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PubMedDate not supplied

[The possibilities of using fiber optic luminescent light sources in medical-biological studies].

The use of optical fibers with luminescent spectrum-displacing admixtures inserted into their core enables the prototherapeutic devices to be designed. The paper provides the principle for designing optofiber luminescent light sources. Experiments with laboratory animals and donor blood have indicated that incoherent homogeneous light may produce effects in regenerating damaged tissue surfaces.

Equipment Design↗
PubMed2004

Finite-element modal analysis of large-core multimode optical fibers.

Plastic optical fibers that are a typical large-core multimode optical fiber support a great number of modes compared with conventional silica-glass multimode optical fibers. So far the WKB method hasbeen used for most of the modal analyses of these fibers because of a great number of guided modes. We describe the accurate eigenmodal analysis of large-core multimode optical fibers with the finite-element method (FEM) and compute the propagation constants of all LP modes. In addition, the FEM has a strong advantage for arbitrary core profiles whereas the WKB method is not suitable fornonmonotonic profiles. To demonstrate the advantage, we apply the FEM to the fiber having sinusoidal fluctuations.

Journal Article↗
PubMed2005

Optical-fiber-to-waveguide coupling using carbon-dioxide-laser-induced long-period fiber gratings.

Optical fibers are expected to play a role in chip-level and board-level optical interconnects because of limitations on the bandwidth and level of integration of electrical interconnects. Therefore, methods are needed to couple optical fibers directly to waveguides on chips and on boards. We demonstrate optical-fiber-to-waveguide coupling using carbon-dioxide laser-induced long-period fiber gratings (LPFGs). Such gratings can be written in standard fiber and offer wavelength multiplexing-demultiplexing performance. The coupler fabrication process and the characterization apparatus are presented. The operation and the wavelength response of a LPFG-based optical-fiber-to-waveguide directional coupler are demonstrated.

Journal Article↗
PubMed2000

Fiber optic monitoring of carbamate pesticides using porous glass with covalently bound chlorophenol red.

An optical fiber biosensor for the determination of the pesticides propoxur (Baygon) and carbaryl, two of the most commonly used carbamate insecticides in vegetable crops, is described. A pH indicator, chlorophenol red, is used as optical transducer of the inhibition of the enzyme acetylcholinesterase by the analytes. The biorecognition element is covalently immobilized onto controlled pore glass beads (CPG) and packed in a thermostatized bioreactor connected to a flow-through cell that contains CPG-immobilized chlorophenol red placed at the common end of a bifurcated fiber optic bundle. In the presence of a constant acetylcholine concentration, the colour of the pH sensitive layer changes and the measured reflectance signal can be related to the carbamate concentration in the sample solution. The performance of the biosensor has been optimized using a flow injection system. The linear dynamic range for the determination of carbaryl and propoxur spans from 0.8 to 3.0 mg l(-1) and from 0.03 to 0.50 mg l(-1), respectively. The detection limit (3 s) of the biosensor for propoxur (0.4 ng) is lower than that measured for carbaryl (25 ng). Reproducibility, stability and interference studies of the optical device are reported. The biosensor has been applied to the determination of propoxur in spiked vegetables (onion and lettuce) using ultrasound extraction, achieving recovery values between 93 and 95% for onion samples at the different concentration levels assayed.

Acetylcholine↗
PubMed1993

Surface refractive index of the eye lens determined with an optic fiber sensor.

The use of a fiber-optic sensor for measurement of the refractive index on the surface of eye lenses is described. The technique makes use of the fact that the amount of light reflected at the interface of two media (Fresnel reflectance) depends on the refractive-index difference between them. The sample is probed with a single-mode fiber, and the refractive index is calculated from the proportion of light reflected at the probe-sample interface.

Animals↗
PubMed1987

Transscleral iridotomy using a neodymium: YAG laser operated both with standard equipment and an optical fiber system--a preliminary report: Part II--Light and electron microscopic findings.

We report the morphology of transscleral iridotomies applied to human cadaver eyes using a free-running Nd:YAG laser (pulse duration: 20 ms, pulse energy: 1.5-6 J) with and without a fiber optic system. The pigment epithelium, which represents the barrier to the aqueous humor for passing through the iris, is damaged and blasted away over great areas. The mesothelial layer at the anterior surface of the iris is also broken up by the laser beam. Using low pulse energies, the iris stroma is only partially damaged. The destruction of the iris is caused by generation of heat due to absorption of radiated energy.

