Abstract: Aspects are generally directed to free-space transmitters, free-space receivers, and free-space communication methods. In one example, a free-space communication method includes acts of mapping a data payload to one or more symbols based on a symbol set defined by a digital modulation scheme, varying one or more properties of a signal waveform to phase modulate the signal waveform with the data payload, the one or more symbols each having a symbol duration that defines a timing structure of the modulated signal waveform, and fragmenting the timing structure of the modulated signal waveform to conceal one or more waveform properties of the modulated signal waveform.

Abstract: Optical signal receivers and methods are provided that include multiple optical resonators, each of which receives a portion of an arriving optical signal. Various of the optical resonators are tuned or detuned from a carrier wavelength, and produce an intensity modulated output signal in response to modulation transitions in the arriving optical signal. A detector determines phase transitions in the arriving optical signal, by analyzing the intensity modulation output signals from the optical resonators, and distinguishes between differing phase transitions that result in a common final state of the arriving optical signal.

Abstract: Photo-resonator optical detectors and optical receiver systems incorporating same, In one example, an optically resonant detector includes a housing having an optical window, a photodetector disposed within the housing, and an optical resonator disposed in optical alignment with the photodetector within the housing and positioned between the optical window and the photodetector, the optical resonator being configured to receive an input optical signal via the optical window and to provide an output optical signal to the photodetector.

Abstract: Optical receivers and methods for balanced signal detection using an optical resonator.

Abstract: Optical receivers and methods for balanced signal detection using an optical resonator. In one example, an optical receiver includes an optical resonator that receives an optical signal, accumulates resonant optical signal energy, and emits first output optical signal energy from a first output and second output optical signal energy from the second output. In response to a modulation of the optical signal, the optical resonator is configured to disrupt the first and second output optical signal energies to convert the modulation of the optical signal into an intensity modulation of the first and second output optical signal energies. The optical receiver includes a first detector that receives the first output optical signal energy and detects the intensity modulation of the first output optical signal energy, and a second detector that receives the second output optical signal energy and detects the intensity modulation of the second output optical signal energy.

Abstract: Optical receivers configured to demodulate phase modulated optical signals. In one example, an optical signal receiver includes an optical resonator configured to receive an arriving optical signal and to emit an output optical signal in response to receiving the arriving optical signal, the optical resonator being further configured to transform phase transitions corresponding to phase modulation of the arriving optical into intensity modulation of the output optical signal, an opto-electrical converter configured to convert the output optical signal into an electrical signal, a pulse detector configured to detect pulses in the electrical energy indicative of the phase transitions in the arriving optical signal, and a memory configured to record timing information associated with the pulses detected by the pulse detector.

Abstract: A phase detection system includes first and second phase mixing circuits in signal communication with a signal phase adjuster module. The first mixing circuit generates a first digital modulated frequency signal based on an input signal and a first reference phase signal. The second mixing circuit generates a second digital modulated frequency signal based on the input signal and a second reference phase signal, which phase shifted with respect to the first reference phase signal. The phase detection system further includes a phase identification (ID) module in signal communication with the first mixing circuit and the second mixing circuit. The phase ID module generates a phase signal based on the first digital modulated frequency signal and the second digital modulated frequency signal. The phase signal indicates a phase of the input signal.

Abstract: Methods and apparatus for measuring thickness and related properties of transparent objects, such as glass.

Abstract: Optical signal receivers and methods are provided that include an optical resonator that allows optical signal energy of multiple wavelengths to enter and accumulate inside the optical resonator. A portion of optical signal energy of each wavelength is emitted from the optical resonator at an output, and the individual wavelengths may be separated. A detector aligned with the output detects the emitted optical signal energy of at least one of the wavelengths. The detector is configured to detect disturbances to the emitted optical signal energy and determine a modulated characteristic in the received optical signal energy of the wavelength.

Abstract: Aspects are generally directed to receivers and methods for actively demodulating optical signals. In one example, a receiver includes an optical resonator to receive an optical signal, the optical resonator including an active optical medium interposed between first and second semi-reflective surfaces, where the active optical medium is configured to accumulate resonant optical signal energy inside the optical resonator based on the received optical signal, the second semi-reflective surface is positioned to emit output optical signal energy, and the optical resonator is configured to disturb the output optical signal energy in response to a variation in the received optical signal. The receiver may further include a detector configured to detect the disturbance in the output optical signal energy, and a pump source coupled to the active optical medium to excite the active optical medium to generate an optical gain in the received optical signal.

Abstract: Optical signal receivers and methods are provided that include multiple optical resonators, each of which receives a portion of an arriving optical signal. Various of the optical resonators are tuned or detuned from a carrier wavelength, and produce an intensity modulated output signal in response to modulation transitions in the arriving optical signal. A detector determines modulation transitions in the arriving optical signal by analyzing the intensity modulation output signals from the optical resonators.

Abstract: Optical signal receivers and methods are provided that include an optical resonator that allows optical signal energy of multiple wavelengths to enter and accumulate inside the optical resonator. A portion of optical signal energy of each wavelength is emitted from the optical resonator at an output, and the individual wavelengths may be separated. A detector aligned with the output detects the emitted optical signal energy of at least one of the wavelengths. The detector is configured to detect disturbances to the emitted optical signal energy and determine a modulated characteristic in the received optical signal energy of the wavelength.

