[Show abstract][Hide abstract] ABSTRACT: This study proposed and demonstrated a fiber Bragg grating sensor for simultaneous detection of the temperature and refractive index of a liquid. The fiber Bragg grating is composed of three index layers: an inner core, an outer core, and a cladding. The cladding was etched for evanescent wave coupling between the outer core mode and an external liquid. The Bragg wavelength of the inner core mode is used for obtaining temperature data, while the refractive index for the liquid was determined by using the difference between the Bragg wavelength of the inner core mode and that of outer core mode.
Fiber and Integrated Optics 01/2013; 32(3). · 0.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High performance plastic optical fiber (POF) star couplers are implemented based on fusing and combining technology. A set of cladding-removed POFs are fused into a solid body by heating and pressing them together to form the transition region between the input and output sides. The operation principle of the proposed star coupler is explained based on ray optics. To demonstrate the performance of the device, , and type POF couplers were fabricated and characterized. Performances of the POF star couplers were evaluated in terms of the flatness of the coupling ratios and excess losses.
[Show abstract][Hide abstract] ABSTRACT: We propose and demonstrate a low-loss 1× 2 plastic optical fiber
(POF) coupler incorporating a tapered polymeric waveguide and two POF
transition regions. The design concept for acquiring a low optical loss
is presented. The measured excess losses of coupler for the optical
splitting and optical combining were 0.7 and 1.4 dB, respectively.
Japanese Journal of Applied Physics 09/2012; 51(9):2502-. · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To compensate for the temperature dependency of a standard FBG, a cladding-etched FBG immersed with a liquid mixture having a negative thermo-optic coefficient is presented, and its characteristics are investigated. The Bragg wavelength of the cladding-etched FBG is shifted counter to the direction of the Bragg wavelength shift of a conventional FBG according to the mixing ratio of glycerin to water; thus, the temperature-dependent Bragg wavelength shift was almost compensated by using a liquid mixture of water (50%) and glycerin (50%) having the negative thermo-optic coefficient of -5 × 10(-4) °C(-1).
[Show abstract][Hide abstract] ABSTRACT: High performance plastic optical fiber (POF) N × N star couplers are implemented based on fusing and combining technology. A set of cladding-removed POFs are fused into a solid body by heating and pressing them together to form the transition region between the input and output sides. The operation principle of the proposed star coupler is explained based on ray optics. 2×2, 4×4, 6×6 type POF couplers were fabricated and characterized.
Opto-Electronics and Communications Conference (OECC), 2012 17th; 01/2012
[Show abstract][Hide abstract] ABSTRACT: To measure a level of a flammable liquid, optical sensing methods have been reported more effective than other methods based on mechanical and electrical methods. This paper reports a new method that uses a collimator and a pipe to measure the liquid level. The presented liquid-level sensor consists of a gradient-index lens (GRIN lens), a metal pipe with small holes, and a floating buoy as a mirror. The liquid in the tank flows into the pipe through small holes and the floating buoy coated with aluminum will float over the liquid. The light collimated by a GRIN lens will be reflected at the floating buoy, which operates like mirror. The light reflected from the mirror is refocused through the GRIN lens and is varied as a function of the liquid distance. It is a simple design using a pipe to collect easily the. The experimental result was obtained using a pipe with the height of 2 m and width of 10 mm. The power loss was decreased with the ratio of 30 dB/m. This low-cost configuration easily collects the reflected light from the liquid surface without complicated aligning.
[Show abstract][Hide abstract] ABSTRACT: We propose a novel method for fabricating fused fiber couplers whose transmission spectrum and sensitivity can be controlled in the wet-etching process. A wide tuning of the transmission spectrum during wet etching was observed experimentally. It was demonstrated that etched fused fiber couplers with reduced waist size had high sensitivity to the refractive index of an external medium. The sensitivity achieved by the present fiber coupler sensor was a 1125 nm/refractive index unit.
[Show abstract][Hide abstract] ABSTRACT: This study examined the bending effects of a thermally-expanded-core (TEC) fiber for an application as an in-line variable optical attenuator (VOA). The effects of the structural parameters of the TEC fiber and the refractive index of the external medium surrounding the clad layer on the bending loss are experimentally investigated and the device structure and fabrication process of the VOA are presented. The desired attenuation is obtained by mechanical bending of the TEC fiber. A wide range of attenuation exceeding 55 dB and low excess loss of
Japanese Journal of Applied Physics 01/2011; 50. · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.
