Showing papers on "Fiber optic sensor published in 1993"
TL;DR: In this paper, a fiber-optic chemical sensor is presented which utilizes surface plasmon resonance excitation, which is fabricated by removing a section of the fiber cladding and symmetrically depositing a thin layer of highly reflecting metal onto the fiber core.
Abstract: A fiber-optic chemical sensor is presented which utilizes surface plasmon resonance excitation The sensing element of the fiber has been fabricated by removing a section of the fiber cladding and symmetrically depositing a thin layer of highly reflecting metal onto the fiber core A white-light source is used to introduce a range of wavelengths into the fiber optic Changes in the sensed parameters (eg, bulk refractive index, film thinkness and film refractive index) are determined by measuring the transmitted spectral-intensity distribution Experimental results of the sensitivity and the dynamic range in the measurement of the refractive indices of aqueous solutions are in agreement with the theoretical model of the sensor
1,145 citations
TL;DR: The use of a fiber Fabry–Perot filter for detecting the wavelength shift of a Fiber Bragg grating sensor or network of sensor elements along a common fiber path is described.
Abstract: The use of a fiber Fabry–Perot filter for detecting the wavelength shift of a fiber Bragg grating sensor or network of sensor elements along a commonfiber path is described. Results obtained by using a system with four sensor elements are presented.
798 citations
TL;DR: This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.
Abstract: The operation of a fiber Bragg grating strain sensor system that uses interferometric determination of strain-induced wavelength shifts and incorporates a reference channel to compensate for random thermal-induced drift in the output is described. This system is shown to be capable of resolving sub-microstrain changes in the quasi-static strain applied to a grating and has a resolution of ~6 x 10(-3) microstrain/ radicalHz at a strain perturbation frequency of 1 Hz.
235 citations
TL;DR: A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor.
Abstract: A new approach for the interrogation of a large number of fiber-optic grating sensors is proposed and demonstrated for a small number of sensors in which signal recovery is achieved by matching a receiving grating to its corresponding sensor. This technique is demonstrated for both quasi-static and periodic measurands, and the resolution achieved for a single sensor–receiving grating pair for quasi-static strain is 4.12 μ∊.
217 citations
28 Jan 1993
TL;DR: The revolutions in the fiber optic telecommunication and optoelectronic industries have enabled the development of fiber optic sensors that offer a series of advantages over conventional electrical sensors as mentioned in this paper, and this development in combination with advances in composite material technology have opened up the new field of fiber-optic smart structures that offers mechanical and structural engineers the possibility of incorporating fiber optic nervous systems into their designs.
Abstract: The revolutions in the fiber optic telecommunication and optoelectronic industries have enabled the development of fiber optic sensors that offer a series of advantages over conventional electrical sensors. This development in combination with advances in composite material technology have opened up the new field of fiber optic smart structures that offers mechanical and structural engineers the possibility of incorporating fiber optic nervous systems into their designs.
208 citations
Patent•
12 Apr 1993TL;DR: In this paper, the authors provide fiber optic sensors, apparatus, methods of optical detection, and methods of sensor manufacture for detection of organic analytes having a fixed polarity, which requires an optical fiber strand; an immobilized polarity sensitive dye; and an immobilised polymeric material which not only contains the polarity-sensitive dye but also absorbs and partitions the organic analyte of interest.
Abstract: The present invention provides fiber optic sensors, apparatus, methods of optical detection, and methods of sensor manufacture for detection of organic analytes having a fixed polarity. The sensor requires an optical fiber strand; an immobilized polarity-sensitive dye; and an immobilized polymeric material which not only contains the polarity-sensitive dye but also absorbs and partitions the organic analyte of interest.
181 citations
TL;DR: In this paper, a tunable erbium doped fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in side-pump configuration is described.
Abstract: The development of a fiber laser sensor system which permits efficient interrogation of Bragg grating sensors is reported. A tunable erbium doped fiber laser which utilizes a broadband mirror and an intracore Bragg grating reflector in side-pump configuration is described. The wavelength of the laser oscillation is determined by the Bragg grating, which is remotely located and used as a strain sensor. This arrangement is used in conjunction with a passive wavelength demodulation system (WDS) to form a self-contained fiber laser strain sensor system, allowing efficient interrogation of the Bragg sensor. This device provides interrupt-immune sensing of static and dynamic strains with a bandwidth of 13.0 kHz. >
170 citations
Patent•
13 Jan 1993TL;DR: In this paper, a unique fiber optic sensor is presented which is able to provide a visual examination of a sample and its surrounding environment concurrent with the ability to conduct chemical sensing and detection of at least one ligand of interest.
