Abstract: The invention relates to a new method and new apparatus for determining the hottest temperature or the coldest temperature prevailing along the length of an optical-fiber light guide. The invention is conducted with an optical fiber capable of supporting multidiode propagation of light and comprising a core, a cladding, and a jacket. The core is selected to have (1) a higher refractive index than the core and the cladding and (2) a relatively high negative temperature coefficient of refractive index. A light beam capable of establishing substantially single-mode propagation in the core is launched into an end thereof at an angle to the axis. The angle is increased to effect the onset of light refraction from the core into the cladding. The value of the launch angle corresponding to the onset is determined and then used to establish the refractive index of the core corresponding to the onset angle.

Abstract: An apparatus and method is described that determines the temperature distribution of an environment proximate a cable of optical fibers. No additional transducers are required to be inserted within the environment and the presence of electrical magnetic fields does not adversely affect the operation or results of the temperature measurement. The characteristic of materials which enables them to generate spontaneous thermal radiation as a function of their temperature is used to map the temperatures along the cable. A plurality of optical fibers, each having a measurably distinct absorption constant, are used in order to generate a sufficient number of known parameters to enable the temperature of a number of zones to be determined along the length of the cable. Measurement accuracy can be enhanced by the use of known heat sources in the choice of temperature zone dimensioning.

Abstract: Fiber optic waveguides exhibiting a blackout phenomenon can be used for temperature sensing. A temperature sensing waveguide can be used in such applications as maintaining a material within a selected temperature range, freeze protection, viscosity control of liquids in pipelines, leak detection of cryogenic fluids, fire detection, application of heat-recoverable materials, and fluid level detection. Novel waveguides exhibiting blackout at selected temperatures for use in these applications are described. Among the novel waveguides are those having a cladding comprising a polyalkylphenyl siloxane and those having a cladding comprising a cross-linked polymethylalkyl siloxane. Also described are waveguides where only a section of the waveguide exhibits blackout and methods for making such waveguides.

Abstract: The invention relates to a measuring signal transmission device for transmitting signals between a rotating portion and a rotationally stationary portion, for example in a large electrical machine. The rotationally stationary portion is journalled to the rotating portion in such a way as to accompany the latter portion in its axial and radial movements, and light is arranged to be transmitted in both directions between the rotating portion and the rotationally stationary portion by light conductors at the center axis of rotation and/or at specified radii and at least one light-conducting fiber is located in the rotating portion and at least one light-conducting fiber is located in the rotationally stationary portion, whereby the light signal transmission is arranged to take place between fibers located at the same radii in both portions.

Abstract: A light-guide unit comprises a light-forming rod and a light-transmitting rod, both rods being made from a light-permeable corrosion-resistant refractory material, for instance synthetic corundum, and coaxially arranged relative each other. According to the invention the length of the light-forming rod is equal to the thickness of the metallized layer of a lining, and the length of the light-transmitting rod is not less than the thickness of the remaining portion of the lining. The rods are connected by a protection sleeve made from a material featuring plasticity at the operating temperature of the lining, and disposed in the tube. The tube at the portion wherein the light-forming rod is disposed is filled with a first refractory material having a sintering temperature not higher than the sintering temperature of the lining, and whose resistance to the action of the products of melting is similar to that of the lining.

Abstract: An optical system for exciting a temperature dependent phosphor with radiation and detecting independently emissions therefrom in optically isolable first and second wavelength ranges that gives an indication of the temperature of the phosphor. The optical system is carried by a heat-insulating housing disposed between a heat generating light source and the heat sensitive detectors. Dichroic mirrors are utilized to separate the two wavelength ranges emitted by the phosphor and to allow the sharing of a common optical path by three different radiation wavelength ranges without an undue loss of radiation intensity in any of the wavelength ranges. The light source may be of a helically shaped filament that is tilted with respect to an imaging optical axis so that the side of the helix is imaged with a minimum amount of the space between the turns showing, thereby maximizing the optical energy imaged from the light source.

Abstract: The temperature measuring device comprises a rod which passes approximately vertically through the anode block and terminates at the level of the working face of the anode. Fitted over the rod at the top is a light plug which provides an optical connection to the fiber bundles with the minimum of reflection. This optical connection is usefully in a coupling fluid which, like the rod and the bundle of fibers, is able to transmit infra-red radiation.

