Abstract: A gauging system for a fluid tank includes means for determining fluid pressure data for the tank; means for determining acceleration data of the tank; and means for determining quantity of fluid in the tank as a function of the pressure and acceleration data. A method for determining quantity of fluid in a tank is also provided and includes the steps of:a. determining an orientation vector for each of a plurality of sensing areas of the tank;b. producing an output corresponding to pressure of the fluid on each of the respective sensing areas;c. determining an acceleration vector of the tank; andd. calculating quantity of fluid in the tank as a function of the pressure output signals, the orientation vectors and the acceleration vector.

Abstract: What is hereof proffered is a method and apparatus for optically multiplexing together a plurality of optical modulation devices on a limited number of optical transmission paths utilizing electrically passive photoactivated optical switches. The switches have the characteristic that prior to illumination, an input channel is coupled to a specific output channel. Following illumination, after a characteristic time delay, t, a first switch activates so that the input channel is disconnected from the first output channel and connected to a second output channel. It remains connected to the second output channel until the illumination is removed at which time the input channel is disconnected from the second output channel and reconnected to the first output channel. The switches are arranged sequentially along an outwardly directed optical transmission path.

Abstract: An optical wavelength detector includes a photoelectric device that produces a signal in response to incident light thereon corresponding to a characteristic of the incident light such as wavelength. A light source is provided that can selectively expose light to the photoelectric device. A memory device stores device characterization data that corresponds wavelength information to current ratio signals from the photoelectric device. The current ratio signals are digitized and form part of the address for the memory. In a temperature compensated embodiment, the optical wavelength detector includes means to determine a temperature dependent electrical characteristic of the photoelectric device. In the preferred embodiment this electrical characteristic is the forward bias voltage detected when a predetermined forward bias current is applied to the photoelectric device in the dark.

Abstract: A debris monitor apparatus and method and optical sensor apparatus and method that use the Faraday Effect to detect accumulation of debris on a magnetic probe. The probe contains a magnet and the optical sensor and is immersible in the fluid. As debris accumulates on the probe, the magnetic field changes. The optical sensor includes a magneto-optic material located within a portion of the changeable magnetic field, preferably near a node of the magnet. Means are provided to bi-directionally address the sensor magneto-optic material with linearly polarized light. Means are also provided to convert rotation of the light polarization angle into a modulation of the light's intensity. An electro-optic transducer converts the light intensity into electrical signals that indicate the quantity of debris accumulation on the probe, with a differentiated value of these signals with respect to time yielding rate of debris accumulation on the probe.

Abstract: An apparatus and method for measuring the torque of a rotating shaft is provided, utilizing a single sensor which provides a signal which is processed to yield a temperature compensated value of the torque applied to a rotating shaft. A magneto-optic material such as a Faraday film is positioned adjacent to the rotating shaft and is subjected to a saturating magnetic field. Ferrous elements are provided about the periphery of the rotating shaft and cause the modulation of the magnetic field applied to the magneto-optic material. The rotation of the linear polarization vector of light passing through the magneto-optic material when the material is magnetized to the saturation level changes in accordance with temperature. Thus, the amplitude of the output optical signal varies in accordance with the temperature of the shaft.

Abstract: The sensor and method of monitoring of the invention uses light diffracted from diffracting elements having at least one region of nonuniformity. The sensor is useful for monitoring displacement, stress, temperature and pressure. In one form of the invention, a diffraction grating is fabricated from first and second gratings and has a step-wise change in the grating period at an inter-grating boundary. The grating is illuminated with broadband light that is diffracted as a function of the irradiated position on the grating with the wavelength of the diffracted light and the change in wavelength being a function of the diffraction grating position. In another form of the present invention, a diffraction grating is provided with a variable grating period than can vary linearly, exponentially, or in accordance with some other function with the wavelength of the diffracted light being a function of the relative displacement of the grating.

