Fiberoptic techniques were first used to measure winding temperatures in power transformers more than ten years ago. Recently interest in such measurements to allow predictive loading and enhanced capacity utilization has increased. As a consequence, a new and more cost-effective fiberoptic temperature measurement system based on the fluorescent decay time technique has been developed for transformer use. The features of this system and its possible use in other power industry applications will be presented.

An optical technique has been developed for the on-line monitoring of rotor surface temperatures in electrical power generators. The method is based on the measurement of the decay time of the ultraviolet-laser-stimulated fluorescence produced by phosphors painted around the circumference of the rotor at selected locations along its length. At each location, a pair of optical fibers installed in stator cooling channels is used for light delivery and collection. The pulsing of the laser and the rotation of the rotor are synchronized so that the laser acts like a stroboscope to illuminate one small spot on the rotor surface, whose position can be altered by varying the triggering of the laser. A microprocessor-based signal analysis system has been designed and constructed to enable temperatures to be determined from the phosphor decay time data. Field tests on an operating 500-MW generator have yielded temperatures from 41 to 73 °C with a spatial resolution of 4 mm and an accuracy of ±2 °C. In the first installation, the phosphor was mixed with a silicone resin to produce a paint which lasted two years in the most adverse environment on the rotor. Efforts to improve the durability of the paint by using alternative binder materials have yielded encouraging results.

Determination of blade temperatures in the high-speed and turbulent environment of a turbine engine is difficult using standard pyrometry techniques because of the presence of high-temperature flame and the reflective nature of the inspection surfaces. A technique utilizing thermographic phosphor compounds bonded to engine vanes and turbine blades is presented that mitigates the negative effects of blackbody radiation while potentially allowing near real-time acquisition of blade temperature information. Specialized single and dual fiber-optic probes were designed to interrogate both fixed and rotating surfaces by delivering ultraviolet light from a quadrupled Nd:YAG (266 nm) laser to phosphor coatings consisting of Y₂O₃:Eu, YVO₄:Eu, and YAG:Th ceramic compounds. This technique utilizes the temperature-dependent fluorescent emission of a ceramic phosphor coating to discern the temperature of the interrogated surface. By using these methods, surface temperature measurements to 1200°C are achievable in the combustion environment.

A fiber optic high temperature sensor operated in the temperature range of 800 to 1800°C has been constructed, calibrated and applied in iron and steel industries. This sensor is a non-contacted pyrometer, and a single optical fiber transmitted the radiant flux, which comes from the surface measured, to two photodiodes. This sensor uses numerical aperture (NA.) of the fiber optic as the design principle to obtain optimal sensitivity and distance coefficient value. The response time of the sensor is 500ms and the basic error is ±0.5%. Calibration and operation of the sensor are relatively simple, and the operational life of the sensor approximately one year. This sensor has been used in various iron and steel industries in China and the results of sensor applications will be discussed.

The perfonnance of a pressure transmission system containing a microbend fiber-optic pressure transducer is reported. The pressure transducer design is described along with the configuration for its installalion in a coal liquefaction reactor operating at a pressure of 3000 psi and temperatures up to 840°F. The modulated light intensity signal proportional to pressure is transmitted to the remote optoelectronic signal conditioner 250 feet from the reactor. The results of.a one-month field test include the calibration, measured pressure versus time, thennal and pressure cycling data, and failure mode.

The development of new infrared transmitting optical fibers with low optical losses, sufficient mechanical strength, and temperature range to meet the demanding conditions of many process environments; and the availability of improved, ruggedized low-cost FTIR spectrometers have made in situ FTIR measurements possible. This paper discusses the development of in situ fiber optic remote FTIR spectroscopy and its application to the characterization of thin polymer coatings on substrates.

The temporal response of fiber optic interferometric thermometers to heat pulses as a function of fiber dimensions is investigated. Theoretical investigations have shown that for applications which require high frequency heat analysis such as turbine engines size of the cladding part of optical fiber is a major limiting factor. To achieve the maximum temporal response a technique is implemented to heat the core of the fiber directly at the cleaved end face. A fiber Fabry-Perot interferometer is formed and its distal cleaved end is black coated. Light from an At⁺ laser is chopped using a Bragg cell and focused at the fiber end to generate high frequency alternating heat source. Time response of 2.5 sec is measured.

