Mr. Seiji Kojima Profile

Seiji Kojima

at Hitachi Cable Ltd

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Author

Publications (11)

Proceedings Article | 7 April 2008 Paper

Improvement of FBG/PZT hybrid sensing system for composite materials

Shinji Komatsuzaki, Seiji Kojima, Akihito Hongo, Nobuo Takeda, Yasuhiro Koshioka

Proceedings Volume 6933, 69330A (2008) https://doi.org/10.1117/12.776079

KEYWORDS: Sensors, Fiber Bragg gratings, Actuators, Ferroelectric materials, Composites, Sensing systems, Damage detection, Signal detection, Signal generators, Lead

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Proceedings Article | 10 April 2007 Paper

Small-diameter optical fiber and high-speed wavelength interrogator for FBG/PZT hybrid sensing system

Shinji Komatsuzaki, Seiji Kojima, Akihito Hongo, Nobuo Takeda, Takeo Sakurai

Proceedings Volume 6530, 65300O (2007) https://doi.org/10.1117/12.715900

KEYWORDS: Fiber Bragg gratings, Sensors, Composites, Optical fibers, Sensing systems, Signal attenuation, Actuators, Ferroelectric materials, Refractive index, Cladding

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We have been developing a sensing system for checking the health of aircraft structures made of composite materials. In this system, lead zirconium titanate (PZT) actuators generate elastic waves that travel through the composite material and are received by embedded fiber Bragg grating (FBG) sensors. By analyzing the change in received waveforms, we can detect various kinds of damage. The frequency of the elastic waves is several hundred kHz, which is too high for a conventional optical spectrum analyzer to detect the wavelength change. Moreover, a conventional single-mode optical fiber cannot be used for an embedded FBG sensor because it is so thick that it induces defects in the composite material structure when it is embedded. We are thus developing a wavelength interrogator with an arrayed waveguide grating (AWG) that can detect the high-speed wavelength change and a small-diameter optical fiber (cladding diameter of 40µm) that does not induce defects. We use an AWG to convert the wavelength change into an output power change by using the wavelength dependency of the AWG transmittance. For this conversion, we previously used two adjacent output ports that cover the reflection spectrum of an FBG sensor. However, this requires controlling the temperature of the AWG because the ratio of the optical power change to the wavelength change is very sensitive to the relationship of the center wavelengths between an FBG sensor and the output ports of the AWG. We have now investigated the use of a denser AWG and six adjacent output ports, which covers the reflection spectrum of an FBG sensor, for detecting the elastic waves. Experimental results showed that this method can suppress the sensitivity of the power change ratio to the relationship of the center wavelengths between an FBG sensor and the output ports. Although our improved small-diameter optical fiber does not induce structural defects in the composite material when it is embedded, there is some micro or macro bending of the fiber, which causes propagation loss. To suppress this embedment loss, we adjusted the refractive index difference of the fiber to have larger value. Experimental result showed that this reduced the embedment loss by about 0.3 dB/cm. These enhancements make our sensing system more practical and should promote the use of composite materials in a wider range of applications.

Proceedings Article | 30 March 2006 Paper

Development of small-diameter optical fiber sensors and high-speed optical wavelength interrogator for damage detection in composite materials

Shinji Komatsuzaki, Seiji Kojima, Akihito Hongo, Nobuo Takeda, Tateo Sakurai

Proceedings Volume 6167, 616703 (2006) https://doi.org/10.1117/12.657796

KEYWORDS: Optical fibers, Fiber Bragg gratings, Sensors, Refractive index, Composites, Actuators, Ferroelectric materials, Connectors, Cladding, Sensing systems

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We have been developing a sensing system for monitoring the structural health of aircraft structures made of composite materials. The sensing system is composed of fiber Bragg grating (FBG) sensors, a wavelength interrogator and piezoelectric actuators. The FBG sensors receive 100 kHz to 1 MHz elastic waves generated by the PZT actuators. For the FBG sensors, we previously developed a polyimide-coated optical fiber with a cladding diameter of 40 μm and core-cladding relative refractive index difference Δ of 0.65 %, that can be embedded in composite materials without inducing any mechanical defects. Since the cladding of that fiber is so thin, however, under embedded conditions, the transmission loss of the fiber is larger than that of a normal single-mode optical fiber. We therefore developed a new small-diameter optical fiber with an Δ of 1.8 %, in order to suppress the loss increase caused by micro-bending or transversely applied strain under the embedded condition. On the other hand, the small-diameter optical fiber needs to be connected to a normal optical fiber whose claddingding diameter is 125 μm, because it is fragile and difficult to handle. For practical use, we developed a small-diameter optical fiber module that has a special connector on both ends of the small-diameter optical fiber. The special connector can connect the small-diameter optical fiber to a normal optical fiber that has a standard MU connector. We also developed a high-speed optical wavelength interrogator that can detect the high-frequency vibration of the FBG sensors. It uses an arrayed waveguide grating (AWG) as an optical filter that converts the wavelength shift of the light reflected from the FBG into the output optical power changes. This wavelength interogator is suiatable for high-speed wavelength detection because it has no mechanical moving parts. The development of these components will help put this system to practical use and thus extend the use of composite materials to a wider range of applications.

