Abstract: A reduced size RF signal and ground electrode interface is configured to provide better field confinement of dominant coplanar waveguide mode in the propagation direction and reduce coupling RF energy into a substrate beneath the launch, while matching the impedance of the launch to both that of the coplanar microwave electrode structure overlying the interaction region, and that of the external RF connection to the launch. In ground plane embodiments, an underlying ground plane provides better modal confinement of the dominant coplanar waveguide mode and precludes coupling of RF power to the substrate under the launch. In other embodiments, finite width electrodes provide better modal transition and mitigate against coupling to substrate modes, while providing a pad geometry that facilitates connections to external transmission line components.

Abstract: An optical digital external modulator having a cascaded arrangement of interferometers is provided. The optical modulator includes an electrode structure for applying an electric field to each interferometer in the cascade and biasing circuitry coupled to the electrode structure for biasing each interferometer at a predetermined bias point. In particular, each predetermined bias point is selected to be above quadrature and for providing improved transmission performance of digital data signals. Preferably, the modulator has a reflective design that helps to increase the modulation bandwidth, lower the drive voltage, and reduce size.

Abstract: An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. Modulator bias and electronic phase delay bias are controlled using dither-based feedback, so as to align the phase of the RZ clock signal with that of the NRZ data. A first method uses an RZ quadrature AM dither or an RZ “hillclimber” bias dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator or NRZ data signal applied to the NRZ modulator. A second method is an RZ quadrature AM dither or “hillclimber” bias dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary modulation of both the RZ and NRZ MZ modulators simultaneously.

Abstract: The invention relates to suppression of high frequency resonance in an electro-optical device. The electro-optical device includes an optical waveguide formed in a substrate and a plurality of electrically floating electrode segments that are positioned on the substrate to intensify an electric field in the optical waveguide. The device also includes a RF ground electrode that is positioned on the substrate. The RF ground electrode defines a slot having a shape that suppresses modal conversion and propagation of high order modes in the RF ground electrode and in the plurality of electrically floating electrode segments, thereby suppressing modal coupling to the substrate. The device further includes a buffer layer formed on the upper surface of the substrate, on the plurality of electrically floating electrode segments, and in the slot. A driving electrode receives a RF signal that induces-the electric field in the optical waveguide.

Abstract: A mixed frequency-based method and arrangement for characterizing an electro-optic modulator is configured to vary the tuning of a laser beam, to be modulated by the optical modulator, simultaneously with and in the same manner as the variation in frequency of the modulation signal. The effect of this dual modulation approach is a modulated laser beam, in which the frequency difference between the carrier component of the laser beam and sideband energy produced by the modulation signal is controlled so that it falls within the sensitivity range of a relatively low cost optical detector.

Abstract: An optical digital external modulator having a cascaded arrangement of interferometers is provided. The optical modulator includes an electrode structure for applying an electric field to each interferometer in the cascade and biasing circuitry coupled to the electrode structure for biasing each interferometer at a predetermined bias point. In particular, each predetermined bias point is selected to be above quadrature and for providing improved transmission performance of digital data signals. Preferably, the modulator has a reflective design that helps to increase the modulation bandwidth, lower the drive voltage, and reduce size.

Abstract: The invention relates to suppression of high frequency resonance in an electro-optical device. The electro-optical device includes an optical waveguide formed in a substrate and a plurality of electrically floating electrode segments that are positioned on the substrate to intensify an electric field in the optical waveguide. The device also includes a RF ground electrode that is positioned on the substrate. The RF ground electrode defines a slot having a shape that suppresses modal conversion and propagation of high order modes in the RF ground electrode and in the plurality of electrically floating electrode segments, thereby suppressing modal coupling to the substrate. The device further includes a buffer layer formed on the upper surface of the substrate, on the plurality of electrically floating electrode segments, and in the slot. A driving electrode receives a RF signal that induces-the electric field in the optical waveguide.

Abstract: A reduced size RF signal and ground electrode interface is configured to provide better field confinement of dominant coplanar waveguide mode in the propagation direction and reduce coupling RF energy into a substrate beneath the launch, while matching the impedance of the launch to both that of the coplanar microwave electrode structure overlying the interaction region, and that of the external RF connection to the launch. In ground plane embodiments, an underlying ground plane provides better modal confinement of the dominant coplanar waveguide mode and precludes coupling of RF power to the substrate under the launch. In other embodiments, finite width electrodes provide better modal transition and mitigate against coupling to substrate modes, while providing a pad geometry that facilitates connections to external transmission line components.

Abstract: An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. Modulator bias and electronic phase delay bias are controlled using dither-based feedback, so as to align the phase of the RZ clock signal with that of the NRZ data. A first method uses an RZ quadrature AM dither or an RZ “hillclimber” bias dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator or NRZ data signal applied to the NRZ modulator. A second method is an RZ quadrature AM dither or “hillclimber” bias dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary modulation of both the RZ and NRZ MZ modulators simultaneously.

Abstract: The invention relates to apparatus and methods for suppressing high frequency resonance in an electro-optical device. The electro-optical device includes an optical waveguide formed in the upper surface of a substrate. The device further includes a plurality of electrically floating electrode segments that are positioned on the substrate to intensify an electric field in the optical waveguide. The device also includes a plurality of electrically grounded electrode segments that are positioned on the substrate for prohibiting modal conversion and propagation of high order modes in the plurality of electrically grounded electrode segments and in the plurality of electrically floating electrode segments, thereby suppressing modal coupling to the substrate. The device further includes a buffer layer formed on the upper surface of the substrate and a driving electrode formed on an upper surface of the buffer layer for receiving an RF signal that induces the electric field in the optical waveguide.

