USA As Represented by Secretary of the Navy

Robert P Moeller

William K Burns

Marta M Howerton

James H Cole

Alan D Kersey

Nicholas J Frigo

Lew Goldberg

Michael L Dennis

Elias Snitzer

Ganesh K Gopalakrishnan

Irt N Duling, Iii

Roger Krahenbuhl

Leslie E Chipman

An electro-optic modulator having a substrate, one or more optical waveguides, at least one active electrode formed on the substrate and aligned over the optical waveguide, the active electrode operating to induce a refractive index change in the optical waveguide. The active electrode has a lower surface arranged facing the substrate, an upper surface arranged away from the substrate, substantially planar side walls, and rounded corners between the side walls and the lower surface of the active electrode. The electrode can be a bridge electrode, with two lower portions and an upper portion connected to the lower portions, the lower portions spaced apart from each other, each of the two lower portions of the active electrode extending over one of the optical waveguides. Each of the lower portions has rounded convex corners. The upper surface of the electrode can also have rounded corners or a completely rounded upper surface.

Low loss bridge electrode with rounded corners for electro-optic modulators

An electro-optic modulator includes a substrate, at least two parallel optical waveguides, at least one ground plane, at least one active electrode with at least two lower portions of the active electrode, and an upper portion connected to the lower portions, the lower portions spaced apart from each other, each of the two lower portions of the active electrode extending over one of the optical waveguides. An electro-optic phase modulator having at least one optical waveguide and at least one active electrode formed on a face of the substrate, the active electrode having a wider upper portion and a narrower lower portion, the lower portions of the active electrode aligned with and extending over one of the optical waveguides. A bridge electrode has at least one narrower lower portion, and a wider upper portion, the lower portion for being arranged over an optical waveguide formed in a substrate.

Low loss electrodes for electro-optic modulators

This invention pertains to a device and method for making same. The device includes a substrate suitable for supporting pathways for optical signals; separate pathways disposed on the substrate suitable for propagating optical signals, the pathways including an input and an output optical pathway; and a reflective surface in operative contact with the input and output pathways for receiving an optical signal from the input pathway and reflecting the optical signal into the output pathway. The method for making the device includes the steps of providing two separate optical pathways on a single substrate, one being an input pathway and the other being an output pathway; providing a reflective surface in operative contact with the pathways whereby an input optical signal is passed through the input pathway, reflected by the reflective surface into the output pathway, and passed out of the output pathway, whereby the device can be made on a lithium niobate substrate with titanium-diffused pathways with a loss of about 1.0 dB or less, in a space that is at least &#x2155; the space required by the same or similar prior art device.

Low-loss compact reflective turns in optical waveguides

Featured is a high power, broadband superfluorescent source with very low relative intensity noise (RIN) including a seed source, a modulator operably coupled to the seed source and a polarization maintaining (PM) amplifier operably coupled to the modulator. The output of the seed source is processed in the modulator so the modulator outputs a polarized optical output to the PM amplifier. The PM amplifier amplifies the modulated, polarized optical output so as to provide an amplified polarized optical output therefrom. Also featured is a feedback circuit operably coupled to the PM amplifier to control the transmission of the modulator so as to minimize the amplitude fluctuations in the output signal. Such a source is advantageous in high precision fiber optical rotation sensors and multiplexed strain sensing arrays.

High power, low noise, fluorescent device and methods related thereto

An optical method and apparatus particularly useful as an intensity modulation system, in which two phase modulators are placed in the loop of a Sagnac interferometer. Selective placement of the modulators, and the amplitude of any modulation signal input to the modulators, varies the bandwidth and frequency response of the system. In a preferred embodiment, the ratio of the optical distances of the modulators from interferometric midpoint, and the ratio of modulation signal amplitudes, is about 3:1, which serves to broaden and flatten the frequency response of the system.

Apparatus and method for improving the frequency response of modulators

A Mach-Zehnder interferometer has electrodes configured to act as a microe transmission line. The optical waveguide arms have a reflective coating on their distal ends so that light is reflected back through the arms. The microwave transmission line is open-ended in a vicinity of the reflective coating so that microwave energy is reflected at the open end. Thus, the interferometer supports a traveling wave in a reflective configuration, and the distance over which interaction takes place can be effectively doubled.

Electro-optic reflection device with traveling-wave structure

The wavelength multiplexed, electro-optically controllable, fiber optic multi-tap delay line utilizes a first output signal from a plurality of amplitude adjustable continuous-wave (CW) optical lasers multiplexed to form a combined optical signal onto which a radio frequency signal is imposed thereby shifting the combined optical signal which is then demultiplexed. A second output signal of the plurality of CW lasers is phase adjusted and combined with the demultiplexed combined optical signal to form a RF phase adjusted modulated optical signal. The plurality of phase adjusted modulated optical signals pass through associated optical delay lines and are multiplexed to form a single optical signal containing a plurality of optical channels having different characteristics which is applied to a detector to produce an output electrical signal for transmission to using devices.

Wavelength multiplexed, electro-optically controllable, fiber optic

An optical link is disclosed that is operated by a balanced detection technique so as to extend its linear dynamic range, yet substantially eliminate even-order harmonic distortion of the modulated signal. The modulator comprises two parallel arranged Mach-Zehnder interferometers that respectively have a steady state DC voltage bias applied so that the operating points of the Mach-Zehnder interferometers are selected to produce two separate modulated signals, one of which is later phase shifted by a phase shift device so as to provide an output that is combined with the other modulated signal in such a manner so as to cause a subtraction, leaving the final output signal substantially free of any unwanted even-order harmonic components in order to provide for a multi-octave response characteristic.

Multi-octave, high dynamic range operation of low-biased modulators by

A system and method for subtracting excess noise from a high sensitivity gyroscope system in which a laser diode array is focused into an Nd-doped active fiber. A resultant gyro signal is polarized, detected, and amplified. A noise signal is polarized, delayed, detected, and amplified such that the noise signal is polarized parallel to the gyro signal and delayed by a fiber delay, of a length equal to a length of a gyroscope fiber coil. The excess noise component in the amplified gyro signal is reduced by modulating the amplified noise signal with a portion of the amplified gyro signal and subtracting the amplitude-modulated noise signal from the amplified gyro signal to produce a reduced noise gyro signal.

Low noise fiber gyroscope system which includes excess noise subtraction

A depolarized fiber optic gyroscope with a detector for detecting a rotat about an axis of rotation and a method therefor is disclosed. The gyroscope includes a depolarized light source for generating the depolarized light; a gyro coil for conducting depolarized light about the axis of rotation, the gyro coil including a coil of a non-polarization preserving fiber having first and second ends; a depolarizer with first and second ports for eliminating birefringence induced scale factor variations caused by the non-polarization preserving fiber, the first port of the depolarizer being coupled to the first end of the gyro coil; and a coupler device for coupling the second end of the gyro coil, the second port of the depolarizer, the detector and the depolarized light source, without utilizing a polarizer.

Fiber optic gyroscopes with depolarized light

A fiber superfluorescent light source is disclosed which suppresses laser cillations without interfering with the pump light or the super luminescence. In a preferred embodiment of the invention, the fiber superfluorescent light source comprises a laser diode array for providing a pump beam at a wavelength of 0.81 microns, a first fiber doped with neodymium activator ions and being responsive to the pump beam for providing a spontaneous emission at a wavelength of 1.06 microns, and a second fiber optically coupled between the laser diode array and the first fiber for passing the pump beam therethrough to the first fiber to enable the first fiber to spontaneously emit light at the 1.06 micron wavelength and for suppressing backemissions of the 1.06 micron wavelength from the first fiber toward the laser diode array to prevent back reflection from the laser diode array and oscillations in the first fiber.

Super luminescent light source

An apparatus comprised of a depolarized light source for fiber optic sensors is disclosed. In a preferred embodiment, the depolarized light source of the apparatus comprises: a first laser for generating a first beam at a first frequency, the first beam having a linear polarization state; a second laser for generating a second beam at a second frequency, the second beam having a linear polarization state; a means for rotating the polarization state of the second beam so that the first and second beams have orthogonal linear polarization states with respect to each other; and a means for combining the first beam with the polarization-rotated second beam to obtain a composite beam which is depolarized. In a system operation, the apparatus comprises: a source of depolarized light; an integrated optic modulator means for receiving a modulator drive signal; a first low-birefringence fiber for conveying the depolarized light beam from the depolarized light source to the integrated optic modulator means, the integrated optic modulator means modulating only one linear polarization state in the depolarized light beam as a function of the modulator drive signal to produce a modulated beam; a photodetector; and a second low-birefringence fiber for conveying the modulated light beam to the photodetector, the photodetector being responsive to the modulated light beam for developing an electrical signal proportional to the modulator drive signal.

Depolarized light source for fiber optic sensors

Successive waveguide regions in a birefringent waveguide host electric fields oriented transverse to any optical wave propagated through the waveguide. A scheme of cascaded electrodes biased by voltage(s) applied to the electrodes dictate instantaneous field polarity. Cascaded electrodes are sited in nonopposed, noninterleaved relation on opposite sides of a long electrode partially overlapping the waveguide.

Optical waveguide device for frequency shifting and mode conversion

A fiber optic gyroscope comprising a Sagnac interferometer including a (3.times.3) optical directional coupler. The gyroscope is driven with an essentially unpolarized broadband spatially coherent light beam supplied by a super-luminescent diode source. A significant reduction in baseband noise occurs due to the use of the essentially unpolarized light beam.

Fiber optic gyroscope operating with unpolarized light source

A gyroscope system for obtaining an extended linear dynamic range for platform rotation rate measurements comprising a first fiber optic gyroscope with a first optical fiber coil described by a first quantity L.sub.1 R.sub.1 /.lambda..sub.1 where L.sub.1 is the length of the first optical fiber coil, R.sub.1 is the radius of the first fiber coil, and .lambda..sub.1 is the light source wavelength, this first quantity being chosen to provide a linear output for a first range of small rotation rates of the platform; a second fiber optic gyroscope with a second optical fiber coil described by a second quantity L.sub.2 R.sub.2 /.lambda..sub.2 with this second quantity being chosen to provide a linear output for a second range of large rotation rates of the platform, with this second range partially overlapping the first range; voltage controlled oscillators for converting the gyroscope signals to pulse frequency signals; a circuit for determining whether a reference rotation rate within the overlap between the first and second ranges has been reached and generating a control signal in accordance therewith; a pulse counter; and a switch for switching one or the other of the pulse frequency signals to the pulse counter in accordance with the control signal so that a gyroscope which is operating within its linear range is utilized.

Growing community of inventors

Ft. Washington, MD, United States of America

Robert P Moeller