Analysis of a phase mismatched three waveguide coupler with an optical amplifier

A novel optical amplifier is proposed and analyzed. This device consists of three parallel waveguides and each has a slightly different propagation constant, that is, each waveguide is slightly phase mismatched and couplings among these waveguides are weak. Two adjacent waveguides are passive and the third one is active and all end facets of waveguides are antireflection coated, so that optical feedback can be eliminated and the active waveguide is a traveling wave type amplifier. Because of a phase mismatched configuration, this device can be used to tap optical signals without much power reduction in optical transmission lines. Signals coming into the device are weakly coupled to the active waveguide via the passive waveguide in between and they are amplified through the active waveguide. Characteristics of this device are studied and parameters which are required to design the device are also given as an example.     

Time-domain analysis of multiple parallel transmission lines by means of equivalent circuits

Thévénin's equivalent circuit for a single transmission line is well known. The letter presents an application of Thévénin's equivalent circuit for multiple parallel transmission lines to the time-domain analysis of wave propagation over such lines. For purposes of illustration, a system of two coupled transmission lines is treated.     

Numerical solution of lossy waveguides: t.l.m. computer program

The transmission-line-matrix method is a time-domain numerical method for solving wave problems. The method uses a mesh of transmission lines to represent a propagation space, and the losses in the space are accounted for by making the transmission lines lossy. Lossy boundaries are simulated by imperfect boundary reflections on the transmission lines. A FORTRAN program implementing this technique is presented.     

Vectorial FDTD Technique for the Analysis of Optical Second-Harmonic Generation

A vectorial time-domain simulator of integrated optical structures containing second-order nonlinearities has been formulated and tested. The technique is based on the direct time-domain representation of the coupled nonlinear Maxwell's equations of the propagating fields. The proposed algorithm accounts for the full optical coefficient tensor, input depletion, and device-wave interactions, where the inaccuracies associated with the scalar and paraxial approximations are avoided. Error analysis associated with the proposed scheme is also given. The proposed model should find application in a wide range of device structures and also in the analysis of short-pulse propagation in second-order nonlinear devices.      

Time-domain analysis of propagation in inhomogeneous anisotropiclossy slabs

An equivalent-transmission-line-circuit (ETLC) model is developed to discuss the transient propagation problem of a plane wave in inhomogeneous, anisotropic, and transversely lossy slabs. This model is based on the analogy between the field equations and the coupled transmission line equations. By establishing the analogy, suitable lumped-circuit models are proposed to treat the equivalent transmission lines, which may then be solved by the circuit simulation program. In this study, the accuracy and convergence of the lumped-circuit models are examined. The ETLC model is then applied to discuss the propagation problem in anisotropic graphite/epoxy laminates with numerical results presented to show the transient responses due to the electromagnetic pulse and Gaussian pulse     

NILT法求解高速集成电路芯片内频变互连线的瞬态响应

频变参数互连线的瞬态响应分析在高速集成电路的设计很重要,本文运 拉普拉斯变换法分析高速集成电路中频变参数互加线的时域响应。提出了一种离散频变参数的拟合方法,应用于多导体传输线的复频域建模。     

Optical Delay Lines Based on Soliton Propagation in Photonic Crystal Coupled Resonator Optical Waveguides

In this paper, a study of optical delay lines based on soliton propagation in coupled resonator optical waveguides is performed. For a given bit rate and required delay, design equations are given that relate the soliton peak power and collision period to the soliton width. To study the influence of higher order linear and nonlinear dispersion, a continuous wave propagation model incorporating these effects is also derived. Using this model, the soliton stability in the presence of higher order dispersion, optical loss and adjacent soliton pulses is numerically verified. It is also shown that soliton-based delay lines can achieve nanosecond delay at a propagation length of a few millimeters due to the high slow down factors that can be obtained.     

Optoelectronic measurements of picosecond electrical pulsepropagation in coplanar waveguide transmission lines

Observations are presented concerning the effects of coplanar waveguide transmission lines on the propagation of picosecond electrical pulses using an optoelectronic time-domain measurement technique. Effects of various test structure design factors such as substrate thickness, thickness of transmission line metallization, discontinuity spacing, ground plane width, pulser/sampler line length, and pulser/sampler geometry on picosecond electrical pulse propagation in microwave/millimeter wave coplanar waveguide transmission lines are discussed, and schemes for minimizing the adverse effects of each of the above factors are provided     

Analytical timing model for inductance-dominant interconnect based on traveling wave propagation

As accurate and efficient timing prediction is very important for integrated circuit design, an analytical timing model for inductive-effect dominated resistance-inductance-capacitance (RLC) transmission line with resistive driver and capacitive load is proposed by virtue of traveling wave propagation and perturbation technique. This model is theoretically stable and computationally efficient. Comparison with other analytical and SPICE models illustrates that this timing model can achieve excellent accuracy for inductance-dominant interconnect. Incorporating with decoupling technique, this model could be readily extended to coupled interconnects.     

Field Solution, Polarization, and Eigenmodes of Shielded Microstrip Transmission Line

Application of the reciprocity theorem leads to a variational expression for the propagation constant of the fields inside shielded microstrip-like transmission lines. The resulting equation involves both the propagation constant and the tangential fields at the air-dielectric interface. Using the Rayleigh-Ritz optimization technique, both the propagation constant and the fields are completely determined. The calculated results of the propagation constant compare well with other available data. Moreover, the field solution obtained is presented in the form of a polarization ratio relating the axial to the transverse electric field. Results cover both low and high frequencies, and the technique proves valid at both frequency ranges. The method may be extended to other configurations of planar striplines by proper adjustment of the integration limits.     

