摘要:

AbstractSeveral methods have been proposed for estimating the structural parameters of a waveguide from transmission characteristics of the guided mode. In this paper, a simple and effective method is proposed for estimating the index profile in the cross section of the optical waveguide. In this method the measured field distribution of the guided mode and that calculated from the assumed index profile are compared directly and the index profile is sought for which the two field distributions coincide. To confirm the validity of the method, numerical simulations have been carried out for several graded index slab waveguides. Even if the simplest step index profile is assumed as the initial guess of the profile, the index profile of the waveguide can be estimated with practically sufficient accuracy. In this method, no differential process is needed for the measured values nor a high‐degree smoothing operation. Hence, the method is expected to be superior to others in terms of noise toleranc

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWhen a dc electric field is applied to molten polystyrene and α‐methylstyrene, the molecules are aligned in the direction of the electric field. Since this state is maintained even in a solid state, birefringent bulk plastics are easily obtained. The merit of this technique is that the magnitude of birefringence is contained by controlling the dc electric field. Since there is no size limitation, λ/4 and λ/2 plates were obtained easily at low cost. Furthermore, these optical retardation plates can be used for a wide range of wavelengths. It was found that the temperature dependence of the optical properties does not cause problems at normal usage temperat

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of the dielectric constant on the transmission characteristics of multilayer ceramic circuit boards were examined. Multilayer ceramic circuit boards were fabricated using various kinds of ceramic materials with different dielectric constants, and their characteristic impedances, crosstalk, and propagation delays were measured. Experimental results show that the lower the dielectric constant, the higher the characteristic impedance, with less crosstalk and propagation delay. Based on these results, lowering the dielectric constant of the board material is found to be essential for realizing higher‐density wiring, e.g., the reduction in the dielectric thickness and transmission line spacing in multilayer ceramic circuit board

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractSince the CCD can handle analog signals directly, it is used widely for delay lines, filters, imaging elements and imaging memories. This paper considers the multilevel storage memory of an SPS (serial‐parallel‐serial)‐CCD applied to field memories of image signals. First, a charge transfer model for an SPS‐CCD is created. By means of the transfer function derived from this model, it is clarified that the transfer losses of the serial register and the parallel register degrade the frequency characteristics of the amplitude and phase. It is pointed out that this degradation can be improved significantly by compensation of the transfer losses of the two serial registers and the parallel register. Since realization of a circuit for rigorous compensation of the transfer loss is extremely difficult, a simple transfer loss compensation method is also studied in which the SPS‐CCD is considered as a cascade connection of two serial registers. It is found that the difference in the effect of simple and rigorous compensations is at most 0.6 percent in the case of 50 percent eye degradation. Hence, the effectiveness of the simple compensation is confirmed. Also, by using a commercially available CCD, an experiment for eight‐level storage memory is carried out in which a simple transfer loss compensation is applied. It is confirmed that agreement of the calculated and measured signal error rates i

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA method of analyzing the effects of clock feedthrough and power supply noise on CMOS comparators is described. In addition, a new flip‐flop type comparator with large tolerance to clock feedthrough and power supply noise is developed.First, a method of analyzing clock feed‐through and power supply noise tolerance using small signal analysis of the inverter chopper comparator is described. Next, a new flip‐flop comparator whose tolerance to clock feedthrough and power supply noise is significantly greater than that of the inverter chopper comparators is proposed. Experimental results are also described. The new comparators fabricated using 1.5 μm CMOS technology show a small offset voltage (⩽ 1.5 mV) which is caused mainly by clock feedthrough imbalance. The power supply noise tolerance of these new comparators is almost twenty times larger than that of the inverter chopper com

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe increase in infrared transmission loss due to hydrogen has to be removed completely with good understanding of its mechanism before practical utilization of a 1.55‐μm window in germania‐doped silica fibers for a long‐haul optical transmission system. Many kinds of fibers with various compositions from different processes have been manufactured and subjected to hydrogen acceleration tests to solve this problem. From these studies, such alkali impurities as sodium and potassium have been found to have a negative effect on germania‐doped silica causing an increase of infrared transmission loss as well as phosphorus. Such alkalis exist in some of the natural silica tubes used widely as a supporting tube in the MCVD process or as a jacketing tube in the VAD and MCVD processes. Most of them have been found to be removed during the MCVD process, while residual alkali impurities in the jacketed tube have been found to migrate into the central part of the fiber during the fiber drawing process and form germania‐associated defects. These experiments show that removal of alkali impurities and phosphorus is essential in protecting germania‐doped silica fibers from the adverse effect of hydrogen and maintain a minimized transmission loss in the 1.55‐μm window with smaller excess loss than in the 1.3‐μm window. Electron spin resonance analysis has helped in understanding the behavior of phosphorus and alkali impurities and establishing a reaction m

