Novel ring-based WDM-PON architecture with high-reliable remote nodes

A self-healing WDM-PON access ring architecture with high-reliable remote nodes is proposed and demonstrated in this paper. Four protecting modes are designed for protection of different fiber failures. The protecting fiber of the central ring can provide protection for working fiber. Optical line terminal and remote nodes can automatically switch to protecting fiber when working fiber fails. Network scale and system reliability are also analyzed at the end of this paper.     

Design considerations for shaped-beam reflectors

A modified procedure is proposed for the design of shaped-beam reflectors in general. The procedure involves explicitly the size of the reflector as a parameter and can thus be used to check quickly the minimum size of a reflector needed for a given shaped beam. Experimental results are given for a reflector designed on this basis.     

Design considerations for acousto-optic devices

The design and fabrication of wide-band bulk acousto-optic modulators (temporal modulation) and beam deflectors (spatial modulation) are described. Optimized device parameters can be obtained systematically for given specifications of the desired modulation bandwidth, throughput efficiency and number of resolvable elements. As the device operating frequency goes beyond a few hundred megahertz, the acoustic transducer response becomes sensitive to the intermediate metal layers between the piezoelectric transducer and the acoustooptic interaction medium. Transducer bandwidth and impedance matching can be optimized using computer modeling programs. Criteria for material selection based on performance requirements and propagation loss are presented. Practical considerations for the fabrication of high performance devices and specific device parameters are discussed.     

Design considerations for high-current photodetectors

This paper outlines the design considerations for gigahertz-bandwidth, high-current p-i-n photodiodes utilizing InGaAs absorbers. The factors being investigated are photodetector intrinsic region length, intrinsic region doping density, temperature effects, illumination spot size, illumination wavelength, frequency, and illumination direction. Space-charge calculations are used to determine optimal device geometry and conditions which maximize saturation photocurrent. A thermal model is developed to study the effects of temperature on high-current photodetector performance. The thermal and space-charge model results are combined to emphasize the importance of thin intrinsic region lengths to obtain high current. Finally, a comparison between surface-illuminated p-i-n structures and waveguide structures is made to differentiate between the problems associated with achieving high current in each structure and to outline techniques to achieve maximum performance     

Design considerations for submillimeter-wave reflex klystrons

The problems facing the development of klystrons for use at submillimeter wavelengths are reviewed. Analytical formulas for reentrant cavity resonance, starting conditions, output power, and oscillation buildup are presented. This paper describes methods of calculating cavity Q-factor, output coupling, focusing potentials, electron paths, and heating effects. The scaling of output power with frequency is derived. Examples of techniques that might be used to realize a working device are presented.     

Design considerations for multi-fiber ferrule manufacturing

Fiber optic connectors are bridges linking the key elements of optical communication devices. Among them, ferrules used to position and align fibers are essential and the most critical component for fiber optic connectors. In this paper, design accuracy of ferrules will be studied. Factors affecting the fiber eccentricity during ferrule connections, including dimensions and tolerances, will be discussed and expressed in mathematical models. The 2MT ferrule was used as an example. Also, the precision plastic injection molding technique will be used to manufacture the ferrules. In order to reduce the eccentricity values for the required insertion loss, the Taguchi method is first used to simplify the optimization problems of the injection molding process. The design of experiment methodologies are then used to obtain more accurate settings for the parameters. Using these settings, ferrules with a 0.00055 mm mean eccentricity value can be obtained, and insertion losses were measured to verify the mathematical model.     

Design considerations for complementary inchworm actuators

An inchworm actuator is described, which uses complementary configurations for the two clamping sections. In one configuration, clamping and release are achieved using high and low voltages, respectively, while for the other, clamping and release are achieved using low and high voltages, respectively. The resulting inchworm actuator can be driven by a two-channel controller with the two clamps sharing the first channel and the extender piezoelectric actuator using the second channel. The paper also describes a diode-shunted delay circuit that causes unclamping to occur more slowly than clamping. It is shown that by using the delay circuit in series with each clamp, the overall force drive capability of the actuator is increased. The paper presents simulated and experimental results of clamp force versus time during the switching transient. An analysis of a generalized delay circuit having both resistive and reactive elements shows that a purely resistive design provides the better tradeoff between increased force drive capability and power loss in the delay circuit.     

