Review of the present status of optical fiber sensors

CRYSTALLINE MATERIALS Introduction Physical Properties Optical Properties Mechanical Properties Thermal Properties Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties GLASSES Introduction Commercial Optical Glasses Specialty Optical Glasses Fused Silica Fluoride Glasses Chalcogenide Glasses Magnetooptic Properties Electrooptic Properties Elastooptic Properties Nonlinear Optical Properties Special Glasses POLYMERIC MATERIALS Optical Plastics Index of Refraction Nonlinear Optical Properties Thermal Properties Engineering Data METALS Physical Properties of Selected Metals Optical Properties Mechanical Properties Thermal Properties Mirror Substrate Materials LIQUIDS Introduction Water Physical Properties of Selected Liquids Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Commercial Optical Liquids GASES Introduction Physical Properties of Selected Gases Index of Refraction Nonlinear Optical Properties Magnetooptic Properties Atomic Resonance Filters APPENDICES Safe Handling of Optical Materials Abbreviations, Acronyms, and Mineralogical or Common Names for Optical Materials Abbreviations for Methods of Preparing Optical Materials and Thin Films Fundamental Physical Constants Units and Conversion Factors

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Handbook of Optical Materials

http://www.qpsmonitoring.com/applicationreview.pdf

Recent progress in applications of in-fibre Bragg grating sensors

A robust interferometric fiber-optic current sensor with inherent temperature compensation of the Faraday effect is presented. Sensor configurations based on Sagnac and polarization-rotated reflection interferometers are considered. The sensing fiber is residing and thermally annealed in a coiled capillary of fused silica. The capillary is embedded in silicone within a ring-shaped housing. It is theoretically and experimentally shown that the temperature dependence of the birefringent fiber-optic phase retarders of the interferometers can be employed to balance the temperature dependence of the Faraday effect (0.7/spl times/10/sup -4///spl deg/C). Insensitivity of the sensor to temperature within 0.2% is demonstrated between -35/spl deg/C and 85/spl deg/C. The influence of the phase retarders on the linearity of the sensor is also addressed. Furthermore, the sensitivity to vibration of the two configurations at frequencies up to 500 Hz and accelerations up to 10 g is compared. High immunity of the reflective sensor to mechanical perturbations is verified.

Temperature and vibration insensitive fiber-optic current sensor

From molecules to bismuth oxide-based materials: Potential homo- and heterometallic precursors and model compounds

Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850 degrees C. The residual birefringence and induced loss, are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of +8.4*10/sup -5//K over the range from -75 to +145 degrees C has been demonstrated. This is approximately 20% greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about +1.6+10/sup -4//K over the range from -20 to +120 degrees C has also been demonstrated. >

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Annealing of linear birefringence in single-mode fiber coils: application to optical fiber current sensors

Measured temperature dependences of the Verdet constants of SiO2, SF-57, and BK-7 are ~10−4/K within 3–20% of Becquerel formula estimates.

Temperature dependence of the Verdet constant in several diamagnetic glasses.

Magnetic-field sensors based on the Faraday effect in ferrimagnetic iron garnets are investigated in terms of their sensitivity, speed, and directionality. Signal-to-noise measurements at 80 Hz on small (typically 5-mm-diameter*3-mm-long) samples of yttrium iron garnet (YIG) yield noise equivalent magnetic fields of 10 nT/ square root Hz. Frequency-response measurements exhibit virtually flat response to approximately 700 MHz. >

Fast, sensitive magnetic-field sensors based on the Faraday effect in YIG

To assess the suitability of bismuth germanate as an electro-optic material for high precision applications, we have confirmed and extended previous data on its refractive index, electro-optic tensor element r(41), and thermal expansion coefficient. In addition, we have measured the thermo-optic coefficient dn/dT, the temperature dependence of the electro-optic coefficient, and the stress-optic tensor elements. From the stress-optic tensor elements and previously published data, we have computed the strain-optic tensor elements. The index of refraction is given, to a good approximation, by the single-term Sellmeier equation, n(2) - 1 = S(0)λ(0)(2)/[1 - (λ(0)/λ)(2)], with S(0) = 95.608 µm(-2) and λ(0) = 0.1807 µm. The thermo-optic coefficient is 3.9 × 10(-5)/°C at 632.8 nm and 3.5 × 10(-5)/°C at 1152.3 nm. The electro-optic tensor element varies between approximately 1.05 and 1.11 pm/V over the spectral range of 550-1000 nm; its normalized effective change with temperature is approximately 1.54 × 10(-4)/°C. The thermal expansion coefficient is 6.3 × 10(-6)/°C over the range 15-125 °C. Values of the stress-optic tensor elements are q(11) - q(12) = -2.995 × 10(-13) m(2)/N and q(44) = -0.1365 × 10(-12) m(2)/N. The strain-optic tensor elements are p(11) - p(12) = -0.0266 and p(44) = -0.0595.

Optical, thermo-optic, electro-optic, and photoelastic properties of bismuth germanate (Bi 4 Ge 3 O 12 )

The Faraday effect is becoming widely used as an optical method of measuring electric cur-rent or magnetic field. It is particularly advantageous where the measurements must be made at high voltage or in the presence of electromagnetic interference, and where, speed or stability are considerations. In this paper we review the development of the technology over the last twenty years, with an emphasis on the basic principles, design considerations, and performance capabilities of sensors that represent the latest achievements. Faraday effect current sensors are now used routinely in the measurement of large current pulses, and are starting to become available for ac current measurements in the power industry. Recent developments include their extension to the measurement of currents in the milliampere range and substantial reductions in size. Similar devices, in slightly different configurations, can be used for magnetic field measurements. Further improvements, based on new fiber types and new materials, are projected.

Allen Rose

Papers

Annealing of linear birefringence in single-mode fiber coils: application to optical fiber current sensors

Temperature dependence of the Verdet constant in several diamagnetic glasses.

Fast, sensitive magnetic-field sensors based on the Faraday effect in YIG

Optical, thermo-optic, electro-optic, and photoelastic properties of bismuth germanate (Bi 4 Ge 3 O 12 )

Faraday Effect Sensors: The State Of The Art