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ABSTRACT: A mode scrambler based on an annealed step-index fibre is shown to
have reproducible performance and source-launch-alignment insensitivity.
Devitrification produces scattering centres in the fibre that distribute
light uniformly over both angle and radius. An all-fibre mode scrambler
with a 10 cm length and an insertion loss <3.5 dB is demonstrated
Electronics Letters 02/2001; · 0.96 Impact Factor
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ABSTRACT: We show that the dispersion of multiple cascaded components can be determined from a single low-coherence interferometric measurement. This measurement is not adversely affected by other components in the system, regardless of their wavelength reflection bands.
Optical Fiber Communication Conference and Exhibit, 2001. OFC 2001; 02/2001
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ABSTRACT: We have directly measured the retardance versus temperature for single-crystal quartz (SiO(2)) and magnesium fluoride (MgF(2)) at wavelengths of 633, 788, 1318, and 1539 nm and over a temperature range of 24-80 degrees C. To our knowledge, the temperature dependence of retardance for these two materials has not been directly measured. We compared our direct measurements of the normalized temperature derivative of the retardance gamma with derived values from previously reported indirect measurements and found our results to be in agreement and our measurement uncertainties to be typically a factor of 4 smaller. Our overall mean value for gamma(SiO(2)) is -1.23 x 10(-4) with a combined standard uncertainty of 0.02 x 10(-4) and little wavelength dependence over the 633-1539-nm range. Our overall mean value for gamma(MgF(2)) is -5.37 x 10(-5) with a combined standard uncertainty of 0.17 x 10(-5) and with a small wavelength dependence over the 633-1539-nm range.
Applied Optics 12/2000; 39(31):5796-800. · 1.41 Impact Factor
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ABSTRACT: This paper analyzes the response of optical fiber current sensors
that are subjected to high electric fields, such as fields encountered
in gas-insulated systems. This paper shows that through the electrooptic
(EO) Kerr effect, these fields can cause harmonic distortion of the
measured ac current waveform. This harmonic distortion was confirmed
experimentally. Also, this paper shows that it is possible to
simultaneously measure both current and voltage waveforms and the phase
between them using this effect. To minimize the electrooptic Kerr
effect, optical fiber current sensors must be screened from
high-electric fields
Journal of Lightwave Technology 07/1999; · 2.78 Impact Factor
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ABSTRACT: We demonstrate an automated polarimeter based on a rotating polarizer for the measurement of linear retardance independent of laser power and detector gain. The retardance is found when a curve is fitted to a unique normalization of the intensity response of the polarimeter over a range of input polarizer orientations. The performance of this polarimeter is optimal for measurements of quarter-wave retardance and minimal for half-wave retardance. Uncertainties are demonstrated by measurements on six stable double Fresnel rhombs of nominal quarter-wave retardance, yielding expanded uncertainties between 0.031 degrees and 0.067 degrees . The accuracy has also been verified by blind comparisons with interferometric and modified null retardance measurement techniques.
Applied Optics 10/1997; 36(25):6466-72. · 1.41 Impact Factor
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ABSTRACT: The National Institute of Standards and Technology (NIST) has developed a nominally quarter-wave linear retarder for wavelengths near 1.3 mum that is stable within +/-0.1 degrees retardance over a range of wavelength, input angle, temperature, and environmental variations. The device consists of two concatenated Fresnel rhombs made from a low stress-optic-coefficient glass that minimizes the residual birefringence from machining and packaging. Device machining, assembly, and antireflection coating tolerances are discussed, and the theoretical performance is compared with measurements. Humidity can modify retardance of the total-internal-reflection surfaces; we discuss packaging that mitigates this effect and provides an estimated 10-year lifetime for the device. Several measurement methods were intercompared to ensure that the device retardance can be measured with an uncertainty less than 0.1 degrees . Similar retarders will be certified by NIST and made available as Standard Reference Materials.
