Abstract: A fiber optic sensor comprises two independent fibers having Bragg gratings which are coupled to commutating broadband optical sources through splitters and wavelength discriminators. The ratio of detected optical energy in each of two detectors examining the wave intensity returned to a wavelength discriminator coupled with the characteristic of the wavelength discriminator determines the wavelength returned by the grating. In another embodiment, tunable filters are utilized to detect minimum returned wave energy to extract a sensor wavelength. Reference to the original grating wavelength indicates the application of either temperature or strain to the grating. In another embodiment, a plurality of Bragg grating sensor elements is coupled to sources and controllers wherein a dimensional change in a fiber having a Bragg grating is detected using a measurement system comprising broad-band sources, optical power splitters, a high-sensitivity wavelength discriminator, optical detectors, and a controller.

Abstract: New elements mode-converting two-mode grating and mode-filtering two-mode coupler are disclosed and used as elements in a system for communications, add-drop filtering, and strain sensing. Methods of fabrication for these new two-mode gratings and mode-filtering two-mode couplers are also disclosed.

Abstract: A tunable filter comprises either an internal or an external grating proximal to a variable index of refraction material. This variable index of refraction material may vary upon the application of an external electrical potential or the application of a change in temperature of the polymer. Additionally, the grating may comprise a periodic modulation of the index of refraction, this periodic modulation comprising an isoplanar modulation of the index of refraction at an angle to the central axis of the waveguide, thereby causing conversion of fundamental mode waves to second mode waves, and by reciprocity, conversion of second mode waves to fundamental mode waves.

Abstract: New elements mode-converting two-mode grating and mode-filtering two-mode coupler are disclosed and used as elements in a system for communications, add-drop filtering, and strain sensing. Methods of fabrication for these new two-mode gratings and mode-filtering two-mode couplers are also disclosed.

Abstract: A high-speed light modulator employing surface plasmon wave coupling comprises a metal-dielectric interface positioned adjacent to and externally of a waveguide carrying totally internally reflected light waves. A high frequency voltage applied to the interface causes the dielectric, in the preferred case an ultra-fast electro-optic polymer, to resonate, generating a surface plasmon wave at the interface. The plasmon wave couples with the evanescent wave portion of the light waves in the waveguide. The output intensity of the light waves varies inversely with the strength of coupling between the light wave and surface plasmon wave modes. The modulator eliminates bulk and alignment problems associated with state of the art modulators and can be employed in integrated optic circuits.

Abstract: A method and apparatus for wavelength stabilization of an optical source uses three birefrigent crystals that are temperature-compensated as a whole to function as the two arms of a reference interferometer. Only phase differences resulting from shifts in the wavelength of the optical source are measured. Synchronous detection of a light intensity signal representative of the phase difference between light waves of orthogonal polarization is made possible by making one of the three crystals an electro-optic material and applying a modulating voltage to it. The remaining two crystals are a pair of different passive birefringent crystals. The three interferometer crystals are cut and polished to prescribed lengths and orientations; optical path length changes with temperature in one crystal are compensated for by opposite and equal optical path length changes in the other two.

Abstract: A wavelength division multiplexer/demultiplexer having optical path lengths between a fiber array and a Fourier transform lens, and between a dispersion grating and the lens equal to the focal length of the lens. The equal optical path lengths reduce losses due to angular acceptance mismatch in the multiplexer. Close orientation of the fiber array about the optical axis and the use of a holographic dispersion grating reduces other losses in the system. Multi-exposure holographic dispersion gratings enable the multiplexer/demultiplexer for extremely broad-band simultaneous transmission and reflection operation. Individual Bragg plane sets recorded in the grating are dedicated to and operate efficiently on discrete wavelength ranges. A volume Bragg vertically non-uniform holographic grating enables operation of the multiplexer or other devices that act on light waves according to wavelength over nearly the full usable 0.8-1.3 .mu.m wavelength range.

Abstract: An array (48, 49, 50, 51) of fiber optic couplers coupling an input (45) and an output (46) waveguide. The output waveguide (46) is routed among the couplers of the array such that either backward or forward coupling exists. With backward coupling, energy coupled into the output waveguide (46) in a coupler of the array is guided back to the preceding coupler for coupling back into the input waveguide (45).The backward coupling allows recirculations to occur between couplers to create poles and zeroes in the transfer function of the array which transfer function can be programmed or tailored somewhat to have specific characteristics. Further, the backward coupling allows the array to be used for matrix-vector multiplication.