Abstract: Described herein is the use of large phase transformational strain in relaxor ferroelectric single crystals for broadband sound generation. The technique exploits the thermo-optical triggering and thus an opto-acoustic effect of ferroelectric phase transformation piezocrystals under mechanical bias conditions.

Abstract: Described herein is the use of large phase transformational strain in relaxor ferroelectric single crystals for broadband sound generation. The technique exploits the thermo-optical triggering and thus an opto-acoustic effect of ferroelectric phase transformation piezocrystals under mechanical bias conditions.

Abstract: A device and system is provided for amplifying vibrations resulting from underwater acoustic signals. In operation, a laser interrogation beam is directed along an axis at the retro-reflector device and is responsive to reflections directed along the axis of the interrogation beam. The retro-reflector device reflects a signal back to a source and a tracking signal superimposed on an interrogation beam enables continuous sensing of the reflected signal to reduce signal dropout. A glint tracker is provided for steering the tracking beam on the surface. A tracker system superimposes the tracking and interrogation beams and is responsive to reflected glints in order to establish a directional location. An interferometer responsive to the reflected interrogation beam produces an interference signal for enabling continuous measurement of surface vibrations.

Abstract: A sensor system is provided comprising a Laser Doppler Vibrometer (LDV) that senses underwater sound via vibrations on an ice surface. In operation, a beam of the LDV measures a surface velocity and therefore an associated pressure signal from the ice surface due to an impinging underwater sound. The beam reflected from the surface carries the acoustic information back to the LDV. Using interferometry to derive the acoustic signal carried on the reflected beam; the LDV provides acoustic signal data in the form of a voltage signal. A computer processes the voltage signal as data that estimates a sound pressure level of the underwater source.

Abstract: An iterative joint Minimum Mean Square Error (MMSE) decision feedback equalizer and turbo decoder includes a turbo decoder portion and a decision feedback equalizer (DFE) portion. The DFE receives input signals and processes these input signals to generate an estimated symbol sequence that is communicated to the turbo decoder portion. The estimated symbol sequence is also communicated to the feedback portion of the DFE. The feedback portion of the DFE includes a symbol-by-symbol detector and a feedback filter. The soft decoder output values generated by the turbo decoder portion are communicated to the feedback portion of the DFE and are combined with the coded output as log likelihood ratio values in a multipass, iterative fashion whereby the equalizer and decoder are linked via iterative feedback to provide communication performance enhancement.

Abstract: A device and system is provided for amplifying vibrations resulting from underwater acoustic signals. In operation, a laser interrogation beam is directed along an axis at the retro-reflector device and is responsive to reflections directed along the axis of the interrogation beam. The retro-reflector device reflects a signal back to a source and a tracking signal superimposed on an interrogation beam enables continuous sensing of the reflected signal to reduce signal dropout. A glint tracker is provided for tracking the tracking beam on the surface. A tracker system superimposes the tracking and interrogation beams and is responsive to reflected glints in order to establish a directional location. An interferometer responsive to the reflected interrogation beam produces an interference signal for enabling continuous measurement of surface vibrations.

Abstract: The invention as disclosed is a system for real time detection of tsunami waves. A tsunami is considered a “shallow water wave”, having a large wavelength compared to the ocean depth. A tsunami can have wavelengths ranging from 100 to 500 km, and amplitudes up to 60 cm (i.e., a pressure signal of up to 1 psi). At least one telecommunications grade optical fiber cable fitted with repeaters spanning the length of an ocean, a laser and a signal processor are used to measure pressure signals over spatial cells as small as 0.5 meters in width based on Rayleigh scattering effects and employing optical time delay reflectometry. The tsunami pressure signals are extracted from the pressure signals generated by wind-generated water waves (having much shorter wavelengths) through signal processing to distinguish between the substantial differences in wavelength, period and propagation speed.

Abstract: An Unmanned Undersea Vehicle (UUV) docking system is provided in which the UUV is responsive to a first rotating light beam (which emits from a submarine) to begin a docking procedure. The UUV utilizes a photodetector to detect the first light beam and to guide the UUV toward the submarine by utilizing the first light beam. In one embodiment, the UUV reflects light from the first light beam back to the submarine. A photodetector on the submarine detects the reflected light to ascertain that the UUV is locked onto the first light beam. The submarine then stops rotating the light beam so that a trajectory of the UUV heads in the direction of a docking station which is positioned on the submarine.

Abstract: A target for a test range includes an impact plate having at least three strain sensors positioned on the plate. The sensors are connected to a data acquisition board for receiving a signal from each sensor upon impact of a projectile on the plate. The data acquisition board is joined to a processor for calculating impact location and energy. Optionally multiple sensors can be provided having different orientations for accounting for different strain components in the plate.

Abstract: The present invention includes a system and method of use for communications from an in-air platform to a submerged platform. The system includes a laser positionable on the in-air platform above a water medium that sends a pulsed information-bearing laser beam containing a modulated communications signal to create and react in a non-linear regime manner with the water medium at an air/water interface. The beam vaporizes and optically breaks down a portion of the water medium, creates a shock wave and generates bubble oscillations at the vaporized portion. An acoustic sensor on the submerged platform detects these shock wave oscillations within the water medium and a demodulator-decoder that identifies these broadband acoustic transients that contain deterministically placed energy and demodulates-decodes the acoustic transients into the transmitted communications signals from the in-air platform.