Fiber and Integrated Optics 01/2011; 30(4):265-277. · 0.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reports a fiber-optic hydrogen sensor based on a side-polished single-mode fiber coated with a palladium (Pd) thin film whose optical characteristics change as it absorbs hydrogen. The optical transmission loss of the sensor depends on the hydrogen gas concentration through the complex electric permittivity of the Pd film. An optimal design for the sensor has been pursued to obtain both high sensitivity and short response time. When exposed to 4% hydrogen gas, the optimal change output power obtained in this experiment was 1.2 dB (32%) with a rise time of 100 s.
[Show abstract][Hide abstract] ABSTRACT: This paper presents the work of developed sensor system for indoor map building. One of the objectives of this work is to develop a low-cost product. Most robots are equipped with obstacle detectors that operate using ultrasound. However, ultrasonic sensor has major problems: the uncertainty information of sensor, false readings caused by specular reflection and multi path effect. In order to resolve these problems, we developed a range finder sensor module which consists of low cost photo PSD (position sensitive detector) sensors. PSD sensor is cost effective and light weighting but its signal has many noises. We propose an effective filter to remove these noises. The map building system consists of navigation module and map building module based on developed PSD sensor module. In this paper, we represent a cost effective map building system using developed PSD sensor controller. We proved this system's validity through field test
SICE-ICASE, 2006. International Joint Conference; 11/2006
[Show abstract][Hide abstract] ABSTRACT: A fiber-optic liquid refractometer based on fiber-to-planar waveguide coupler is proposed and demonstrated. The liquid plays a role of highly multimode planar waveguide (PWG), which is evanescently coupled to a side-polished single mode fiber. A simple method, which acquire the refractive index (RI) of a liquid using two adjacent resonance wavelengths of the coupler, is presented. Furthermore, it is experimentally shown that the measurement range of RI can be expanded by series connection of two different fiber-to-PWG couplers. The resolution of the proposed and fabricated refractometer is of the order of 10−5 to 10−4.
[Show abstract][Hide abstract] ABSTRACT: Characteristics of the side-polished thermally expanded core (TEC) fiber have been investigated theoretically and experimentally. The effect of core expanding on the transmission of the side-polished TEC fiber is predicted theoretically and demonstrated experimentally. The side-polished TEC fiber covered with an external medium whose chromatic dispersion is much different from the fiber materials, is applied to a band-edge filter with a high cut-off. The relationship between the expanded core diameter and the performance of the band-edge filter was measured and discussed.
[Show abstract][Hide abstract] ABSTRACT: We present tunable mechanically formed long-period fiber gratings whose resonance peaks are shifted by the thermo-optic effect of a medium surrounding the fiber cladding. A novel grating formation method and tuning principles that use periodically arrayed metal wire are described. The performance as an active gain equalizer of an erbium-doped fiber amplifier is also reported.
[Show abstract][Hide abstract] ABSTRACT: A new formula for a catadioptric panoramic lens with an equidistance projection scheme has been derived. The fabricated lens has a field of view that is wider than that of any previously reported panoramic lens, and the nonimaged region near the back of the camera has a constant volume with zero angular extension.
[Show abstract][Hide abstract] ABSTRACT: A fiber-to-planar waveguide coupler has been investigated theoretically and experimentally as a sensor to measure the optical properties of a thin metal film. A method to get optical constants of the metal films is presented and its validity is demonstrated experimentally. Optical characteristics of the device are analyzed employing the normal-mode theory. The device reveals that the resonance sharpness as well as resonant wavelength are very sensitive to the thickness and optical constant of the metal film deposited on the planar waveguide (PWG). The couplers incorporating low loss metal claddings such as Ag and Au exhibited a strong selectivity and small throughput loss (
Sensors and Actuators A-physical - SENSOR ACTUATOR A-PHYS. 01/2005; 117(1):82-87.
[Show abstract][Hide abstract] ABSTRACT: A fiber-optic displacement sensor based on a side-polished single-mode (SM) fiber in contact with a tapered planar waveguide (PWG) is investigated theoretically and experimentally. The thickness variation of the tapered PWG in the side-polished region leads to a shift in the resonance wavelength, and the sensor revealed a highly linear relation between the variation of the resonance wavelength and the displacement of the tapered PWG. The design and fabrication technique are presented, and the spectral and polarization characteristics measured and explained.