Numerical method for the calculation of mode fields and propagation constants in optical waveguides

The scalar wave equation for optical waveguides with arbitrary refractive index profiles is solved using a numerically stable integration method. The mode fields and the corresponding propagation constants are determined iteratively. Results for waveguides based on different well-known fabrication techniques are shown and the design of a new sensitive integrated optical switch is proposed.     

Investigation of tapered multiple microstrip lines for VLSIcircuits

The analysis of tapered, coupled microstrip transmission lines is presented. These lines, used as interconnects between integrated circuit devices, are modeled using an iteration-perturbation approach applied in the spatial domain. From this model, a frequency-dependent scattering parameter characterization is determined. A time-domain simulation of pulse propagation through the tapered, coupled microstrip lines is performed. The frequency-domain scattering parameters are inverse Fourier transformed to obtain the time-domain Green's function. The input pulse is convolved with the Green's function, and a Newton-Raphson algorithm is applied to account for nonlinear loads. Some experimental results are shown, and a simulation approximation is proposed     

Coplanar transmission lines on thin substrates for high-speedlow-loss propagation

We investigate the attenuation and phase velocity characteristics of coplanar strip (CPS) transmission lines designed for high-speed, low-loss propagation at sub-THz frequencies. Photoconductor switches driven by femtosecond optical pulses were used to generate propagating picosecond electrical transients. External electrooptic sampling was used to measure the time-domain impulse-response characteristics with subpicosecond time resolution. The finite-difference transmission-line-matrix (FD-TLM) numerical method was used to model picosecond pulse propagation on identical transmission lines. The experiment and the numeric simulations have clarified nonquasistatic high-frequency effects and were shown to agree over a 500 GHz frequency range. Additionally, analytic quasi-static velocity and characteristic impedance formulas have been verified and their frequency range of validity established for the investigated CPS geometries. Radiation into the substrate is the dominant loss mechanism at frequencies above ~100 GHz for the CPS lines on thick substrates. CPS transmission line fabrication on thin substrates has been proposed as a method for reducing high-frequency loss and increasing the microwave propagation velocity. CPS transmission lines fabricated on 8-μm-thick Si membranes have been studied and demonstrated to possess the desired high-speed, low-loss properties     

Guided Waves in Limit Cases of Microstrip (Correspondence)

The great difficulty in solving for the propagation constant and effective characteristic impedance for microstrip transmission lines is invariably avoided by assuming quasi-TEM propagation and solving Laplace's equation rather than the wave equation. Deschamps and Wu have qualitatively discussed aspects of the hybrid-mode problem. Zysman and Varon have presented a solution for the related but distinctly different problem of closed microstrip. In this communication we present the basis through which the quasi-TEM analysis may be justified for the limit cases of guided waves on microstrip in which the dielectric constant approaches that of free space or becomes very large. The guided wave problem is formulated exactly in terms of longitudinal electric and magnetic field components satisfying the wave equation and coupled through the boundary conditions at the dielectric interface.     

Improved bidirectional beam propagation method for analysis ofreflection on nonparallel interfaces

An improved bidirectional beam propagation method (IBBPM) is proposed, to allow the analysis of optical wave reflection and transmission in waveguiding structures with multiple nonparallel interfaces     

Complex modes in shielded suspended coupled microstrip lines

The existence of complex modes in electrically shielded suspended coupled microstrip lines has been studied extensively, and the results are presented. A rigorous full-wave spectral-domain approach (SDA) with a newly proposed and tested set of basis functions can efficiently and accurately determine the propagation characteristics of the dominant, higher-order, and complex modes for planar or quasi-planar transmission lines. These basis functions are validated by comparing the convergence study of field solutions with those obtained by various sets of preconditioned bases and by the unconditioned subdomain ones. Excellent agreement is obtained for the propagation constants and the normalized complex longitudinal and transverse current distributions on conducting strips for the strongly coupled microstrip lines. For all the particular case studies discussed, it is shown that the complex modes may exist in all the shielded suspended coupled microstrip lines, even when the substrate dielectric constant is low. Theoretical results for the fundamental, higher-order, evanescent, and complex modes are presented for suspended coupled microstrip lines     

Analysis of the Impacts of Signal Slew and Skew on the Behavior of Coupled RLC Interconnects for Different Switching Patterns

This paper presents an in-depth analysis of signal slew and skew variations in coupled inductive lines for different switching patterns. It is revealed that variations of rise/fall time and skew alter the behavior of coupled inductive lines under different switching patterns. We observe that crosstalk noise reduces with increasing signal skew, and the impact of skew variation on crosstalk noise is more prominent for lines with strong capacitive coupling. A performance comparison is done between power supply and ground line as inductive shield, and it is found that ground lines work better than power lines in inductive crosstalk minimization. The 100%-delay measurement technique has been proposed as opposed to the conventional 50%-delay method, and we notice that the 50%-delay technique underestimates the propagation delay for an inductive dominant line with varying signal slew times. Closed-form equations for propagation delay in terms of signal slew time have been derived, which are within 9% of HSPICE-simulated results for a set of interconnect structures. These expressions are simple, and accuracy increases with growing number of interconnect lines.      

连续偏光干涉法测量波片宽波段延迟量变化

为了测量石英波片宽光谱下相位延迟量,根据连续偏光干涉原理,提出了一种新的测量方法,并给出了相应波长的延迟量数据处理办法。采用岛津UV-3101PC分光光度计双光路比对测量方法,增加了采集数据的稳定可靠性,获得了已知厚度的石英波片300nm~800nm波段的连续偏光干涉谱,进行了理论分析和实验验证,获得了波片的宽光谱相位延迟量数据。结果表明,实验曲线和理论曲线吻合较好,测量平均误差不大于2°。这一结果对研究波片延迟量色散性质以及工艺进程的引导有重要实际意义。