Abstract: 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.

Abstract: 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.

Abstract: A digital audio system and method for accessing digital audio broadcasts and files over a computer network. The digital audio device of the present invention provides an apparatus for connecting to and receiving digital audio broadcasts and files without the need for a personal computer. A method is provided for simplifying access to the broadcast and file addresses. Each address is assigned a channel number for entering into the digital audio device in lieu of its URL. With the system and method of the present invention the digital audio device provides features much like a standard radio, but when connected to the Internet it is capable of accessing any radio station in the world that broadcasts over the Internet. The digital audio device can also provide features similar to that of a jukebox, in that individual songs or programs can be purchased for single or multiple uses.

Abstract: Ideographic keyboard and method in which an array of characters are printed on one side of a panel and optically readable data corresponding to the characters is recorded on the other side of the panel. A character selector is moved about the first side the panel for selective alignment with the characters, and an optical reader is linked to the character selector for movement about the recorded data in concert with the character selector. The data corresponding to a selected character is read, and a coded signal for the selected character is output in response to the data which is read. In one disclosed embodiment, the data is recorded in the form of bar coding, and the reader is a bar code reader. Precise alignment of the reader with the data for the selected character is assured by reading data from a region larger than the data field itself and extracting the character data in software.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.