improved fibre amplifier for operation around 1300 nm

A model for Nd3+-doped ZBLANP fibres is verified. The model predicts high gain improvements by suppressing the 1050 nm amplified spontaneous emission. The gain in dB can be more than tripled and a gain to pump power ratio of 0.16 dB/mW is obtained independently of the pump power.

The design of erbium-doped fiber amplifiers

An accurate model for the erbium-doped fiber amplifier is presented. The model is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline- and preamplifiers as well as for power booster amplifiers. The predicted pump efficiencies (maximum gain to pump power ratios) are in agreement with experimental results presented in the literature. The choice of codopant is shown to be very significant for the pump efficiency when pumping in the 0.98 mu m. The pump efficiency in the 0.98- mu m pump band is shown to be twice the pump efficiency in the 1.48- mu m pump band. >

Effect on heat transfer augmentation by some geometric shapes of a turbulence promoter in a rectangular duct.

This paper investigates how the local heat transfer coefficient is affected by geometric shape and the clearance "C", when turbulence promoters of various types (blockage ratio D/2H=0.22) are set in staggered arrangement in a rectangular duct in order to augment heat transfer from the wall. The distribution of local heat transfer coefficients depend son the clearance "C", which can be further differentiated by the presence or absence of the Karman vortex shedding. The degree of augmentation is also analysed, taking account of the pressure loss. It was found that the performance ratio η(the ratio of average pumping power) is larger than unity for all types, when the range of clearance "C" is smaller than 3 mm.

Performance Enhancement in L-Band Edfa Through Dual Stage Technique

An experiment on gain enhancement in the long wavelength band erbium doped fiber amplifier (L-band EDFA) is demonstrated. It uses a dual stage technique with dual forward pumping scheme. Compared to a conventional single stage amplifier, the small signal gain for 1580nm signal can be improved by 5.5dB without paying much noise figure penalty. The corresponding noise figure penalty was 0.3dB due to the insertion loss of the optical isolator. The optimum pump power ratio for the first pump is experimentally determined to be 33%. The maximum gain improvement of 8.3dB was obtained at a signal wavelength of 1568nm while signal and total pump powers were fixed at -30dBm and 92mW, respectively. The employment of dual stage amplifier system seems to play an important role in the development of practical L-band EDFA from the perspective of economical usage of pump power.Key Words: erbium doped fibre; optical amplifier; L-band EDFA; dual stage EDFA; amplified spontaneous emission