Abstract: The sensor and method of monitoring of the invention uses light diffracted from diffracting elements having at least one region of nonuniformity. The sensor is useful for monitoring displacement, stress, temperature and pressure. In one form of the invention, a diffraction grating is fabricated from first and second gratings and has a step-wise change in the grating period at an inter-grating boundary. The grating is illuminated with broadband light that is diffracted as a function of the irradiated position on the grating with the wavelength of the diffracted light and the change in wavelength being a function of the diffraction grating position. In another form of the present invention, a diffraction grating is provided with a variable grating period that can very linearly, exponentially, or in accordance with some other function with the wavelength of the diffracted light being a function of the relative displacement of the grating.

Abstract: An optical frequency domain distributed strain sensor for determining the strain distribution along an optical fiber includes an optical source that provides a polarization controlled optical interrogation signal having a frequency that varies in a recurring linear manner. The interrogation signal is injected into a sensor fiber embedded within a composite structure that places the fiber under strain. A portion of the interrogation signal is backscattered from the sensing fiber as a consequence of the strain experienced by the fiber and is mixed with a reference signal to produce beat frequency signals. The frequency of the beat signals is directly related the to position of backscatter in the sensing fiber while the amplitude of each beat frequency signal is directly related to the integrated strain-induced birefringence up to the backscatter point.

Abstract: An optically powered sensor system with improved signal conditioning includes a plurality of sensors connected to a system optical bus that communicates with a system controller. Optical energy is transmitted along the bus for distribution to all sensor in the system with return pulses from the various sensors transmitted on the bus to the system controller. Each sensor includes a photodiode array for converting optical energy transmitted system-wide by the controller into electrical energy for storage in a storage capacitor associated with each sensor. A capacitance probe transducer and a fixed-value reference capacitor are connected to a resettable integrating pulse encoder that produces a series of short-duration pulses having a pulse spacing that is dependent upon the fixed value of the reference and the parameter-affected value of the transducer. The pulses are used to drive an optical source for transmitting optical pulses from the sensor to the system controller.

Abstract: The system and method provide an electrically passive optically controlled acoustic transceiver system which measures the quantity of a liquid, such as aircraft fuel, in a tank. Pulsed electromagnetic radiation, such as light or infrared radiation, is guided through an optical fiber and impinged upon a flexible member adapted to flex when heated and transmit acoustic pulses. An optical fiber detector, is used to monitor the acoustic pulses reflected from the liquid level in a fuel tank. The system is electrically passive and does not require or use electrical power at the sensing location.

Abstract: A sensor testing apparatus which is capable of testing any sensor regardless of the type of polarization the sensor is sensitive to. The testing apparatus comprises a source conditioning apparatus to produce a beam of optical energy of a known polarization state. A polarization conditioning apparatus changes the polarization state of the optical energy beam to any desired polarization state. A transmit quadrant detector detects the polarization of the optical energy and the optical energy is directed to a sensor to be tested. The optical energy transmitted by the sensor is detected by a receive quadrant detector. The polarization state is displayed on the monitor of a computer by virtue of a computer interface with both quadrant detectors.

Abstract: The system and method provide an electrically passive optically controlled acoustic transceiver system which measures the quantity of a liquid, such as aircraft fuel, in a tank. Pulsed electromagnetic radiation, such as light or infrared radiation, is guided through an optical fiber and impinged upon a flexible member adapted to flex when heated and transmit acoustic pulses. An optical fiber detector, is used to monitor the acoustic pulses reflected from the liquid level in a fuel tank. The system is electrically passive and does not require or use electrical power at the sensing location.

Abstract: A displacement detector provides a light beam which impinges on an article with different combinations of light altering materials such as reflecting and non-reflecting surfaces, wave retarding plates, and linear polarizers attached to the article to determine angular position, relative angular displacement, and speed of rotatably mounted articles. These beam altering materials change either the polarization state or the magnitude of the light in a predictable manner. When used on different ends of a rotating shaft, the shaft speed and torsional displacement of the front shaft end with respect to the rear shaft end can be determined. When used with an article such as a rotatably mounted throttle, the angular displacement of the throttle can be determined.

