Abstract: A photonic compressive sampling system includes a photonic link with at least one electro-optic modulator that modulates a continuous wave optical energy with both an electrical analog signal and a pseudorandom bit sequence signal. A photodetector receives the modulated optical energy from the electro-optic modulator, and an electrical digitizer digitizes the output from the photodetector. The system enables signal recovery beyond the Nyquist limit of the digitizer. The signal being recovered has a sparse (low-dimensional) representation and the digitized samples are incoherent with this representation. An all-photonic system can faithfully recover a 1 GHz harmonic signal even when digitizing at 500 MS/s, well below the Nyquist rate.

Abstract: A system testing the speed of a microwave photonic system, having a Mach Zehnder interferometer that includes a first arm with a photonic system to be tested and an amplifier arranged to amplify the output of the photonic system, and a second arm with an attenuator configured to match the output power of the amplifier, with at least one filter arranged at the output of the Mach Zehnder interferometer, the filter having a pass band that includes the center frequency of a continuous wave microwave signal applied to the Mach Zehnder interferometer arms. A continuous wave microwave signal is applied to the input of the Mach Zehnder interferometer, a signal is applied to only the second arm with the photonic link, and the output of the bandpass filter is measured with an oscilloscope and a microwave power detector.

Abstract: A true time delay system for optical signals includes a hollow core optical waveguide, a droplet of reflective liquid metal disposed in the hollow core, and an actuator coupled to a first end of the waveguide to move the droplet longitudinally within the hollow core. In one example, the waveguide is a hollow core photonic bandgap fiber. In one example, the actuator is a pressure actuator that introduces or removes gas into the core. Light enters the optical fiber, is transmitted through the fiber toward the reflective surface of the droplet, and is reflected back through the fiber and exits at the same end of the photonic bandgap optical fiber that it entered. The fiber optic device can provide a continuously-variable optical path length of over 3.6 meters (corresponding to a continuously-variable true-time delay of over 12 ns, or 120 periods at a 10 GHz modulation frequency), with negligible wavelength dependence across the C and L bands.

Abstract: A system testing the speed of a microwave photonic system, having a Mach Zehnder interferometer that includes a first arm with a photonic system to be tested and an amplifier arranged to amplify the output of the photonic system, and a second arm with an attenuator configured to match the output power of the amplifier, with at least one filter arranged at the output of the Mach Zehnder interferometer, the filter having a pass band that includes the center frequency of a continuous wave microwave signal applied to the Mach Zehnder interferometer arms. A continuous wave microwave signal is applied to the input of the Mach Zehnder interferometer, a signal is applied to only the second arm with the photonic link, and the output of the bandpass filter is measured with an oscilloscope and a microwave power detector.

Abstract: A true time delay system and method for an optical carrier signal modulated with a microwave signal. The system includes a beam deflector, with the optical signal being imaged onto the beam deflector, a stationary reflective diffractive grating arranged in a Littrow configuration, a focusing element arranged between the beam deflector and the stationary reflective diffractive grating. In operation, the beam deflector steers the optical beam across the clear aperture of the focusing element and the focusing element transmits the steered beam to the reflective diffractive grating. A change in optical path length experienced by the optical beam as the beam is scanned across the grating surface results in a relative phase delay in the optical beam. The beam deflector can be a rotating mirror, an acousto-optic beam deflector, or an electro-optic beam deflector. The focusing element can be a lens or a curved mirror.

Abstract: A true time delay system for optical signals includes a hollow core optical waveguide, a droplet of reflective liquid metal disposed in the hollow core, and an actuator coupled to a first end of the waveguide to move the droplet longitudinally within the hollow core. In one example, the waveguide is a hollow core photonic bandgap fiber. In one example, the actuator is a pressure actuator that introduces or removes gas into the core. Light enters the optical fiber, is transmitted through the fiber toward the reflective surface of the droplet, and is reflected back through the fiber and exits at the same end of the photonic bandgap optical fiber that it entered. The fiber optic device can provide a continuously-variable optical path length of over 3.6 meters (corresponding to a continuously-variable true-time delay of over 12 ns, or 120 periods at a 10 GHz modulation frequency), with negligible wavelength dependence across the C and L bands.

