Toshiki P. Tanaka

Monolithic integration of laser diodes, photomonitors, and laser driving and monitoring circuits on a semi-insulating GaAs

A monolithic optoelectronic-integrated circuit (OEIC) incorporating laser diodes, photomonitors, and laser driving and monitoring circuits has been fabricated on a semi-insulating GaAs substrate. The structure and circuit design considerations, the fabrication processes, and the static and dynamic characteristics of the device are described. The device has been successfully operated up to 2 Gbit/s.

Microbending losses of doubly clad (W-type) optical fibers.

The microbending of optical fibers causes some additional transmission losses. In this paper, the theoretical and experimental results on the microbending characteristics for doubly clad (W-type) fibers are described. A simple approximation in which W-type fibers are considered as equivalent singly clad fibers is employed to calculate the additional losses due to microbending. It is shown that the additional losses of W-type fibers depend on the optical wavelength. Further, it is shown that the structural imperfections of the guide can be also considered a kind of microbending which affects the spectral loss characteristics of W-type fibers.

Numerical solution of power flow in multimode W-type optical fibers

Transmission characteristics of multimode step-index W-type optical fibers are theoretically investigated by numerically solving the complex power flow equations. Spatial transients of power distribution and power level, as well as transmission length dependence of transmission bandwidth, are calculated for the mode-coupling condition from guided to lossy leaky modes, a characteristic of W-type fibers. The transmission characteristics of W-type fibers change from those of two singly clad reference fibers when the width of the intermediate layer is changed. The trade-off relation between the bandwidth and steady-state loss is also discussed.

Steady-state characteristics of multimode W-type fibers

The steady-state characteristics of multimode W-type fibers are investigated by solving the coupled-power equation numerically. It is shown that the steady-state power distributions depend on both the intermediate layer width and the coupling strength. Unlike singly clad fibers, the steady-state loss (coupling-induced loss) in W-type fibers is not proportional to the coupling strength. The loss in W-type fibers varies between the value for two types of singly clad reference fibers as the coupling strength changes.

W fiber design considerations.

The baseband frequency characteristics and the average confinement of light to core properties of a W fiber are analyzed in conjunction with corresponding singly clad (SC) fibers under some ideal assumptions It is found that the bandwidth of a W fiber is almost equal to that of the SC fiber that has no intermediate layer and is much wider than that of the other SC fiber in which the intermediate layer extends to infinity. The average fractional power flow outside the core in a W fiber is drastically reduced in comparison with both SC fibers. Practical design considerations are deduced from a typical example.

Optoelectronic integrated light sources for high-speed optical communication systems

It has been predicted that monolithic optoelectronic integrated light sources will play a major role in future high-speed optical communication systems.1 Recently, several integrated light sources were developed for the short-wavelength2,3 and long-wavelength regions.4 Problems to be solved with integrated light sources are: (1) how to use the vertical laser structure with the planar electronic IC structures, and (2) how to develop low-threshold high-slope efficiency lasers without utilizing the conventional cleaving technique for a cavity formation.

Consideration of a slot access method for backbone local area networks

Abstract The standardization of LANs has been fundamentally completed by IEEE, and recently, high-speed backbone local area networks (BLANs) for integrated services (voice, video and data) are actively studied. This paper proposes a new slot access method for BLANs. The proposed method improves ring topology efficiency and increases throughput using slot concatenation and multi-slot access. System applications and the performance are also discussed.

Paired optical-fiber switch for optical data-bus systems

A new type of optical switch, which is suitable for application to data paths with a loop bus-line configuration, is described. The switching action is obtained by moving a fiber directly. The insertion loss in the bypass mode is as low as 0.82 dB. Results of temperature, durability, and vibration tests are also described.

A consideration on ATM technology in private networks

A development scenario for ATM (asynchronous transfer mode) private networks and possible architectures for inter- and intra-premises private networks are discussed. It is pointed out that ATM is a promising technology for advanced private networks aiming at wideband and multimedia communication. It is suggested that ATM technology will be introduced first into private networks to support advanced and sophisticated applications in business communication environments. It is shown that MBLAN (multimedia backbone local area network) and SPN (super packet node) are possible architectures employing ATM technology.<<ETX>>

Properties of multimode W-fibres

Abstract The base-band frequency characteristics of a multimode W-fibre which consists of three layers (including a low-index intermediate layer) are analyzed under some idealized assumptions. It is found that the transmission band-width of the W-fibre is almost equal to that of the corresponding singly clad fibre which has no intermediate layer, while the fractional power flow outside the core can be drastically reduced. As a result, the W-fibre holds great potential for use as a wide-band optical waveguide achieving good light confinement without loss of core size.