Abstract: An implantable medical lead may include an electrode at a distal portion of the lead that is configured to monitor or provide therapy to a target site. The lead may include a visible indicator that is visible to the naked eye of a clinician at a medial portion of the lead that is configured to indicate when the electrodes of the lead are longitudinally and radially aligned properly to monitor or treat the target site. A clinician may insert the lead into the patient using an introducer sheath inserted to a predetermined depth into the patient and subsequently aligning the distal portion of the lead by orienting the indicator at an entry port of the introducer sheath.

Abstract: An apparatus includes a finite impulse response demodulator. The finite impulse response demodulator includes least one stage. Each stage includes a cascaded pair of interferometers. The cascaded pair of interferometers includes a first interferometer and a second interferometer. Optionally, the first interferometer includes a first delay. The second interferometer includes a second delay. The first delay and the second delay are fixed or variable. Optionally, the first delay is unequal or equal to said second delay. Optionally, the first interferometer includes first internal power monitors, and the second interferometer includes second internal power monitors. The first power monitors monitor phase bias conditions within the first interferometer. The second power monitors monitor phase bias conditions within the second interferometer. Optionally, the first interferometer includes a first adjustable coupler, and the second interferometer comprises a second adjustable coupler.

Abstract: An apparatus includes an input radio frequency waveguide. The apparatus includes a radio-frequency-to-optical-radio-frequency-impedance-matching interface communicating with the input radio frequency waveguide. The apparatus includes a plurality of optical modulators communicating with the radio-frequency-to-optical-radio-frequency-impedance-matching interface. The apparatus includes a plurality of respective optical waveguides communicating with the plurality of optical modulators. The plurality of respective optical waveguides in operation includes a plurality of respective optical waveguide fields. The input radio frequency waveguide in operation includes an input radio frequency waveguide field. The input radio frequency waveguide field interacts with the plurality of respective optical waveguide fields to convert an input radio frequency signal into a plurality of optical signals.

Abstract: Systems and method are provided to for suppressing interference signals in optical systems, without prior knowledge of the type of location of the interferers, while maintaining a linear response to small signals of interest (SOI). By exploiting the unique power (or voltage) dependent transmission function of an externally angle-modulated photonic link, embodiments of the present disclosure are configured to provide strong, wideband interference suppression without requiring detailed knowledge of the interfering signal.

Abstract: Systems and method are provided to for suppressing interference signals in optical systems, without prior knowledge of the type of location of the interferers, while maintaining a linear response to small signals of interest (SOI). By exploiting the unique power (or voltage) dependent transmission function of an externally angle-modulated photonic link, embodiments of the present disclosure are configured to provide strong, wideband interference suppression without requiring detailed knowledge of the interfering signal.

Abstract: A system for suppressing even-order distortion in a photonic link includes a laser for providing laser light to a first input of a Mach-Zehnder modulator (MZM), where the MZM has a second input for receiving an RF input signal, a third input for applying a DC bias voltage to the MZM, and an optical signal output. A dc-voltage-biased photodiode has an input, coupled to the MZM optical signal output, and a modulated RF signal output. The MZM DC bias voltage is set at a value to generate an even-order distortion amplitude substantially equal to an even-order distortion amplitude from the photodiode and 180 degrees out of phase so as to substantially cancel the photodiode even-order distortion. The invention provides the cancellation of photodiode even-order distortion via predisortion linearization with a MZM biased slightly away from quadrature, employing a single fiber run and a single photodiode. The invention provides an improvement in carrier-to-intermodulation ratio (CIR) upwards of 40 dB.

Abstract: A system for suppressing even-order distortion in a photonic link includes a laser for providing laser light to a first input of a Mach-Zehnder modulator (MZM), where the MZM has a second input for receiving an RF input signal, a third input for applying a DC bias voltage to the MZM, and an optical signal output. A dc-voltage-biased photodiode has an input, coupled to the MZM optical signal output, and a modulated RF signal output. The MZM DC bias voltage is set at a value to generate an even-order distortion amplitude substantially equal to an even-order distortion amplitude from the photodiode and 180 degrees out of phase so as to substantially cancel the photodiode even-order distortion. The invention provides the cancellation of photodiode even-order distortion via predisortion linearization with a MZM biased slightly away from quadrature, employing a single fiber run and a single photodiode. The invention provides an improvement in carrier-to-intermodulation ratio (CIR) upwards of 40 dB.

