Integrated detection optics for magnetooptical (MO) disk pickup are proposed. The pickup consists of a waveguids device, external lenses, a beam splitter and a laser diode. The detection optics is constructed by integrating a trifocal focusing grating coupler and five photodiode elements in a glass-film waveguide on a Si substrate. The design considerations and fabrication are described, and experimental results are reported. The wavelength bandwidth of the devices are discussed in relation to the wavelength instability of laser diode. Although the obtained performances are not sufficient for practical application, the elementary functions, i.e., MO signal readout, focusing error detection and stabilization by multimode LD, were successfully demonstrated in the simulation experiments.

Using an interferometric detection technique with AC modulation for searching the interference fringe signal, highly accurate polarization mode dispersion (PMD) measurement with about 0.003 ps/m resolution has been developed, and the PMD measurement in a 60 km-long installed optical submarine cabled fiber is presented. Also, fiber length dependence of PMD and comparison of the interferometric PMD measurement with other wavelength scanning PMD method are described.

The effect of well number in 1.3 µm GaInAsP Graded-Index Separate-Confinement-Heterostructure Multiple-Quantum-Well (GRIN-SCH-MQW) laser diodes (LDs) is examined experimentally in terms of threshold current density Jth, differential quantum efficiency ηd and internal loss α. For LDs with cavity length L of 270 µm, Jth as low as 0.9 KA/cm2 was obtained with 5 quantum wells. ηd as high as 81% and α as low as 5 cm-1 were obtained with 4 quantum wells. Taking these parameters into account, 4 or 5 is calulated to be the optimum number of quantum wells for the present structure, which was confirmed experimentally. Light output power of 56 mW/facet with a narrow and circular output beam was obtained in a buried heterostructure (BH) GRIN-SCH-MQW LD entirely grown by Metalorganic Chemical Vapor Deposition (MOCVD). These results indicate that the use of a GRIN-SCH in a MQW LD of the GaInAsP/InP system is effective in the improvement of laser characteristics.

A 161 km non-repeatered transmission and a 216 km transmission with a linear repeater have been achieved at 10 Gbit/s using Er3+-doped fiber amplifiers. It is also verified that GaAs-IC technology is applicable to 10 Gbit/s optical transmission systems.

LiNbO3 switch matrices are attractive devices for small scale optical digital data interchange and service routing. This paper gives an overview on the state of the art of the first generation of photonic switch matrices as well as some future prospects.

In high-speed digital land mobile radio communication, frequency-selective fading is the most serious obstacle to high quality transmission radio links. Diversity reception is an effective method to overcome this obstacle. In this letter, a selection combining diversity reception method suitable for coherent QPSK is proposed, and the effect on bit-error-rate (BER) performance under frequency-selective fading is described.

Lasing action in GaInAs/GaInAsP quantum-wire structure, fabricated by two-step OMVPE growth, electron beam lithography, and wet chemical etching techniques, was obtained for the first time at 77 K with pulsed current injection. GaInAs quantum-wires with size of 10 nm thick and about 30 nm wide were completely separated and embedded in GaInAsP optical confinement layers so as to form a separate-confinement-heterostructure quantum-wire (SCH-QW) laser. The evidence of quantum-wire levels was confirmed by comparing its emission spectrum with that of quantum-film (QF) structure both experimentally and theoretically. The results indicate that there is no serious defects or damages in the laser operation of quantum-wires fabricated by the combination of electron beam lithography, wet chemical etching, and regrowth techniques.

As an estimating method of the threshold current level on experimental data of the semiconductor injection laser, finding peak position on second order derivative of I-L (injection current vs. light output) characteristics is popularly in use. A theoretical proof of this method is given in this letter.

As a candidate for a laser structure which reduces spatial hole burning and provides narrower linewidths, we propose a coupled structure of phase shift DFBs with asymmetric cavity lengths. Mode properties of this asymmetric structure are analysed based on the transfer matrix method. It is found that its threshold gain difference between the fundamental mode and the next higher order mode is about 1.9 times larger than that of the conventional single phase-shift DFB structure, when the asymmetry parameter is optimally adjusted. The linewidth calculation taking into account the spatial hole burning effect predicts that, for a linewidth enhancement factor of α4, the minimum feasible linewidth is about 0.1 MHz, which is three times narrower than what can be achieved by the conventional single phase-shift structure.

The purpose of this paper is to investigate the ray focussing of whistler-mode waves in the outer magnetosphere which results in an enhanced wave-particle interactions. The critical frequency in a homogeneous plasma is first studied, at which the refractive index surface of whistler-mode waves indicates a zero curvature at a longitudinal wave normal angle. This critical frequency is also found to be consistent with the zero diffraction coefficient in the full-wave theory for a slightly inhomogeneous plasma. The two-dimensional ray-tracing computations for varying the frequency and initial wave normal direction in an inhomogeneous realistic model of the outer magnetosphere, have yielded that although the critical frequency for the homogeneous case has its importance even in the inhomogeneous plasma, the strongest ray focussing seems to occur at a frequency slightly below the above critical frequency, and hence that an enhanced gyroresonance wave-particle interaction is anticipated at this frequency.

This letter describes the experimental study on the problems of gain enhancement for a radiating element between a finite ground plane and a finite dielectric plate. It is shown that, in the case of rectangular dielectric plate, this type antenna has 17 dBi antenna gain with 210% aperture efficiency if the dimensions of the rectangular parallelepiped dielectric are 1.375λ01.375λ0 the cross-sectional area parallel to the ground plane and 1.7λ0 thickness (λ0: free space wavelength).

