Abstract: The disclosed Mach-Zehnder (MZ)-type devices are planar waveguide devices, with interferometer arms of essentially equal length, with a maximum spacing between the arms (e.g., between the waveguide core centers) selected to make possible simultaneous exposure of both arms to refractive index-altering radiation. Exemplarily the maximum spacing is in the range 20-100 .mu.m. The simultaneous exposure of both waveguides makes it possible to form gratings of essential equal strength, such that typically no individual trimming is required. The resulting devices (typically add-drop filters) are substantially less sensitive to environmental changes (e.g., temperature gradients, mechanical vibrations) than prior art fiber-based devices, and are advantageously used in, for instance, WDM optical communication systems.

Abstract: The present invention relates to a waveguide taper. The waveguide taper has a first end and a second end for being coupled with a fiber. The core has an overall width that progressively increases from the waveguide end toward the fiber end such that the width of the fiber end of the taper corresponds to the diameter of the core of the fiber. Side-gaps are disposed in the sides of the core and extend into the core but not across the entire width of the core. The depth of the side-gaps progressively increases from the waveguide end to the fiber end of the taper. In one embodiment, the side-gaps may be aperiodically and/or randomly disposed along the length of the taper and the side-gaps can be disposed at different angles to a direction of light propagation along a length of the core.

Abstract: In accordance with the invention, a new type of monolithic optical waveguide filter comprises a chain of optical couplers of different effective lengths linked by differential delays of different lengths. The transfer of the chain of couplers and delays is the sum of contributions from all possible optical paths, each contribution forming a term in a Fourier series whose sum forms the optical output. A desired frequency response is obtained by optimizing the lengths of the couplers and the delay paths so that the Fourier series best approximates the desired response. The filter is advantageously optimized so that it is insensitive to uncontrolled fabrication errors and is short in length. The wavelength dependence of practical waveguide properties is advantageously incorporated in the optimization. Consequently, the filter is highly manufacturable by mass production. Such filters have been shown to meet the requirements for separating the 1.3 and 1.551 .mu.

Abstract: An integrated optical device for tapping signal power provides a tap which is substantially independent of wavelength and polarization. The optical device includes a first tap consisting of a first optical waveguide carrying an input signal S disposed in coupling relation with a second optical waveguide for providing an output cross-state transmission T.sub.1. The cross-state transmission T.sub.1 is polarization and wavelength dependent. The optical device further includes a second tap consisting of a third optical waveguide disposed in coupling relation with and in series with the second optical waveguide carrying the output cross-state transmission T.sub.1 for providing an output bar-state transmission T.sub.2. The bar-state transmission T.sub.2 has an opposite dependency on waveguide coupling than that of the cross-state transmission T.sub.1 and, thus, compensates for wavelength and polarization dependencies of the cross-state transmission signal T.sub.

Abstract: A waveguide Bragg reflector is made by forming periodic grooves in either the undercladding or the core, applying a high index coating on the grooved surface and selectively removing the coating from the horizontal surfaces while leaving the coating on the vertical surfaces. The waveguide is then completed.

Abstract: An optical communication network includes a novel, passive optical component. This component combines the function of a splitter with the function of a wavelength-division multiplexer. These functions are performed in distinct wavelength bands. In one embodiment, the inventive component is made using silicon optical bench technology.

Abstract: An optically switches relatively low power requirements and a relatively broad operating bandwidth. This switch includes a Mach-Zehnder interferometer (MZI) optically coupled at respective ends to an input coupler and an output coupler. One arm of the MZI includes a thermo-optic phase shifter. The output coupler is an adiabatic 3-dB coupler. In one embodiment, the input coupler is a Y-branch coupler having one input port. In a second embodiment, the input coupler is an adiabatic 3-dB coupler having two input ports.

Abstract: In accordance with the invention the birefringence induced by compressive strain in silica waveguides on silicon substrates is compensated with a high index patch--such as silicon nitride--placed adjacent the core. The patch is disposed sufficiently close to the core to optically couple with the transmitted optical mode. The patch is preferably wider than the core to intersect the exponential tail of the transmitted optical mode. Such a high index patch preferentially couples TE polarization modes. By choosing an appropriate length for the patch, both strain and bend birefringence can be compensated.

Abstract: We describe an interferometric, channel-dropping, optical filter that includes a pair of planar waveguides. The two waveguides are spaced apart by a distance which is periodically varied along the longitudinal axis of the filter in order to effect a periodic optical coupling between them. There are at least three coupling locations, each associated with a coupling constant. The two waveguides have nominally equal effective refractive indices. In preferred embodiments of the invention, the coupling constants decrease symmetrically from the center of the filter toward the ends.

