Abstract: A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

Abstract: A system and method for mitigating nonlinearity in an optical communication link with multiple carriers uses mutual frequency referencing to stabilize at least a portion of the multiple carriers. Using at least one frequency-referenced signal, carrier nonlinearity can be determined and compensated within the link by pre-distortion, back-propagation, or a combination of both. Mutual frequency referencing may be performed at the emitting end of the link, at the receiving end, or a combination of both.

Abstract: Methods and systems for measuring muscle sarcomere length are disclosed. In an embodiment, a method comprises illuminating a set of muscle fibers with electromagnetic radiation, measuring an intensity of the electromagnetic radiation as reflected from the muscle fibers, the measuring occurring as a function of wavelength, determining wavelengths corresponding to maximums of reflected intensity, and correlating the determined wavelengths with respective muscle sarcomere lengths. In an embodiment, a system comprises an illumination source system for illuminating the set of muscle fibers with electromagnetic radiation, and an analyzer for measuring the intensity of the electromagnetic radiation as reflected from the muscle fibers.

Abstract: A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

Abstract: A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

Abstract: A spread spectrum receiving method receives a spread spectrum signal. An optical signal frequency comb is generated. Modes of the optical signal frequency comb are modulated with a received spread spectrum signal. An optical local oscillator comb is generated that is mutually coherent with the signal frequency comb. A code word is applied to the local oscillator comb. The combs are combined and the received spread spectrum signal is detected from the combined combs.

Abstract: A system and method for mitigating nonlinearity in an optical communication link with multiple carriers uses mutual frequency referencing to stabilize at least a portion of the multiple carriers. Using at least one frequency-referenced signal, carrier nonlinearity can be determined and compensated within the link by pre-distortion, back-propagation, or a combination of both. Mutual frequency referencing may be performed at the emitting end of the link, at the receiving end, or a combination of both.

Abstract: A spread spectrum receiving method receives a spread spectrum signal. An optical signal frequency comb is generated. Modes of the optical signal frequency comb are modulated with a received spread spectrum signal. An optical local oscillator comb is generated that is mutually coherent with the signal frequency comb. A code word is applied to the local oscillator comb. The combs are combined and the received spread spectrum signal is detected from the combined combs.

Abstract: Observation of random, non-repetitive phenomena is of critical importance in astronomy, spectroscopy, biology and remote sensing. Heralded by weak signals, hidden in noise, they pose basic detection challenges. In contrast to repetitive waveforms, a single-instance signal cannot be separated from noise by averaging. The present invention demonstrates that a fast, randomly occurring event can be detected and extracted from a noisy background without conventional averaging. An isolated 80-ps pulse was received with confidence level exceeding 99%, even when accompanied by noise. The detector employed in the present invention relies on instantaneous spectral cloning and a single-step, coherent field processor. The ability to extract fast, sub-noise events is expected to increase detection sensitivity in multiple disciplines. Additionally, the new spectral-cloning receiver can potentially intercept communication signals that are presently considered secure.

Abstract: A spread spectrum receiver and receiving methods are provided. Received data is physically reconstructed in the optical domain using a pair of coherently coupled frequency combs, one modulated by the received signal and one modulated by the code word, and then detecting the received data with a subrate detector comprised of detector array. Particular methods and receivers extract a timing difference between the received spread spectrum signal and the codeword from the phase shifts of Fourier terms of the product of the received spread spectrum signal and the codeword that can be measured from the combined combs.

Abstract: A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

Abstract: Methods and systems for measuring muscle sarcomere length are disclosed. In an embodiment, a method comprises illuminating a set of muscle fibers with electromagnetic radiation, measuring an intensity of the electromagnetic radiation as reflected from the muscle fibers, the measuring occurring as a function of wavelength, determining wavelengths corresponding to maximums of reflected intensity, and correlating the determined wavelengths with respective muscle sarcomere lengths. In an embodiment, a system comprises an illumination source system for illuminating the set of muscle fibers with electromagnetic radiation, and an analyzer for measuring the intensity of the electromagnetic radiation as reflected from the muscle fibers.