An integrated-optic Mach-Zender interferometer is used as a Fourier transform spectrometer to analyze the input and output spectra of a temperature-sensing thin-film etalon. This configuration provides a high degree of iinmunity to the effects of charges in the source spectrum, and it readily permits the interrogation of a number of different sensors using a single spectrometer. In addition, this system has a potentially low cost because it uses optical communications hardware that may in the future be manufacturel in large quantities.

A fiber Fabry-Perot interferometric (FFPI) temperature sensor system with digital signal processing scheme is introduced. Major functions of this digital processor is to determine the difference between the round trip optical phase shift of the sensor and reference FFPIs as changes occur in the temperature at the sensor location. The interference fringe shift caused by thermally induced chirping of laser diode light source is utilized in this scheme. The system is developed as a stand-alone instrument which has its own LCD display and a control keyboard.

A series of new fiber optic temperature sensors is proposed. The new design uses the fluorescent emission amplitude of inorganic ions doped in a host matrix in the near infrared region as the temperature determining method and graded index fiber optics as the transmission medium. Four materials are investigated: Er³⁺:Glass; Cr³⁺, Er³⁺, Y₃Sc₂Ga₃O₁₂; Nd³⁺:Gd₃Sc₂Al₃O₁₂; and Nd³⁺:Glass. Feasibility in the design of a 10 km length point sensor with an accuracy of ±0.2 °C between 0°C and 300°C is presented.

This paper presents the basic principle and system research of touching type self-emission high tenperature fiber optic temperature sensor based on black—body radiation. In this system ,we solved the problem of "length effect" using a optical subsystem, developed superlower current of 10^-10A, improved the resolution of the A/D converter by adding a noise source. This system can continuously measure the temperature from 300°C to over 1200°C with the precision of 1°C.

We designed a new optical fiber current sensor based on the Faraday Effect. The electronic detection scheme uses two polarizers in order to avoid ambiguities due to polarimetric detection. In this way we may detect current beyond the folding point of the square cosine law inherent to that sensing technique. The sensor presents excellent linear response in the measured range, front 0 to 7.5 kA (peak to peak) , 60 Hz AC current.

We present a dual channel current sensor using the Faraday effect in two square bulk glass sensor heads capable of measuring two currents independently and simultaneously with a current resolution of 1.2 Amps/√Hz. Psuedoheterodyne signal processing and phase demodulation is used to recover the phase modulation caused by the Faraday effect.

Intensity type electric current sensors have been developed specifically for fault detection on electric power transmission lines. The transduction element consists of a pair of multimode optical fibers, one mounted on a ferromagnetic cantilever, the second on a fixed anvil such that light coupled from one fiber to the other is directly proportional to the magnetic field strength. The basic operating characteristics of the sensors, detailed laboratory test results and preliminary field data are presented. Their use for fault detection is also discussed.

A technique for the measurement of electric current using highly-birefingent optical-fibre is reported. The technique involves a resonant coupling between the fibre beat length and the period of a spatially-varying magnetic field. The resonant nature of the coupling makes the sensor less susceptible to environmental perturbations, than conventional lowbirefringence optical-fibre current sensors. The response of the coupling to distributed loads, and temperature compensation of the coupling are reported.

Magnetic materials with high Faraday effect were studied for fiber—optic magnetic fields and electric currents sensors design. Different compositions of semimagnetic semiconductors were grown to measure high frequency magnetic fields (up to several GHz). For moderate frequency sensors < 50 MHz the most perspective material was found to be Bi-substituted yttrium—iron gamete . Several ways to achieve high sensitivity and wide frequency band are discussed. Sensors on the basis of the investigated materials for various spheres of applications were constructed.

Terbium—doped optical fiber has high Verdet constant and is called magnet—sensitive fiber. It is of importance for a variety of applications including magnetic field sensor, current sensor, and fiber—type isolator. In this paper, we describe magnet—sensitive optical fiber fabrication, magnetooptic coefficient measurement, and its application in current sensor system. Experimental results show that the Verdet constant of magnet—sensitive fiber containing high rare—earth content (~4000 parts in 10⁶) is 2.7 times as high as that of ordinary silica based fiber. When tested in current sensor system, it gives similar performance observed in ultralow birefringent fiber. These results are new and have not been published before.

A simple fiber-optic sensor (FOS) based on Faraday effect in an isotropic single-mode fiber (SMF) was developed for discharge current diagnostics in tokamaks.. Current resolution of 30 Ampere/turn and temporal resolution of ~1ms have been obtained in the hostile electromagnetic and radiation environment of an operating tokamak. These resolution values were stipulated by quasi-isotropic SMF and differential photoreceiver shot—noise limited outputThe first experiments with the FOS application for plasma current measurements in tokamak FT-1 are discussed.

