The various propagation characteristics of millimeter waves in silicon rib and image guides containing the optically induced plasma region have been investigated. Phase shift and attenuation properties resulting from the presence of plasma are evaluated using the effective dielectric constant method. Experiments have been carried out to demonstrate the optical control of millimeter waves at frequencies ranging from 3350 GHz using high-resistivity silicon illuminated by a high-power Xenon arc lamp and light emitting diodes. Optical control of millimeter wave attenuation of 20dB has been confirmed for a guide of length 90 mm and plasma density of 10²¹/m³ with average plasma thickness of 20 µm. To increase the sensitivity of optical control, Bragg reflection filter characteristics are studied and its stop band characteristics have been calculated using the transmission line model, and confirmed experimentally. To further develop the Bragg reflection filter, a Mach-Zehnder interferometer guide with one of the arms periodically corrugated is newly proposed and its optical control performance is confirmed by experiments. Finally the field distributions of the Mach-Zehnder configuration of rib waveguides are measured by a simple optical probing technique using the focused laser spot.

This paper reviews Ti:LiNbO₃ and semiconductor optical waveguide modulators. The operating principle of the Ti:LiNbO₃ optical waveguide modulator is based on the Pockels effect. On the other hand, semiconductor optical modulators can be operated based on the Pockels effect, the Franz-Keldysh effect, or the quantum confined stark effect (QCSE) by employing multiple quantum wells (MQWs). Ti:LiNbO₃ optical waveguide modulators are discussed with emphasis on the velocity-matching and optical waveguides. MQW optical waveguide modulators are discussed in view-point of design of a MQW structure, waveguide and modulation bandwidth.

Research in optical microwave interaction, at its earlier stages, was spured by the desire to make an optically fed and controlled phased array antenna with monolithic microwave integrated circuit (MMIC) transmit/receive (T/R) modules. In the first part of this paper experimental results are presented demonstrating an optically fed phased array antenna operating at C-band in the 5.5 to 5.8 GHz frequency range. The present system consists of two optically fed 14 subarrays with MMIC based active T/R modules. Custom designed fiber optic links have been employed to provide distribution of data and frequency reference signals to phased array antenna. One of the challenges of the future is the development of better interfaces between electronic (microwave) and optical components, including the chip level merging of photonic and electronic components on III-V compounds. This aspect of the research is covered in the second half of the paper.

This paper reviews the application of optical technologies to phased array antennas. The performance of the fibre transmission medium and of sources and detectors is reviewed, leading to simple expressions for transmission loss and noise performance. Both coherent and non-coherent beam forming techniques are considered. Future trends, including the use of optical amplifiers and coherent signal generation, will also be discussed.

For a method to control the microwave coupled lines with optically induced plasma effectively, we propose the selective mode-control method, which restricts controlled modes to a selected one. We analyzed the basic characteristics of coupled microstrip lines theoretically by using the spectral domain technique and indicated the effectiveness of this method with the aid of numerical results. Further, we designed an optically controlled change-over switch as an application of this method.

We show the design of the bandwidth and the external quantum efficiency (including the coupling efficency to a single-mode fiber) of p-i-n photodetectors. Based on their design procedures, the performance limits of both conventional surface-illuminated photodetectors and side-illuminated photodetectors are evaluated. We point out that in the ultrawide-band region, optical waveguide photodetectors have great advantages over conventional surface-illuminated photodetectors in terms of the product of the bandwidth and the external quantum efficiency. It is shown that a 100-GHz bandwidth can be achieved with little degradation of the external quantum efficiency by a multimode waveguide photodetector structure. We also present a design concept for overcoming the performance limits of solitary waveguide photodetectors by including an input tapered optical waveguide.

