United Technologies Corporation

Uniphase Telecommunications Products, Inc.

Gregory J McBrien

Karl M Kissa

James D Farina

Richard E Swarts

Daniel J Fritz

David M Cramp

Edward Wooten

Winthrop H McClure

A differential input optical modulator, suited for an electrical driver with complementary outputs is provided by the present invention. One embodiment uses a X-cut LiNbO3 substrate, with or without a buffer layer, to reduce cost of manufacture in comparison to some known devices that employ a Z-cut LiNbO&tilde; substrate. These prior art devices require both buffer and charge bleed-off layers. The present invention also includes a quasi-symmetric electrode structure in which the applied fields run parallel to the surface of the substrate.

Differential drive optical modulator

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 &ldquo;heat spreaders&rdquo; 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.

Method and apparatus for stable control of electrooptic devices

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.

Apparatus for linearization of optic modulators using a feed-forward

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.

Cascaded optic modulator arrangement

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.

Optical measurement of the position of an object

An accelerometer arrangement includes an acceleration sensor that includes two capacitor plates having respective parallel mutually facing major surfaces which bound a sensing gap therebetween. A plate-shaped electrically chargeable proof mass is resiliently mounted in the gap in parallelism with the major surfaces for displacement in response to the action of acceleration forces thereon out of a substantially central rest position toward one or the other of the major surfaces depending on the direction of the acceleration forces. An electrical potential difference is established between the capacitor plates to generate respective electrostatic fields between the capacitor plates and the proof mass which cause a proof mass electrical potential variation having a magnitude and sense depending on the extent and direction of the displacement of the proof mass out of its rest position. The variation is evaluated and an a pulse train that is proportionate to the variation is generated and supplied to the proof mass to esatablish thereat a voltage sufficient for electrostatic forces caused thereby between the proof mass and the capacitor plates to return the proof mass to the rest position thereof against the action of the acceleration forces on the proof mass.

Pulse-driven accelerometer arrangement

A sawtooth voltage is applied to an integrated optic phase modulator by means of a high impedance variable current source in response to a charge rate control signal. The phase modulator's capacitance accumulates the charge which manifests a voltage comprising the sawtooth signal. The sawtooth signal is also provided to a comparator which in turn provides a discharge signal upon detecting the sawtooth voltage as being greater than a selected reference signal magnitude. The discharge signal is provided to a means for discharging the accumulated charge from the capacitance of the integrated optic phase modulator. A compensating resistor may be connected between the current source and the phase modulator to automatically correct for sawtooth overshoot. Various data extraction techniques are disclosed, without limiting the invention since others may be used, including counting sawtooth resets, among others, and using a current splitter to store charge separately from the serrodyne modulation circuit and relating separately stored charge to angle or rate.

Measuring the relative effective lengths traversed by counterpropagating

Apparatus and method is disclosed for determining position with light by providing input light at an input light port of an optical cavity having a variable length dimension and detecting light which has traversed the variable length dimension at an output light port of the optical cavity and determining the present length of the variable length dimension using the detected light as a measure.

Apparatus and method for determining position with light

A differential torquer having at least one bifilar winding mounted on the torquer is disclosed. The bifilar winding has opposing polarities and the torquer is particularly well suited for use in reducing the temperature sensitivity of torquer servo loops.

Differential torquer

A differential torquer servo loop having means for comparing the balance between a torquer position related signal and a signal indicative of the difference in the magnitudes of the currents in the differential torquer and for rebalancing any difference therebetween is disclosed. Total current in the torquer is maintained at a constant level to provide a quiet control loop which promotes temperature stabilization.

Low noise differential torquer servo loop and circuitry

Serial to parallel conversion circuitry achieves phase synchronization and signal bit sampling of received asynchronous serial data through use of a gate enable delay line oscillator having a selected response time, and selectably enabled in the presence of the received serial data to provide a sampling clock signal for shifting the serial data into register for parallel formatting at a frequency equal to the line frequency.

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Cromwell, CT, United States of America

Gregory J McBrien