Abstract: In filters fabricated on a birefringent electrooptic substrate (28), a tunable electrooptic add-drop filter apparatus (10) includes two input single mode waveguides (44) and a first beam splitter (24) connected to the waveguides (44). A polarization converter (42) is connected to the waveguides (44) after the first beam splitter (24) wherein each polarization converter (42) includes more than one set of spaced apart, spatially periodic, strain-inducing pads (18). Electrode(s) (30) are provided in proximity to the polarization converter (42). A second beam splitter (24) is provided connected to the waveguides (44) after the polarization converter (42). Finally, two output single mode waveguides (48) are connected to the second beam splitter (24).

Abstract: In a system for transmitting intensity modulated light waves (20) over an optical fiber (18), an optical data transmission apparatus (10) includes a cw laser (12) conformed to emit light at substantially a single frequency. A phase modulator (14) is connected in series with the cw laser (12), wherein the phase modulator (14) is conformed to cause the light from the cw laser (12) to vary in substantially a quadratic manner as a function of time during a time interval T. An intensity modulator (16) is connected in series with the phase modulator (14), wherein the intensity modulator (16) is conformed to transmit or block the light from the phase modulator (14) in accordance with an intensity modulation scheme for transmitting binary data, such that the transmitted light consists of pulses (22) of temporal width T during which the phase of the light varies in substantially a quadratic manner as a function of time.

Abstract: A two-port guided wave tunable filter in a birefringent electrooptic and/or acoustooptic substrate material includes two 3-port, symmetric Y-branch beam splitters connected by two waveguide sections in which phase-matched polarization coupling occurs, with an input port and an output port. The optical path difference between the beam splitters is half an optical wavelength, and the polarization coupling regions between the beam splitters are relatively displaced by an odd integral multiple of half the spatial period of the perturbation responsible for the coupling. In one embodiment, an electrooptic tunable filter, the polarization coupling in the waveguides is caused by a spatially periodic strain-inducing film and tuning results from an applied electric field. In another embodiment, an acoustooptic tunable filter, polarization coupling results from a surface acoustic wave and tuning is accomplished by changing the acoustic frequency.

Abstract: A multireflector fiber optic filter apparatus, wherein the transmittance and reflectance spectra are periodic in frequency, the apparatus comprising an etalon with N equally spaced reflectors wherein the transmittance and reflectance spectra of said etalon are periodic in optical frequency with a period given by the formula: &Dgr;&ngr;FSR=c/(2ngL), where c=the free space speed of light; ng=the group refractive index for the light propagating in the medium between the reflectors, L=separation between said reflectors, and N is an integer=3,4,5, . . . In a further aspect, an optical circulator is connected to the etalon and an optical fiber is connected to the optical circulator for reflected output.

Abstract: A two-port guided wave tunable filter in a birefringent electrooptic and/or acoustooptic substrate material includes two 3-port, symmetric Y-branch beam splitters connected by two waveguide sections in which phase-matched polarization coupling occurs, with an input port and an output port. The optical path difference between the beam splitters is half an optical wavelength, and the polarization coupling regions between the beam splitters are relatively displaced by an odd integral multiple of half the spatial period of the perturbation responsible for the coupling. In one embodiment, an electrooptic tunable filter, the polarization coupling in the waveguides is caused by a spatially periodic strain-inducing film and tuning results from an applied electric field. In another embodiment, an acoustooptic tunable filter, polarization coupling results from a surface acoustic wave and tuning is accomplished by changing the acoustic frequency.

Abstract: A highly efficient electrooptic means and method of light modulation utilizing slow wave optical propagation is provided. A grating structure (35) integrated with a single mode optical waveguide (32) on an electrooptic substrate (30) induces coupling between forward- and reverse-propagating light waves. This contradirectional coupling leads to a reduction in the optical propagation speed in the forward direction. Electrodes (38a and 38b) are provided for applying an electric field to modulate the light propagating in the waveguide (32) via the linear electrooptic (Pockels) effect. In a preferred embodiment, a modulating radio frequency or microwave signal applied to the electrodes (38a and 38b) propagates in the same direction as the modulated light wave at substantially the same velocity.