Abstract: A multi-mode optoelectronic oscillator (MM-OEO) includes an OEO cavity having an input for receiving an RF signal and an RF output. The OEO cavity includes a) a first laser having a first laser output, a second laser having a second laser output, b) a modulator having i) a first input coupled to the first laser output, ii) a second input coupled to the second laser output, iii) a third input, iv) a first modulator output, and v) a second modulator output, c) a semiconductor optical amplifier (SOA) having an input coupled to the first modulator output and having an SOA amplified output, d) a photodetector coupled to the SOA amplified output and having an output, and e) a coupler having an input coupled to the photodetector output and having a first output coupled to the third modulator input and a second output, whereby an amplified RF signal is produced at the OEO RF output.

Abstract: A multi-mode optoelectronic oscillator (MM-OEO) includes an OEO cavity having an input for receiving an RF signal and an RF output. The OEO cavity includes a) a first laser having a first laser output, a second laser having a second laser output, b) a modulator having i) a first input coupled to the first laser output, ii) a second input coupled to the second laser output, iii) a third input, iv) a first modulator output ,and v) a second modulator output, c) a semiconductor optical amplifier (SOA) having an input coupled to the first modulator output and having an SOA amplified output, d) a photodetector coupled to the SOA amplified output and having an output, and e) a coupler having an input coupled to the photodetector output and having a first output coupled to the third modulator input and a second output, whereby an amplified RF signal is produced at the OEO RF output.

Abstract: A method and system for processing analog optical signals to produce a single RF output free from even-order harmonic distortion. Two analog optical signals of different wavelengths ?1, ?2 are input into a dual-output Mach-Zehnder modulator (MZM), where one wavelength input is high-biased and one wavelength is low-biased. The complementary high- and low-biased wavelengths are output from each arm of the MZM to a multiplexer, which filters out the unwanted high- or low-biased wavelengths from each MZM arm so that both wavelengths are low-biased or high-biased. The signals are passed to a pair of photodiodes, and the photocurrents from the photodiodes are differenced to produce the final RF output. Because of the complementary phase differences between the two low- or high-biased signals generating the photocurrent, all components of the photocurrent except the fundamental and odd-order harmonics cancel each other, resulting in a high-quality RF output free from harmonic distortion.

Abstract: A method and system for processing analog optical signals to produce a single RF output free from even-order harmonic distortion. Two analog optical signals of different wavelengths ?1, ?2 are input into a dual-output Mach-Zehnder modulator (MZM), where one wavelength input is high-biased and one wavelength is low-biased. The complementary high- and low-biased wavelengths are output from each arm of the MZM to a multiplexer, which filters out the unwanted high- or low-biased wavelengths from each MZM arm so that both wavelengths are low-biased or high-biased. The signals are passed to a pair of photodiodes, and the photocurrents from the photodiodes are differenced to produce the final RF output. Because of the complementary phase differences between the two low- or high-biased signals generating the photocurrent, all components of the photocurrent except the fundamental and odd-order harmonics cancel each other, resulting in a high-quality RF output free from harmonic distortion.

Abstract: An apparatus and method to increase the output power from LiNbO3 MZM style optical intensity modulating without exceeding the optical power damage threshold imposed by LiNbO3 is described. The optical path from a laser source is divided into two paths by a polarization maintaining (PM) coupler. The two paths form a Mach Zender Modulator (MZM) with a LiNbO3 phase modulator in one path and a fiber looped PZT in the other. The LiNbO3 phase modulator imprints an RF signal onto one path of the MZM cavity, while the fiber wrapped PZT is used to control the path length difference between the two optical paths. The two optical paths are recombined in a second PM coupler.

Abstract: The remotable, ultrawide band optical image rejection downconverter uses sub-carrier modulation techniques without concern for image frequency interferences in the shifted signal, thereby allowing telecommunications systems to downconvert densely multiplexed communications channels into a low frequency band where conventional electronics can perform signal-processing functions. This invention has the image rejection (>120 dB) to provide unambiguous signals for direction finding applications and exhibits an efficient image that permits multi-octave microwave frequency reception and compression. This invention is intrinsically remoteable, and due to the various optical and electrical components proves to be very useful and practical in numerous fiber optic and antenna systems.

