Masahiro Komachiya

Knocking Detection of a Gasoline Engine by Utilizing an Optical Fiber with Specific Refractive-index Composition.

Abnormal combustion of a gasoline engine is often accompanied by a sharp metallic noise called knocking. A recently proposed method of in-cylinder pressure measurement is applied to detect the knocking, where the bending power loss of a single-mode fiber with specific refractive-index composition is utilized. The high-frequency response of a prototype sensor is obtained with a small structure to utilize the bending mechanism that is installed into an engine head gasket. Knocking signals are detected in a wide range of trace- to heavy-knock conditions.

Multiplex in-cylinder pressure measurement utilizing an optical fiber with specific refractive-index composition

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed.

Secondary-phase-modulation method for open-loop fiber-optic gyroscopes

A proposed method of secondary phase modulation for open-loop fiber-optic gyroscopes is examined in general terms. To detect the rotation rate of a system through a beat-frequency channel, we employ linearly combined signals with different frequencies for the optical phase modulation. We find that the proper combinations of the modulation frequencies can optimize the sensitivity of gyroscopes. With this method we can employ a high-frequency band for optical phase modulations while keeping relative a lower-frequency band of the detection channel. The theoretically derived result is experimentally confirmed by using a lithium-niobate (LiNbO(3)) optical phase modulator. We also discuss the combination setup with an optical integrated-circuit device and digital signal processing.

Design of a sensing glass fiber with specific refractive-index composition for a system with 1.3 μm wavelength light source

Abstract We propose a design of a sensing glass fiber for sensors that utilize optical power loss associated with bending of the fiber. First, we examine the optical power losses by simulation to determine the prototype design. Then three types of the fiber with different cutoff wavelengths are made. Each fiber exhibits a sensitive change in optical power near the bend radius R of 10 mm because of a leaky profile of the core-cladding. The fibers are designed for the combinatorial use of 1.3 μm wavelength light sources that are commonly employed in optical communications. The sensing system which utilizes the fiber developed has merits of low cost (compatibility with a light module and other optical components for 1.3 μm wavelength band), high sensitivity (leaky refractive-index composition for the fiber-optic sensor of the bend type), and long-term durability (suppression of glass-fiber static fatigue due to the relatively large bend radius (ca. 10 mm)).

Fabrication of integrated optical gyrochip pigtailed with elliptical-core polarization-maintaining optical fiber for industrial applications

An integrated optical gyrochip has been developed for industrial and consumer fiber-optic gyroscope applications. The gyrochip is pigtailed with low-cost elliptical-core polarization- maintaining optical fiber. An alignment technique was developed that uses image processing technology to align the polarization axis of the fiber without launching light into its core. The fiber-to-fiber insertion loss deviation of the pigtailed waveguide was less than +/- 0.8 dB at a wavelength of 0.78 micrometers over 100 temperature-change cycles, ranging from -30 to +80 degree(s)C, with a fiber mode-field size as small as 3.5 X 2.6 micrometers .