A He-Ne Zeeman laser has been utilized as a two-frequency light source in a Michelson-type micro-displacement fiber sensor. A polarization maintaining fiber has been installed in the sensing arm, which facilitates flexibility and allows the sensing region to be remotely located. This fiber sensing arm is arranged to replace a quarterwave plate component. The fiber sensor system has a resolution of half a micrometer

A mechanism which leads to a significant increase in sensitivity and linear operating range in reflective type fiber optic pressure transducers with minute active dimensions is studied. A general theoretical formalism is presented which is in good agreement with the experimental data. These results are found useful in the development of small pressure sensors used in turbulent boundary layer studies and other applications.

A new type of high hydrostatic pressure sensor up to 100 MPa, utilizing single-mode and two-mode ellipticalcore optical fibers is presented in this paper. The sensor exploits pressure-induced effects on both fundamental and second-order modes in highly birefringent elliptical-core polarization-maintaining optical fibers. The paper discusses the principles on which the design is based, construction of the sensor in two possible configurations, instrumentation and operation, and performance under various conditions, including pressure and temperature coefficients of the output signal. In addition, pressure-induced birefringence calculated from our experiments is compared with recent theoretical results.

Commercial multimode optical fibers, coated with aluminum, gold, or polyimide were used in a pressure sensor that squeezed the fiber between a serrated disk and a compliant material. The sensor was tested up to 400F, and was found to perform well only in a uniform temperature environment. Differential thennal expansion within the sensor made the sensor unusable in temperature transients. Preliminary tests show that mode stripping before the photo-detector can improve the transient temperature response.

An optical fibre pressure sensor has been developed using an in-line plasmon polariser and a short probe optical fibre for the sensing element. The design of the optical sensor and results obtained from the sensing system are described. One key element to the operation of this sensor is the polariser and the design and performance of this element will also be described in the paper.

A surface acoustic wave (SAW) sensor based on an extrinsic Fabry-Perot mterferometer is described. A single-mode fiber, used as the input/output fiber, and a multimode fiber, used solely as a reflector, form an air-gap that acts as a low-finesse Fabry-Perot cavity. The Fresnel reference reflection from the glass/air interface at the front of the air-gap interferes with the sensing reflection from the air/glass interface at the far end of the air-gap. Strains in the silica tube housing the two fibers change the air-gap length, thereby altering the phase difference between the reference and sensing reflections. A theoretical analysis of the interaction between the strain induced by elastic stress wave fields and the fiber sensor is presented. A dual optical wavelength stabilization technique is used to minimize signal drifts. Signal to noise ratios on the order of 39 dB are obtained with a sensitivity of 4° μstrain cm^-1 for strain measurements.

The time division multiplexed (TDM) digital optical position transducer (5" stroke, 1 2 bit) was successfully tested for performance, environmental response and life cycle. In particular, the performance was measured in terms of transducer insertion loss, linearity, tracking accuracy and resolution whereas the environmental tests included temperature cycling from -55°C to 135°C and the vibration from 5 Hz to 5,000 Hz. The transducer exhibited an insertion loss of ~23 dB and a linear position measurement range of ±2.4993 inches with a linearity of ±0.024 % full-scale, tracking accuracy on the order of resolution, 0.0012 inches. When temperature cycled, the change in the insertion loss of the transducer measured at 25°C was negligible. In addition, the transducer did not exhibit any hysteresis on completion of each thermal cycle. Both random and sinusoidal vibration test were conducted on the transducer which neither affected the optical perlormance nor induced any mechanical/optical failures. Although the life cycle test was limited to 15,000 full strokes, it demonstrated the ruggedness of the design and proved the maturity of TDM technology under extreme environmental conditions.

This paper reviews the theory, implementation, and broad application base of the following fiber optic and laser based non-intrusive sensing and measurement techniques : 1.FiberFlow Laser Doppler Anemometer, for accurate measurements of turbulent flow velocity with high resolution, 2.Modular Vibrometer, and 3.Fiber Vibroxneter, for measurements of vibrations of surfaces with wide amplitude and frequency ranges, 4.Torsional Vibrometer, for measurement of angular velocity and vibrations of rotating shafts, 5.Surface Velocity Sensor, for high accuracy surface velocity and length measurements.