Design considerations for a-Si solar cells

Amorphous Si (a-Si) is potentially an attractive material for thin-film solar cells. However, its potential for high-efficiency devices to date has not been realized. In this paper, we examine the design considerations which can be used to develop high-efficiency devices from a-Si. The design analysis takes full advantage of the flexibility in bandgap and other material properties offered by a-Si. Several structures, such as light-trapped cells, graded layer cells, and tandem junction a-Si/a-Si cells are analyzed in detail for collection efficiency, Voc, and fill factors. It is shown that using these innovative structures, realistic conversion efficiencies exceeding 10 percent can be realized in a-Si in spite of the very low diffusion lengths (∼0.1 µm). Technological considerations for achieving such structures are also discussed.     

Design considerations for the gyro-peniotron oscillator

The gyro-peniotron shows great promise as a source of microwave radiation. In this paper we investigate the stability and the non-linear saturated efficiency of a gyropeniotron oscillatro with an axis encircling beam operating at the TE₂₁₁ and the TE₃₁₁ cylindrical cavity modes. Beam and cavity parameters for stable high efficiency operation are presented from a linear theory analysis of the start-oscillation condition. Using design parameters taken from the linear analysis, the strong field non-linear emission efficiencies are studied numerically. The sensitivity of the saturated efficiency to beam axial velocity and guiding center spread is also considered. The results of our modeling indicate that high efficiency (70–90%) operation of the gyro-peniotron oscillator is possible, even with large guiding center \((\delta r_{gc_ \circ } \mathop< \limits_ \sim 0.2 - 0.4r_{L_ \circ } )\) and large axial velocity \((\delta \beta _{||} \mathop< \limits_ \sim 0.3\beta _{||_ \circ } )\) spread.     

Design considerations for high-frequency crystal oscillators

The deleterious effects of crystal shunt capacitance and series resistance on the performance of series-mode oscillators are discussed. When the parasitic capacitance across the crystal significantly modifies the transconductance of the amplifying stage the circuits can become susceptible to a parasitic second mode of oscillation above the series-resonance frequency of the crystal. A simple model that can sufficiently describe such crystal oscillator circuits was developed and used to derive simple design equations that can accurately predict the behavior of these circuits. The design equations should be especially useful for a reliable design in cases when it is not practical to use an additional inductor to compensate for the parasitic shunt capacitance of the crystal. It is shown theoretically that the inclusion of this capacitance in the feedback path reduces the total effective capacitance in the tank circuit, which is tuned to the desired overtone frequency. This creates a second mode of oscillation frequency which is higher than the desired crystal resonance frequency. The ranges of loop-gain and tank resistance values that can prevent this parasitic mode of oscillations are derived. It is also shown that the useful loop gain for the desired oscillations to start is restricted to a similar region by the crystal shunt capacitance and series resistance     

Design considerations for crossing channel switches

Theoretical and experimental design considerations for single-mode-crossing switches at the wavelength of 1.32 μm are presented. The dependence of extinction ratio on branch angle for the extended electrodes and the estimation of fabrication tolerances of the crossing channel structure are discussed. It is also shown that crossing channel devices required a precise control of fabrication parameters     

Design considerations for p-i-n thyristor structures

An analysis of a high-voltage gate turn-off (GTO) thyristor structure with a double-layered n base (p-i-n structure) is presented. From integration of Poisson's equation, an expression for the forward-blocking voltage at the onset of avalanche breakdown is obtained. Simple design criteria are developed to calculate the optimal thickness and doping density of the n base of a conventional pnpn structure designed for a specific voltage-blocking capability. The same principle is applied to design for the doping densities and thicknesses of the high-resistivity region and the buffer layer of the p-i-n GTO structure. The forward-blocking voltage, as well as the on-state voltage (at a current density of 300 A cm^-2) is predicted for a wide range of base layer thicknesses and doping densities to illustrate the available tradeoff options. Lowest on-state power dissipation for high blocking voltages (>6000 V) is predicted for a doping level of 5×10¹² cm^-3 in the high-resistivity layer     

Design considerations for microwave light modulators

The effect of a quarter-wave plate on the performance of an electro-optic modulator is considered, and it is shown that, contrary to previous reports, the inclusion of such a plate will reduce the overall sensitivity of the system, unless the detector is capable of responding to the modulating frequency and is followed by a tuned amplifier or synchronous rectifier operating at this frequency.     