Abstract: A fiber optic fiber Fabry-Perot interferometer diaphragm sensor and method of measurement is provided. A fiber Fabry-Perot interferometer diaphragm sensor (12a, 12b, 12c) includes a base (54a, 54b, 54c) and a diaphragm (52a, 52b, 52c) with an optic fiber (30) coupled under tension between the base (54a, 54b, 54c) and the diaphragm (52a, 52b, 52c). A fiber Fabry-Perot interferometer element (40) is contained within the optic fiber (30) and operates to sense movement of the diaphragm (52a, 52b, 52c). In a particular embodiment, the diaphragm (52a) moves in response to a pressure (P) applied to the diaphragm (52a). In another embodiment, a proof mass (72) is coupled to the diaphragm (52b) such that the diaphragm (52b) moves in response to an acceleration (A). In yet another embodiment, a magnetic body (80) is coupled to the diaphragm (52c) such that the diaphragm (52c) moves in response to a magnetic field (M).

Abstract: A method and apparatus are provided for measuring pressure in a combustion chamber of an internal combustion engine is provided with a non-intrusive, metal-embedded fiber optic pressure sensor. A Fabry-Perot Interferometer is arranged in a terminated, single mode fiber to function as a pressure gauge. The fiber Fabry-Perot Interferometer (FFPI) is embedded in a metal part which is disposed in the cylinder head of the engine. The metal part and FFPI experience a longitudinal compression in response to the pressure in the chamber. In another aspect of the invention, a non-intrusive fiber containing the FFPI is embedded in a hole drilled or otherwise provided in the metal housing of a spark plug. The spark plug is threaded into the cylinder head of an internal combustion engine and is directly exposed to the combustion chamber pressure. Consequently, the spark plug housing and FFPI experience a longitudinal strain in response to the pressure in the chamber.

Abstract: Apparatus and method (10, 50) for determining the value of a measurand measured by a fiber optic interferometer sensor (24, 72, 110) is provided. The apparatus includes a light source (16, 58, 102) emitting a light having a periodically modulated frequency which is injected into the interferometric sensor. A modulation cycle is initiated by the microcontroller's (12, 56, 116) generation of a trigger signal. A counter (42, 86) begins counting in response to the trigger signal. A first photodetector (20, 66) is coupled to the light source (16, 58, 102) and produces a first electrical signal proportional to the light. A second photodetector (36, 76, 114) is coupled to the fiber optic interferometer sensor (24, 72, 110) and produces a second electrical signal proportional to the light reflected by the sensor or passed through the sensor and affected by the measurand.

Abstract: A method and apparatus is provided for measuring pressure in a pressure containing vessel with a non-intrusive, metal-embedded fiber optic pressure sensor. The pressure containing vessel may, for example, be the combustion chamber of an internal combustion engine. A Fabry-Perot Interferometer is arranged in a terminated, single mode fiber to function as a strain gauge. The fiber Fabry-Perot Interferometer (FFPI) is embedded in a metal part which may be disposed in a wall of the pressure containing vessel. The metal part and FFPI experience a longitudinal strain in response to the pressure in the vessel. In another aspect of the invention, a non-intrusive fiber containing the FFPI may be embedded along the axis of a metal bolt. The bolt may be used to attach a part or structure, which is directly exposed to the pressure, to the wall of the vessel. Consequently, the bolt and FFPI experience a longitudinal strain in response to the pressure on the part or structure.

Abstract: Optical fibers are embedded in metal structures and components by using a pair of stress-relieving tubes at the air-metal interface of the optical fiber.

Abstract: Apparatus for sensing intrusion into a predefined perimeter comprises means for producing a coherent pulsed light, which is injected into an optical sensing fiber having a first predetermined length and positioned along the predefined perimeter. A backscattered light in response to receiving the coherent light pulses is produced and coupled into an optical receiving fiber. The backscattered light is detected by a photodetector and a signal indicative of the backscattered light is produced. An intrusion is detectable from the produced signal as indicated by a change in the backscattered light. To increase the sensitivity of the apparatus, a reference fiber and an interferometer may also be employed.