Abstract: The present invention provides a unique fiber optic sensor which is able to provide a visual examination of a sample and its surrounding environment concurrent with the ability to conduct chemical sensing and detection of at least one ligand of interest. The present invention also provides apparatus for making precise optical determinations and measurements for the ligand of interest which can be correlated with specific parameter or other ligands for specific applications and purposes.
168 citations
TL;DR: An experimental distributed temperature sensor that uses the temperature dependence of the Brillouin frequency shift and has observed a temperature resolution of 1 degrees C and obtained a spatial resolution of 10 m.
Abstract: We describe an experimental distributed temperature sensor that uses the temperature dependence of the Brillouin frequency shift. When a 22.2-km sensing length is used, we have observed a temperature resolution of 1°C and have obtained a spatial resolution of 10 m.
166 citations
TL;DR: A white-light interferometric extrinsic Fabry-Perot strain sensor that uses a multimode fiber and the design of a thermally autocompensated strain sensor is presented.
Abstract: A white-light interferometric extrinsic Fabry-Perot strain sensor that uses a multimode fiber is demonstrated. The Fabry-Perot cavity length is measured with the help of a Fizeau interferometer. The sensor is described, and some results obtained at this time are given. The strain measurements are absolute and perfectly linear, with a sensitivity of 0.25 micrometers per meter (micro). the design of a thermally autocompensated strain sensor is also presented.
165 citations
TL;DR: In this paper, a unified theory that relates optical phase changes to applied strain and temperature fields in structurally embedded interferometric optical fiber sensors of all types, as applied to Mach-Zehnder, Michelson, intrinsic and extrinsic Fabry-Perot, polarimetric, dual-mode, and Bragg grating sensors, with resistance strain gauge concepts and the theory of elasticity solutions, is theoretically explored.
Abstract: Using the unified theory that relates optical phase changes to applied strain and temperature fields in structurally embedded interferometric optical fiber sensors of all types, as applied to Mach-Zehnder, Michelson, intrinsic and extrinsic Fabry-Perot, polarimetric, dual-mode, and Bragg grating sensors, with resistance strain gauge concepts and the theory of elasticity solutions, the response of optical fiber sensors that are embedded in transversely isotropic composite materials is theoretically explored. The concepts of transverse strain sensitivity and thermal apparent strain are carefully defined for embedded optical fiber sensors, and it is found that errors resulting from these effects completely dominate the desired sensor response for all sensors except the extrinsic Fabry-Perot. Conditions that minimize these errors are presented. The theory of elasticity solutions used in this analysis encompasses six different thermomechanical loading conditions. Comparisons to Buffer and Hocker's model are also presented.
TL;DR: A fiber-optic strain gauge system for use in structural monitoring and smart-structure applications is described, which permits the measurement of both static and dynamic strains with a noise-limited resolution.
Abstract: A fiber-optic strain gauge system for use in structural monitoring and smart-structure applications is described. The strain gauge uses a fiber-optic Bragg grating sensor to measure strain and a passive, wavelength demodulation system to determine the wavelength of the narrow-band, backreflected spectrum from the grating sensor. The fiber-optic strain gauge system permits the measurement of both static and dynamic strains with a noise-limited resolution of 0.44 microstrain/√Hz, a measurement dynamic range of 27.8 dB, and a bandwidth of 250 Hz.
Patent•
27 Sep 1993
TL;DR: A measurement system for fiber sensors includes a broadband light source providing continuous light which is launched into a fiber 20 having a plurality (or string) of Bragg grating sensors 24, 28, 34.
Abstract: A measurement system for fiber sensors includes a broadband light source 11 providing continuous light which is launched into a fiber 20 having a plurality (or string) of Bragg grating sensors 24, 28, 34. Each sensor has a predetermined central reflection wavelength which shifts as a function of applied strain. Reflected light 40 from the sensors 24, 28, 34 are fed to a plurality of optical bandbass filters 50, 64, 78, each having a monotonic region in a passband corresponding to one of the sensors. Each monotonic region transmits the reflected wavelength from a corresponding sensor. Light 52, 66, 80 is passed from the filters 50, 64, 78 to optical detectors 54, 68, 82 each providing an electrical signal having a magnitude related to transmission of the filter at the reflection wavelength of the sensor. Optional demodulators 58, 72, 86 are connected to each of the detectors 54, 68, 82 if the light source 10 is modulated. Such modulation provides noise immunity and allows demultiplexing of several strings of sensors.