Abstract: A photonically-assisted cyclostationary analyzer eliminates the need for high-bandwidth digitization and real-time Fourier processors by using mutually-coherent frequency combs to generate a Fourier representation of the received signal in a computation-free manner.

Abstract: Methods and systems for measuring muscle sarcomere length are disclosed. In an embodiment, a method comprises illuminating a set of muscle fibers with electromagnetic radiation, measuring an intensity of the electromagnetic radiation as reflected from the muscle fibers, the measuring occurring as a function of wavelength, determining wavelengths corresponding to maximums of reflected intensity, and correlating the determined wavelengths with respective muscle sarcomere lengths. In an embodiment, a system comprises an illumination source system for illuminating the set of muscle fibers with electromagnetic radiation, and an analyzer for measuring the intensity of the electromagnetic radiation as reflected from the muscle fibers.

Abstract: A receiver architecture for physically-assisted computing of transforms, such as discrete Fourier transforms (DFT) and discrete Hilbert transforms (DHT), employs mutually-coherent optical frequency combs for detection of the coherent beating between an optical signal and a reference optical tone generated by a local oscillator (LO). A signal replication mixer generates a plurality of signal optical tones having a frequency pitch with an input signal mapped thereon. A reference mixer (local oscillator) generates a plurality of reference optical tones having an offset frequency pitch relative to the signal tones. A receiver backplane detects coherent beating between the signal optical tones and the reference optical tones. The input signal may be in the optical domain or in the radio-frequency domain.

Abstract: A spread spectrum receiver and receiving methods are provided. Received data is physically reconstructed in the optical domain using a pair of coherently coupled frequency combs, one modulated by the received signal and one modulated by the code word, and then detecting the received data with a subrate detector comprised of detector array. Particular methods and receivers extract a timing difference between the received spread spectrum signal and the codeword from the phase shifts of Fourier terms of the product of the received spread spectrum signal and the codeword that can be measured from the combined combs.

Abstract: A photonically-assisted cyclostationary analyzer eliminates the need for high-bandwidth digitization and real-time Fourier processors by using mutually-coherent frequency combs to generate a Fourier representation of the received signal in a computation-free manner.

Abstract: A receiver architecture for physically-assisted computing of transforms, such as discrete Fourier transforms (DFT) and discrete Hilbert transforms (DHT), employs mutually-coherent optical frequency combs for detection of the coherent beating between an optical signal and a reference optical tone generated by a local oscillator (LO). A signal replication mixer generates a plurality of signal optical tones having a frequency pitch with an input signal mapped thereon. A reference mixer (local oscillator) generates a plurality of reference optical tones having an offset frequency pitch relative to the signal tones. A receiver backplane detects coherent beating between the signal optical tones and the reference optical tones. The input signal may be in the optical domain or in the radio-frequency domain.

Abstract: Observation of random, non-repetitive phenomena is of critical importance in astronomy, spectroscopy, biology and remote sensing. Heralded by weak signals, hidden in noise, they pose basic detection challenges. In contrast to repetitive waveforms, a single-instance signal cannot be separated from noise by averaging. The present invention demonstrates that a fast, randomly occurring event can be detected and extracted from a noisy background without conventional averaging. An isolated 80-ps pulse was received with confidence level exceeding 99%, even when accompanied by noise. The detector employed in the present invention relies on instantaneous spectral cloning and a single-step, coherent field processor. The ability to extract fast, sub-noise events is expected to increase detection sensitivity in multiple disciplines. Additionally, the new spectral-cloning receiver can potentially intercept communication signals that are presently considered secure.

Abstract: A wide-band optical frequency comb is provided to estimate an optical phase shift induced in a dispersive material. In contrast to the conventional techniques that rely on a single tunable laser for extracting the dispersion parameter at different frequencies, the wide-band optical frequency comb uses multiple comb lines for simultaneously evaluating the dispersion induced phase shifts in different frequencies. Since the frequency response of the dispersive material is a phase function, a phase associated with each comb line passed through the material represents a discrete measure of the material frequency response.