A novel scheme of plastic optical fiber (POF) based arc flash sensor capable of tracing arc event locations is presented. Incident position of flash light can simply be known by measuring the ratio of intensities at both fiber-ends, since the intensity of the flash light assisted by side-coupling of the fiber is generally attenuated a the fiber length. The arc flash sensor which can cover a wide range up to 10 m with a high spatial resolution of ±10 cm is experimentally demonstrated using the POF. Arc flash intensity can also be known by analyzing the coupled light intensity level at both fiber ends.
Measurement range enhancement technique is proposed for distributed sensing of optical frequency domain reflectometry (OFDR) system. By using quadrature detection method in detection part, measurement range can be two times extended compared to conventional OFDR. Distributed strain sensing capability is experimentally reported with extended range up to full coherence length of tunable laser source by analyzing Rayleigh back-scattering signal obtained from the proposed quadrature detection of OFDR system.
We present an arc flash sensor that can trace the arc event position as well as intensity by utilizing conventional plastic optical fibers (POFs). In order to check the possibility as a light-receiving sensor, we experimentally confirm that the externally irradiated flash light can be coupled into the fiber core through the surface of POF without any additional treatment. After the incident light is divided in two optical paths toward opposite directions, they have the different attenuation values determined by the propagation distance. Since the optical transmission loss of a POF is constant regardless of the irradiated energy, the intensity ratio for two signals measured at both fiber ends is given as a function of position. The experimental results show that we can successfully trace the event position from this intensity ratio. In addition, it is possible to define the illuminated energy by comparing the absolute value of the intensity measured from one side. According to the experimental results, the proposed sensor has a relatively fine spatial resolution, ±10 cm, despite having a simple structure.
This paper suggests an optical printed circuit board (OPCB) having new optical coupling structures, including a laser-drilled and under-filled structure (LD-UFS) and a vertical waveguide structure (VWS). The suggested OPCB has the features of high-speed data transmission as well as highly efficient optical coupling because it was fabricated with low-dielectric and transparent electrical PCB materials through a PCB compatible process. To evaluate and compare the optical and electrical performances of the suggested OPCB with those of other OPCBs, the various types of OPCBs were fabricated and measured. The optical coupling losses of the LD-UFS and the VWS were measured with excellent results of 9.8 and 7.8 dB, respectively, which are lower than that of the basic structure. The electrical 3-dB bandwidth of the OPCB was also evaluated up to more than 40 GHz.
We propose the noncontact photoacoustic tomography system that reads the acoustic signal by using an optical fiberbased heterodyne interferometer. The surface displacement of a specimen, resulting from the acoustic wave generated by irradiation of a laser pulse and its absorption inside the specimen, is optically measured by the heterodyne interferometer. With the data set of the surface displacement, the photoacoustic image of the specimen is reconstructed by a Fourier transform based reconstruction algorithm. This proposed method is experimentally evaluated by using a phantom sample that contains PET fibers.
Fiber-optic hydrogen sensing technique based on an extrinsic Fabry-Perot interferometer (FPI) composed of a palladium
(Pd)-coated high finesse cavity is proposed and experimentally demonstrated. As the Pd layer absorbs hydrogen gas, the
FPI cavity length is reduced so that we can measure the wavelength shift of its interference spectrum. The sensing
performance of the proposed sensor is presented in terms of spectral response to hydrogen and recovery by nitrogen.
Optical coherence tomography (OCT) has been developed particularly for biomedical and industrial fields owing to the
advantage of in vivo real time optical imaging with a micro-scale high resolution. Depending on specific imaging
purposes, various dedicated OCT systems have been proposed and implemented. We present the recent achievements of OCT systems and their applications such as monitoring of cross-sectional biological specimen, discrimination of living human breast cancer cells, and characterization of wet pad surface in chemical mechanical polishing (CMP) process.
A fiber optic sensor based on the wavelength division multiplexer coated with a palladium (Pd) thin film is designed for
hydrogen gas detection. The sensing mechanism of this sensor is measuring the wavelength shift that is induced by the
evanescent field interaction with the refractive index change of Pd film when it absorbs hydrogen.
An optical interferometric system for the simultaneous measurements of physical thickness and refractive group index is
implemented. The proposed system is based on a spectral-domain optical low coherence interferometry with two sample
probes facing to each other. The two-probe approach enables simultaneous measurements of thickness and group index
of a transparent sample. The average measurement errors were ~0.112 % in the physical thickness and ~0.035 % in the
group index, respectively.
We demonstrate a simple but highly sensitive hydrogen sensor based on palladium-coated long-period fiber grating
(LPG) inscribed in low core index fiber, which induces higher order cladding modes. As palladium layer absorbed 4% of
hydrogen gas, the dual resonant wavelengths of the higher order cladding mode (LP08) are shifted to the opposite
direction. The spectral sensitivity was much higher than those of other fiber-optic palladium-coated hydrogen sensors.
We propose a simple method to self-compensate temperature which can affect the sensitivity of palladium-based
hydrogen gas sensor. When a long-period fiber grating is fabricated in a double cladding fiber, the fundamental core
mode is coupled to the inner cladding mode as well as the outer cladding mode. Since the inner cladding mode is
insensitive to the external contact, it is independent to the thin palladium layer coated out of cladding surface. Thus, the
spectrum corresponding to outer cladding modes reflects the reaction between hydrogen and palladium while that of the
inner cladding mode indicates the ambient temperature only.
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