Design considerations for databus charge recovery

The charge recovery databus is a scheme which reduces energy consumption through the application of adiabatic circuit techniques. Previous work gives a solid theoretical analysis of this scheme, including quantitative data assuming random bus values. We extend this earlier work by presenting a quantitative analysis of the charge recovery databus using 15 benchmarks and four high level bus coding schemes. We show that a very simple implementation of the charge recovery databus is capable of reducing average energy consumption by 28% beyond traditional high-level bus encoding techniques. In addition, we examine delay and energy consumption in the added hardware     

C波段高可靠星用介质振荡器、上下混频器一体化模块

在高可靠星用模块研究中 ,采用特殊工艺 ,将介质振荡器、上下混频器、微波放大器、中放等微波单元集成在尺寸为 1 0 0 mm× 40 mm× 45 mm模块中 ,大大减小了体积、降低了重量 ,从而应用更广泛 ,使用更灵活。     

Design considerations for an electrooptic directional couplermodulator

A rigorous numerical model is presented for an electrooptic directional coupler (DC) modulator. It was observed that it is possible for such a device to be optimized by the variation of a number of fabrication parameters. The applied field, the induced refractive index changes, and hence the change in the waveguide optical field due to the antisymmetric refractive index change are calculated for an elected structure. Finally, the product of switching voltage and coupling length, the power transfer efficiency, obtained using the least squares boundary residual (LSBR) method, and the optical loss due to the metal electrodes are also given     

Design considerations for an integrated low-noise preamplifier

Design and processing considerations pertinent to integrating an audio-frequency, low-noise preamplifier are discussed. Performance characteristics of an integrated circuit "mock-up," an experimental model integrated circuit, and the final design integrated circuit are compared with one another and with the theoretically predicted performance. The wide range of design flexibility and tight performance parameter control attained through use of compatible thin-film/monolithic processing technologies is demonstrated. It is further demonstrated that an overall design approach which considers both the electronic functions to be performed and limitations and advantages of the processing technologies involved can result in integrated circuit performance characteristics which are superior to those of the "discrete component" counterpart.     

Design considerations for high-voltage overlay annular diodes

The physical parameters necessary to achieve high breakdown voltages in planar diodes with metal junction overlay and annular guard rings are considered. The experimental data are derived from p-ν-n structures with ν resistivity greater than 300 Ω . cm and the primary parameters considered are the extent of junction overlay metallization, the effect of lateral junction curvature, the nature of the annular field terminator and its spacing from the overlay, the dielectric thickness beneath the overlay metallization, and the use of auxiliary dielectric material to obviate arcing and desensitize the structure to ambient effects. By appropriate manipulation of these parameters, diode chips with 10^-2-cm²junction area were fabricated to leakages less than 1 µA at 1500 V.     

Design considerations for Parallel pseudoRandom Pattern Generators

The design of a Parallel (pseudo)Random Pattern Generator (PRPG) based on a Linear Feedback Shift Register (LFSR) involves the selection of the number of stages (degree of the characteristic polynomial), selection of the feedback taps (the characteristic polynomial), and selection of a phaseshift network to remove the effects of correlations that exist between the bit streams from adjacent stages of the LFSR. The design considerations for decimated sequences are discussed, as is linear dependency density. A new phaseshift network is presented which uses only one 2-way EXCLUSIVE-OR per output. Appendixes contain a listing of the prime factors of the sequence length, an exhaustive list of primitive trinomials to degree 100, and a selected list of primitive polynomials that can be used to realize LFSRs with only two 2-way EXCLUSIVE-ORs.