Abstract: A light guide element, secured in a spark plug-like housing and positioned, for example, within a metallic tube forming a spark plug connector, is coated at the end facing the combustion chamber with a light-impervious material viz: graphite, the graphite emitting radiation upon influence of heat arising within the combustion chamber, which radiation is transmitted to the optical pick-up for subsequent photo-electric evaluation thereof. The optical pick-up is, for example, a quartz glass rod coupled to a light guide cable, or directly coupled to an opto-electrical transducer.

Abstract: An infrared temperature probe for high pressure use is in the form of a hollow bolt adapted to be threaded into a complementary threaded aperture in the wall of a pressure vessel with the end thereof disposed flush with the internal surface of the pressure vessel wall. An infrared transparent window is secured in the end of the hollow bolt with one surface thereof disposed flush with the end of the bolt. A bundle of optical fibers is secured within the opposite end of the hollow bolt and a glass rod is mounted within the hollow bolt in operative relation to the window and the optical fiber bundle for transmitting infrared radiation from the window to the optical fiber bundle. The interior of the hollow bolt may be supplied with a circulating cooling liquid or gas.

Abstract: A thermometry system utilizes the thermally sensitive time dependent emission properties of luminescent materials. In one embodiment the system includes a probe constructed with an optic fiber bundle for conducting light both toward and away from the temperature sensitive luminescent element located at one end of the optic fiber bundle, a source for transient and/or modulated excitation of the temperature sensitive element, and a light responsive detection element located at the output end of the optic fiber bundle for detecting the transient and/or modulated light emissions by the luminescent temperature sensitive element. The emission signal received by the light responsive detector can be analyzed in a well defined manner to determine the temperature of the luminescent element and of any materials in thermal equilibrium with the luminescent material.

Abstract: An optical temperature sensor and method of manufacture therefor in which the intensity of light reflected from a first dielectric interface or from first and second dielectric interfaces, wherein one of the dielectrics has a temperature dependent index of refraction is measured. The intensity of light refleted from such dielectric interfaces will vary depending on the index of refraction which in turn is temperature dependent, thus providing a temperature dependent light signal.

Abstract: Fiber optic waveguides exhibiting a blackout phenomenon can be used for temperature sensing. A temperature sensing waveguide can be used in such applications as maintaining a material within a selected temperature range, freeze protection viscosity control of liquids in pipelines, leak detection of cryogenic fluids, fire detection, application of heat-recoverable materials, battery charging, and fluid level detection. Novel waveguides exhibiting blackout at selected temperatures for use in these applications are described.

Abstract: A well tool for developing measurements of pressure or temperature in a well bore comprising an elongated well tool which utilizes a coherent beam of light which is applied to the ends of separate fiber optics and the other ends of the fiber optics are detected to produce an electrical signal in response to differences between the outputs of the fiber optics to the detector. For measuring pressure, one fiber optic may be coiled in a temperature insulated chamber and sense a discrete sample from the earth formations while the other fiber optic is coiled in a temperature insulated reference pressure chamber. In another embodiment both fiber optics are subjected to pressure samples from longitudinally spaced locations of the earth formations. In still another embodiment, the fiber optics are subjected to the temperature in the bore hole at longitudinally spaced locations for obtaining a temperature gradient measurement.

Abstract: Fiber optic waveguides exhibiting a blackout phenomenon can be used for temperature sensing. A temperature sensing waveguide can be used in such applications as maintaining a material within a selected temperature range, freeze protection, viscosity control of liquids in pipelines, leak detection of cryogenic fluids, fire detection, application of heat-recoverable materials, and fluid level detection. Novel waveguides exhibiting blackout at selected temperatures for use in these applications are described. Among the novel waveguides are those having a cladding comprising a polyalkylphenyl siloxane and those having a cladding comprising a cross-linked polymethylalkyl siloxane. Also described are waveguides where only a section of the waveguide exhibits blackout and methods for making such waveguides.

Abstract: A photoluminescent indicator apparatus having automatic feedback means to maintain the sensitivity of the indicator apparatus with respect to variations in environmental conditions. The apparatus includes a sample of photoluminescent material having a photoluminescent decay rate which varies as a function of environmental conditions. The sample is positioned in a remote location having some unknown aspect of the environment desired to be measured. The sample is optically excited with a modulating signal to generate an excitation output signal functionally dependent on the modulating signal and indicative of the unknown environmental condition. A phase detection means is provided for comparing difference in phase between a phase reference signal and the excitation output signal to generate a phase differential signal functionally related to the photoluminescent decay rate of the sample.

