Abstract: An optical sensor system uses a light source which outputs light at a plurality of wavelengths which vary with time in a manner such that only one wavelength is output at any one point in time; and a transducer which modulates light at each wavelength in a manner indicative of the parameter (for example, position or temperature) begin sensed. The transducer's output is, therefore, an optical signal in which the modulated intensity varies with time since only one wavelength is output at any one point in time. Because only a single wavelength is output at any one time, there is no need for an optical demultiplexer and detector array. Only a single detector is needed.

Abstract: A method for optically powering and controlling a hydraulic actuator in which the electrohydraulic servo valve is powered and controlled by a solar cell, with incident light at optimum level, but frequency-modulated at low amplitude, allowing optimum impedance matching to the servo valve solenoids. The signal is F.M. detected using a discriminator, which outputs are applied to the bases of two transistors in series with the electrohydraulic servo valve solenoids. The nearly constant output impedance of the solar cell or a follow-up amplifier allows optimum performance of the discriminator. The unique feature is the operation of the solar cell at a light level which is optimum for efficiency of the system.

Abstract: A spectrograph usable as a demultiplexer/detector in a wavelength division multiplexing optical system. The spectrograph comprises a planar waveguide and a detector array. The planar waveguide has a dispersive edge having an inwardly concave shape, an input edge, and a straight output edge. The dispersive edge has a reflective diffraction grating formed on it, the grating having a variable line spacing. An optical input signal comprising a plurality of different wavelength ranges enters the waveguide at the input edge, and travels through the waveguide and strikes the grating. The grating focuses the optical energy in each of the wavelength ranges at a focal spot at the output edge, the position of each focal spot being a function of wavelength. The detector array comprises a plurality of photodetectors positioned along a straight line, such that the photodetectors are positioned at the focal spots. Each photodetector therefore detects the optical energy in one of the input ranges.

Abstract: A three-phase angular position sensor is described in which three beams of light having polarization directions rotated 60.degree. to each other are passed through a polarizer, the rotational position of the polarizer representing an angle to be measured. The intensities of the beams transmitted through the polarizer uniquely encode its angle over a 180.degree. range. This range may be doubled, for example, by including a binary track. A two-phase angular position sensor is also described in which two beams have polarization directions oriented 45.degree. with respect to one another.

Abstract: An optical sensor in which both analog and digital techniques are employed. The sensor comprises an encoder and a detector. The encoder includes a plurality of tracks extending along a sensing axis. Each track has a property that varies along the sensing axis, such that the property can have one of three or more distinguishable levels. The detector detects the levels of the tracks at a position along the sensing axis, and produces corresponding output signals. The levels vary in a manner such that the output signals encode the position of the encoder with respect to the detector. The levels may vary in steps or continuously. For stepwise variable tracks, preferably only one track changes its level at any given position, and all changes in level occur in single steps. Both optical and electrical implementations are described.

Abstract: An optical fiber mounting device is shown which assembles the optical fiber in a ferrule which is inserted in a spherical member. The spherical member is then assembled in a spherical housing cavity and clamped by conventional means. To allow for vertical adjustment of the fiber, a spherical member may be slotted allowing sliding engagement of the ferrule. The ferrule is clamped in place when the slots are closed by the clamping action of the housing.

Abstract: A sensor that comprises an encoder that includes three or more tracks extending along a sensing axis. Each track i has a modulus m.sub.i, and a property that varies along the sensing axis such that the property can have one of m.sub.i distinguishable levels. The moduli m.sub.i of the tracks are all pairwise relatively prime. The tracks are formed such that a value is associated with each position along the sensing axis, the level of each track i at a given position being equal to the residue of the value at that position to modulus m.sub.i. The detector detects the levels of the tracks at a detection position along the sensing axis, and produces output signals corresponding to such levels. The track with the largest modulus comprises a redundant track that provides error detection capability.