Abstract: In accordance with the invention an integrated optic device useful as a low level polarization independent optical tap comprises a pair of optical waveguides intersecting at an angle of 10.degree.-25.degree. to provide a tap signal in the range minus 20 dB to minus 60 dB. In a preferred embodiment for use in a passive repeater for undersea cable, the device comprises fiber-matching waveguides of phosphorus silicate glass on an oxide covered silicon substrate with a boron and phosphorus silicate cladding. The waveguides preferably intersect at an angle of 13.degree.-16.degree.. The preferred repeater further comprises a 3 dB coupler for averaging the power provided by two external pumping sources and a pair of wavelength division multiplexers for applying the pumping power to the outputs of the tap.

Abstract: An integrated optic device useful as a planar lens or a low order array multiplexer comprises a pair of optical couplers and an array of plural waveguides extending between the couplers in an "S" configuration to provide closely spaced optical path lengths. An "S" configuration provides equal path lengths for an optical lens. Incremental lengths added to the "S" in the region between curve reversal can provide small path length increments for a low order array multiplexer or demultiplexer.

Abstract: Disclosed are planar waveguides comprising substantially polarization-independent Bragg gratings. A preferred embodiment of the invention comprises a Si body with a silica lower cladding layer thereon, and a phosphorus P-doped silica core on the lower cladding. Appropriate periodic recessed features are etched into the core, and phophorus P- and B-doped silica upper cladding is deposited over the core. The dopant concentrations are adjusted such that the refractive index difference between core and upper cladding is small (0.35-1.45.times.10.sup.-2), and such that the flow temperature of the upper cladding material is lower than that of the core material. In another preferred embodiment a thin layer of Si.sub.3 N.sub.x (x.about.4) is conformally deposited over the core after the grating etch, and the upper cladding material is deposited onto the Si.sub.3 N.sub.x layer. Bragg devices according to the invention are advantageously used in Integrated Optical Circuits (IOCs), e.g.

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping filter and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping filter and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.

Abstract: A TE-TM polarization manipulating (i.e., splitting, combining or filtering) device is constructed from substrate-supported dielectric thin film waveguides. In a 3-port device, two waveguides have cores of different materials and different effective refractive indices. The waveguide cores overlap in a first transition section and one waveguide core has an adiabatic taper; in this section they also separate adiabatically in and are coupled to a second (e.g., output) section where the waveguides are physically separate and optically decoupled. In a 4-port device, two additional waveguides are coupled in a second adiabatic transition section to the first transition section to enable TE or TM modes to be coupled straight through the device from one input port to a directly opposite output port or to be crossed-over from one input port to a diagonally opposite output port.

Abstract: An optical circulator/isolator is implemented in a semiconductor package formed by a semiconductor substrate, which supports integral thin film waveguide polarization splitters and combiners, and a semiconductor lid, which supports four spherical lenses and a polarization rotator. The latter is a composite of at least two adjacent slabs of optically active material, one slab serving as a nonreciprocal 45.degree. rotator (e.g., a Faraday rotator) and the other as a reciprocal 45.degree. rotator (e.g., half-wave device). The lenses, serving both as beam expanders/condensers and as collimators, are positioned between the waveguide ends and major surfaces of the composite slab. When used with means for reversing the direction of the magnetic field in the nonreciprocal rotator, the device functions also as a switch. Also described are system architectures made possible by these devices; e.g.

Abstract: In a fiber-optic communication system, a polarization independent semiconductor optical amplifier structure is achieved by tailoring the height-width aspect ratio of its active region to a value at least close to unity and at the same time using a laser cavity structure in which the end mirrors are buried in the semiconductor body in which the optical amplifier structure is built.

Abstract: An optical device is disclosed which provides wavelength multiplexing/demultiplexing utilizing a plurality of focusing Bragg reflectors. Each Bragg reflector includes a plurality of confocal (i.e., common foci) elliptical grating lines, with the exit/entrance ports of the input/output waveguides located at the foci of the ellipse. By virtue of the elliptical design, the signal propagating outward from the exit port of the input waveguide will be reflected by the appropriate Bragg reflector and focused into the entrance port of the appropriate output waveguide. When each Bragg reflector exhibits a different ellipticity, but shares one common focal point, optical multiplexing/demultiplexing may be achieved. Optical filtering may be achieved when all Bragg reflectors are designed to have common foci.

Abstract: In the interest of ease of manufacture, hybrid lasers of distributed-Bragg-reflector type are preferred for use as light sources in optical communications. Such lasers are made to operate away from mode instabilities by adjusting a laser parameter such as, e.g., laser temperature, thereby assuring highly error-free transmission. Alternatively, by suitable design of the Bragg reflector it is possible to render mode instability of negligible influence on error rate.

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping fiber and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.