As one of the approaches to developing a monolithic integrated device, optical coupling efficiency between a monolithically integrated DFB laser and a passive waveguide is experimentally evaluated. A butt-joint coupling is selected in this study, because it is expected to produce a higher coupling efficiency than any other coupling techniques. The DFB laser is butt-jointed with the waveguide by a low-pressure MOVPE selective growth, which produces no overgrowth at the butt-joint region. The average efficiency is evaluated to be 60%. The distribution of the evaluated efficiency indicates that the coupling efficiency of more than 50% can be obtained with good reproducibility.

Small-size directional coupler type optical multi/demultiplexers using high refractive-index-difference composite-glass waveguides have been investigated. A novel design to minimize wavelength response sensitivity to waveguide width deviation in the coupler part was proposed. Composite glass waveguides with 5% were fabricated using Corning 7059 glass for the core and SiO2 for the cladding. 1.3/1.55-µm optical multi/demultiplexers with short coupler length of 300 µm, low insertion loss of 5 dB and high crosstalk attenuation of more than 25 dB were realized.

Nonlinear phenomena in semiconductor laser amplifiers are reviewed, in terms of gain saturation and four-wave mixing characteristics. Dominant nonlinearity in semiconductor laser amplifiers results from injected carrier-density change due to signal amplification. Signal gain saturation characteristics for single- and multi-channel CW input and pulse input signals are successfully described by treating the semiconductor laser gain medium as a homogeneously broadened system. Nearly degenerate four-wave mixing arising from injected carrier-density modulation is promising as a highly efficient optical nonlinear operation, suitable for frequency conversion. Operating conditions for suppressing/enhancing these nonlinear phenomena are also discussed in terms of amplifier saturation parameters and channel spacing.

Wavelength-selective optical integrated switch modules using collinear acousto-optic interaction are investigated for applications to an optical frequency shifter and numerical processors. First, an optical frequency shift of 30 MHz was demonstrated with a slab-waveguide device. Next, an experiment of wavelength-selective switching was made at wavelength 632.8, 755 and 785 nm by surface acoustic waves of 19.8, 72.2 and 81.9 MHz, respectively. Matrix-vector multiplication in analog representations was demonstrated using optical multiple-wavelength pulses at 755 and 785 nm. Theoretical limitations of the numerical processing speed are discussed.

This paper presents an efficient piecewise-linear (PL) homotopy method for solving systems of nonlinear equations. In the conventional PL homotopy methods, a simplicial subdivision is used for solving general problems, and a rectangular subdivision is used for solving special problems, namely, systems of nonlinear equations with separable mappings. Although the rectangular algorithm is much more efficient than the simplicial algorithm, it cannot be applied to a problem which contains only one non-separable element. In this paper, we use a polyhedral subdivision, which is a hybrid concept of both a simplicial subdivision and a rectangular subdivision. For this purpose, we adopt the Newton homotopy as a homotopy, because it contains parameter t separately. It is shown that the polyhedral algorithm can be applied to systems of nonlinear equations with partially separable or non-separable mappings, and is much more efficient than the conventional simplicial algorithms. Then, we propose an efficient acceleration technique which improves the local convergence speed of the polyhedral algorithm. By this technique, the sequence of the approximate solutions generated by the algorithm converges to the exact solution quadratically. And in this case, the computational work involved in each iteration is almost edentical to that of Newton's method. Therefore, our algorithm becomes as efficient as Newton's method when it reaches sufficiently close to the solution.

Novel structure TE and TM mode selective optical channel waveguides are proposed and fabricated in GaAs/AlAs superlattices (SLs) using impurity-free disordering induced by SiO2 cap annealing. The disordered SL regions are found to be useful as low-loss waveguides even at a wavelength close to the absorption-edge of the as-grown SL. By observing the near-field petterns, it is confirmed that these channel waveguides could selectively confine TE or TM polarized light. These waveguides are applied to TE and TM mode filters using a bending waveguide to disperse unwanted signals. The extinction ratio is 14 dB for both types of filters. This value can be improved by optimizing the device structures.

Polarization-maintaining optical fibers with Al2O3 doped silica glass as stress-applying parts (SAPs) and fluorine doped silica glass as cladding are investigated. A high modal birefringence of 1.210-3 due to both thermally and mechanically induced stress is achived.

The optical undersea system technique has already proven its performance through major realizations of regenerated and repeaterless links. A new development programme has been undertaken so has to obtain within the next few years technical and economic optima in various fields, such as: fibre transmission and mechanical properties, fibre protection in the cable structure, capacity and flexibility of regenerated systems, length and capacity of regeneratorless systems. Today, still newer technics, such as optical amplification or heterodyne detection, are merging very quickly. They would still permit to increase the performance and reduce the cost of submarine systems. They may be introduced in an early stage in regeneratorless links to increase the range of application of these systems. However, they need to be thoroughly evaluated as regards their impact on reliability before being used in submerged equipment.

This paper proposes a new heuristic algorithm for the building block compaction problem considering routing region. At first, we define generalized constraint graphs which are constructed by adding channel edges to the conventional constraint graphs, and by which we can estimate the chip area including routing region. Secondly, we describe an iterative improvement method based on the graphs. In this method blocks on the chip are successively compacted two dimensionally with considering the necessary channel width. Finally, experimental results are shown to compare our method with the previous method.