Abstract: Composite cascode power amplifiers for envelope tracking applications are provided herein. In certain embodiments, an envelope tracking system includes a composite cascode power amplifier that amplifies a radio frequency (RF) signal and that receives power from a power amplifier supply voltage, and an envelope tracker that generates the power amplifier supply voltage based on an envelope of the RF signal. The composite cascode power amplifier includes an enhancement mode (E-MODE) field-effect transistor (FET) for amplifying the RF signal and a depletion mode (D-MODE) FET in cascode with the E-MODE FET.

Abstract: Composite cascode power amplifiers for envelope tracking applications are provided herein. In certain embodiments, an envelope tracking system includes a composite cascode power amplifier that amplifies a radio frequency (RF) signal and that receives power from a power amplifier supply voltage, and an envelope tracker that generates the power amplifier supply voltage based on an envelope of the RF signal. The composite cascode power amplifier includes an enhancement mode (E-MODE) field-effect transistor (FET) for amplifying the RF signal and a depletion mode (D-MODE) FET in cascode with the E-MODE FET.

Abstract: Composite cascode power amplifiers for envelope tracking applications are provided herein. In certain embodiments, an envelope tracking system includes a composite cascode power amplifier that amplifies a radio frequency (RF) signal and that receives power from a power amplifier supply voltage, and an envelope tracker that generates the power amplifier supply voltage based on an envelope of the RF signal. The composite cascode power amplifier includes an enhancement mode (E-MODE) field-effect transistor (FET) for amplifying the RF signal and a depletion mode (D-MODE) FET in cascode with the E-MODE FET.

Abstract: The invention relates to a method of detecting the particles of a tobacco particle stream in the production of smokable articles by scanning by means of a fine-beam light barrier, the diameter of which is smaller than the dimensions of the tobacco particles, and from the distribution of the dimensions of the tobacco particles determined by darkening of the fine-beam light barrier.

Abstract: The invention provides a method and a system for measuring geometric properties, such as diameter, shape and surface roughness of single rough particles by an optical method. The particle may be immersed in a gaseous or liquid fluid. A volume of the fluid, containing the particles to be measured, is illuminated by a beam of coherent electromagnetic radiation, resulting in a distribution of scattered radiation with a speckle structure. This distribution is detected with a one-dimensional or two-dimensional image detector. An autocorrelation function RI(r) of the detected intensity distribution is calculated, and from the position .delta.r of its first zero the diameter d.sub.P of the scattering particle is evaluated based on I, the wavelength of the electromagnetic radiation, and Z.sub.0, the distance from the particle to the detector.

Abstract: The invention provides an apparatus, and method of making the apparatus, for optical sensing of parameters in high temperature environments, such as chemical reaction zones, combustion zones, high temperature drying processes, and the like. Moreover, the optical apparatus of the invention are able to operate in high temperature environments without need for associated cooling equipment. The optical elements of the sensors are fabricated from a material that is refractory, is transparent to electromagnetic radiation, has low thermal conductivity, and that reduces in viscosity when heated to a temperature well above the operating temperature to which it will be subjected in the monitoring environment. Preferably, the optical elements, and even mechanical elements, are made of a vitreous silica material.

Abstract: An apparatus for detecting the longitudinal edges of a rod-shaped object moving in its longitudinal direction, in particular a tobacco or filter rod, comprises a light source, at least one beam divider for dividing the light beam coming from the light source into at least two light beams sweeping over the edge regions of the object, an optical deflection system for sweeping the two light beams over the object, two photodetectors for the light beams and an evaluating means for determining the position of the longitudinal edges from the instants of the bright/dark transitions at the two photodetectors on the one hand and the instantaneous positions of the light beams on the other hand. The or each beam divider generates two light beams which are parallel to each other and move in opposite directions over the object.