This paper theoretically evaluates the external electro-optic (EO) sampling of high-speed electrical signals using poled polymers as materials for a proximity electric-field sensor. Based on the derivation of the half-wave voltage and the analysis of a static electric field coupled to the polymeric media placed over IC interconnections, invasiveness, voltage sensitivity, and spatial resolution have been discussed. The polymeric sensors have shown to be used in contact with the IC interconnections with negligibly small invasiveness, thus making polymeric sensors provide higher sensitivity and spatial resolution than inorganic crystals such as GaAs and KD^*P.

The inverted slot line (ISL) has been propoaed for millimeter-wave LiNbO₃ optical modulator. It is simple in structure, and capable of achieving the perfect velocity matching between carrier and modulating waves. The excellent performance of the ISL optical modulator has been demonstrated at 100 GHz, and the extension into the 50 GHz range is being expected. This paper addresses the analysis of the ISL based on the spectral domain approach. The major results obtained here are the demonstration of the perfect velocity matching not only at 10 GHz but also at 50 GHz, and the characterization of the ISL in terms of effective refractive index, characteristic impedance, overlap integral factor and transmission loss. The depth of optical phase modulation is also estimated at 50 GHz to show a promising performance in the millimeter-wave frequency range. The effective refractive index and the characteristic impedance are found to be theoretically predictable, but the field profile, the overlap integral factor and the transmission loss are not necessarily in good agreement with measurements. As a result of analysis, it can be concluded that the Y-cut substrate is superior to the Z-cut substrate in the following respects: 1. Coupling with the surface wave mode hardly occurs near the operating frequency range. 2. The perfect velocity matching can be attained with a larger spacing between the electrode and the ground plane. 3. The transmission loss is smaller. 4. The field intensity and the voerlap integral factor do not seem to be much deteriorated in the actual ISL.

A shielded velocity-matched Ti:LiNbO₃ optical modulator with a ridge is investigated. The analytical method is based on the second-order triangular element finite element method. The thickness of the coplanar waveguide traveling-wave electrode is taken into consideration and the relationship between the electrode thickness and optimum overlaid layer thickness is clarified. Incorporating a ridge into these Ti:LiNbO₃ optical modulators can improve not only their modulation bandwidth but also their driving voltage.

A coplanar-type TW electrode is analyzed for the use within a Ti:LiNbO₃ optical modulator. The quasistatic analysis is developed based on the variational principle and the incremental inductance formula. The anisotropy of the LiNbO₃, the effect of the SiO₂ buffer layer, the overlaid conductor and the electrode thickness can be taken into consideration easily by using the extended spectral domain approach (ESDA) as the formulation procedure. It is shown numerically that the TW electrodes thickness, t, and the overlay spacing, p, are as dominant as the buffer layer thickness d, i.e., the microwave effective index and the product ΔfL is affected significantly by the electrodes thickness t and the overlay spacing, whereas the product V_π・L is insensitive. Therefore, the introduction of the overlaid conductor and the use of thicker electrodes can be utilized effectively to achieve higher values of the figure of merit Δf/V_π.

This paper proposes the laser diode receiving mixer which utilizes the laser diode nonlinearity. The laser diode receiving mixer can make the bidirectional fiber optic link simple and cost-effective. These laser diodes are applied to configure the LD-LD MIX link which consists of two laser diodes, two local oscillators, two microwave switches and one fiber cable. The LD-LD MIX link configuration is extended to introduce novel two fiber optic links, i.e. the local suppression link and the image cancellation link. These links utilize the combination of microwave circuits and optical devices. These configurations are experimentally investigated at microwave frequencies and the QPSK signal transmission is successfully demonstrated.

The performance of a traveling wave Mach-Zehnder external optical modulator (EOM) mixer is described and compared with a conventional diode mixer's performance. Additionally, by incorporating external circuitry, the EOM mixer can provide single sideband suppression in addition to the inherent local oscillator suppression. The basic frequency mixing function of the EOM mixer is first described theoretically and then extended to the sideband suppression case. The performance of both configurations is also presented. Achievable electrical isolation between LO (carrier) and RF (upconverted data signal at LOIF) frequencies is greater than 95 dB and total link conversion loss is 37 dB in this demonstration with a laser diode source. Sideband suppression of greater than 43 dB with respect to the desired sideband at the photodetector output is achieved.

