A Three-Dimensional EFD-BPM for Optical Directional Couplers
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A kind of three-dimensional EFD-BPM scheme and its stability were presented in this paper. And a calculation result of optical field distribution at the fully coupled distance was also given.Cite
The paper presents the design of a broadband 8.34-dB directional coupler in a stripline technique. In order to obtain broadband frequency response a three-section asymmetric coupled-line directional coupler has been chosen. The influence of discontinuities in the regions of coupled and transmission line connections, as well as intersection connections, has been taken into account in the design stage. The parasitic reactances associated with the discontinuities have been compensated using the developed capacitive compensation technique which allows for directional couplers' design with improved directivity and return loss characteristics. The compensation technique has been for the first time applied for the design of directional couplers with the coupling weaker than 3 dB. The designed coupler has been manufactured and measured to validate the presented compensation technique.
Directivity
Return loss
Stripline
Rat-race coupler
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In this paper, we propose the use of the invariant based shortcuts to adiabaticity for the analysis of directional couplers. By describing the dynamical evolution of the system using the eigenstates of the invariant through new parameterizations, the system stability against errors in coupling coefficient and propagation constants mismatch is connected with the new parameters, which can be linked back to system parameters through inverse engineering. The merits and limitations of the conventional tapered directional coupler designs with various window functions are obtained through the analysis. We then propose an optimal design of compact directional couplers that is stable against errors in input wavelength and coupling coefficient simultaneously. The designed directional coupler has better tolerance, as compared to the conventional resonant couplers with smooth shape functions of Hamming and Blackman. These results are verified by beam propagation simulations.
Beam propagation method
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The effect of coupling waveguide structure weighted by hamming function for optical directional full couplers is investigated. The validity of approximation theory of optical directional full couplers becomes questionable when the coupling length is not enough long.We propose a new design and numerically show that some optical properties of the optimized one are better than the optimized coupler with hamming function weighting.The objective of the work includes two parts: the first part defines theory ranges and processing tolerance of optical directional full couplers.The second part is optimization waveguide structure of optical directional full couplers for low crosstalk, broad bandwidth and short coupler length. Definitely hamming function weighting which proposed can obtain better result after the structural design.
Hamming distance
Crosstalk
Waveguide
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This paper presents a design mapping formula, which is the relation between performance specification and design parameters, for asymmetrical multi-section coupled transmission line directional coupler. The presented mapping function can provide convenience in its use and accurate design parameters for a given design specification. Simulations and experiments on designed three-, five-, and seven-element coupled line directional couplers with 16 dB/spl plusmn/0.2 dB coupling show the validity of the presented design mapping formula.
Line (geometry)
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An analysis and optimization procedure is described for the design of branch-waveguide directional coupler which gives results showing a significant improvement over previous researchers' theory. A Ka-band 10dB directional Coupler is designed based on theories synthesized by former researchers; however, it is impossible to utilize the certificated models directly, because some of them can not be realized by present fabrication technology. Simulations and optimizations were carried out, and finally a model satisfied our needs is obtained. Measurement results show its good performance over the frequency band of 24GHz to 34GHz.
Ka band
Waveguide
Frequency band
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Stub (electronics)
Multi-band device
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Waveguide structure effect for the suitable length of adiabatic directional full couplers by modified-hamming weighting function is described. The validity of approximation theory of adiabatic directional full couplers becomes questionable when the coupling length is not enough long so the beam propagation method is used. We propose a new design and numerically show that some optical properties of the optimized one are better than the optimized coupler with hamming function weighting. The objective of the work includes in the new design of adiabatic directional full couplers can obtain low noise, short couplers respectively. It is surely that the proposed modification-hamming function weighting is more effective than convention weighting for adiabatic directional full couplers.
Hamming distance
Beam propagation method
Waveguide
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This paper describes a design of microstrip rectangular disk quadrature directional couplers on the basis of a modified eigenfunction expansion method with consideration of frequency dependences of an effective width and an effective relative permittivity of a microstrip disk circuit. Using this approximate method, we can optimize the disk configuration of directional couplers in a reasonable computational time. The validity of the design method is examined by comparison with the numerical results by the FDTD method.
Eigenfunction
Quadrature (astronomy)
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Using Poincaré coordinates we show that any relative amplitude and phase between the two modes of a directional coupler can be obtained through varying a single electrode voltage and by selecting the correct length for the coupling region. Alternatively, curved waveguide sections can be employed to accomplish the same feat without applied voltage, which we demonstrate using beam propagation simulations.
Relative phase
Biasing
Waveguide
Beam propagation method
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A novel approach to the analysis and design of grating-assisted directional couplers is proposed. Power exchange between the waveguides is maximized through phase matching of two power-orthogonal modes of the parallel coupler. It is shown that either complete power transfer or zero crosstalk can be achieved at two different coupling lengths even when the two wavelengths are strongly coupled and/or close to synchronism. An analytical solution to the coupled-mode equations is obtained for the grating of rectangular shape. A grating-assisted coupler made of two slab waveguides is examined as an example to illustrate the salient features of the scheme.< >
Synchronism
Coupled mode theory
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