Abstract: A method and apparatus are disclosed for coupling a multimode laser to a multimode fiber using a multimode tapered structure. The disclosed multimode tapered structure accepts an optical beam having a highly elliptical beam shape and converts the optical beam for acceptance by the circular multimode optical fiber. According to one aspect of the invention, the multimode tapered structure has a tapered form having an elliptical cross section at one end to match the rectangular laser aperture, and a circular cross section at the other end to match the fiber core. The disclosed multimode tapered structure is tapered from a smaller dimension at the input end that matches the dimension of the multimode light source to a larger dimension at the output end that matches the circular core of the multimode fiber. Depending on the selection of the numerical aperture and the length of the multimode tapered structure, coupling efficiencies up to 98 percent may be achieved with the present invention.

Abstract: Disclosed is the use of a polymer material in an optical waveguide structure. The polymer material may be used in either the cladding or the core material of an optical waveguide. The use of polymer material as such is advantageous in that the index of refraction of polymer material varies significantly with changing temperature. The polymer material is subjected to a heating mechanism and/or a cooling mechanism to manipulate the index of refraction as desired.

Abstract: A low-rate data transmission system and method are disclosed that use the Faraday effect to modulate the polarization state of light traveling in an optical fiber. The resulting change in polarization is used to communicate information over the fiber. The low-rate data transmission system includes a low-rate signal source producing current in a wire coil wrapped around an optical fiber. Information is conveyed in accordance with the present invention by the selectively introducing a polarization change into the light carried by the fiber. Generally, the source light at the input of the optical fiber can be randomly polarized and information is conveyed in accordance with the present invention by the presence or absence of a predefined polarization introduced into the light. The longitudinal magnetic field produced by a current in the coil rotates the plane of polarization of the light, in accordance with the well-known Faraday effect.

Abstract: An optical attenuator and method, the optical attenuator having a core which is covered by a cladding material with a section of polymer cladding of an identifiable length. The polymer cladding has an index of refraction that varies with temperature. A thermal device such as a thermoelectric heater or cooler is placed adjacent to the polymer cladding to control the temperature of the cladding. The index of refraction of the polymer cladding is manipulated by changing its temperature by supplying power to the thermal device. The index of refraction of the polymer cladding will range from values below and above the index of refraction of the core material. A light wave transmitted through the core will experience a degree of attenuation due to leakage into the polymer cladding material when the index of refraction of the polymer cladding is equal to or greater than the index of refraction of the core. The light wave may be either attenuated or blocked entirely.

Abstract: An optical coupler and method is disclosed in which a polymer material is employed to optically couple a first and second waveguide in a transfer region. In the transfer region, the first and second waveguides are positioned in parallel separated by a specific distance. The polymer material has an index of refraction which varies with temperature. The optical switch device is controlled by adjusting the temperature of the polymer material to obtain a desired index of refraction, thereby resulting in the desired transfer of an optical wave from on waveguide core to another.

Abstract: A Mach-Zender interferometer employing a section of polymer cladding in one branch. The polymer cladding has an index of refraction that varies with temperature. The temperature of the section of polymer cladding is adjusted to cause a corresponding change in the phase of the laser light flowing through the waveguide core bounded by the polymer cladding to effect a desired switching or modulation of the laser light.

Abstract: An optical switch having a straight waveguide core with a lateral waveguide core extending therefrom. A region of polymer material is disposed in the straight waveguide core to deflect optical waves from the first waveguide core into the lateral waveguide core depending on the relative indexes of refraction between the first waveguide core and the polymer material. The temperature of the polymer material is adjusted, thereby adjusting the index of refraction of the polymer material so as to cause the deflection in a switched state, and to allow light radiation to pass through the polymer material in an un-switched state.

Abstract: An integrated optical circuit having a turning mirror formed by an end surface of a planar waveguide forms a turning mirror deflector surface. More specifically, the integrated optical circuit includes a planar optical waveguide formed within a cladding layer wherein the planar waveguide has a deflector end surface positioned adjacent to a region, such as a gap. The refractive indices of the planar waveguide and region are in a ratio of no less than approximately 1.3 to provide a desired refractive index discontinuity. This refractive index discontinuity in combination with the positioning of the deflector end surface at an angle relative to an axis extending perpendicular to the direction of the waveguide in the range of 24.degree. and 67.degree. enables an advantageous deflection of an optical signal.

Abstract: Measuring and setting techniques for relative component orientations and separations is accomplished by projecting a coherent light beam into one end of a gap formed between facing surfaces of adjacent components. This light beam projection causes a corresponding light ray pattern to be projected out of an opposite end of the gap. The arrangement of light rays in the resulting pattern is indicative of the relative positions of, and distance between, the facing surfaces. Such a projected pattern is used for determining the relative positions between adjacent components, alone, or as feedback for adjusting such component positions to achieve a desired orientation and/or separation distance between the components.

Abstract: An exemplary embodiment of an acousto-optic planar waveguide modulator includes a planar waveguide structure with an input section connected to a multimode section connected to an output section. The input and output sections have structures for propagating an optical signal in a first transmission mode. The multimode section has a structure in which an optical signal can propagate in the first transmission mode and a second transmission mode. A surface acoustic wave source is used to direct a surface acoustic wave at the multimode waveguide section to cause a periodic change in the refractive index for coupling optical signal energy between the even and odd transmission modes. As a consequence, power of an optical signal propagating in the even transmission mode is transferred to the odd transmission mode. This power transfer causes an attenuation of the optical signal propagating in the even transmission mode from the multimode section to the output section.