TL;DR: In this article, an optical fiber cable that can suppress stimulated Brillouin scattering (SBS) has been developed, which was caused by a sinusoidal fiber strain distribution of + or 0.35%, which was generated in fiber by a strain holding, double-stranded cable.
Abstract: An optical fiber cable that can suppress stimulated Brillouin scattering (SBS) has been developed. Fiber cabling expanded the Brillouin gain bandwidth from 50 MHz to 400 MHz (9 dB). The expansion was caused by a sinusoidal fiber strain distribution of +or-0.35%, which was generated in fiber by a strainholding, double-stranded cable. This work explains the relationship between the cable structure and fiber strain, as well as with the Brillouin gain bandwidth expansion. Fiber loss caused by cabling was studied and found to be small; also, the strained fiber reliability of the cable is assured with the use of carbon-coated fiber. >
Patent•
27 Dec 1993
TL;DR: In this article, an endoscopic light delivery system for delivering light to tissue includes a laser source for generating light, and fiber optics encased in a plastic buffer for conveying the light generated by the laser source.
Abstract: An endoscopic light delivery system for delivering light to tissue includes a laser source for generating light. Fiber optics encased in a plastic buffer are optically coupled to the laser source for conveying the light generated by the laser source. A tip member secured to the fiber optics positions a mirror adjacent to the light delivery end of the fiber optics. The mirror redirects light conveyed by the fiber optics in a direction lateral to the fiber optics. A heat resistant ring encircling the fiber optics near the light delivery end shields the fiber optics from heat to prevent the plastic buffer near the light delivery end from melting. A lateral extension of the tip member spaces the mirror and fiber optics away from tissue. A band with a circumferential groove encircles the light receiving end of the fiber optics. A connector having a bore is capable of receiving the light receiving end of the fiber optics in the bore and locking the band within the bore by engaging the groove with a locking device.
TL;DR: A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented.
Abstract: A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented. The hollow-core fiber is specifically manufactured to have an outer diameter that is equal to the outer diameter of the single-mode lead fibers, thereby combining the best qualities of existing intrinsic and extrinsic Fabry–Perot sensors. A dynamic strain resolution of ∼22n∊/Hz at frequencies of >5 Hz with a sensor gauge length of 137 μm is demonstrated.
TL;DR: The photoinduced periodic refractive-index perturbations have been observed directly with an optical microscope and are shown to have the same period as the phase mask and to be highly localized on one side, the irradiated side of the fiber core-cladding boundary.
Abstract: Optical fiber Bragg reflectors have been written by irradiating the fiber from the side through a phase mask with a single pulse of high-power 249-nm excimer-laser light. Efficient tapping of light to the radiation modes has been achieved for light at wavelengths shorter than the Bragg wavelength. The photoinduced periodic refractive-index perturbations have been observed directly with an optical microscope and are shown to have the same period as the phase mask and to be highly localized on one side, the irradiated side of the fiber core–cladding boundary.
TL;DR: In this article, a combination taper fiber was proposed to provide an even signal return along the length of the fiber's length, where the fiber tapers down to the V-number matching radius over 1 cm, maintaining total internal reflection, then continues to taper gently along the following 9 cm to near the distal end.
TL;DR: It is shown that the sensitivity of displacement can be in the submicrometer range and the dynamic range of the displacement sensing are quantitatively analyzed.
Abstract: A multimode fiber sensor using the intensity inner product of speckle fields is presented. The sensitivity and the dynamic range of the displacement sensing are quantitatively analyzed. We show that the sensitivity of displacement can be in the submicrometer range. Experimental performances show that the results are consistent with the calculated results.
TL;DR: In this article, the authors present a review of distributed optical fiber sensors, where measurements may be taken along the length of a continuous section of optical fiber and thus the information can be obtained from a single instrument and hence the cost per sensing point can be more acceptable.