Proceedings Article | 16 March 2006 Paper

Evaluation of debonding progress in composite bonded structures by ultrasonic wave sensing with fiber Bragg grating sensors

Yoji Okabe, Junichiro Kuwahara, Nobuo Takeda, Toshimichi Ogisu, Seiji Kojima, Shinji Komatsuzaki

Proceedings Volume 6179, 61790G (2006) https://doi.org/10.1117/12.657510

KEYWORDS: Fiber Bragg gratings, Sensors, Ultrasonics, Adhesives, Wave propagation, Wavelet transforms, Skin, Actuators, Wavelets, Optical filters

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Proceedings Article | 23 May 2005 Paper

Joining techniques for small-diameter optical fiber used in embedded sensor

Seiji Kojima, Sinji Komatsuzaki, Akihito Hongo, Nobuo Takeda, Tateo Sakurai

Proceedings Volume 5855, (2005) https://doi.org/10.1117/12.623628

KEYWORDS: Optical fibers, Sensors, Composites, Connectors, Fiber Bragg gratings, Cladding, Coating, Refractive index, Structured optical fibers, Zirconium dioxide

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Proceedings Article | 16 May 2005 Paper

Lamb wave sensing using fiber Bragg grating sensors for delamination detection in composite laminates

N. Takeda, Y. Okabe, J. Kuwahara, S. Kojima

Proceedings Volume 5758, (2005) https://doi.org/10.1117/12.598594

KEYWORDS: Fiber Bragg gratings, Sensors, Ultrasonics, Wave propagation, Actuators, Wave sensors, Wave plates, Optical filters, Composites, Damage detection

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Proceedings Article | 16 May 2005 Paper

Development of high-speed optical wavelength interrogation system for damage detection in composite materials

Shinji Komatsuzaki, Seiji Kojima, Akihito Hongo, Nobuo Takeda, Takeo Sakurai

Proceedings Volume 5758, (2005) https://doi.org/10.1117/12.599391

KEYWORDS: Fiber Bragg gratings, Composites, Sensors, Sensing systems, Ferroelectric materials, Wave propagation, Wave plates, Actuators, Optical filters, Optical fibers

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Proceedings Article | 27 July 2004 Paper

High-speed optical wavelength interrogator using a PLC-type optical filter for fiber Bragg grating sensors

Seiji Kojima, Akihito Hongo, Shinji Komatsuzaki, Nobuo Takeda

Proceedings Volume 5384, (2004) https://doi.org/10.1117/12.539427

KEYWORDS: Fiber Bragg gratings, Sensors, Optical filters, Ferroelectric materials, Sensing systems, Composites, Photonic integrated circuits, Actuators, Silica, Defect detection

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Proceedings Article | 22 July 2003 Paper

Embedded small-diameter fiber Bragg grating sensors and high-speed wavelength detection

Akihito Hongo, Keisuke Fukuchi, Seiji Kojima, Nobuo Takeda

Proceedings Volume 5050, (2003) https://doi.org/10.1117/12.484249

KEYWORDS: Fiber Bragg gratings, Optical fibers, Sensors, Wavelength division multiplexing, Composites, Reflection, Cladding, Photonic integrated circuits, Connectors, Coating

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Proceedings Article | 9 September 2002 Paper

Optical water-level sensing systems using fiber Bragg grating

Keisuke Fukuchi, Seiji Kojima, Yasuyuki Hishida, Akihito Hongo

Proceedings Volume 4920, (2002) https://doi.org/10.1117/12.482013

KEYWORDS: Fiber Bragg gratings, Sensors, Optical fibers, Water, Temperature metrology, Head, Refractive index, Sensing systems, Fabry–Perot interferometers, Modulation

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Proceedings Article | 27 June 2002 Paper

Development of multipoint strain measurement systems using small-diameter fiber Bragg gratings

Seiji Kojima, Kouji Satori, Keisuke Fukuchi, Akihito Hongo, Nobuo Takeda

Proceedings Volume 4694, (2002) https://doi.org/10.1117/12.472619

KEYWORDS: Fiber Bragg gratings, Wavelength division multiplexing, Sensors, Optical fibers, Polarization, Modulation, Fiber couplers, Composites, Light sources, Refractive index

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Showing 5 of 11 publications

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