The first four techniques are based on measurement of the Doppler shift of light scattered from the moving particles or surfaces through interferometric principles (optical heterodyning) . Frequency shifting using Bragg cell enables measurements of motions that change direction.

The last technique is based on calculation of the transit time of a surface through two spots of known distance, aligned along the direction of motion, through a correlation principle.

A new version of a contactless opticl position sensor is presented. The basic sensing mechanism in both the original and the new sensors consists of injecting a light signal into a lossy optical waveguide, and detecting the attenuated guided waves at the extremities of the guide. While the original approach uses a moving point source located at the position to be sensed, the new approach utilizes a stationary, extended light source that illuminates the whole extent of the detecting waveguide. A blocking screen moves with the moving object and blocks part of the light between the source and the detector. The amount of light detected is the integral over the unblocked portion of the light coupled into and transmitted through the sensing waveguide. It is demonstrated both theoretically and experimentally that the detected light is a linear function of the position of the screen, for the case of an exponentially decaying light source with similar attenuation characteristics as those of the sensing waveguide. This approach is a lower cost version of the original approach where a logarithmic amplifier is needed for linearizing the response.

A low coherence ("white light") interferometric approach to the measurement of vibration using a fibre optic probe to interrogate the vibrating surface is described. The recovery interferometer is a novel adaptation of a Michelson interferometer which provides two independent outputs, the relative phase of which may be controlled. Controlling this phase difference to be π/2 allows the direction of motion of the vibrating surface to be deduced.

Ordinary single-mode optical fibers embedded in solid materials are used for the detection of high frequency elastic strain waves in interferometric configurations. The strong state-of-polarization (SOP) dependence and lead sensitivity to external perturbations present a major limit. Neither the feedback control nor the scrambling of the input SOP will eliminate the sensitivity variations due to the measurand induced birefringence in the interferometric arms. We will show, however, that such sensors can still be used for ultrasonic pulse delay and relative ultrasonic spectrum measurement.

A dual-eigenstate polarization preserving fiberoptic sensor is tested. in which each eigenstate in a polarization preserving fiber forms an interferometer which could measure the temperature and the strain simultaneously. The temperature and strain coefficients for different polarization fibers are measured at the room temperature, indicating that there exist differences in temperature coefficients between two eigenstates in a polarization preserving fiber. The different temperature effects from those eigenstates make it possible to perform the temperature measurement and/or temperature compensation.

Coronas are localized discharges which occur adjacent to high voltage points in gases at around atmospheric pressure. A corona may be in the form ofa steady glow or it may be pulsing. Ions produced in the corona rapidly move away from the point, transfer momentum to the neutral gas molecules and thus generate a corona wind with speeds ofa few meters per second. The corona environment involving high electric fields, small dimensions and often electromagnetic and acoustic noise, is difficult to examine with good spatial resolution using conventional sensing techniques. We have found that the use ofan optical fiber interferometer to study the corona causes negligible disturbance to its voltage, current and structure. By heating a short length of fiber in the corona region with a pulse of CO₂ laser radiation and monitoring the interferometer signal we have measured corona wind speeds, and with a short length of polyvinylidene film bonded to a fiber passing through the corona region, the interferometer has been used to provide information on electric field distribution.

In near-wall measurement appl ications (viz ., boundary layer flow characterization) of the laser Doppler velocimeter, light scattered from the wall tends to swamp the scattered light from the flow-tracing particles. This reduces the signal-to-noise ratio (SNR) . This paper describes a technique to improve the SNR by using a microscope objective in the receiving optics train.

Active and passive configurations of a fiber optic probe comprising of a linear array of optical fibers positioned in the front focal plane of a graded index microlens are assessed for use as convenient particle sizing sensors for a process control environment.

It was found experimentally that the coupling ratio of a fused biconically tapered coupler changes when the coupler is subjected to an axially applied mechanical strain. A new type of ratiometric fibre—optic sensor, based on this principle, was developed. Due to analog signal conditioning, this sensor is insensitive to fluctuations in the light source power and has an output that is directly proportional to the measurand. Temperature and strain sensors with a linear output were realized by employing this method.

A novel fiber optic sensor has been developed to measure surface profile. The system is largely independent of surface reflectivity variations. Operations in both triggering and scanning modes are possible. A mathematical model has been produced and initial experimental results show close agreement to theoretical predictions. An integrated, software controlled system has been developed to allow real time surface information to be gathered. The system is both compact and inexpensive.