Abstract: An optical image reject down-converter for mapping a received radio frequency (RF) into an arbitrary intermediate frequency range and for precluding interference between the received signals. A received radio frequency signal is down-converted into an intermediate frequency band for use by an electronic circuit in other devices. Optical light is divided into a first path and a second path. Light in the first path is transferred into an optical sideband by a first optical modulator or phase modulator. Light in a second path is converted into sidebands by a second, non-cascaded optical modulator and then passed through a tunable narrow-band optical filter which selects the desired sideband. The optical spectrum of the second path then primarily includes light at the frequency equal to the original laser frequency plus the additional sidebands. The filtered sideband is heterodyned with the light from the first path, resulting in a down-conversion to the desired intermediate frequency.

Abstract: A method and apparatus to enable the use of low cost high RIN optical sources for microwave photonic links by combining the wide-gain bandwidth and low cost of an EDFA, with the narrow gain bandwidth of a Brillouin amplifier. The hybrid Brillouin/EDFA (“hybrid amplifier”) apparatus of the present invention includes at least two couplers, a phase modulator, an Erbium-doped fiber, a laser source to pump the Erbium fiber, an optical circulator, and a length of fiber used for Brillouin amplification. Optical signals from the laser source are split into two optical paths by a polarization maintaining coupler. Optical signals passing through a first path are amplified by the Erbium doped fiber, and the amplified signals are passed through the optical circulator before sending the optical signals into one end of a spool of fiber in order to pump the Brillouin acoustic wave.

Abstract: A method and apparatus to enable the use of low cost high RIN optical sources for microwave photonic links by combining the wide-gain bandwidth and low cost of an EDFA, with the narrow gain bandwidth of a Brillouin amplifier. The hybrid Brillouin/EDFA (“hybrid amplifier”) apparatus of the present invention includes at least two couplers, a phase modulator, an Erbium-doped fiber, a laser source to pump the Erbium fiber, an optical circulator, and a length of fiber used for Brillouin amplification. Optical signals from the laser source are split into two optical paths by a polarization maintaining coupler. Optical signals passing through a first path are amplified by the Erbium doped fiber, and the amplified signals are passed through the optical circulator before sending the optical signals into one end of a spool of fiber in order to pump the Brillouin acoustic wave.

Abstract: The optical image reject down converter maps a received radio frequency (RF) into an arbitrary intermediate frequency range and precludes interference between the received signals. A received radio frequency signal is downconverted into an intermediate frequency band for use by an electronic circuit in other devices. Optical light is divided, in a first path light is transferred into an optical sideband by a first optical modulator or phase modulator. Light in a second path is converted into 18 GHz sidebands. The signal is amplified and additional sidebands are generated by a received 9 GHz signal. The filtered sideband is heterodyned with the 25 GHz signal of path one, resulting in downconversion to 2 GHZ. Image frequencies which are present in the optical link are filtered and are rejected.

Abstract: An image rejecting microwave photonic downconverter uses a microwave sub-carrier modulation technique without concern for image frequency interference in the shifted signal, thereby allowing telecommunications systems to downconvert densely multiplexed communications channels into a low frequency band where conventionqal electronics can perform signal-processing functions. The image rejecting microwave photonic downconveter incoming microwave signals can be processed without ambiguity in direction finding applications, allowing remotable, multioctave microwave signal processing for frequency and phase determination.

Abstract: An apparatus and method to increase the output power from LiNbO3 MZM style optical intensity modulating without exceeding the optical power damage threshold imposed by LiNbO3 is described. The optical path from a laser source is divided into two paths by a polarization maintaining (PM) coupler. The two paths form a Mach Zender Modulator (MZM) with a LiNbO3 phase modulator in one path and a fiber looped PZT in the other. The LiNbO3 phase modulator imprints an RF signal onto one path of the MZM cavity, while the fiber wrapped PZT is used to control the path length difference between the two optical paths. The two optical paths are recombined in a second PM coupler.

Abstract: An optical image reject down-converter for mapping a received radio frequency (RF) into an arbitrary intermediate frequency range and for precluding interference between the received signals. A received radio frequency signal is down-converted into an intermediate frequency band for use by an electronic circuit in other devices. Optical light is divided into a first path and a second path. Light in the first path is transferred into an optical sideband by a first optical modulator or phase modulator. Light in a second path is converted into sidebands by a second, non-cascaded optical modulator and then passed through a tunable narrow-band optical filter which selects the desired sideband. The optical spectrum of the second path then primarily includes light at the frequency equal to the original laser frequency plus the additional sidebands. The filtered sideband is heterodyned with the light from the first path, resulting in a down-conversion to the desired intermediate frequency.