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 data channel system and method provide a composite signal having an overt, persistent signal channel and a non-persistent channel encoded onto a signal in the persistent channel by timing variation of the persistent channel 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.

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 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: 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: 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 an optical resonator that allows an optical signal to enter and optical signal energy to accumulate at regions inside the optical resonator. A portion of optical signal energy is emitted from among various regions of the optical resonator, such that a combination of the emitted optical signal energy is disturbed when a phase transition occurs in the received optical signal. A detector aligned with the output detects the combined emitted optical signal energy and is configured to detect the disturbance and determine a characteristic of the phase transition in the received optical signal based upon the disturbance.

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: 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 an optical resonator that allows an optical signal to enter and optical signal energy to accumulate at regions inside the optical resonator. A portion of optical signal energy is emitted from among various regions of the optical resonator, such that a combination of the emitted optical signal energy is disturbed when a phase transition occurs in the received optical signal. A detector aligned with the output detects the combined emitted optical signal energy and is configured to detect the disturbance and determine a characteristic of the phase transition in the received optical signal based upon the disturbance.

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: A free-space optical signal receiver includes a plurality of detectors whose individual outputs are delayed to correct for variations in arrival time caused by aberration in the medium through which the optical signal propagates, and combined to provide a single output. Each of the plurality of detectors sense the free-space modulated optical signal and provide a detector signal representative of the modulation of the optical signal. Each detector signal is delayed by a delay value to generate a delayed signal, and each delay value is selected to correct for variation in arrival time of the optical signal at each of the detectors, resulting in the delayed signals being substantially time-aligned. The delayed signals are constructively combined into a combined signal representative of the modulation aspect, and the combined signal is provided as an output.