Abstract: An acousto-optic silica optical circuit switch that selectively routes signals to one of two outputs includes a surface-acoustic-wave source and a coupler waveguide structure formed within silica glass. The waveguide structure includes a single mode input section connected to a multimode section connected to first and second single mode output sections. The first output section has a structure capable of accepting power from an optical signal propagating in a first transmission mode of the multimode section, and the second output section has a structure capable of accepting power from an optical signal propagating in a second transmission mode in said multimode section. In operation, RF excitation is selectively provided to the SAW source to selectively cause coupling of the first and second transmission modes in the multimode section.

Abstract: Efficient coupling between multimode optical fibers and optical devices, such as optical detectors and light emitting diodes, is realized by means of a coupling arrangement comprising a length of homogeneous glass fiber, terminated by a convex microlens. One end of the glass, whose length is greater than the focal length of the microlens, is fusion-spliced to the multimode fiber. The convex microlens is formed at the other end of the homogeneous glass member.

Abstract: In external modulation, a modulated light signal is shaped to decrease pulse transition times resulting in less chirp. Accordingly, the modulated signal travels greater distances with less pulse distortion over an optical medium. For an integrated-type of external modulator, chirp is reduced further by using a laser modulator coupled to multiple complementary output ports.

Abstract: Communication between an upstream point, such as a TV-source headend followed by a fiber optic line, and a number of downstream points, such as coaxial cable connected subscriber locations, is achieved by wavelength or frequency demultiplexing a spectrum of downstream radio-frequency signals with a surface-acoustic-wave (SAW) demultiplexer-multiplexer and distributing the demultiplexed signals to the downstream points, for example through the cables.

Abstract: In soliton optical fiber communication systems that comprise a multiplicity of spaced-apart intermediate non-electronic amplifiers, pulse arrival time jitter can be substantially reduced by incorporation into the transmission path of spaced-apart bandwidth-limiting elements. Exemplarily, the bandwidth-limiting elements are optical filters of bandwidth B.sub.f, with a filter associated with each intermediate amplifier, and with B.sub.f chosen to fall within the range B.sub.sol (N.sub.f /3).sup.1/2, where B.sub.sol is the FWHM spectral width of the soliton pulses, and N.sub.f is the number of intermediate filters in the system. More generally, the bandwidth-limiting elements are selected such that >.delta.t.sup.2 >, the variance of the jitter, is at most 90% of the variance associated with an, otherwise identical, comparison system that does not contain the bandwidth-limiting elements. Systems according to the invention thus can overcome the Gordon-Haus limit on the bit rate/distance product.

Abstract: Unwanted, monotonic growth of sideband energy is avoided in wavelength-division-multiplexed and frequency-division-multiplexed lightwave communication systems by transmitting adjacent channels approximately 2 nm to 3 nm apart in the normal dispersion regime of the optical fiber for the system and by transmitting each channel more than 0.4 nm below a mean zero dispersion wavelength, .lambda..sub.0, of the optical fiber. Interchannel spacing and individual channel separation from the zero dispersion wavelength are measured with respect to a nominal carrier wavelength for each channel.

Abstract: Various techniques for examining the core region of optical fibers and fiber preforms involve placing a portion of the fiber/preform in an index-matching fluid and transversely illuminating the immersed portion. As described herein, the use of an index-matching fluid can be eliminated by illuminating the fiber/preform with a diverging beam. By the suitable selection of parameters, refraction at the air-fiber/preform interface can produce a well colliminated beam within the core region.

Abstract: In a double-clad, single mode fiber with depressed inner cladding, reduced losses at the longer wavelengths are realized when the ratio of the radius of the inner cladding to the radius of the core is at least 6.5 to 1.

Abstract: Optical power is coupled into an optical waveguide system such as an optical fiber with maximum efficiency by a superluminescent light-emitting diode having lateral confinement of the light in the junction plane. The waveguide developed in the light-emitting diode is constructed to have an effective numerical aperture equal to the numerical aperture of the optical waveguide, and the refractive index n, the length L and width D of the waveguide in the diode is constructed such that the parameter nD/2L is much less than the numerical aperture. As a result, the inverted population of electrons within the active region are utilized with maximum efficiency to develop rays that are coupled into, and can be guided by, the optical waveguide system.

Abstract: The refractive index profile of an optical fiber preform is controlled during manufacture by illuminating the gaseous precursor being fed to the preform substrate tube with ultraviolet radiation, measuring the intensity of either the uv that traverses the gas or the induced fluorescence, comparing this measurement with a reference signal, generating an error signal, in response to this comparison, and controlling composition of the gaseous precursor in response to said error signal. A similar technique can be used to control the thickness and refractive index of each layer deposited upon the substrate tube by forming an x-ray shadowgraph of the layers as they are deposited and comparing the shadowgraph characteristics with appropriate reference signals to form a second set of error signals. The latter are then used to fine tune the fabrication process. The invention can also be employed in conjunction with the vapor axial deposition method of fabricating preforms.