We propose two temperature-compensated strain sensing methods that combine the properties of a two-mode, elliptical-core (e-core) fiber sensor and (i) a bimetallic strip, or, (ii) refractive-index changes in a liquid-filled hollow-core fiber. The output from a conventional two-mode, e-core fiber sensor is (i) projected upon a multimode fiber attached to a bimetallic strip, or, (ii) projected from an angular endface on a multimode fiber. The multimode fiber acts as a spatial filter and picks up part of the two-lobe pattern incident upon its core. A measurement of the differential phase variation gives an indication of the strain. The modulation depth of the output signal is shown to be a faithful indication of the temperature in both cases. Strain sensitivities typical of two-mode fiber sensors (0.033°phase shift per tstrain-cm, minimum detectable strains of 0.17 μm/m for one meter sensing length) have been obtained with a temperature compensation accuracy of ±1°C over a 75°C range.

We propose an optical fiber interferometric sensor for X-ray dosimetry. The temperature rise ΔT produced in a silica optical fiber irradiated with chopped monochromatic X-ray induces a phase shift in the propagation of a He-Ne laser beam with respect to the unirradiated arm of the interferometer. ΔT is proportional to the energy released in the fiber. A prototype Mach-Zehnder fiber interferometer has been realized and tested using a laser source to heat the measurement arm; a maximum phase sensitivity of the order of 10^-3 radians has been achieved, corresponding to an energy of about 10^-5 J absorbed in the irradiated fiber. A possible application is for synchrotron radiation dosimetry.

Optical fibers are protected with a variety of materials which act as buffers and jackets. These protective coatings enhance their handling characteristics as well as their resistance to various adverse environments. It is also known that these materials can have an effect on the optical performance of the fiber. This testing explored the effect of bending and temperature variations on the optical performance of fibers protected with various materials.

A detection technique for intensity type fiberoptic sensors is described. It employs a multimode fiber interferometer, with the sensor in one arm, excited by an LED modulated at RF frequencies f_o and 2f_o. Sensor induced changes in intensity result in corresponding changes in the ratio of the detected f_o and 2f_o signals, thus eliminating various common mode effects. Results obtained with a displacement sensor and preliminary results from a pressure sensor illustrate the capabilities of this technique.

A method for demodulation of fiber optic interferometric sensors that utilizes a 3 x 3 coupler is described. The passive demodulation scheme does not require carrier (phase) modulation. The demodulation scheme relies on the three outputs of a 3 x 3 coupler and uses all three of its phase modulated output signals to recreate the stimulus inducing the original optical phase modulation. The demodulator scale factor (volts/radian) is stable against fluctuations in both fringe visibility and average received power. Upon initial implementation of the scheme, a dynamic range of 116 dB was obtained (at 600 Hz in a 1 Hz bandwidth with maximum THD at 4%). The minimum detectable signal at 600 Hz was 220 μrad/√Hz and the maximum tolerable signal was 140 radians. Both the maximum tolerable signal and the minimum detectable signal (noise floor) was observed to increase with decreasing frequency. Thus, depending on the frequency, the demodulation scheme is capable of detecting phase signals less than a milliradian to in excess of kiloradians.

We have considered some problems of applicability ofmultimode optical fibers in various interferometric configurations for optical fiber sensors development. The analysis was based on theoretical and experimental studies of spatial—temporal coherence function propagation in muitimode fibers Changing of the decree of coherence depending on the parameters of a fiber and sources is demonstrated experimentally. Configurations and experimental performance of local and distributed interferometric sensors with multiinode fibers are reviewed

The multifunction Iight source based on index—guided AIGaAs Fieterostructure with three isolated electrodes is realized.Three diffe- rent operation modes are available by simple change of electrode's connection, narnely LD, SLD and mode-locking LD. The output power in single-mode fiber pigtail is about 500 uW for SLD, more than 5mW for LD and 1-2 W for mode-locking LD with pulse duration 20-30 ps.

A sensor by means of optical fiber bundle was developed for detecting microscopic displacement and vibration in tympanic membrane. Illuminating a planer object and detecting the reflected light with the bundle, we experimentally investigated the received optical intensity against the distance from the object. As a practical application to clinical examinations, we then measured the displacements and vibrations of tympanic membranes of a dog.

