Abstract: 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.

Abstract: 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.

Abstract: A fiber optic interferometric sensor system utilizing a reference transducer and an optical source having a short coherence length in comparison to the optical transit time through the sensor. The optical source is used to interrogate a remotely located fiber optics sensor which has an optical path difference between two reflecting surfaces or between one reflecting surface and a beam transmitted through the sensor such that the optical beams are incoherent for the optical source used. The reflected and transmitted beams are then coupled to a reference transducer, located remotely from the sensor and preferably near the electronic processing circuitry. The reference transducer is designed with an optical path length difference to produce a coherent combination for the optical path length differences of both the sensor and the reference transducer thereby forming a highly sensitive interferometer.

Abstract: A fiber optic interferometric sensor system utilizing a reference transducer and an optical source having a very short coherence length, typically about 80 microns. The optical source is used to activate a remotely located fiber optic sensor which has an optical path defference between two reflecting surfaces such that the reflected optical beams are incoherent for the optical source used. The reflected beams are then coupled to a reference transducer, located remotely from the sensor and preferably near the electronic processing circuitry. The reference transducer is designed with an optical path length difference to produce a coherent combination for the optical path length differences of both the sensor and the reference transducer thereby forming a highly sensitive interferometer.

Abstract: An electronic receiver circuit for receiving and amplifying optical signals is disclosed. The optical signal is applied to a photodiode which generates a current signal that passes through a source load with a high resistance or impedance relative to the impedances associated with the desired bandwidth of the optical signal. The current signal is amplified and buffered by an amplifier circuit which can drive low output impedances while maintaining the proper voltage level on the high impedance source load. The receiver circuit also maintains a wide signal bandwidth from RF to microwave frequencies, holds pre-amplifier distortion to very low levels and still yields a high signal-to-noise ratio.

Abstract: An optical sensor and method for measuring naturally occurring phenomena such as vibrations is disclosed. An optic fiber is wound as a coil and placed such that strain is introduced in it by the phenomena. Low coherence light is launched through a coupler and split to produce counter rotating beams in the coil. The counter rotating beams are phase modulated by an optical modulator driven by an oscillator and by naturally occurring phenomena. The sensitivity and response of the sensor increases dependent on the length of fiber in the coil and improves linearly as the frequency of source signal increases. The modulated counter rotating beams are recombined in the coupler to produce an intensity modulated optical signal on a photodetector. The output of the detector is an electrical signal containing the signal of interest as modulation which is recovered througth demodulating circuits mixing the fundamental and second harmonic frequencies.

Abstract: A pressure insensitive optical fiber waveguide comprising an optical fiber including an optical core and a concentric cladding; a substrate concentrically surrounding the optical fiber; and a fiber jacket substrate including at least two coatings concentrically surrounding the substrate wherein the innermost coating has a small Young's modulus and the outermost coating has a high Young's modulus.

Abstract: A test signal waveform detector that includes a fiber optic interferometer wherein the phase difference of the two parts of a split laser beam is modulated by the waveform of a sinusoidal test signal which is to be detected and by the waveform of a sinusoidal reference signal, and the two parts of the split beam are recombined and mixed on the face of a photodetector. A signal conversion circuit converts the ac signal produced by the photodetector to another ac signal that carries the test signal information as an equivalent frequency modulation, and a demodulator extracts the test signal information from the latter ac signal.

Abstract: An optical system for frequency-modulation heterodyne detection of an acoustic pressure wave signal. An optical beam is directed into a Bragg cell outside of the fluid medium in which acoustic signals are to be detected. The Bragg cell modulates the incident beam such that two beams of different frequency exit the cell. The two beams are directed into an input optical fiber and the resultant combined beam is transmitted over a desired distance to a fiber optic transducer disposed in the fluid medium. The transducer includes two coiled optical fibers, a reference fiber and a signal fiber, each of which has a different sensitivity to incident acoustic pressure wave signals. The transmitted beam is directed from the input optical fiber through a power divider which splits the beam into two equal parts, one part passing through the reference fiber, the other part passing through the signal fiber. A filter in the signal fiber transmits only a fraction of the light at one of the two frequencies.