Abstract: A multi-channel optical sensing system for measuring temperature at a number of measuring points includes optical sensors, each of which modulates the incident light beam by light intensity modulation according to the temperature at each measuring point and returns the modulated light beam back to the same optical path. The individual optical sensors are coupled to optical fibers which transmit respective light beams of different wavelengths. These optical fibers are coupled to a wavelength multiplexer/demultiplexer unit, which receives modulated light beams and supplies non-modulated light beams. This unit spectroscopically multiplexes the modulated light beams and spectroscopically demultiplexes the non-modulated light beams. It is optically coupled to another spacially spaced-apart wavelength multiplexer/demultiplexer via an optical system for transmitting light.

Abstract: The self-generating thermal radiation properties of an optical fiber element are employed to determine the temperature, location and length of a hot spot, or region, of an object.

Abstract: The disclosed invention concerns a process for the optical measurement of temperature, a probe device for the carrying out of the process, and a process for producing probe. The probe device contains a pellet of liquid crystals which is contained within an envelope and arranged at the end of an optical fiber. The optical fiber receives light, which is continuously swept by different wavelengths and the light reflected by the liquid crystal is analyzed to detect the reflection peaks and deduce the probe temperature.

Abstract: A transducer (14) including an optical fiber core (15) having a first refractive index profile, and an optical cladding (16) encircling the core and having a second refractive index profile different from that of the profile of the optical core. At least one of the core and cladding is formed of a photoresponsive material providing a variable difference between the refractive indices of the core and cladding as a function of a physical effect applied to the transducer. Light may be propagated through the core from a suitable light source (18) and the light which is lost from the core to the cladding may be detected by a suitable detector (22,23) providing an output signal corresponding to the force applied to the transducer. In one form, the detector receives light from the end (21) of the transducer, and in another form, the detector (23) receives light through the outer surface (24) of the transducer.

Abstract: A temperature responsive device, such as a fuse or a temperature measuring apparatus, is disclosed including a temperature sensor having a light reflective (or light transmissive) characteristic which varies with temperature, and a device for receiving the light reflected from (or transmitted through) the sensor and to provide an output in accordance with the state of the characteristic. As shown, the sensor (perhaps an adhesive temperature indicator) is used as a fuse and, upon its color-change, it interrupts a switch 2 connecting a power source to a load the temperature of which the sensor senses.

Abstract: A multicore optical fiber having a plurality of cores positioned across the diameter of a common cladding can be so optimized to respond to either temperature or strain by the selection of materials, spacing and shape of the cores in the fiber. The cross-talk between adjacent cores in the fiber changes in response to either a change in temperature or a strain along the length of the fiber. The temperature, strain or pressure change, can be determined by measuring the relative intensity of light emerging from the different cores of the fiber. If the fiber is optimized to respond to temperature change, then a high degree of temperature sensitivity can be provided over a large unambiguous range. Alternatively, cross-talk can be made temperature insensitive so that the intensity pattern of light emerging from the various cores in the fiber is only a function of the strain exerted on the fiber.

Abstract: A substantially solid temperature-dependent light absorbing mass including multiple-faceted randomly oriented and distributed reflecting chips is optically coupled on the terminal end of a fiber optical light conductor.

Abstract: A fiber optical temperature measuring apparatus is based on the ability of certain materials to change color in dependence on changes in temperature. Visible or invisible light having at least two different wavelengths is supplied to the material and the light emanating from the material is detected for determining the changes in the absorption characteristic of the material at the emitted wavelengths by determining the quotient between the detected signals from the material.

Abstract: A temperature probe measures temperature changes within biological material while the tissue is being irradiated with microwaves. In order to measure tissue temperatures accurately a probe must be designed to function in a microwave field while causing minimum perturbation to the microwave field. This generally requires a probe being constructed of dielectric (non-metallic) material which utilizes physical phenomena which are thermally dependent yet unaffected by electromagnetic fields at the field strength and frequencies of interest. In one embodiment the structure of the probe basically includes an optical fiber bundle for conducting light both toward and away from a temperature sensitive luminescent element located at one end of the optical fiber bundle, the source for exciting the temperature sensitive element and a light responsive detection element located at the output end of the optical fiber bundle for detecting light emitted from the temperature sensitive element which is temperature dependent.

