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 residing thermally annealed in a coiled capillary fused silica. embedded silicone within ring-shaped housing. It theoretically experimentally shown that dependence birefringent phase retarders can be employed to balance (0.7/spl times/10/sup...

We report what is to our knowledge the first simultaneous measurement of two-photon absorption coefficient and free-carrier cross section above bandgap in a semiconductor. This also observation 1 μm radiation single-crystal Si at room temperature regime where stepwise process involving indirect followed by usually dominant. A critical pulsewidth (and fluence) established below above) which cannot be neglected. Pulses that range from 4 100 ps duration are then used isolate...

A highly accurate fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include the control of electrolysis process production metals such as aluminum, copper, zinc, magnesium, and others. The offers significant advantages with regard performance ease use compared state-of-the-art Hall-effect-based transducers. makes Faraday effect in an optical fiber loop around current-carrying bus bars. novel scheme a polarization-rotated reflection interferometer...

The strength, formation, and decay of photorefractive free-carrier gratings written in GaAs by 43-ps pulses at a wavelength 1 mu m are investigated using picosecond-time-resolved two-beam coupling, transient grating, degenerate-four-wave-mixing techniques. Photorefractive weak-beam gains few percent measured fluences pJ/ m/sup 2/ (0.1 mJ/cm/sup 2/), gain from energy transfer is observed larger than approximately 10 the beam-coupling experiments. roles saturation two-photon absorption...

Abstract The reflection and gain spectra of CdS ZnO are investigated as a function excitation intensity temperature. For the spectroscopy two beam method variation strip length used. results indicate, that an electron–hole plasma is formed under high excitation, preferentially if small spots comes close to its thermal equilibrium only in especially favourable cases. Excitonic recombination processes predominant, larger

An intrinsic absorptive optical bistability is observed in the transmission of high intensity, nanosecond laser pulses through thin CdS platelets at liquid helium temperature. The due to a renormalization band gap which caused by formation an electron hole plasma and occurs broad spectral range below excitonic resonances. switching times are subnanosecond range. dependence on photon energy investigated discussed.

We present studies on the long-term reliability of interferometric fiber-optic current sensors (FOCS) for use in electric power transmission systems. Accelerated ageing tests are performed crucial optical sensor components and a three-phase system is subjected to an extended field trial. The under test include sensor's superluminescent light emitting diode source, integrated-optic phase modulator various passive such as fiber couplers, polarizers, polarization-maintaining connectors,...

We investigate the various contributions to temperature dependence of an interferometric fiber-optic current sensor employing spun highly-birefringent sensing fiber, in particular, from fiber retarder at coil entrance, fiber's birefringence, and Faraday effect. theoretically experimentally demonstrate that appropriately designed inherently compensates birefringence insensitivity within ± 0.2% between -40 + 85 °C. Furthermore, we analyze influence parameters on linearity recovered...

We theoretically and experimentally investigate intrinsic temperature compensation of interferometric polarimetric fiber-optic current sensors with a coil spun highly birefringent fiber operated in reflection mode. The sensor recovers the differential magneto-optic phase shift left- right-handed circular (or slightly elliptical) polarization states by means non-reciprocal modulation, whereas employs simple passive analyzer. show that two types exhibit substantial differences their response...

We report the first observation to our knowledge of photorefractive effect on picosecond time scales. Photorefractive beam coupling in GaAs with picosecond, 1.06-μm pulses is observed owing charge separation between electrons and ionized defect EL2+ at low fluences free holes created by two-photon interband absorption for high fluences. The accompanying processes linear absorption, transient energy transfer are also observed.

A fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include measurement process control and protection in the electrowinning industry, example at aluminum smelters. The offers significant advantages with regard performance ease of installation compared state-of-the-art Hall-effect-based transducers. exploits Faraday effect an optical fiber measures path integral magnetic field along a closed loop around current-carrying bus bars. differential magnetooptic...

We report on a simple, metering class polarimetric fiber-optic current sensor (FOCS) for electric power transmission systems. The uses fiber coil operated in reflection mode and an integrated-optic polarization splitter (IOPS) interrogation. At alternating currents, the performs comparably to high-end interferometric FOCS that work with phase modulator closed-loop detection circuit. Besides passive interrogation scheme, particular advantage of is use standard single-mode leads head instead...

We investigate the effect of polarization cross-coupling at polarization-maintaining (PM) fiber connectors on accuracy an interferometric fiber-optic current sensor. The sensor uses Faraday in a coil operated reflection mode and interrogator based nonreciprocal phase modulation. PM link between sensor's opto-electronic module give rise to signal instability due limited insufficiently stable extinction ratio (typically <;25-30 dB). As result can be well outside allowed tolerances applications...

A polarimetric distributed feedback fiber laser sensor for the measurement of fluid pressure up to 50 MPa is investigated between room temperature and 250/spl deg/C. The isotropic acts directly on fiber, which eliminates need a mechanical transducer. resolution about 20 kPa (0.2 bar) demonstrated. Furthermore, protection silica against deterioration by thermomechanical effects various coatings response are studied.

Photorefractive gratings are written, read out, and erased with single 30-psec pulses at fluences of 1–15 mJ/cm2 a wavelength 0.532 μm in BaTiO3 crystal. The consist one component that is fully formed 50 psec after the peak writing beams second grows for approximately 30 sec until it starts to decay by dark erasure. photorefractive index change per absorbed photon picosecond same as obtained when cw beam 0.515 used factor smaller than observed fluence GaAs 1.06 laser system used.

Abstract The real and imaginary parts of the complex dielectric function CdS are experimentally investigated for low temperatures various excitation conditions. Strong changes observed at high in spectral region below band edge. Emphasis is put on variations part transition from a density exciton phase to plasma phase. It shown, that Kramers‐Kronig relations also valid highly excited semiconductors. experimental results compared with recent theoretical predictions.

We report the observation of photorefractive index gratings written and read out in BaTiO(3) using single pulses 30-psec duration fluences 1 to 15 mJ/cm(2) at a wavelength 0.532 microm. While are masked during formation by large free-carrier grating, they clearly seen from 50 psec many minutes following peak writing beams. The rapid complete grating decay on scale 100 indicate either that carrier-recombination time our sample is less than or mobility carriers >23 cm(2)/V sec.

A fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include the control of electrolysis process production metals such as aluminum, copper, magnesium, etc. The offers significant advantages with regard performance and ease installation compared state-of-the-art Hall effect based transducers. novel scheme a polarization-rotated reflection interferometer fiber gyroscope technology used measure magneto-optic phase shift. new technique has been developed...