Abstract: Communication devices and a method of providing secure electronic content are general described. Content is encrypted using a time-invariant encryption algorithm on the binary bits and a time-varying baseband key encryption waveform with a time-varying phase or amplitude. The content is recovered using a waveform with a reference phase mixed with a reference LO signal or combining the waveform and content using an XOR to measure a change of the phase/amplitude of the received signal relative to the LO signal. The key for the time-invariant binary bit level encryption may be communicated on a different channel than the content prior to communication of the content or concurrently with the content. The phase/amplitude of the baseband key may vary after baseband waveform encryption of a predetermined number of symbols, independent of the time, or after a predetermined time independent of an amount of baseband signal encrypted.

Abstract: Aspects are generally directed to receivers and methods for optically demodulating optical signals. In one example, a receiver includes an optical resonator to receive an optical signal, the optical resonator including an optical medium interposed between first and second semi-reflective surfaces, where the first and second semi-reflective surfaces are positioned to resonate optical signal energy, and the optical resonator is configured to disrupt the optical signal energy resonance responsive to a variation in the received optical signal. The receiver may further include a probe source positioned to provide an optical probe beam to the optical medium, the optical medium being configured to interrupt the optical probe beam during the optical signal energy resonance and to transmit at least a portion of the optical probe beam in response to the disruption of the optical signal energy resonance, and a detector to detect the transmitted portion of the optical probe beam.

Abstract: An optical receiver and communication method receives an optical signal by an optical resonator to provide an intensity modulated signal indicative of a modulation of the optical signal. The intensity modulated signal is provided to a channel receiver of a plurality of channel receivers, and the channel receiver recovers from the intensity modulated signal a multipath version of a transmitted signal embedded in the modulation of the optical signal. The channel receiver's output is combined with an output of at least one other of the plurality of channel receivers to provide a combined output signal.

Abstract: Aspects are generally directed to optical signal receivers and methods. In one example, a receiver includes an optical resonator assembly configured to receive an optical signal at each of a plurality of optical resonators, each optical resonator configured to resonate optical signal energy at a corresponding frequency of the received optical signal, each optical resonator being tuned to a different corresponding frequency of the received optical signal, and each optical resonator being configured to output corresponding output optical signal energy. The receiver includes a detector assembly to detect the corresponding output optical signal energy from each optical resonator, and a signal processing circuit configured detect a frequency variation of the received optical signal based on the corresponding output optical signal energy from at least two of the plurality of optical resonators, and configured to generate a digital signal based on the frequency variation.

Abstract: Communication devices and a method of providing secure electronic content are general described. A plainmodulation containing user content is encrypted using a modulation key to form a ciphermodulation having a different magnitude and/or phase than the plainmodulation. Symbol representations of the plainmodulation and ciphermodulation in a QAM constellation are different. The ciphermodulation symbol representation is in a location non-coincident with an expected QAM constellation symbol. The symbol location of different plainmodulations when encypted using different modulation keys may be the same such that the corresponding ciphermodulation symbol representations are co-located. Different modulation keys are used for different plainmodulations, with a modulation key change occurring after transmission of a predetermined number of ciphermodulations and/or time. The modulation key and/or change is transmitted to enable coherent demodulation of the ciphermodulation to be performed.

Abstract: Aspects are generally directed to optical signal receivers and methods. In one example, a receiver includes a pump assembly configured to produce an encoded pump signal. The receiver includes an optical resonator positioned to receive an optical signal and the encoded pump signal, the optical resonator including an optical medium to accumulate resonant optical signal energy based on the optical signal, and the optical resonator being configured to emit output optical signal energy and disturb the output optical signal energy in response to a variation in the optical signal, the optical medium being further configured to modify a waveform shape of the output optical signal energy based on the encoded pump signal. The receiver further includes a detector to detect the output optical signal energy and determine a characteristic of the variation in the optical signal based on the waveform shape of the output optical signal energy.

Abstract: Optical signal receivers and methods are provided that include first and second optical resonators, each of which receives a portion of an arriving optical signal. The first optical resonator is tuned to a carrier wavelength and accumulates resonant optical signal energy whose output is disturbed responsive to a transition in the arriving optical signal. The second optical resonator is detuned from the carrier wavelength but also exhibits a disturbed output responsive to the transition in the arriving optical signal. Detectors detect the output disturbances from the two optical resonators to determine characteristics of the transition in the arriving optical signal.

Abstract: A system, method, and computer program product for chaotically generating a pseudorandom number sequence, such as for use in spread spectrum communications systems and in cryptographic systems. Chaotically generated pseudorandom numbers are not cyclostationary in nature, so output values encoded via such non-cyclostationary bases have no clear correlations. Spread signal communications systems using chaotically generated spreading codes thus operate without rate line artifacts, increasing their resistance to signal detection and to determinations of underlying signal chip rates and signal symbol rates. Broadcasts and guided transmissions (including either conductive wire or optical transmission media), in both radio frequency and optical systems are supported. Common spread spectrum communications systems including DSSS and FHSS may be strengthened through the use of chaotically generated spreading codes.