This paper proposes fiber optic link configurations for use in microwave and millimeter-wave transmission Higher frequencies,such as millimeter-waves, are well suited to transmission of broadband signals. Photodiodes can operate simultaneously as optical detectors and microwave frequency mixers thanks to their inherent nonlinearities. This allows us to increase the output radio frequncy. But, this also generates undesired spurious frequencies, necessitating the use of microwave filters. We discuss here two fiber optic link configurations, i.e., balanced/image canceling photodiode mixing links utilizing the combination of microwave functional components and optical devices to suppress the local/image frequency without filters. These configurations are experimentally investigated at microwave frequencies and local/image frequency suppression is successfully demonstrated.

Recently, making good use of the advantages of optical fibers such as wide bandwidth and low loss, it has been investigated to apply optical fiber link to microcellular mobile communication systems. This system allows complex equipment to be located at microcell control station, and can simplify the equipment of microcell base stations compared with the conventional systems. In this paper, we analyze the performance of optical fiber link for microcellular mobile communication systems, taking radio link fading and optical link nonlinear distortions into consideration. From the calculated results, it is disclosed that the effect of both items does not generate the significant excess CNR degradation, and the correct CNR can be approximately calculated by using CNR of non-faded case. And it is also disclosed that the degradation of CNR due to optical link nonlinearity is slightly improved by taking adjacent channel signal fade into consideration.

This paper describes a fiber-optic microcell radio system with a spectral delivery switch to meet traffic demands. Optical link performance is discussed from the view points of link loss and noise figure aimed at system design. The theoretical carrier-to-noise ratio (CNR) performance is shown as a function of the input electrical power of the laser and the received optical power. Improvement of dynamic range defined by both CNR and intermodulation distortion is proposed by using the frequency modulation (FM) technique. The experimental results using the proposed technique indicate that the performance is much better than that of conventional methods. Moreover, economical diversity planning delivery methods over fibers are presented. This strategy will provide more cost effective and flexible networks.

This paper reports the influence of optical reflection induced noise and distortion for optical fiber feeder systems for microcellular mobile communication systems. Since the optical feeder requires very wide dynamic range, noise and distortion must be suppressed to an extremely low level. From optical transmission experiments and theoretical analysis, the basic characteristics of the reflection induced noise and distortion were investigated. By using these results, it was estimated that, for currently used analog mobile telephone systems, the number of connectors with 35 dB reflectance must be limited to less than 17, in order to suppress the noise caused by the connector reflections. Moreover, it was confirmed that the reflection induced distortion drastically decreases according to the increase of the length between reflectors. Therefore, the distortion can be suppressed by expanding the connector spacing to more than 7 meters.

In coherent optical subcarrier multiplexing (SCM) systems, the performance degradation of the system due to the phase noise of lasers restricts the maximum number of stations and channels that the system can serve. However, the effects of phase noise on the performance of the coherent SCM system with distributing Local Oscillator (LO) in local loop have not been analyzed. On the other hand, a limit on both the number of channels and stations can be effectively alleviated by using coding technique. In this paper, the effects of phase noise of lasers on the performance of frequency shift keying (FSK) SCM system with distributing LO in local loop are analyzed in terms of carrier-to-noise ratio (CNR) penalty. Second, the effects of Reed-Solomon (RS) coding on FSK SCM system with distributing LO in local loop are analyzed. It is shown that both the number of channels and stations can be increased by using coding technique.

This letter discusses a microstrip line with an open-end termination in which the reflected microwaves can be optically controlled by a laser illumination. The frequency characteristics are emphasized rather than the time domain ones. The reflection characteristics have been demonstrated experimentally and theoretically for the frequency range of 24 GHz. In the theoretical treatment both the conductance and the capacitance are considered in the equivalent circuit model of the open end of the strip.