Abstract: A transducer system that uses diffracted light energy in a transducer application analyzes light diffracted from a diffraction grating to provide an indication of displacement or other measurable environmental changes, such a temperature changes. In one form of the invention, a diffraction grating is fabricated from first and second gratings and has a step-wise change in the grating period at an inter-grating boundary. The grating is illuminated with broadband light that is diffracted as a function of the irradiated position on the grating with the wavelength of the diffracted light and the change in wavelength being a function of the diffraction grating position. In another form of the present invention, a diffraction grating is provided with a variable grating period that can vary linearly, exponentially, or in accordance with some other function with the wavelength of the diffracted light being a function of the relative displacement of the grating.

Abstract: A rotating shaft torsional displacement and speed detector provides a light beam which impinges on one or both ends of the rotating shaft. Different combinations of beam altering materials such as reflecting and non-reflecting surfaces, wave retarding plates, and linear polarizers are attached to the front shaft end and rear shaft end. These beam altering materials change either the polarization or magnitude of the light beam in a predictable manner that allows for the detection of shaft speed and torsional displacement of the front shaft end with respect to the rear shaft end.

Abstract: A multi-mode fiber optic sensor and method for optically sensing a physical perturbation includes a multi-mode optical fiber segment that accepts coherent monochromatic radiation from a suitable source. As the radiation is propagated in the fiber the various modes form a complex interference pattern that changes in response to a physical perturbation of the fiber. A detector provides an output signal to a signal processor that analyzes the signal as a function of the change in intensity to provide an information signal that is functionally related to the perturbation.

Abstract: An optical frequency domain distributed strain sensor for determining the strain distribution along an optical fiber includes an optical source that provides a polarization controlled optical interrogation signal having a frequency that varies in a recurring linear manner. The interrogation signal is injected into a sensor fiber embedded within a composite structure that places the fiber under strain. A portion of the interrogation signal is backscattered from the sensing fiber as a consequence of the strain experienced by the fiber and is mixed with a reference signal to produce beat frequency signals. The frequency of the beat signals is directly related the to position of backscatter in the sensing fiber while the amplitude of each beat frequency signal is directly related to the integrated strain-induced birefringence up to the backscatter point.

Abstract: A speed sensor for sensing the rotational speed of an N bladed fan in a turbo-machine application includes a polarization-preserving optical circuit positioned adjacent the locus described by the remote ends of the blades. First and second sets of sensing segments of the optical circuit are spaced apart from one another by an angular spacing equal to that of the blades and with the first set of sensing segments angularly offset from the second set and with the first and second sets cross-coupled to transpose the polarization modes. The orthogonal polarization modes of optical energy launched into the optical circuit are subjected to phase shifts as the optical fiber is perturbed by pressure variations caused by the moving fan blades with the cumulative phase shift in each portion of the optical circuit subtracted as a consequence of the cross-coupling and the resulting light output having an intensity or other characteristics that vary as a function of the rotational speed of the fan.

Abstract: Apparatus and method for self-referencing and multiplexing light intensity modulating fiber optic sensors provides a pulsed or chirped source light beam. The light beam is propagated through an input fiber optic cable into at least a first loop path. In the first loop path, the source light beam is modulated in accordance with a detected phenomenon to provide a modulated light beam. In the first loop path, a coupler splits-off (a) a portion of the source light beam, and (b) a portion of the modulated light beam. The split off portions are directed through an output fiber optic cable to a photo detector which thus receives a pulse train having a modulated pulse and an unmodulated pulse. The output of the photo detector is supplied to a processor which forms a ratio of the modulated and unmodulated pulses and provides an output signal which varies in accordance with the detected phenomenon but is relatively insensitive to optical transmission losses and optical source drift.

Abstract: Method and apparatus for compensating a phototransducer system for fiber optic transmission losses and optical source power fluctuations includes generating a broadband source light beam having a plurality of spectral components. The source light beam is transmitted to a polarizer which polarizes the light beam and directs it to a multiple wave retardation device. The retardation device retards the spectral components of the polarized light beam. The retarded light beam is injected into a photoelastic transducer which modulates the polarizations of the retarded light beam in accordance with pressure applied to the transducer. Each spectral component of the retarded light beam will be modulated by the transducer. However, the broadband light beam will remain, in sum, relatively invariant to the applied pressure. The modulated light beam is then passed through an analyzer, injected into a fiber optic cable, and transmitted to a beam splitter.