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.

Abstract: Optoelectronic oscillator systems and an optoelectronic oscillator noise reduction method. One example of an optoelectronic oscillator system includes an optical source positioned at a first end of a fiber-optic path, the optical source being configured to transmit an optical signal along the fiber-optic path, an optical modulator positioned to receive and modulate the optical signal based on at least a reference signal, a retro-reflector positioned at a second end of the fiber-optic path, the retro-reflector being configured to receive and retro-reflect the optical signal, the retro-reflected optical signal having at least a frequency range of inherent fiber noise canceled, and an optical circulator positioned along the fiber-optic path between the optical modulator and the retro-reflector, the optical circulator being configured to direct the optical signal to the retro-reflector and direct the retro-reflected optical signal along a feedback path to a first photodetector to generate the reference signal.

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: Optical signal receivers and methods are provided that include an optical resonator that allows optical signal energy to enter and accumulate inside the optical resonator. A portion of optical signal energy is emitted from the optical resonator at an output, such that the emitted optical signal energy is disturbed when a transition occurs in the received optical signal energy. A detector aligned with the output detects the emitted optical signal energy and is configured to detect the disturbance to the emitted optical signal energy and determine a characteristic of the transition in the received optical signal energy based upon the disturbance.

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: Generally discussed herein are systems, devices, and methods for waveform watermarking. A device can include an overt symbol modulator to receive mapped overt data and provide overt data modulated in accord with an overt data modulation scheme, a covert symbol modulator to receive mapped covert data and provide, using dither modulation and micro-amplitude modulation, covert data modulated in accord with a covert data modulation scheme, a switch to receive the modulated covert data and the modulated overt data and forward the covert data and modulated overt data based on a signal indicating whether covert data is to be transmitted or covert data is to be transmitted, and transmission circuitry to produce an electromagnetic waveform of the modulated data from the switch.

Abstract: Aspects are generally directed to optical receivers and methods for detecting a non-persistent communication superimposed on an overt communication channel. In one example, an optical receiver includes an optical resonator to receive an optical signal having one or more symbols encoded thereon at a modulated symbol repetition rate, the modulated symbol repetition rate being modulated relative to a nominal symbol repetition rate. The optical resonator is configured to emit an intensity-modulated output optical signal that has a variation in an intensity thereof corresponding to a symbol transition in the optical signal. The optical receiver further includes signal processing circuitry including a clock configured to generate a reference signal, a photodetector configured to generate a trigger signal, and a non-persistent communication decoder configured to determine a temporal misalignment between the symbol transition and the nominal symbol repetition rate based on the reference signal and the trigger signal.

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

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: An apparatus, method and article of manufacture comprise a transceiver coupled to a phased array of antenna elements that are configured into pluralities of antenna elements to generate N modes of orthogonal radio waves where N is equal to or greater than 2. The coupling is via a plurality of 16-quadrature phase shift key (16-QPSK) modulators, each which is coupled to a respective one of the pluralities of antenna elements to modulate data onto a respective one of the N modes of orthogonal radio waves, to cause each of the N modes to operate as an independent data channel. For the case of N=2 modes, two 16-QPSK modulators generate independent 16-QPSK constellations, one for the first of the two modes and one for the second of the two modes, such that two 16-QPSK constellations are independent of each other, are orthogonal, and are on the same frequency.