Abstract: A high-efficiency electro-optic modulator with an equalized frequency response is described. The modulator includes an optical waveguide formed in an electro-optic material that propagates an optical signal along a first direction of propagation. An electrical waveguide is formed on the electro-optic material and positioned generally co-linear relative to the optical waveguide and in electromagnetic communication with the optical waveguide. The geometry of the electrical waveguide is selected to achieve a modulation efficiency at a frequency in a bandwidth of a digital spectrum. A compensation network is electrically coupled to the electrical waveguide at a junction. The compensation network reduces an electro-optic response of the electro-optic modulator below the mean frequency bandwidth of the digital spectrum, thereby causing an increase of the electro-optic response above the mean frequency of the digital spectrum.

Abstract: A mixed frequency-based method and arrangement for characterizing an electro-optic modulator is configured to vary the tuning of a laser beam, to be modulated by the optical modulator, simultaneously with and in the same manner as the variation in frequency of the modulation signal. The effect of this dual modulation approach is a modulated laser beam, in which the frequency difference between the carrier component of the laser beam and sideband energy produced by the modulation signal is controlled so that it falls within the sensitivity range of a relatively low cost optical detector.

Abstract: An electro-optic device including an optical waveguide formed in an electro-optic material that propagates an optical signal along a first direction of propagation is described. The device also includes an electrical waveguide formed in the electro-optic material and positioned co-linear relative to the optical waveguide and in electromagnetic communication with the optical waveguide, where the electrical waveguide also propagates the electrical signal in the first direction of propagation. A compensation network is electrically coupled to the electrical waveguide at a junction and propagates the electrical signal in a second direction of propagation that is substantially non-co-linear with the first direction of propagation.

Abstract: A co-planar waveguide interferometric electro-optic modulator that reduces the bias point sensitivity of the modulator to ambient temperature and to applied RF is described. The modulator includes a first and second waveguide that are formed in an electro-optic substrate. A RF electrode is positioned on the electro-optic substrate between the first and the second waveguide. A ground electrode that may include a slot is positioned proximate to the second waveguide. A guard ground electrode is positioned proximate to the first waveguide to sink heat from the RF electrode and may also balance the thermal stress in the two waveguides. A dielectric material may also be positioned proximate to the first waveguide to balance the thermal stress in the two waveguides.

Abstract: An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. DC bias and modulation signal drive levels of the two modulators are controlled using dither-based feedback, so as to align the phase of the RZ signal with that of the NRZ data. A first method uses an RZ quadrature phase dither or an RZ hillclimber phase dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator. A second method is an RZ quadrature phase dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary amplitude modulation of both the RZ and NRZ MZ modulators simultaneously.

Abstract: An optical pulse generator having a high order transfer function that comprises a first and a second nested interferometric modulator, each modulator comprising an optical input, an electrical input, a first arm, a second arm and an optical output. The second interferometric modulator is optically coupled into the second arm of the first interferometric modulator. The optical output of the first interferometric modulator generates pulses at a repetition rate that is proportional to a multiple of a frequency of an electrical signal applied to the electrical input of at least one of the first and second interferometric modulator and at a duty cycle that is inversely proportional to the order of the transfer function of the optical pulse generator. The multiple may be any integer equal to or greater than one.

Abstract: Method and apparatus are disclosed for the stable control of electrooptic devices, such as for providing a stable bias point for operation of a lithium niobate interferometer-type modulator. The bias point of the modulator is thermally controlled by providing a selected difference in the temperatures of optical waveguide lengths of the interferometer. Heaters can be disposed with the lithium niobate substrate for transferring thermal energy with the optical waveguide lengths. A thermally conductive element can be disposed adjacent the optical waveguide lengths to act as “heat spreaders” to facilitate providing the selected difference in temperature. The invention also includes phase shifters, attenuators, and other optical devices formed from single and multiple optical waveguide lengths propagating separate optical beams.

Abstract: A feed-forward predistortion circuit to provide improved linear response in optic modulators. The circuit includes a non-linear element, an amplifier/delay means and a power combiner. The non-linear element generates a first signal sin(X), where (X) is the input signal. The amplifier/delay means generates a second signal 2(X). The first and second signals are combined in the power combiner to produce a modulating signal 2(X)-sin(X) which is fed to an optic modulator. The modulating signal 2(X)-sin(X) compensates for the transfer function of the optic modulator which has a transfer function sin(X), thereby producing a linear output.

Abstract: A pair of interferometers, such as Mach-Zehnders, are disposed in a series arrangement in which a signal fed to an input of the first Mach-Zehnder is modulated by an optic modulator, the modulated signal is fed to an input of the second Mach-Zehnder and is modulated by a second optic modulator, the two optic modulators effectively being connected in a series or cascade arrangement. The phase offset of both modulators and the contrast of one modulator are adjusted to minimize both second and third order harmonics inherently generated by the modulation process of each modulator, thereby providing an improved linear response in the output signal of the second Mach-Zehnder.

Abstract: The invention teaches determining position with light by providing amplitude modulated input light at an input light port of an optical cavity having a variable length dimension, detecting light at an output light port of the optical cavity and varying the frequency of amplitude modulation until a peak is detected. The maximizing frequency can then be related to the length of the cavity. The cavity may comprise an optical fiber inserted into a variable length cavity filled with a liquid having an index of refraction which matches that of the fiber. Mirrors may be placed at either end of the cavity.