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractGraded refractive index rod (GRIN‐rod) lenses are used widely in optical devices for optical fiber communication systems. Insertion loss is a major criterion for evaluating optical devices, especially those used in single‐mode fiber systems, and aberration is a dominant factor in insertion loss. Thus, aberration analysis is essential in designing high‐perfomance optical devices. This paper presents ray traces within the third‐order aberration when light propagates through GRIN‐rod lenses. Using the fact that the ray is the orthogonal trajectory of the wavefront, we derive a novel wave optical description of GRIN‐rod lenses to the degree of third‐order aberration. This paper shows the relatinship between coupling efficiency and lens parameters. The necessity of considering aberration effects in designing low insertion loss optical devices is shown. The experimental results are in very good agreement with the calculated values, and the validity of the present analysis is confirmed. This paper proves that GRIN‐rod lenses are superior to ball lenses in terms of aberration, and provide higher coup

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA few comprising methods of mode‐conversion type low‐loss optical branching waveguides are proposed anew, and the fundamental properties are clarified by numerical analysis based on the coupled mode theory. For the analytical model, we select a singlemode slab waveguide, and assume that the waveguide possesses mode transducers at the input and output sides, respectively. The mode transducers are designed in the best possible way for mode conversion from the input to the main part of the branch waveguide and also from that main part to the output waveguide, that is, so as to minimize the radiation loss at the output end of the branching waveguide. The waveguide thus designed has a taper at the input side, and the cross‐sectional shape varies in the direction of the transmission axis. For the analysis, first we calculate the coupling coefficients between the coupled modes of the tapered and branch sections of the three‐layered slab waveguide, respectively. Then we substitute the coefficients into the corresponding coupled mode equation whose solutions are obtained numerically by the Runge‐Kutta‐Gill method. The result of numerical simulations shows that the comprising methods proposed in this paper can reduce the mode conversion loss more remarkably than the other methods kno

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTo explain the experimental characteristics of a laser Doppler velocimeter using the self‐mixing effect of a semiconductor laser diode (LDV) with a rotating disc as a target, a theoretical analysis of a Doppler beat waveform was carried out, and its approximate solution was obtained by using the perturbation method. The theoretical characteristics based on this solution agreed fairly well with the experimental ones. The operating conditions of the LDV required for forming the beat wave into a sawtooth waveform, and the reasons why the sawtooth wave is transformed into a mirror image depending on the sign of the Doppler frequency were found, i.e., the phase angles of the second and third higher harmonics of the beat wave are inverted by the inversion of the direction of rotation. The upper limit of the Doppler frequency and the range ofRparameter of the LD were estimated theoreticall

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWhen Waveguide I supporting several guided modes and Waveguide II supporting a single mode are coupled in a parallel orientation, the electromagnetic field distributions in this coupled guided system are analyzed in such a way that the mode coupling is represented as a weighted sum of the guided modes. In general, when two waveguides are placed closer so that the coupling becomes stronger, the existence of one guide can no longer be neglected by the guided eigenmode of another guide, and its field distribution is perturbed. The method of analysis presented in this paper takes into account this effect by way of weighted expansion coefficients of the mode. Hence, the analysis can be applied even when the coupling is rather dense. As an example, the field distribution of the coupled guided system is analyzed for the case where two rectangular dielectric waveguides having one and two modes, respectively, are placed in parallel. Next, the field distribution along the coupled waveguide is measured and the spatial spectrum is analyzed. A characteristic spatial spectrum is found which is proportional to the difference of the phase constants of the three eigenmodes. It is found that this corresponds to the difference of phase constants of each mode obtained analytically.The present analysis method can readily be extended to the case in which each of the coupled waveguides has multiple guided modes, including the case where both have only one mode. The theory can be used for the design of couplers, dividers, and mode filters made of dielectric waveguides.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420720210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY