Leland Stanford Junior University

Tft, Inc.

Keysight Technologies, Inc.

Stratos International, Inc.

Kenneth A Fesler

Herbert J Shaw

Michel J Digonnet

Byoung Y Kim

Byoung Yong Kim

Janet L Brooks

Robert C Youngquist

Martin M Fejer

John J Fling

Karen Liu

Moshe Tur

Aharon Kapitulnik

Cassius C Cutler

James S Bunn, Jr

Robert H Wentworth

Xiaojie Xu

Kaine Mildenberger

Kenneth Crandall

Carl Goy

Generally, in accordance with the various illustrative embodiments disclosed herein, a homodyne optical interferometer can include a multi-phase beam combining system that receives a composite beam from an optical beam guidance system and uses a diffraction grating to produce a diffracted plurality of light beam members. Each of the diffracted plurality of light beam members is propagated through a birefringent optical element that imposes a differential phase shift on each member based on polarization and differing optical path lengths. In one example implementation, the birefringent optical element can be a parallel plate optical element arranged at an angle with respect to a light-propagation axis of the multi-phase beam combining system and in a second example implementation, the birefringent optical element can be a multifaceted optical element having a first planar external surface that is sloped with respect to an opposing external planar surface.

Homodyne optical sensor system incorporating a multi-phase beam combining system

A device includes a first fiber collimator, a second fiber collimator, a third fiber collimator, a first beam splitting prism, a second beam splitting prism, a spacer, a resonator cube, and a dielectric beam splitting coating. The dielectric beam splitting coating separates the second beam splitting prism from the resonator cube. The spacer and the first fiber collimator straddle the first beam splitting prism. The first beam splitting prism and the second beam splitting prism straddle the spacer. The second fiber collimator and the spacer straddle the second beam splitting prism. The third fiber collimator and the spacer straddle the second beam splitting prism.

Micro optical design for DWDM interleavers with narrow channel spacing

An encoder/decoder for an emergency alert system to enable broadcasters to receive, store, re-broadcast and originate emergency alert messages. Multiple emergency alert signals are received by the encoder/decoder. A digital signal processor of the encoder/decoder scans the reception of the multiple emergency alert messages to determine the presence of an incoming emergency alert signal. The digital signal processor provides digital implementation of a frequency shift key modulation and a frequency shift key demodulation to encode and decode emergency alert messages. Additionally, the digital signal processor functions as a central processing unit to control input/output ports over a digital signal processor bus for performing all encoding and decoding functions and to control all encoding and decoding functions.

Encoder/decoder for emergency alert system

An emergency alert communication system comprising a radio frequency receiver. The radio frequency receiver decodes incoming emergency alert signals and demodulates data header signals and emergency alert voice message signals of the emergency alert signals. Included in the data header signals are event and location code signals, which are followed by the emergency alert voice message signals. The demodulated data header signals in the form of digital data header signals are applied to a microcontroller. A telephone keypad of a telephone device is actuated to enter into the microcontroller event and location code signals. Should the event and location code signals demodulated by the receiver and applied to the microcontroller match the event and location code signals entered into the microcontroller by the telephone keypad, the microcontroller routes through an audio switching circuit the emergency alert voice message signals to a speaker, a recording device and a telephone handset of a telephone device. The radio frequency receiver, the microcontroller, the telephone handset, the telephone keypad, the speaker, and the recording device are embodied in the telephone device.

Emergency alert communication system wherein emergency messages are

An interferometer used as a rotation sensor is constructed using a strand of optical fiber, a portion of which is formed into a sensing loop. A pair of light waves are caused to counterpropagate in the sensing loop and are combined to form an optical output signal that has an intensity that varies in accordance with the difference in the phases of the two counterpropagating light waves. A phase modulator is positioned on the optical fiber in the sensing loop at a location such that the two counterpropagating light waves are modulated approximately 180 degrees out of phase. The time-varying phase modulation causes a time-varying phase difference that is combined with a rotationally-induced Sagnac effect phase to provide a total phase difference that is detected by a photodetector. The photodetector provides an electrical output signal that is processed to determine the Sagnac phase difference. The rotation rate is then calculated from the Sagnac phase difference. The processing occurs in a feedback loop in which a reference signal is multiplied by the electrical output signal to provide a feedback signal. The reference signal is adjusted so that the feedback signal is maintained at a predetermined value. The magnitude of the adjustment of the reference signal is measured and the Sagnac phase difference is determined from the measured magnitude.

Optical fiber sensor having digital integrating detection system

A method and apparatus for measuring nonreciprocal optical effects contemplates directing two circularly polarized optical beams having a known phase relation to each other at a sample, and detecting the difference in phase between the two beams after they have encountered the sample. In a transmission measurement the two circularly polarized beams have the same handedness, but pass through the sample in opposite directions. In a reflection measurement, the two circularly polarized beams have opposite handedness, but encounter the sample in the same direction. In a particular embodiment of the invention a linearly polarized beam is introduced into a Sagnac interferometer and split into two linearly polarized beams which are ultimately recombined.

Interferometric technique for measurement of nonreciprocal optical

An improved broadband light source for a Sagnac interferometer includes a waveguide, such as a fluorescent optical fiber, that is pumped by a pump source with a sufficient intensity to generate temporally incoherent light. The fluorescent optical fiber has first and second ends, one end being an input end of the fiber. The broadband light is provided at an output of the fluorescent optical fiber and is input to the interferometer. In order to prevent laser oscillations between the light source and the interferometer, one end of the fluorescent optical fiber is formed so as to prevent reflections. The light output from the fluorescent fiber to the interferometer comprises only that light that initially propagates toward the output of the optical fiber. In one embodiment of the light source, the pump light from the pump source is coupled into the fluorescent optical fiber in a direction so that it travels away from the output of the fluorescent optical fiber towards the first end. In an alternative embodiment, the fluorescent optical fiber is a doubly clad optical fiber having a first acceptance region and a second acceptance region at the first end. The pump light is introduced into an aperture window between the two acceptance regions so that the pump light can be introduced into the first end at an angle without requiring a reflective surface at the first end.

Interferometer utilizing superfluorescent optical source

An improved broadband light source for a Sagnac interferometer includes a fluorescent optical medium that is pumped by light from a pump source with a sufficient intensity to cause the fluorescent optical medium to generate temporally incoherent light by superfluorescence. In the preferred embodiment, the superfluorescent optical medium comprises an optical fiber which is backward pumped. The signal output from the interferometer loop is amplified by the optical gain of the superfluorescent fiber which acts as a light source and as an amplifier. In order to avoid gain modulation in the superflorescent fiber, the modulation frequency is selected so that the modulation gain depth is substantially reduced.

Optical waveguide amplifier source gyroscope

An optical fiber laser includes a single-mode optical fiber doped with a lasing material such as Neodymium. The optical fiber is pumped with a pump optical signal having a pump wavelength selected to cause spontaneous emission of an optical signal at a second wavelength different from the pump wavelength. The optical fiber is formed into a laser cavity such as by including a suitable reflector at each of the two ends of a suitable length of the optical fiber so that the emitted optical signal oscillates therein. One of the reflectors has a reflectivity at the wavelength of the emitted light so that most (e.g., approximately 95%) of the emitted light is reflected back into the laser cavity and a smaller portion (e.g, approximately 5%) is transmitted through the mirror as a laser output signal. Alternatively, the optical fiber can be formed into a ring laser structure using an optical coupler that couples a substantial portion (e.g., approximately 95%) of the emitted light back into the ring for recirculation therein and provides a smaller portion of the emitted light (e.g., approximately 5%) as a laser output signal. The wavelength of the pump optical signal is selected to be outside the pump variable tuning range of the Neodymium-doped optical fiber (i.e., the range of pump wavelengths which stimulate emitted wavelengths having a average wavelengths with a generally one-to-one correspondence to the pump wavelength). Pumping with a pump signal outside the pump variable tuning ranges causes the emitted light to have a broad spectral envelope of longitudinal modes having emission wavelengths corresponding to substantially all the pump variable tuning range. Thus, by pumping the optical fiber with a single pump wavelength, a broadband laser output signal is generated.

Broadband optical fiber laser

A sensor array and method for remotely monitoring environmental effects on a selected sensor. In a sensor array comprising a plurality of interferometers, an optical signal of a selected configuration is provided so that portions of the optical signal are propagated through the interferometers. The optical signal configuration causes optical signal portions which have traveled the same signal path, except where separated on signal paths in a selected interferometer, to coherently mix when combined at an output of the selected interferometer. No other optical signal portions in the sensor array will coherently mix. The optical signal comprises plural components such as side bands which are configured to form a power spectrum defining an optical signal coherence function having a maximum which repeats periodically at a rate substantially corresponding to optical signal travel time difference in the selected interferometer. Also, the coherence function has minimums or zero values at times such that intervals between various minimums substantially correspond to optical signal travel time differences through non-selected interferometers, thus precluding coherent mixing of optical signal portions emerging from those non-selected interferometers. By modifying characteristics of the optical signal components, one may change the repetition period of the coherence function maximum and of selected coherence function minimums to produce coherent mixing of signal portions from another interferometer while precluding coherent mixing of signals from all other interferometers, including the previously selected interferometer. Accordingly, a given sensor may be selected from monitoring, to the exclusion of all others.

Sensor array and method of selective interferometric sensing by use of

A distributed sensor system using pulsed optical signals optionally produced by a short coherence length source to provide a phase difference output signal representative of conditions affecting a selected sensor. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light pulses transmitted through the sensors are multiplexed onto a return arm of the ladder. The multiplexed signals are received by an optical fiber compensating interferometer which coherently couples portions of adjacent multiplexed light signals to produce a phase difference signal representing conditions influencing selected sensors. In other preferred embodiments, the system is configured to define a plurality of adjacent Mach-Zehnder interferometers which provide output signal pairs which coherently couple to yield a phase difference signal directly representing the environmental effects on a particular sensor. Functional equivalents of the Mach-Zehnder interferometer configurations comprise configurations including adjacent Michelson interferometers. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.

Distributed sensor array and method using a pulsed signal source

A fiber optic frequency shifter comprises an optical fiber having an acoustic conducting medium for propagation of an acoustic signal. The acoustic medium is preferably shaped as a rod, and the acoustic signal propagates longitudinally down the rod. The optical fiber is wound around the rod with plural turns such that the axis of the fiber is at an angle relative to the wave fronts of the acoustic signal. As the acoustic signal propagates through the rod, it causes stress on the portions of the fiber in contact with the rod. The stress on the fiber caused by the acoustic wave causes optical energy to be transferred between two propagation mdes of the fiber. This transferred energy is shifted in frequency by the frequency of the acoustic signal. By tightly winding the turns of the fiber, high frequency shifts can be obtained. The invention is also advantageous in that it provides a large amount of acoustic contact between the acoustic wave fronts and the fiber over a relatively short acoustic propagation distance. Thus, the device is quite compact.

Acousto-optic frequency shifter utilizing multi-turn optical fiber

A distributed sensor system including an optical source having a short coherence length for optionally continuously monitoring each sensor in the system. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light transmitted through the sensors is multiplexed onto a return arm of the ladder, with sensor spacing being such that interference between light from different sensors is prevented. The multiplexed signals are received by an optical fiber receiver which couples the multiplexed light with an interfering optical reference signal to produce a phase difference signal representing conditions influencing selected sensors. Embodiments are disclosed for use of either pulsed or continuous wave light sources. In another preferred embodiment, the sensors comprise a plurality of Mach-Zehnder interferometers connected in series configuration by a common optical fiber, which provides multiplexed output signals from the sensors to a plurality of Mach-Zehnder interferometers comprising receivers. The optical path length differences between the arms of each of the sensors are selected to prevent interference between the multiplexed sensor output signals from various sensors. The optical path lengths through the sensors and receivers are structured so that each receiver produces a phase difference signal relating to conditions affecting light transmission through a specific sensor. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.

Growing community of inventors

Sunnyvale, CA, United States of America

Kenneth A Fesler