Fiber Optic Technology↗
PubMed2000

Determination of carbaryl and biphenyl through optical fiber ccd-assisted flash lamp induced room temperature phosphorescence.

A fiber-optic sensor for solid surface room temperature phosphorescence of carbaryl and biphenyl pesticides was designed. A xenon flash lamp was used as excitation source, and a cooled two-dimensional charge coupled device was employed as the detector. Room temperature phosphorescence spectra of carbaryl and biphenyl were recorded by an imaging spectrograph. Limits of detection at the picogram/spot level were obtained for the investigated compounds. The linear dynamic range extended over three orders of magnitude. The standard addition method and the internal standard method were employed to analyze the studied compounds in mixtures. The feasibility of the SS-RTP apparatus developed was evaluated by the identification of carbaryl in a real sample.

Biphenyl Compounds↗
PubMed2006

Experimental retinal ablation using a fourth-harmonic 266 nm laser coupled with an optical fiber probe.

PURPOSE: To explore the ablation potential of 266 nm laser pulses, with an intact porcine retina preparation. METHODS: Segments of porcine eyes were used in an in vitro preparation in which localized areas of intact retina and choroid could be exposed to 266 nm laser irradiation. The segments of ocular tissue were bathed in fluid, to mimic the intraocular environment. Contact between the probe and the retinal surface was established before the first laser pulse. Single or multiple pulses (5-7 ns duration) at fluence levels of 0.4 to 1.2 J/cm2 were delivered via a tapered fiber optic probe with a tip size of approximately 110 microm. The retinal tissue was then fixed and sectioned for histologic examination. The ablation depth and extent of damage were measured and related to fluence level and the number of pulses applied. RESULTS: Ablation of the inner retina was achieved by single pulses at fluence levels of 0.6 J/cm2 and higher. The depth of retinal ablation was highly dependent on fluence for lesions generated with a single pulse but less so for multiple pulses (3-10), particularly at lower fluence levels. Higher numbers of pulses (50-100) did not increase ablation depth in a predictable manner. CONCLUSIONS: Pulsed laser (266 nm) irradiation at low pulse counts and high fluence levels is a possible alternative for localized retinal ablation with minimal collateral damage in a fluid environment.

Animals↗
PubMed2006

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme.

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods.

Journal Article↗
PubMed2003

Fiber optic probes for biomedical optical spectroscopy.

Fiber optic probes are a key element for biomedical spectroscopic sensing. We review the use of fiber optic probes for optical spectroscopy, focusing on applications in turbid media, such as tissue. The design of probes for reflectance, polarized reflectance, fluorescence, and Raman spectroscopy is illustrated. We cover universal design principles as well as technologies for beam deflecting and reshaping.

Equipment Design↗
PubMed2005

Refractive-index profiling of azimuthally asymmetric optical fibers by microinterferometric optical phase tomography.

Accurate nondestructive refractive-index profiling is needed in the modeling, design, and manufacturing of optical fibers and fiber devices. Most profile measurement techniques cannot correctly characterize fibers with small or irregular refractive-index variations over their cross sections. Microinterferometric optical phase tomography (MIOPT) is a technique that allows measurement of fiber refractive-index profiles exhibiting such variations. We present the first demonstration, to our knowledge, of MIOPT. The profile of a polarization-maintaining fiber is measured by MIOPT and shown to be in agreement with (destructive) fiber end-face measurements. MIOPT is also applied to the limiting case of a symmetric single-mode fiber.

Journal Article↗
PubMed2006

In-line fiber optic structures for environmental sensing applications.

Fiber optic sensors based on the interaction of surface plasmons or evanescent waves with the surrounding environment are usually obtained by tapering an optical fiber, which significantly weakens the structure, or by use of just the end of the optical fiber. A fiber optic structure that maintains the structural integrity of the optical fiber with a long environmental interaction length is presented. Graded-index optical fiber elements are used as lenses, and a coreless optical fiber acts as the environmental interaction area. These elements are fused by an optical fiber splicer and result in a continuous fiber optic sensing system.

Journal Article↗
PubMed1997

Effectiveness of protein A for antibody immobilization for a fiber optic biosensor.