Abstract: A device and system to remotely detect vocalizations of speech. The skin located on the throat region of a speaking person or a reflective layer on the skin on the throat region vibrates in response to vocalizations of speech by the person. The vibrating skin or reflective layer is reflective of impinging radiation. A laser Doppler vibrometer transmits radiation onto the vibrating skin or the covering reflective layer and receives reflected radiation from the vibrating skin or reflective layer. The laser Doppler vibrometer generates voltage output signals that are representative of the speech causing the vibrations. A target tracker directs the impinging radiation and detects the reflected radiation to pass between the throat region and the laser Doppler vibrometer and includes a processor that removes non-speech signal artifacts from the voltage output signals. An interconnected audio speaker reproduces the speech from the voltage output signals.

Abstract: The present application provides a linear mechanism for optical-to-acoustic energy conversion for optoacoustic communication from an in-air platform to an undersea vehicle. Signals used in underwater acoustic telemetry applications are capable of being generated through the linear optoacoustic regime conversion process. A number of issues concerning linear optoacoustic communication is addressed that lead to a formulation of a linear regime optoacoustic communication scheme. The use of oblique laser bean incidence at an air-water interface to obtain considerable in-air range from the laser source to the vehicle is also addressed. The effect of oblique incidence on in-water range is addressed as well. Optimum and sub-optimum linear optoacoustic sound-generation techniques for selecting the optical wavelength and signal frequency for optimizing in-water range are identified.

Abstract: A device and system to remotely detect vocalizations of speech. The skin located on the throat region of a speaking person or a reflective layer on the skin on the throat region vibrates in response to vocalizations of speech by the person. The vibrating skin or reflective layer is reflective of impinging radiation. A laser Doppler vibrometer transmits radiation onto the vibrating skin or the covering reflective layer and receives reflected radiation from the vibrating skin or reflective layer. The laser Doppler vibrometer generates voltage output signals that are representative of the speech causing the vibrations. A target tracker directs the impinging radiation and detects the reflected radiation to pass between the throat region and the laser Doppler vibrometer and includes a processor that removes non-speech signal artifacts from the voltage output signals. An interconnected audio speaker reproduces the speech from the voltage output signals.

Abstract: An undersea communications system in which a message is converted to a redundant fixed-length data packet and transmitted acoustically as a quadrature phase-keyed signal in a frequency band with a continuous pilot signal at a frequency closely adjacent to the frequency band. A receiver uses the received continuous pilot signal to Doppler compensate the incoming quadrature phase keyed signal by estimating any Doppler distortion in the received pilot signal. The resultant redundant signals are then robustly processed coherently and jointly by the adaptive decision feedback equalizer and decoder to provide the original transmitted data.

Abstract: A passive acoustic sensor that may be employed to detect sounds emanating from under the surface of a body of water. The sensor uses optics to determine vibration on the surface of a water body to detect sound pressure waves from underwater sound sources. The sensor is deployed above the surface and has no direct interaction with anything under the surface that may be emanating sounds. This allows the invention to operate without interfering with potential sound sources as well as allows for numerous deployment methods.

Abstract: An apparatus for enabling acousto-optic communication comprising an in-water platform comprising means for emitting an acoustic signal to an acousto-optic interaction zone, an in-air platform comprising the ability for transmitting a first optical interrogation beam, the ability for receiving a portion of the first interrogation beam and a second laser beam formed from the reflection of the first interrogation beam off of the acousto-optic interaction zone, the ability for measuring and outputting a plurality of optical interferences between the portion of the first interrogation beam and the second reflected beam, and a signal converter receiving as input the plurality of optical interferences and outputting an electrical signal representing the received acoustic telemetry signal at the interrogation point at the air-water interface.

Abstract: The present invention provides a receiver for underwater acoustic telemetry which combines a decision feedback adaptive equalizer structure with a modified turbo-equalizer structure. The modified turbo-equalizer structure is of significantly reduced complexity because the decision feedback adaptive equalizer structure is operable to process a plurality of data channels to provide a single symbol data output stream for application to the input of the modified turbo-equalizer which uses a decision feedback equalized, interleaver, deinterleaver and a decoder. Either a hard viterbi decorder for single iteration processing or a soft in/soft out decorder such as a MAP decoder for multiple iteration can be used. The iteration provide improved performance compared to a normal DFE and lower complexity compared to the traditional turbo-equalizer.

Abstract: A buoy system bi-directionally communicates in-air and underwater. A buoy having a shell to float on water has an upper portion in air and a lower portion in water. An array of acoustic transducers which is disposed in the lower portion receives acoustic signals and transmits acoustic signals. A dome-shaped retro-reflective coating on the upper portion is vibrated for retro-reflecting impinging laser illumination as data signals in air. An array of photo-detectors on the upper portion are responsive to impinging laser control signals and/or signals which may be transmitted as acoustic signals in water.

Abstract: The present invention provides a receiver for underwater acoustic telemetry which combines a decision feedback adaptive equalizer structure with a turbo-equalizer structure. The turbo-equalizer structure is of significantly reduced complexity because the decision feedback adaptive equalizer structure is operable to pre-process a plurality of data channels to provide a single symbol data output stream for application to the input of the turbo-equalizer. The turbo-equalizer structure is also of reduced complexity due to use of a correlator to provide channel response data to the turbo-equalizer. The channel response data is produced by comparing received data comprising a training sequence with a locally produced training sequence.

Abstract: A low power transmitter providing selectable waveforms includes a self-coined power source, such as a battery. A timer powered by the battery provides a transmitter actuation signal after a predetermined delay. A voltage regulator coupled to the power source and to the timer provides power in response to the transmitter actuation signal. A waveform generator coupled to the voltage regulator provides one or more selected continuous or pulse waveforms when power is supplied by the voltage regulator. The waveform generator is pre-programmed with one or more selected continuous or pulse waveforms in digital format. The waveform generator outputs at least one selected waveform selected when power is provided by the voltage regulator. Any waveform may be selected by appropriately programming the waveform generator.