Abstract: An optical source for use in an optical sensing system such as a wavelength division multiplexing system. The source produces an optical interrogation signal comprising a plurality of component signals, each component signal comprising light in a wavelength band different from the wavelength bands of the other component signals. The source comprises a concave diffraction grating, means for forming an aperture at which the interrogation signal will be formed, and a plurality of optical emitters. Each emitter is positioned such that the emitter output signal strikes the concave diffraction grating, and is focused onto the aperture, such that a portion of the emitter signal enters the aperture and forms one of the component signals. As a result, the component signal wavelengths are not sensitive to temperature-induced fluctuations in the emitter output signal.

Abstract: An optical WDM sensor and sensing system for determining a value of a measurand, such as an encoder position. An optical source produces a composite input signal that includes a plurality of different wavelength component signals. The sensor includes an encoder and a concave diffraction grating. The encoder has a plurality of tracks, each track being responsive to the value of the measurand for modulating the intensity of light incident thereon to produce a modulated signal. The grating demultiplexes the composite input signal to produce separate component signals that are directed to an incident upon the respective tracks. Each track produces a modulated signal, and the modulated signals are multiplexed, preferably by the grating, to produce a return signal that may be demultplexed and detected to determine the measurand value. Preferably, the sensor comprises a planar optical waveguide having the grating formed on one side surface.

Abstract: An optical sensor and an optical sensing system and method in which both analog and digital techniques are employed. The sensor comprises an encoder and an illumination source. The encoder includes a plurality of tracks, and the illumination source illuminates each track with an associated optical input signal. Each input signal comprises light in a wavelength range different from the wavelength ranges of the other input signals. Each track includes means responsive to the value of a measurand for modulating the intensity of the associated input signal, in one of N different ways, to produce a corresponding modulated signal, N being greater than 2. The intensities of the modulated signals thereby encode the value of the measurand. The illumination source may also produce a reference signal that is not modulated by the measurand.

Abstract: A sensor for determining the value of a measurand, such as the rotational position of a shaft (32). The sensor includes a wavelength sensitive beamsplitter (44), an encoder (30), and a wavelength sensitive modulator (48). A beamsplitter receives an optic input signal (60) having first (80) and second (82) wavelength bands, and forms the input signal into first (62) and second (64) beams corresponding to the wavelength bands. The encoder includes a track (36). The modulator preferentially modulates the intensity of light in the first wavelength band in comparison to light in the second wavelength band. The first beam is modulated by the encoder to form a modulated first beam (66), and the second beam is modulated by the modulator to form a modulated second beam (68). A differential embodiment is also provided in which the encoder comprises a pair of mechanically coupled tracks, one track modulating each beam.

Abstract: An optical switch and a wavelength division multiplexing system utilizing the switch. The multiplexing system comprises an optical bus, an optical source, and a plurality of optical switches. The source provides light on the bus having a plurality of wavelength bands, and the switches are serially connected along the bus. Each switch includes means for reacting to an external stimulus by assuming one of at least two states. In a first state, light in all wavelength bands is transmitted through the switch. In a second state, light in a modulation wavelength band is attenuated, and light in the remaining bands is transmitted, the modulation band being different for each switch. The switch may comprise an optical bandpass filter onto which light from the bus is directed, such that light within the passband is transmitted, and light outside the passband is reflected. The transmitted beam is selectively attenuated in accordance with the external stimulus.

Abstract: A light transmission filter for transmitting a beam of light of any wave length. The filter is made up of a pattern of opaque figures positioned along a transparent substrate. The spacing between figures is varied along the substrate so that the beam of light intercepted by the filter is variably transmitted as a selected function of the longitudinal position of the filter relative to the beam of light. The spacing of the figures along the substrate is selected to achieve a light transmission characteristic for the film in accordance with a desired mathematical function. An optical analog position sensor for sensing the position of a movable member along a prescribed path including the optical transmission filter attached to the movable member with the substrate having a longitudinal configuration corresponding to the prescribed path. The intensity of a fixed beam of light transmitted through the filter indicates the position of the member.