Abstract: The present invention is directed to a sensor which utilizes an optical fiber interferometer to detect the absorption of a modulated laser beam by a particular chemical species. In particular, one embodiment of the present invention comprises a fiber optic system in which light from a continuously operating laser is modulated prior to passing through a region containing a chemical species of interest. Absorption of the light from the laser causes heating of the chemical species which, in turn, emits thermal energy that is transferred to an optical fiber that is situated in close proximity to the region in which the light is absorbed. In turn, the increase of the temperature of the optical fiber results in a change in the fiber's refractive index, thereby resulting in a change in the transmittance of said interferometer. The change in transmittance of the fiber is converted into an electrical signal in a photodetector.

Abstract: Electrically controlled Fabry-Perot resonator elements are created in a semiconductor channel waveguide by etching two in-channel mirror facets (slots) and by positioning the resulting resonator core in the midregion of a P-I-N diode or field-effect transistor. A large number of FPs can be built monolithically on one semiconductor chip, with FPs connected by on-chip passive waveguides used for multiple on-chip time delays. The low-loss chips are coupled efficiently in end-fire fashion to a group of optical fibers that comprise the optical signal processing system. III-V quantum-well, superlattice, and n-i-p-i materials are preferred for the semiconductor devices, and a variety of electrooptical effects are available for use, including the quantum-confined Stark effect, phase-space absorption quenching, Wannier-Stark effect, plasma dispersion effect, and band-flattening.

Abstract: An electromagnetic signal processor is disclosed comprising an input waveguide, an intermediate waveguide, and an output waveguide. The intermediate waveguide comprises two portions having substantially equal electromagnetic impedances. The two portions of the intermediate waveguide are coupled to each other at a first and a second junction. The input and output waveguides are electromagnetically coupled to the intermediate waveguide at the first and the second junctions, respectively. Electrically coupled to the intermediate waveguide is a semiconductor device responsible for processing input electromagnetic signals. The input waveguide functions to receive and direct an input electromagnetic signal to the first junction of the intermediate waveguide. At the first junction, the intermediate waveguide separates the input signal into two signals having substantially equal amplitudes.

Abstract: A method for producing reflectors in a continuous length of optical fiber is disclosed. The present process includes the steps of preparing the ends of two or more optical fibers, placing one or more of these fibers in a vacuum system and applying a metallic or dielectric coating to the fiber ends, and then fusing the prepared, coated ends of the fibers together until the reflectivity of the region reaches a desired value.

Abstract: A method for producing reflectors in a continuous length of optical fiber is disclosed. The present process includes the steps of preparing the ends of two or more optical fibers, placing one or more of these fibers in a vacuum system and applying a metallic or dielectric coating to the fiber ends, and then fusing the prepared, coated ends of the fibers together until the reflectivity of the region reaches a desired value.

Abstract: A method for producing reflectors in a continuous length of optical fiber is disclosed. The present process includes the steps of preparing the ends of two or more optical fibers, placing one or more of these fibers in a vacuum system and applying a metallic or dielectric coating to the fiber ends, and then fusing the prepared, coated ends of the fibers together until the reflectivity of the region reaches a desired value.

Abstract: A method for producing reflectors in a continuous length of optical fiber is disclosed. The present process includes the steps of preparing the ends of two or more optical fibers, placing one or more of these fibers in a vacuum system and applying a metallic or dielectric coating to the fiber ends, and then fusing the prepared, coated ends of the fibers together until the reflectivity of the region reaches a desired value.

Abstract: A method and means for forming an optical transversal filter and the optical transversal filter itself. The optical transversal filter comprises an optical fiber with a plurality of short reflective phase gratings disposed therein, with each reflective phase grating comprising a periodic variation of the refractive index of the optical fiber. These reflective phase gratings are disposed at predetermined positions along the length of the optical fiber and each reflective phase grating has a predetermined reflectance in order to reflect a predetermined relative amplitude of the light propagating in a first direction within the optical fiber to thereby counterpropagate back along the optical fiber. Modulated light source means are provided for directing light into one end of the optical fiber, and means for detecting light are provided to detect the light reflected by the plurality of reflective phase gratings.