Abstract: A method wherein two light fluxes I.sub.1 and I.sub.2, spectrally encoded by interspersing or alternating line frequency spectra, are transmitted through an optical fiber from a transducer to an evaluation unit which generates an indication signal in relation to the ratio of the optical power of the two light fluxes. Both light fluxes I.sub.1 and I.sub.2 are generated with distinctly different narrow-bandline structures of the spectral distribution of their optical powers with the spectral separation of adjacent lines of the two line fluxes being greater than the linewidth of these lines. The optical power of the spectrally interposed light fluxes I.sub.1 and I.sub.2 are measured individually after spectral separation by filters which are selected to the specific distribution of the light fluxes I.sub.1 and I.sub.2.

Abstract: A rotation rate measuring device is disclosed in which two beam portions travel around an optical-fiber coil (6) in opposite directions, and in which the Sagnac phase difference between the two beam portions after passage through the optical-fiber coil is evaluated. A beam splitter (2) divides a light beam into the two beam portions. Between this beam splitter and one end of the optical-fiber coil (6), an additional beam splitter (4) is inserted which is followed by a spatial filter (13) and a frequency shifter (5). Also provided are means which ensure that the two beam portions which travel around the optical-fiber coil in opposite directions pass through the spatial filter and the frequency shifter by the same path. A fully reciprocal arrangement is thus obtained.

Abstract: A method and apparatus are provided for the remote measurement of a quantity of length or displacement, employing fiber-optical signal transmission between two or more interferometers, one of which acts as an optical transducer while the other acts as the receiver for the information about the quantity to be measured. A major advantage of the arrangement is that it operates with low-power, spatially incoherent broad-bandwidth light. More particularly, the quantity to be measured is represented by the path difference of two partial light beams passing through the arms of one interferometer, thus encoding the information about the path difference onto the light-flux resulting from the recombination of the two partial light beams. The transmitting interferometer is connected by an optical fiber with a receiving interferometer, where the information is recovered by evaluating the autocorrelation signal of the transmitted light.

Abstract: A fiber-optic polarizer comprising the combination of an optical fiber having a core and cladding with different refractive indices and forming a single-mode guiding region, the core having a non-circular cross-section defining two transverse orthogonal axes which, in combination with the different refractive indices, permit the de-coupling of waves polarized along the axes, the guiding region being located sufficiently close to the surface of the fiber, along a selected length of the fiber, to allow coupling to a contiguous medium, and the outer surface of the fiber having a non-circular cross-section with a predetermined geometric relationship to the guiding region and the orthogonal transverse axes so that the location of the guiding region and the orientation of the axes can be ascertained from the geometry of the outer surface.

Abstract: For interferometric measurement of the length of the linear component of movement of a moving point relative to a fixed point and simultaneous recognition of the direction of that movement, two merged or overlapping Fabry-Perot part interferometers are used to form an asymmetric pattern of the reflection or transmission intensity which is periodically dependent on the linear component of the path, the pattern having main and secondary maxima of different heights and main and secondary minima of different depths. The intensity variation is converted by a detector into electrical intensity signals which cross threshold values of trigger circuits to produce output pulses. The pulses are combined and counted to produce displays of the direction and to provide a reading of the instantaneous position of the movable point.

Abstract: In order to measure the intensity of an electric current utilizing the Faay effect, an optical path which is exposed to a magnetic field generated by the current is marked by an optical fiber which is laid in a number of windings in the shape of a coil. In order to minimize the disruptive effect of, for instance, elliptical eigen-birefringence of the fiber, or birefringence caused by the laying of the fiber on the zero point and the calibration factor of the device, the end of the optical fiber which is away from the input point is provided with a reflection unit which reflects back into the fiber the light which arrives there with the same polarization state with which it arrived at the reflection unit. A polarization measurement unit is used to record the polarization state of light flux which, after having traversed the optical fiber a total of twice, again emerges at the input point.

Abstract: A fiber optical arrangement for the transmission, in a manner preserving its polarization, of light of a linear polarization state using an optical fiber having a linear birefringence of an amount sufficient to provide extensive decoupling of the polarization-degenerate modes of oscillation of the light that can propagate within the fiber. The amount of linear birefringence .beta. required for decoupling these modes of oscillation is achieved by winding the optical fiber in an elastically extended condition upon a winding form and fixing it thereon in this elastically extended state, the linear birefringence .beta.=.beta..sub.tc +.beta..sub.b being preferably three times greater than the intrinsic birefringence .beta..sub.i of the optical fiber. The fiber optical arrangement may be used within an interferometer for measuring pressures or, if mounted to rotate, within a Sagnac interferometer also for the exact measurement of rotations and rates of angular displacements.