Abstract: An optical encoder produces a reference signal and compensates for any instability in intensity of a light source which reads the encoder. The optical encoder comprises a movable encoding element having an analog track of variable transmissivity, and a chopping element for alternately transmitting light from the source through the analog track and around the analog track. Light transmitted through the analog track comprises an information signal and light transmitted around the analog track comprises the reference signal. The chopping element comprises an optical switch or a rotatable or stationary element havnig an alternating series of opaque and transparent sections.

Abstract: Integrated optic sensors for measuring electric, magnetic and temperature fields. Each sensor comprises an interferometer that includes first and second arms, each arm comprising an optical waveguide formed in a substrate. The interferometer includes a field sensitive material positioned adjacent the first arm for varying the optical path length of the first arm in accordance with the applied field. Electric, magnetic and temperature field sensors are provided that are based upon stress induced refractive index changes induced in the first arm. Electric and magnetic field sensors are disclosed based upon evanescent field coupling between the field sensitive material and the first arm. A dual ring resonator embodiment is also described.

Abstract: A multiplexed optical communication system comprising a source (12), a common optical bus (18, 20), a multiplexer (14) and a demultiplexer (16). The multiplexer comprises a plurality of modulators (50), each being formed in an electro-optic substrate and comprising a modulated arm (54) and a reference arm (56). Each arm comprises an optical waveguide, and the arms of each modulator have an optical path length difference LM(i) that is greater than the coherence length of the source, and that differs from the path length difference of each other modulator by an amount greater than the coherence length of the source. Each modulator also includes electrodes for varying the optical path length of its modulated arm based upon an electrical input signal representing an input data channel. The demultiplexer comprises a plurality of detectors, each having first and second detector arms, each detector arm comprising an optical waveguide.

Abstract: An optical sensor comprising an encoder having a plurality of tracks, and illumination means for illuminating each track with an optical input signal that includes a plurality of wavelength components. Each wavelength component comprises light in a wavelength range different from the wavelength ranges of the other components. Each track includes means for modulating the input signal, and for dispersing the input signal to produce a plurality of spatially dispersed output signals. Each output signal comprises one of the wavelength components. Output signals having different wavelength components from different tracks are combined to produce a composite output signal, such that each wavelength component in the composite output signal is modulated by a different track. The output signal may therefore be demultiplexed to produce information indicating the position of the encoder. The encoder preferably comprises a masked diffraction grating.

Abstract: An optically powered resolver for detecting an optical property of an encoder at a plurality of encoding sites on the encoder, to permit determination of the position or other state of the encoder. Each encoding site is capable of receiving an optical encoder input signal and of modulating the encoder input signal to produce an optical encoder output signal. The resolver includes a photocell for converting the optical input signals into corresponding electrical input signals, and an energy storage circuit for storing a portion of the energy of the electrical input signals. The resolver also includes an interrogation circuit for interrogating a selected encoding site with an encoder input signal in response to the receipt of an optical input signal by the resolver. Interrogation means provides an optical output signal corresponding to the resulting encoder output signal.

Abstract: A multiplexed optical sensor system comprising a short coherence length source (SLD 60), a plurality of waveguide sensors (62, 64), a corresponding plurality of waveguide detectors (68, 70), and a common optical bus 84. Each sensor comprises a sensor interferometer having sensing and reference arms, each arm comprising an optical waveguide. Means are provided for varying the optical path length of the sensing arm based on a sensed input parameter. In one preferred embodiment, the detection subsystem comprises a plurality of detectors, each comprising a photodetector and a detector interferometer having first and second arms. The arms of each sensor interferometer (i) have an optical path length difference LS(i) that is greater than the coherence length of the SLD, and that differs from the path length difference LS(j) of each other sensor interferometer by an amount greater than the coherence length of the SLD.

Abstract: The present invention is concerned with directly measuring belt speed by placing two high resolution single fiber optical reflectometers a known distance apart on a line parallel to the belt motion. The signal from the first reflectometer is delayed and the cross correlation function of the two signals is calculated in real time. The cross correlation function can be maximized by varying the delay. When the maximum is observed, the belt velocity may be found by dividing the reflectometer separation by the delay.