The fiber optic biosensor performs fluoroimmunoassays at the surface of multimode optical fibers. The effectiveness of protein A, an immunoglobulin binding protein, for antibody immobilization on the surface of these fiber probes has been investigated. No difference was observed in the binding of fluorescently-labeled goat-IgG by rabbit anti-goat IgG regardless of whether the capture antibody was bound to the probe surface via protein A or covalently attached. However, in a sandwich immunoassay for the F1 antigen of Yersinia pestis, probes with rabbit anti-plague IgG bound to the surface via protein A generated twice the signal as probes with the antibody covalently attached. Assay regeneration was also examined with protein A probes since antibody-antigen complexes have been successfully eluted from protein A under low pH conditions. Protein A probes coated with rabbit anti-goat IgG obtained nearly identical signal levels at 500 and 5000 ng/ml of Cy5.5 goat IgG five consecutive times following regeneration with glycine-HCl, 2% acetic acid, pH 2.5.

Antigen-Antibody Reactions↗
PubMed2006

High-speed fiber-optic spectrometer for signal demodulation of inteferometric fiber-optic sensors.

We demonstrated a spectrometer that is capable of acquiring the spectra from interferometric fiber-optic sensors at high speed. The high spectrum acquisition rate is enabled by transforming the spectral information from frequency domain to time domain using a dispersive element and high-speed data acquisition devices. Preliminary results show that the prototype system can record 10,000 frames of spectra per second and achieve a spectrum measurement resolution of 15 nm. Better performance could be realized by using a Raman amplifier and by optimizing the parameters of the system and data processing methods.

Journal Article↗
PubMed2003

Optical bio-sniffer for ethanol vapor using an oxygen-sensitive optical fiber.

An optical bio-sniffer for ethanol was constructed by immobilizing alcohol oxidase (AOD) onto a tip of a fiber optic oxygen sensor with a tube-ring, using an oxygen sensitive ruthenium organic complex (excitation, 470 nm; fluorescent, 600 nm). A reaction unit for circulating buffer solution was applied to the tip of the device. After the experiment in the liquid phase, the sniffer-device was applied for gas analysis using a gas flow measurement system with a gas generator. The optical device was applied to detect the oxygen consumption induced by AOD enzymatic reaction with alcohol application. The sensor in the liquid phase was used to measure ethanol solution from 0.50 to 9.09 mmol/l. Then, the bio-sniffer was calibrated against ethanol vapor from 0.71 to 51.49 ppm with good gas-selectivity based on the AOD substrate specificity. The bio-sniffer with the reaction unit was also used to monitor the concentration change of gaseous ethanol by rinsing and cleaning the fiber tip and the enzyme membrane with buffer solution.

Alcohol Oxidoreductases↗
PubMed1991

Excitation and detection of action potential-induced fluorescence changes through a single monomode optical fiber.

An optical probe capable of detecting intracellular potential changes in individual cells, in vitro, which has the potential for in vivo applications, has been developed. A single-mode optical fiber directs laser light onto cells stained with the voltage-sensitive fluorescent dye, WW781 and also returns part of the resulting fluorescence to a detection system. Frog cardiac cells in vitro were used in these initial experiments. The fractional change in fluorescent intensity of 10(-3) for a 50 mV shift in transmembrane potential obtained from a heart immobilized in zero calcium Ringer's solution is comparable to that reported for other optical methods. For hearts in normal calcium Ringer's solutions, very large reproducible motion related artifacts were detected.

Animals↗
PubMed2004

Comment on "Optical-fiber-based Mueller optical coherence tomography".

We comment on the recent Letter by Jiao et al. [Opt. Lett. 28, 1206 (2003)] in which a polarization-sensitive optical coherence tomography system was presented. Interrogating a sample with two orthogonal incident polarization states cannot always recover birefringence correctly. A previously presented fiber-based polarization-sensitive system was inaccurately characterized, and its method of eliminating the polarization distortion caused by single-mode optical fiber was presented earlier by Saxer et al. [Opt. Lett. 25, 1355 (2000)].

Algorithms↗
PubMed2003

Fiber-optic delivery of high-peak-power Q-switched laser pulses for in-cylinder flow measurement.

A bundle of optical fibers was constructed to deliver Q-switched frequency-doubled Nd:YAG laser pulses for the purpose of particle image velocimetry. Data loss that is due to fiber speckle was reduced by ensuring that each fiber was different in length by more than the coherence length of the laser being delivered. Hence, their speckle patterns will overlap but not interfere, producing more even illumination that is shown to reduce data loss. A custom-made diffractive optical element and careful endface preparation help to reduce damage to the fibers by the required high peak powers. With this method, pulse energies in excess of 25 mJ were delivered for a series of experimental trials within the cylinder head of an optically accessed internal combustion engine. Results from these trials are presented along with a comparison of measurements generated by conventionally delivered beams.

Journal Article↗