Abstract: This review paper covers the field of distributed optical fiber sensors, where measurements may be taken along the length of a continuous section of optical fiber. Such a feature greatly increases the information that can be obtained from a single instrument and hence the cost per sensing point can be more acceptable. The review does not attempt to cover all methods, but gives a selection of some of the more interesting theoretical concepts, describes the current status of research, and indicates where optical sensing methods are being applied in commercial instruments.
TL;DR: An active, single-frequency, polarimetric, Bragg-grating fiber-laser strain sensor that yields a single beat frequency that varied at a rate of -4.1 MHz/mstrain for linear strain and -0.37 MHz/(deg/cm) for torsional strain is reported.
Abstract: We report the operation of an active, single-frequency, polarimetric, Bragg-grating fiber-laser strain sensor. The short Bragg-grating fiber-laser design limited lasing to two orthogonal polarization modes that, when optically mixed, yielded a single beat frequency that varied at a rate of -4.1 MHz/mstrain for linear strain and -0.37 MHz/(deg/cm) for torsional strain.
TL;DR: In this article, a new method, based on a renewable-reagent fiber optic sensor, for measuring the partial pressure of CO[sub 2] (pCO[sub2]) in seawater is presented.
Abstract: A new method, based on a renewable-reagent fiber optic sensor, for measuring the partial pressure of CO[sub 2] (pCO[sub 2]) in seawater is presented. The sensor operates by measuring the light intensity at the absorbing wavelengths of a colorimetric acid-base indicator which is continuously delivered to the fiber tips through capillary tubing. The light intensity is modulated by pH changes that occur when CO[sub 2] diffuses across a gas-permeable membrane. The sensor operates both in a diffusion-dependent steady state and equilibrium regime depending upon the indicator flow rate. At low flow rates, an equilibrium model can be used to predict the response of the sensor. The results indicate that the sensor operates within the steady-state regime at flow rates higher than approximately 0.2 [mu]L/min. The optimal precision is [+-]0.8 [mu]atm from 300--550 [mu]atm of CO[sub 2], calculated from the response sensitivity and 3[times] the root mean square noise. Response times (100%) range from 11 to 28 min and depend upon the indicator flow rate. Sensitivity to temperature and sample hydrodynamics is also discussed. The sensor performance was tested on a research cruise, and these results are compared to the underway pCO[sub 2] measured simultaneously by an infrared CO[sub 2] analyzer.more » 18 refs., 8 figs., 2 tabs.« less
30 Dec 1993
TL;DR: In this article, the detection of wavelength shifts of fiber Bragg sensors based on the use of a tunable bandpass filter, interferometric detection, and active laser configurations is described.
Abstract: Techniques for the detection of wavelength shifts of fiber Bragg grating sensors based on the use of a tunable bandpass filter, interferometric detection, and active laser configurations are described. The methods used to multiplex several sensors along a single fiber using these approaches are also discussed, and results presented.
TL;DR: In this article, a fiber-optic sensing system for the continuous in situ analysis of chlorinated hydrocarbons (CHCs) in water is described, which takes advantage of the selectivity and sensitivity of fiber evanescent wave spectroscopy (FEWS) and polycrystalline silver halide fibers.
Abstract: In this work the development and validation of a new MIR fiber-optic physicochemical sensor system for the continuous in situ analysis of chlorinated hydrocarbons (CHCs) in water is described. This study took advantage of the selectivity and sensitivity of fiber evanescent wave spectroscopy (FEWS) and the recent development of polycrystalline silver halide fibers. Since these fibers are transparent up to 20 μm, it was possible for the first time to develop a fiber-optic sensing system for CHCs, which have their strongest absorption bands > 10 μm. The silver halide fibers were coated with low-density polyethylene (LDPE) to enrich the CHC within the evanescent wave and to exclude the IR absorbing water from the measurement. For the quantitative in situ FEWS measurements, the coated silver halide fibers were coupled to a Fourier transform infrared (FT-IR) spectrometer using an off-axis parabolic mirror and a fiber-detector coupling system. This setup enabled the simultaneous in situ detection of the most common chlorinated hydrocarbons in concentrations between 1 to 50 mg/L in water by employing a fiber sensing part only 10 cm in length. A comparative analysis of waste water samples under participation of two experienced head space-gas chromatography (HSGC) laboratories showed good agreement of this continuous sensor system with the established standard techniques. The resulting working curve for tetrachloroethylene showed a correlation coefficient of r2 = 0.968 and a relative standard deviation of 17% in the range from 1 to 10 ppm.