Abstract: A photonic compressive sampling system includes a photonic link with at least one electro-optic modulator that modulates a continuous wave optical energy with both an electrical analog signal and a pseudorandom bit sequence signal. A photodetector receives the modulated optical energy from the electro-optic modulator, and an electrical digitizer digitizes the output from the photodetector. The system enables signal recovery beyond the Nyquist limit of the digitizer. The signal being recovered has a sparse (low-dimensional) representation and the digitized samples are incoherent with this representation. An all-photonic system can faithfully recover a 1 GHz harmonic signal even when digitizing at 500 MS/s, well below the Nyquist rate.

Abstract: A system and method for encoding zero and one bits for transmission, including generating a first signal from a non-linear chaotic system to represent the one bit, with the signal's embedded vectors being within the non-linear system's attractor set, and generating a second signal from the non-linear system to represent the zero bit, with the signal's embedded vectors being outside the non-linear system's attractor set. The second signal encoding the zero bit can be generated by adding together two chaotic signals arising from the non-linear system initialized with different initial conditions, and weighting the second signal to have approximately the same energy as the first signal. One suitable chaotic systems is a Lorenz system. Systems and methods for decoding a transmitted stream of signals compare a detection statistic of the received stream of signals to a threshold value that depends on the chaotic system.

Abstract: A true time delay system and method for an optical carrier signal modulated with a microwave signal. The system includes a beam deflector, with the optical signal being imaged onto the beam deflector, a stationary reflective diffractive grating arranged in a Littrow configuration, a focusing element arranged between the beam deflector and the stationary reflective diffractive grating. In operation, the beam deflector steers the optical beam across the clear aperture of the focusing element and the focusing element transmits the steered beam to the reflective diffractive grating. A change in optical path length experienced by the optical beam as the beam is scanned across the grating surface results in a relative phase delay in the optical beam. The beam deflector can be a rotating mirror, an acousto-optic beam deflector, or an electro-optic beam deflector. The focusing element can be a lens or a curved mirror.

Abstract: A system and method for encoding zero and one bits for transmission, including generating a first signal from a non-linear chaotic system to represent the one bit, with the signal's embedded vectors being within the non-linear system's attractor set, and generating a second signal from the non-linear system to represent the zero bit, with the signal's embedded vectors being outside the non-linear system's attractor set. The second signal encoding the zero bit can be generated by adding together two chaotic signals arising from the non-linear system initialized with different initial conditions, and weighting the second signal to have approximately the same energy as the first signal. One suitable chaotic systems is a Lorenz system. Systems and methods for decoding a transmitted stream of signals compare a detection statistic of the received stream of signals to a threshold value that depends on the chaotic system.

Abstract: A probe position sensing system for accurately determining a spatial location in a coordinate system of a distal end of a probe assembly. The probe assembly includes an articulated arm having a pair of sections interconnected by a flexible joint and at least one element. The element extends through the joint and is positioned to be subjected to a degree of flexure due to relative displacement of the sections. A flexure of the element induces a change in a physical property associated with the element. An instrument monitors the physical property and derives an angle between adjacent sections from variations of the physical property.

Abstract: The fiber-optic pipette (FOP) couples a glass capillary, common syringe and a single optical fiber together to provide for a facile means of achieving long-pathlength capillary spectroscopy. The FOP acquires rapid spectroscopic measurements of small-volume liquid samples, while simultaneously achieving signal enhancements of the collected spectroscopic signal.

Abstract: This invention is a quasi-static fiber pressure sensor using self-referenced interferometry based on a broadband semiconductor source which probes the pressure plate deflection within a Fabry-Perot cavity where phase is demodulated with a dual grating spectrometer providing real-time, high resolution remote measurement of pressure using optical interrogation of a deflecting pressure plate. This technique yields absolute gap measurement in real time over a wide range of gap lengths with nanometer resolution. By tailoring the pressure plate design to cover the range of gaps and deflection that can be resolved, pressure sensing with psi resolution can be obtained in a kpsig pressure range.