Abstract: An improved optical fiber temperature sensor includes at least one optical fiber light conductor including an optical fiber core, cladding material around the core, and a jacket surrounding the core and cladding material. The core exhibits an evanescent field which extends through the cladding material into the jacket in a first selected range of optical wavelengths. Light attenuation in the conductor below a first temperature range is less than light attenuation above the temperature range. By applying light to the conductor at a frequency with the selected optical wavelength range and detecting the light passed through the conductor, an approximate temperature within the temperature range can be sensed. A more accurate temperature can be sensed by using either two optical fiber light conductors having different optical properties or by using two light frequencies with a single conductor which responds differently to the two frequencies.

Abstract: This invention provides apparatus for remote temperature sensing by means of fiber optics in which the sensor is optical and passive, with no electrical power required at the sensor. The temperature-sensing section of the fiber optic makes use of a transparent liquid as core or cladding and in which the transparent liquid has a temperature-dependent index of refraction.

Abstract: This invention relates to the use of a birefringent crystal as the sensing element in a probe thermometer constructed of certain basic optical components utilized in three separate modes. Thus, all of the modes of the invention are directed to a probe thermometer which uses the temperature dependence of the birefringence of certain single crystals as the temperature sensitive parameter. One such crystal is a Y-cut single crystal of LiTaO.sub.3. Alternative crystals having adequate sensitivity in the desired temperature range may be constructed from LiNbO.sub.3 or BaTiO.sub.3. Polarized light propagates through the crystal in two modes, the ordinary ray and the extraordinary ray, which have indices of refraction n.sup.o and n.sup.e. For LiTaO.sub.3 at room temperature, n = 2.2, B = n.sup.e - n.sup.o = 0.004, and dB/dT = 4.4 .times. 10.sup.-5 /.degree. C.

Abstract: A temperature sensor utilizing a semiconductor sensing element which absorbs monochromatic radiant energy as a function of temperature. The apparatus includes a monochromatic radiant energy source, radiant energy guide means, a semiconductor sensing element interposed in the radiant energy guide means and a detector for detecting the intensity of the monochromatic radiant energy transmitted by the semiconductor sensing element. Advantageously, optical fibers may be used as the radiant energy guide means for directing the monochromatic radiant energy to the semiconductor and returning the transmitted radiant energy to the detector. The semiconductor sensing element is fabricated from a suitable semiconductor material such as galium arsenide. Additionally, the semiconductor material can be fabricated as a mirror or reflecting prism so that it serves both as the sensing element and as part of the optical components for the radiant energy guide means.

Abstract: The surface temperature of a body is measured by receiving thermal radiation from a given zone of the surface of the body along a given optical path by means of a sighting instrument. At least that part of the optical path which is adjacent the instrument is protected by means of a shield. The given zone is subjected to a scraping operation.

Abstract: An improved monitoring device for monitoring a crystal pulling process taking place in a high pressure drawing chamber in which the mounting for a high pressure window at the same time encloses the end of a quartz rod whose other end projects freely into the drawing chamber ending in the vicinity of the melt with the mount inserted into the device in a pressure tight manner using a nipple threaded into the drawing chamber, the monitoring device permitting good observation of the process without precipitation of the volatile element of the semiconductor compound on the high pressure window.

Abstract: A hand-held radiometer for non-contact temperature measurement of objects is provided with a probe which is adapted to be mounted on the optical barrel of the radiometer to permit the radiometer to which it is attached to provide contact temperature measurements. The probe comprises a thin plastic film of low thermal mass which is shaped on one end thereof to be easily deformed when brought into contact with a specimen whose temperature is desired to be measured. The inner surface of the plastic film has a high emissivity, and a retainer means is provided on the other end of the thin plastic film for mounting the probe on the optical barrel of the radiometer.

Abstract: A temperature probe measures temperature changes within biological material while the tissue is being irradiated with microwaves. In order to measure tissue temperatures accurately a probe must be designed to function in a microwave field while causing minimum perturbation to the microwave field. This generally requires a probe being constructed of dielectric (non-metallic) material which utilizes physical phenomena which are thermally dependent yet unaffected by electromagnetic fields at the field strength and frequencies of interest. In one embodiment the structure of the probe basically includes an optical fiber bundle for conducting light both toward and away from a temperature sensitive luminescent element located at one end of the optical fiber bundle, the source for exciting the temperature sensitive element and a light responsive detection element located at the output end of the optical fiber bundle for detecting light emitted from the temperature sensitive element which is temperature dependent.