TL;DR: In this article, a tunable diode laser (TDL) source, on a polymer-coated AgClBr infrared transmitting fiber, and on a mercury cadmium telluride detector was used for sensing low levels of chlorinated hydrocarbons in water.
Abstract: A novel fiber optic evanescent wave spectroscopy (FEWS) system is based on a tunable diode laser (TDL) source, on a polymer‐coated AgClBr infrared transmitting fiber, and on a mercury cadmium telluride detector. This system was used for sensing low levels of chlorinated hydrocarbons in water. The detection limit was 100 μg/l (100 ppb), which is an improvement by a factor of 50 in comparison to a similar system that is based on a Fourier transform infrared spectrometer, and the measurement time was reduced by a factor of 3. The TDL‐FEWS system shows significant potential for in situ monitoring of ground water.
Proceedings Article•
02 May 1993TL;DR: In this article, a polymer optical fiber· amplifiers (POPA) of graded-index (GI) type were successfully prepared for the first time and the gain of 27 dB was observed at 591 ran signal wavelength in the GI POFA with a 0.5 m length.
Abstract: Polymer optical fiber· amplifiers (POPA) of graded-index (GI) type were successfully prepared for the first time. The gain of 27 dB was observed at 591 ran signal wavelength in the GI POFA with a 0.5 m length.
TL;DR: In this article, the ion-carrier monomer cobalt(II) tetrakis (p-hydroxyphenyl)porphyrin, [Co(p-OH)TPP] was electrodeposited on glassy carbon disk electrodes.
Abstract: Potentiometric and fiber optic sensors based on polymer films were prepared by electrodeposition of the ion-carrier monomer cobalt(II) tetrakis (p-hydroxyphenyl)porphyrin, [Co(p-OH)TPP]. Fiber optic sensors were developed by electropolymerization of the porphyrin on the surface of indium(tin) oxide glass slides. The optical sensors were highly selective to pH, presenting minimal interferences from anions. They had a linear response from pH 8 to 12. Potentiometric sensors were prepared from porphyrin films electrodeposited on glassy-carbon disk electrodes. These electrodes gave a near-Nernstian response to pH from pH 2 to 12 with minimal interferences
TL;DR: In this article, a model for embedded intrinsic and extrinsic Fabry-Perot fiber optic sensors was developed for reflected light intensity analysis, which relates the strains and the temperature changes in the material surrounding the sensor to the reflected light.
Abstract: A model was developed for embedded intrinsic and extrinsic Fabry-Perot fiber optic sensors. This model relates the strains and the temperature changes in the material surrounding the sensor to the reflected light intensity. The model consists of three parts. Submodel I relates the temperature and the strains in the material to the temperature and the strains inside the sensor. Submodel 2 relates the temperature and the strains inside the sensor to the change in sensor length and to the changes in the optical properties of the sensor. Submodel 3 relates the changes in sensor length and optical properties to the changes in the intensity of the reflected light.On the basis of the model, a computer code SENSOR1 was written which can be used to calculate the reflected light intensity for specified strains and temperature changes inside the material. The model and the code were verified by measuring changes in the light in tensity of an intrinsic Fabry-Perot sensor embedded in a graphite-epoxy composite plate s...
TL;DR: In this article, a sensor based on the optical excitation and interrogation of a surface plasmon on the tip of a single-mode optical fiber is described, which is based on analysis of the state of polarization of the beam reflected in the presence of an excited plasmor.
Abstract: A sensor based on the optical excitation and interrogation of a surface plasmon on the tip of a single-mode optical fiber is described. The new interrogation technique is based on the analysis of the state of polarization of the beam reflected in the presence of an excited plasmon. Preliminary experiments confirm the theoretical analysis and point out the feasibility of a chemical sensor based on the new technique.
Patent•
09 Mar 1993
TL;DR: In this paper, an optical coupling device for coupling light into a selected output fiber via a reflector is presented. But the input fiber and all the output fibers are in fixed position relative to each other.
Abstract: An optical coupling device for coupling light into a selected output fiber. The input fiber is optically aligned with one of a plurality of output fibers via a reflector. By rotating a reflector about an axis, the input light beam can be reflected to a selected output fiber. The input fiber and all the output fibers are in fixed position relative to each other.