Abstract: A system for the in-situ detection of chemicals, including water, in soil comprises: a penetrometer for penetrating the soil, the penetrometer including interior and exterior surfaces, and a window for allowing infrared radiation to be transmitted between the interior and exterier surfaces of the penetrometer; a driver for driving the penetrometer into the soil to a plurality of different depths; a source for providing infrared radiation which passes through the window to irradiate the soil adjacent to the window; an infrared transmitting chalcogenide optical fiber; an optical system disposed within the penetrometer adjacent to the window for transmitting infrared radiation from the source through the window into the soil and for collecting infrared radiation reflected from the soil back through the window into a first end of the chalcogenide fiber; and a spectrometer coupled to a second end of the infrared transmitting chalcogenide optical fiber for receiving and analyzing the reflected infrared radiation pa

Abstract: A fiber optic Faraday flux transformer sensor is disclosed which comprises: a closed loop of wire being responsive to a first time-varying magnetic field from a remote source for producing a secondary time-varying magnetic field which varies as a function of the first time-varying magnetic field, and an optical fiber loop having a plurality of turns arranged in a preselected configuration adjacent to the closed loop of wire and adapted to receive and pass therethrough input light having a fixed state of linear polarization. The optical fiber loop is responsive to the secondary time-varying magnetic field and to the input light for producing light having a polarization state which changes as a function of the secondary time-varying magnetic field applied thereto. In a system implentation, an optical source transmits light having a linear state of polarization to a first polarizer, which selects and sends a fixed predetermined state of polarization to the fiber optic Faraday flux transformer sensor.

Abstract: A fiber optic transducer includes a fiber optic cable or ribbon, a sensor, fluid material for coupling the fiber optic medium to the sensor and an affixing material to optionally affix the position of the sensor position relative to the fiber optic ribbon by affixing only one end of the sensor to the fiber optic ribbon. The sensor can be made from either magnetostrictive or electrostrictive materials. The coupling fluid enables the transducers to be manufactured with substantially similar frequency responses across a range of frequencies.

Abstract: A fiber optic interferometer sensor system utilizing a fiber optic interferometer with an elecrostrictive transducer bonded to one of first and second optical fiber arms of the interferometer for obtaining excellent low frequency voltage detectors and electric field sensors. The non-linear characteristics of the electrostrictive transducer allows for detecting low frequency or dc signals at sidebands of a high frequency carrier, resolving extremely small voltages at low frequencies, or sensing low frequency electric fields. Examples of electrostrictive material include Ba:PZT, PLZT, PMN+PT, and other doped ferroelectric relaxors.

Abstract: The fiber-optic magnetostrictive transducer system consists of a sensing element having three dual-strip fiber optic magnetostrictive transducers bonded into a single fiber Mach-Zehnder interferometer operating single mode mounted in a symmetrical orthogonal geometry. The dual-strip fiber optic magnetostrictive transducers have predictable and consistent reproducibility and are comprised of a pair of field annealed metallic glass strips bonded to a coil of optical fiber. This structure is in turn mounted on a bobbin structure where the fiber ribbon is attached to the bobbin only at the two ends of the bobbin. This reduces the possible loading of the transducer due to friction between the optical fiber and the surface of the mounting structure and at the same time provide a long sensing fiber in contact with the magnetostrictive element for high sensitivity.

Abstract: A three-axis fiber optic vector magnetometer is provided for measuring both he direction and magnitude of a DC or low frequency magnetic field. The magnetometer includes an optical interferometer system including a sensing fiber arm disposed with three respective sensing portions perpendicular to one another and attached to a uni-directional sensor material. The interferometer system also includes a reference fiber arm and a laser light source for generating and introducing a laser light into both of the arms. Respective biasing devices generate a reference AC magnetic bias and a respective reference frequency in the three sensing portions. A detecting device detects a reference light signal from the reference fiber arm and the magnetically altered sensing light signal from the sensing fiber arm and forms an interferometer output signal.

Abstract: An apparatus and method for monitoring a stainless steel decarburization cess includes a flame emission spatial imaging spectrometer and a telescopic lens system coupled to the spectrometer. The telescopic lens system is positioned to direct light from the furnace flame into the spectrometer. The flame emission imaging spectrometer and the telescopic lens system are located at a remote distance away from the harsh environment of the furnace flame.