Richard O. Claus

Quadrature phase-shifted, extrinsic Fabry-Perot optical fiber sensors

We demonstrate the operation of a quadrature phase-shifted extrinsic Fabry-Perot fiber-optic sensor for the detection of the amplitude and the relative polarity of dynamically varying strain. Two laterally displaced single-mode fibers inserted within a hollow silica tube form the 90 degrees phase-shifted sensing system. A multimode fiber, placed in the tube facing the two fibers, acts as a reflector, thereby creating an air gap that acts as a Fabry-Perot cavity. A theoretical description of the sensor is given, and its operation as a dynamically varying strain sensor is described. Strain sensitivities of 5.54 degrees phase shift/microstrain cm(-1) are obtained.

Effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility.

Polymeric biomaterials have extensively been used in medicinal applications. However, factors that determine their biocompatibility are still not very clear. This article reviews various effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility, including protein adsorption, cell adhesion, cytotoxicity, blood compatibility, and tissue compatibility. Understanding these aspects of biocompatibility is important to the improvement of the biocompatibility of existing polymers and the design of new biocompatible polymers.

Polarization-independent all-fiber wavelength-division multiplexer based on a Sagnac interferometer

An all-fiber wavelength-division multiplexer (WDM) based on the nonreciprocity of the birefringence to the polarization states is proposed. The transfer function of a Sagnac interferometer is wavelength dependent if the loop birefringence of the interferometer consists of both circular and linear parts. Theoretical analysis shows that the output characteristics of this WDM are similar to those of a fiber taper-based device. Both the bandwidth and the peak wavelength of the new WDM can be tuned by changing the loop birefringence. Experimental prototypes exhibit a channel isolation greater than 25 dB with peak passband insertion loss of less than 1 dB.

Simultaneous strain and temperature measurement with long-period gratings

The differential modulation of the attenuation bands in a long-period grating is used for simultaneous sensing of axial strain and temperature. A grating fabricated in a conventional optical fiber is demonstrated for concurrent measurements of strain over a range of 2100 micro? and temperature over a range of 125 degrees C, with maximum errors of 58 micro? and 1 degrees C, respectively.

OPTICAL FIBER HUMIDITY SENSOR USING A NANO FABRY-PEROT CAVITY FORMED BY THE IONIC SELF-ASSEMBLY METHOD

Abstract The ionic self-assembly monolayer process was utilized to fabricate a novel optical fiber humidity sensor based on a nano interferometric cavity. A wide operation range, from 11.3% to 100% relative humidity with a maximum variation of 4.77 dB, was experimentally demonstrated. Due to the short length of the interferometric cavity, less than 400 nm, an LED was used as the light source instead of a laser. The fast response time of this humidity sensor, less than 1.5 s, makes it possible to monitor human breathing.

Layer-by-layer ionic self-assembly of Au colloids into multilayer thin-films with bulk metal conductivity

Abstract Colloidal Au nanoparticles, each encapsulated by polyelectrolytes, have been self-assembled into multilayer films in a layer-by-layer fashion. Atomic force microscopy (AFM) demonstrates that close-packed, three-dimensional arrays with uniform roughness have been achieved. Organic interconnects (alternating cationic and anionic monolayers) covalently and electrostatically linked adjacent metal nanoparticles and formed uniform tunnel junctions. Electrical conductance measurements reveal that a resistivity of 5×10−6 Ω cm for 15 layers of 5 nm Au colloid films, the same order of magnitude of that of bulk gold metals, has been achieved for the first time.

Elliptical-core two mode optical-fiber sensor implementation methods

Experimental methods for the practical implementation of few-mode elliptical-core sensors are described. Techniques for desensitizing the lead-in and lead-out fibers are discussed, and results of a vibration sensor embedded in a graphite-epoxy composite are presented. A scheme using a single-mode elliptical-core fiber as the lead-in fiber and an offset circular-core single-mode fiber as the lead-out fiber is successfully implemented. Detection techniques for few-mode fiber sensors are reviewed, and a novel fringe-counting method to unambiguously detect the amplitude and direction of dynamic strain is reported. >

Fiber-optic dual-technique sensor for simultaneous measurement of strain and temperature

Polarimetric and two-mode differential interferometric schemes incorporated in an elliptical-core fiber are able to resolve strain and temperature simultaneously with resolutions of 10 /spl mu/m/m and 5/spl deg/C, respectively. A technique, based on the evaluation of the condition number of a matrix, is shown to be useful in evaluating comparative merits of multiparameter sensing schemes. The determinant of the beat length matrix is expressed in terms of mode propagation constants, and a method for designing specialized fibers suitable for simultaneous measurement of strain and temperature is proposed. Experimental results for four fibers are presented and cross-sensitivity issues are discussed. >

Temperature-insensitive and strain-insensitive long-period grating sensors for smart structures

We demonstrate that temperature- and strain-insensitive long-period gratings can be fabricated in conventional optical fibers. The former is employed to measure strain with resolution of 20 µ? under thermal fluctuations in the surroundings, while the latter is used to detect temperature variations as small as 0.8°C in the presence of axial strain.

The single-fibre pull-out test. 1: Review and interpretation

Abstract For the first time, the load versus extension trace generated by the single-fibre pull-out test is thoroughly interpreted and mathematically modelled. The single-fibre pull-out test is employed experimentally to model the failure of fibre-reinforced composite materials. The interpretation of this model, however, varies between laboratories. In this paper, the test methodologies and the experimental and mathematical interpretations of various scientists are presented and discussed, as is some preliminary work employing optical fibres embedded in various neat resins. Also, a more complete description of the experimental events is presented and described mathematically via the critical strain energy release rate for crack initiation and propagation, the interfacial shear stress of the bond and the coefficient of friction.