Applied Optics 10/1997; 36(25):6458-65. · 1.41 Impact Factor
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A.H. Rose
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ABSTRACT: The decrease in transmittance of annealed optical fiber has been
measured versus temperature and time. The annealing loss is due to the
devitrification of the glass and OH absorption in the 1200 to 1500 nm
wavelength region. Both loss mechanisms propagate primarily from the
surface into the core. However, to increase the OH absorption
significantly, annealing times greater than 10 h are required. Fibers
heated from 1000 to 1300°C in an air atmosphere quickly devitrify
and their transmittance approaches zero. Also, the current sensitivity
of annealed fiber current sensors versus annealing time at 850°C has
been measured. A decrease in the current sensitivity is attributed to
devitrification in the fiber
Journal of Lightwave Technology 06/1997; · 2.78 Impact Factor
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ABSTRACT: The Verdet constant in annealed optical fiber current sensors has
been measured at wavelengths from 636 to 1320 nm. The measurements are
fitted to two models, one classical and the other an expansion of the
classical model that includes a nonlinear term. These measurements and
models are compared to previous measurements made in optical fiber and
bulk SiO<sub>2</sub>. Our measurements have an average accuracy of
±0.6% and an average measurement uncertainty of ±0.5% over
the 636 to 1320 nm range
Journal of Lightwave Technology 06/1997; · 2.78 Impact Factor
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ABSTRACT: As an alternative to bulk transducers, iron garnet films offer cost, fabrication, and performance advantages. Though films can be used in polarimetric systems, a simpler approach exploits the diffraction arising from serpentine domains in thin films. When a saturating field perpendicular to the film is applied, the light is not diffracted and couples into a receiving fiber with high transmission. The diffractive thin-film sensor requires no polarizer, but only a source, detector, 2x2 coupler, lens, and reflective film. It been applied to rotation sensing where magnetized teeth change the transducer transmission so that motion is sensed. Recently, we demonstrated an even simpler system that eliminates the 2x2 coupler and detector. In this system, light retroreflected back to the laser is detected by monitoring the laser terminal voltage as constant current is applied. The method exhibits polarization effects that may require compensation, but has been recently demonstrated using a thin-film magneto-optic sensor
Lasers and Electro-Optics Society Annual Meeting, 1996. LEOS 96., IEEE; 12/1996
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ABSTRACT: We demonstrate that twisting a fiber a few turns per meter before
it is annealed largely eliminates the residual linear birefringence.
This dramatically improves the yield of annealed coils used for current
sensing and makes it possible to use fibers that previously had large
residual linear birefringence. Twisting the fiber is effective because
the residual birefringence, associated with core ellipticity, is reduced
to near zero by twisting. A theoretical model of the twisted and
annealed fiber current sensor is compared to experimental data. We also
show good temperature stability for a sensor made with this new
technique
Journal of Lightwave Technology 12/1996; · 2.78 Impact Factor
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ABSTRACT: The use of single crystal bulk and film iron garnets in optical
sensors is reviewed. Magneto-optic sensitivity and its stability are
important parameters that depend on a variety of factors, including
optical design. Polarimetric and diffractive sensor technologies are
summarized, and several recent demonstrations of magnetic field,
current, and rotation sensing using garnets are described. Garnets also
find application as important nonsensing components in sensor systems
IEEE Transactions on Magnetics 10/1996; · 1.36 Impact Factor
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ABSTRACT: 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.
Applied Optics 07/1996; 35(19):3562-9. · 1.41 Impact Factor
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ABSTRACT: The simultaneous emission and detection of radiation with a semiconductor laser is investigated. Measured signal-to-noise ratios of up to 56 dB demonstrate that self-detecting devices are adequate for sensor applications with discrete measurands. We observed a strong polarization dependence, which can cause response fluctuations, and suggest methods to minimize these fluctuations. This technique could be used for lower-cost sensors without splitters and detectors.
Optics Letters 10/1995; 20(20):2105-7. · 3.40 Impact Factor
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Optics Letters 11/1994; 19(22):1903. · 3.40 Impact Factor
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Optics Letters 09/1993; 18(17):1471-3. · 3.40 Impact Factor
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ABSTRACT: We describe the development of an optical fiber ac voltage sensor for aircraft and spacecraft applications. Among the most difficult specifications to meet for this application is a temperature stability of +/- 1 percent from -65 C to +125 C. This stability requires a careful selection of materials, components, and optical configuration with further compensation using an optical-fiber temperature sensor located near the sensing element. The sensor is a polarimetric design, based on the linear electro-optic effect in bulk Bi4Ge3O12. The temperature sensor is also polarimetric, based on the temperature dependence of the birefringence of bulk SiO2. The temperature sensor output is used to automatically adjust the calibration of the instrument.
02/1992;
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Optical Fiber Sensors Conference, 1992. 8th; 02/1992
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ABSTRACT: In general, the sensitivity of ferrimagnetic Faraday effect magnetic field sensors is a function of both the crystal geometry and composition. The geometrical dependence of the sensitivity in nonellipsoidal crystals, such as cylinders, is complicated by their spatially nonuniform demagnetizing factors. We compare sensitivity data obtained from a variety of cylindrical iron garnet samples with models which predict the effective demagnetizing factor N eff as a function of the length‐to‐diameter ratio. With respect to composition, we present experimental results of sensitivity vs diamagnetic substitution (x) in the iron garnet series Y 3 Fe 5-x Ga x O 12 . As expected, the sensitivity rises sharply as x approaches the compositional compensation point.
Journal of Applied Physics 12/1991; · 2.17 Impact Factor
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ABSTRACT: 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°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</sup>/K over the range from -75 to
+145°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</sup>/K over the range from -20 to +120°C
has also been demonstrated
Journal of Lightwave Technology 09/1991; · 2.78 Impact Factor
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ABSTRACT: 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 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 x 10 to the -5th/K over the range from -75 to 145 C has been demonstrated. This is approximately 20 percent 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 to the -4th/K over the range from -20 to 120 C has also been demonstrated.
09/1991;