Abstract: In order to measure the rotation rate of a rotating light path by the Sag effect, a pair of phase modulated coherent light beams are passed in opposite directions along the light path. After the beams have emerged from respective ends of the light path, the intensity of one of them is detected as a measurement of the phase shift which occurs between the beams along the light path. The detected output is then passed through a synchronous rectifier to produce an error signal for a control loop for the system. In a preferred embodiment, the control loop is formed by a solenoid wound around a portion of an optical fiber located along said light path. By processing the current through the solenoid, a continuous update of a scale factor for the phase shift can be achieved.

Abstract: In order to permit the measurement of very small rotation rates, the rotan rates are measured by the Sagnac effect in a light path encircling an area. To accomplish this, two coherent light beams are coupled into the two ends of said light path of which a section is subject to perturbations that affect the polarizations of said two light beams. After the beams emerge again from the ends of said fiber, they are superimposed so that they interfere. The rotation rate of said light path can then be evaluated from an analysis of the interference. In particular, in order to reduce sensitivity to the perturbations, the two light beams are coupled with defined states of polarization into said light path of which a section is subject to perturbations, and the two interfering beams pass through at least one polarization analyzer, the azimuth and ellipticity of which is adjusted for maximum transmission of light which is the conjugate of one of said light beams coupled into said light path at one end thereof.

Abstract: In a device for determining the influence of physical parameters on the lth of a path, an elastically stretchable optical fiber is guided with minimal pretensioning along the path which is subjected to length changes. The optical fiber is mounted at least sectionally on supports subjected to positional changes with changes in the length of the path. A transit-time measuring device is also provided as part of the measuring device together with the optical fiber. The transit-time measuring device includes a light-pulse repeater forming a closed signal path with the optical fiber. The repeater generates signal pulses circulating in the signal path with the periodicity of the signal circulation time of the signal path. From an electronically measured total travel time through the closed signal path and a total number of which signal pulses the electrical display signal can then be derived to determine the length and change in length of the path being measured.

Abstract: A fibre optical arrangement for measuring the intensity of an electric current using the Faraday effect, in which the path of light whose state of polarization is influenced by the magnetic field surrounding the conductor through which current flows is marked by the core of an optical fibre which is coiled round the conductor in a number of turns, the optical fibre used in the arrangement being one which has a circular double refraction .alpha. at least of the order of magnitude of a linear double refraction .beta. determined by the structure of the fibre and its coiled arrangement. The fibre is preferably twisted about its longitudinal axis so that the twist is substantially evenly distributed over the length of the optical fibre.

Abstract: A fiber-optic circuit element is provided of the type for coupling signal ght from a first optical fiber to at least one second optical fiber wherein at least one of the optical fibers has a free end which is controllably movable to be in or out of alignment with the other fibers. Movement of the free end of the fiber is achieved by an expansion layer applied to the fiber and acting as a heatable bimetallic element. Heating of the expansion layer can be achieved by absorption of electromagnetic radiation, including an independent source of control light and/or a portion of the signal light itself. Electrical heating mechanisms can also be used. This circuit element can be advantageously used without limit in optical switches, astable multivibrators, bistable multivibrators, optical resonators, and environmental temperature and pressure detectors.

Abstract: The present invention is concerned with an imaging system for the self-imaging of objects, using optical waveguides comprising reflecting boundary surfaces, and satisfying the imaging condition L.lambda. = 4hN.sub..mu. W.sup.2.sub.eq, wherein L is the axial distance between the object and the self-image, W.sub.eg is a typical transverse dimension of the waveguide having an effective refractive index N.sub..mu., and .lambda. is the operational wavelength, and h is an integer for single imaging and not an integer for multiple imaging.Many embodiments of dielectric thin film waveguides are described which have the purpose of self-imaging very small objects with good levels of resolution. Magnification or reduction by means of the imaging system are also provided for.