A fibre-optic frequency shifter utilising torsional acoustic waves to produce a travelling perturbation which couples the polarisation eigenmodes of a linearly birefringent optical fibre, is demonstrated. The shift in optical frequency was 3.195MHz and an optical coupling efficiency of 6% was obtained with 780mW of electrical power. The theory of operation of this device is presented using a coupled mode approach, and the coupling coefficient for a fundamental torsional mode is derived in terms of its peak angular displacement.

Exp erimental results on a portable, low speed fiber-optic weigh-in-motion system are described that demonstrate the applicability of fiber-optic-based sensors in transportation, defense, and law enforcement applications where accurate weight determination of moving vehicles is necessary. Results are given on the systems' dynamic range (0.1—30 metric tons), velocity range (up to 5 km/h), accuracy error (0.5—3.0%), and repeatability. Also included in the paper is a discussion of the sources of error associated with low speed weigh-in-motion systems and methods of minimizing these errors for practical deployment.

A new technique for fiber—optical interferometers (FOl ) operating point spatial-temporal adaptive stabilization is theoretically and experimentally studied. It Is shown that under definite conditions dynamic holograms (DII) used as beainscouplers give an opportunity for high-frequency phase-modulation (PM) signals detection together with simultaneous low-frequency phase hindrances reduction. The described technique has been verified experimentally by means of adaptive FOl for harmonic and step Ptl signals measurements. Bacteriorhodopsin-doped non-linear media used for DII recording are reasonable to provide high sensitivity and adaptation frequency band up to 10 - 100 Hz.

Operation of fiber Fabry-Perot interferoineter (FFPI) temperature sensors from -200°C to +1050°C has been demonstrated [1]. These sensors used internal mirrors produced by a fusion splicing technique. Internal-mirror FFPIs have been embedded in graphite-epoxy composites and polymers, where they were used to sense temperature [2] and ultrasonic pressure [3].

We reported a new type of optical fiber sensor (OFS) for gas-liquid two phase flow. The diameter of minimum measurable gas bubble is 100-200um, range of void fraction is 0-100%, response time is l0μs, measure error is about 5% for measuring void fraction in air-water. There are two kinds of sensing head. The design and performance of sensing head are described.

This paper presents the principle of fiber optic sensors for the detection of low frequency magnetic fields. Magnetostrictive materials such as Terfenol-D and Metglas® are used as the sensing elements in a MachZehnder interferometer configuration.

Low frequency fiber optic magnetometers are constructed and tested in both planar and cylindrical geometries. These magnetometers consist of an optical fiber bonded to a magnetostrictive metallic glass ribbon in either strip or cylindrical geometry. The characteristics of specific sensor designs are also discussed and suggestions to improve magnetic field sensor fabrication are given. From a number of experiments, the best sensitivity achieved is with sandwich geometries under the application of a DC biasing field. The performance of these sensors increases with improved mechanical design and thermal annealing of the metallic glass ribbon.

Much of the reported work to date has been concerned with the response of the system in the frequency range of 0.1 10 kHz. The work presented here, however, deals with the response of an interferometric system using metglas in the lower frequency range of 10 - 50 Hz. Key words: Mach-Zehnder interferometer, magnetostriction, magnetometers, fiber optic sensor, Metglas®

Analyses and experiments indicate that fiber specklegrams are highly sensitive to the modal phases of the fiber, not vulnerable to environmental factors, and possess a very narrow spectral response bandwidth. The unique feature of the fiber specklegram is its multiplexing capability. Applications of fiber specklegrams to multiple channel fiber sensing are proposed.

The construction of electronic speckle pattern interferorneters (ESPI) using monomode optical fibre technology and solid state laser diode sources enables the realisation of compact, robust, portable instruments. The wavelength tunability of the diode sources extends the signal processing capability and the measurement techniques. Examples are presented of surface contour measurements in the range 33 μm to 8mm and heterodyne processing of time—averaged vibration fringes to enable determination of amplitude and phase relationships across the object surface.

In this paper we have studied the thermoelectric power in quantum wells, quantum wires and quantum dots of laser and fiber optic materials within the framework of k.p formalism by deriving the respective electron energy spectra in the presence of crossed electric and magnetic fields respectively. It is found, taking n—Cd₃P₂, as an example, that the same power decreases in various manners with increasing electron concentration, decreasing magnetic field arid decreasing film thickness respectively. The theoretical results are in quantitative agreement with the experimental observations as reported elsewhere. In addition, the corresponding expressions for three—band Kane model, two—band Kane model and that of parabolic models fiber optic and laser materials have been obtained as special cases of our generalized analysis.