This paper presents the successful performance of an optical waveguide phase controller for microwave signals generated by heterodyne photodetection. A 22 optical waveguide structure with four optical phase shifters was fabricated on a LiNbO₃ substrate. As a result of heterodyne photodetection of two optical signals from wavelength-tunable laser diodes, two microwave signals at 585 MHz were generated and phase shifted in the manner of electro-optical phase retardation. The monolithic waveguide structure allowed linear phase shifting more than 1800 degrees. Similar phase shifting performances were also confirmed over a wide microwave frequency range from 300 MHz to 1.3 GHz. The optical waveguide structure demonstrated here will be applicable to fiber-optic fed microwave systems such as a phased array antenna.

The erosion of contact metal, which determines the life of contacts in the telephone switching system, is proportional to the arc energy. The equations for arc voltage, arc current, arc duration time and number of arcs are expressed explicitly in terms of circuit parameters and contact properties, and the expression is derived for arc energy that accompanies a single operation of contact closure. Contact erosion is consistent with the calculated arc energy. The erosion rate at closure is estimated based on the measured contact-erosion volume and the calculated arc energy. Arc energy at contact closure becomes as large as that at contact break if the cable is long or the supply voltage is high. This expression in combination with the expression for contact break enabled us to perform contact life design, which is indispensable for maintenance administration of telephone switching systems.

Reactive gases such air pollution agents as H₂S or SO₂ usually corrode the electrical contact surfaces. Since corrosion products formed on the surface increase contact resistance, they harmfully degrades contact reliability. To prevent the corrosion of the surface, oil coating on it may be effective. The oil film acts basically as a barrier for reaction between the corrosive gas and the surface. For thin film coating, the corrosion inhibition can not be expected. However, effect of film thickness on the corrosion property has not been clarified. In the present study, in order to clarify the corrosion inhibition of the oil coating for the contacts, the stearic acid coating on Ag (silver) contact surface was studied from view-point of the relationship between the thickness of the coating film and the contact resistance. As results, the effect of the stearic acid coating on corrosion inhibition in the atmosphere contained with H₂S 3 ppm was found. However, the corrosion of the surface coated with thin stearic acid film occurred at microscopically scattered thin patiches in the specific pattern of the film. Existing of the optimum thickness of the stearic acid coating which gives both minimum contact resistance and effective corrosion inhibition was found. In the intermediate film thickness, this optimum thickness was induced by the increased contact resistance due to corrosion of the thin film region and insulation property of the stearic acid in the thick film region. Moreovr,it was found that this optimum thickness was affected by corrosion time. At the early stage of corrosion, the optimum thickness was about 200 . However, the corrosion time becomes longer as 700 min, this optimum thickness changed to thick as 1000 . With this increase in the thickness, the contact resistance in the optimum thickness rised to high level. Furthermore, the contact resistance in the optimum thickness decreased with increase in the contact load. However, dependence of the contact load on the optimum thickness was not recognized under a certain corrosion time.

The problem of two-dimensional scattering of electromagnetic waves by a grating with several strips arbitrarily oriented in one period is analyzed by means of the Wiener-Hopf technique together with the formulation using the concept of the mutual field. A formulation for the analysis of multiple scattering from the grating is based on the representation of the scattered field by a grating composed of one strip in one period. The Wiener-Hopf equations and a representation of the scattered wave are obtained. The characteristic of the sampling function is used to expand the unknown function associated with the field on the strip into a series, and then the Wiener-Hopf equations are reduced to a set of simultaneous equations. For evaluation of the convergence and the errors in the numerical results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are computed. From numerical comparison of the present method with other various methods, it is found that the present method provides us accurate results. Some numerical examples of the reflection coefficients are presented for the reflection grating and transmission gratings.