Abstract: A methodology and concomitant circuitry wherein an optical attenuator, having a range of settings including a minimum attenuation, is set to a pre-selected value less than the minimum attenuation whenever a loss of incoming signal power is detected in an optical path coupled to the attenuator.

Abstract: An apparatus and method for controlling the gain in an erbium-doped fiber amplifier (EDFA) incorporated into a multi-wavelength communication system so as to amplify each of the wavelength signals. The amplifier operates near to saturation so that, if one or more of the multi-wavelength signals is removed from the transmission, the remaining channels are increasingly amplified, leading to problems with other components in the system which depend upon intensity. According to the invention, an optical signal at a wavelength that is not within any of the transmission channels is selectively fed back around the amplifier and caused to lase in a wavelength-filtered ring-laser configuration. The lasing signal governs the saturation of the amplifier such that any gain shed by a disappearing data signal is predominately used by the lasing signal, not by the remaining data signals. Thereby, the data signals do not experience gain variations dependent upon the number of data signals being amplified.

Abstract: Acousto-optic polarization converters can be used as the primary optical components in a multi-channel wavelength-routing switch (101). Switching efficiency is decreased and the polarization converted wavelength channels are shifted towards each other, however, when closely neighboring channels are selected simultaneously. This degradation has serious consequences for many applications of the acousto-optic polarization converter. By applying counterpropagating acoustic waves from opposite ends of a converter (400) and using an acoustic absorber (417) to separate the left and right sides of the converter at a defined coupler crossover length, L.sub.x, this deleterious degradation is substantially reduced.

Abstract: A passband-flattened acousto-optic polarization converter (100) in which two acoustic waveguides (14, 20) are formed in a substrate and a separated by a small gap (18) such that the two acoustic waveguides act as a directional coupler in which acoustic power is transferred back and forth. An interdigitated transducer (12) launches a surface acoustic wave in the first acoustic waveguide, and an optical waveguide is formed in the middle of the second waveguide. A partial acoustic absorber (27) is formed over both acoustic waveguides at a crossover length at a distance from the transducer equal to the point at which the acoustic wave has transferred from the first to the second waveguides and back again. The partial absorber absorbs most of the acoustic amplitude with the attenuated acoustic amplitude being coupled back again to the second acoustic waveguide but at an opposite sign.

Abstract: An optical switch, particularly useful as a bistable cross-connect matrix. Parallel input waveguides and parallel output waveguides are formed on a substrate at perpendicular angles so as to intersect. A 45.degree. slot is formed across each intersection and is filled with a fluid having a refractive index matching the waveguide material. Electrodes are positioned adjacent the slots and are selectively activated to electrolytically convert the fluid to gaseous bubbles, thereby destroying the index matching across the slot and causing light to be reflected by the slot rather than propagating across the slot. In the presence of a catalyst, a pulse of opposite polarity or of sufficient size and of the same polarity will destroy the bubble.

Abstract: A channel waveguide structure comprises a substrate, a channel pattern defined in the substrate adjacent the top surface of the substrate, and a planar film layer on top substrate. The channel pattern comprises channels having a high index of refraction, while the film layer is made from a nonlinear organic material. In a preferred embodiment, the substrate is glass and the channel pattern comprises ion-exchanged channels. In this preferred embodiment, the nonlinear organic material is a soluble polydiacetylene, such as poly(3BCMU), poly(4BCMU), or poly(TS12). The thicknesses of the ion-exchanged channels and of the film layer can be adjusted so that the channel waveguide structure functions as a single mode waveguide for light having a wavelength in the range of 1.3 to 1.67 microns.

Abstract: A Mach-Zehnder interferometric modulator includes on a Z-cut crystal substrate of LiNbO.sub.3 an input waveguide section (302), an input branching section (303) for dividing an optical signal on the input waveguide into two substantially equal portions, first and second branch waveguides (304, 305) each having an electrode associated therewith (309, 308), an output branching section (306) for recombining the light from each branch waveguide into a single optical signal on an output waveguide section (307). The two branch waveguides are spaced close enough to maximize the field overlap between the applied electrical field and the optical field in the waveguides but are optically decoupled to prevent cross-coupling of light between the branches. This decoupling is achieved by using structures which change the propagation constant of one of the branches with respect to the other along the modulation length.

Abstract: A simple, inexpensive, and reliable technique for substantially preventing the unwanted formation of a surface guiding layer during manufacture of light-guiding structures in LiNbO.sub.3 and LiTaO.sub.3 substrates is disclosed. The technique involves addition of an effective amount of a gaseous hydrogen donor to the processing atmosphere during high-temperature processing. A particularly convenient hydrogen donor is water vapor, which can be added to the atmosphere by, for instance, bubbling of the feed gas through a water column. A partial pressure of more than about 9 Torr of H.sub.2 O has been found effective in the practice of the technique.

Abstract: Method for adjusting the value of birefringence in predetermined sections of waveguides in integrated optics devices fabricated in optically anisotropic substrates such as monocrystalline LiNbO.sub.3 or LiTaO.sub.3. The inventive method comprises in combination methods for changing both refractive indices in a first volume of the substrate, such as, for instance, ion implantation or metal in-diffusion, thereby creating an optical waveguide for both TE and TM modes of radiation, and methods for further changing one of the indices in a second volume of the substrate, without proportionally changing the other index in the second volume, such as, for instance, Li out-diffusion or ion exchange. In a typical application, the first volume comprises waveguiding regions, including the section in which the birefringence is to be adjusted, and the second volume also includes that waveguide section.

Abstract: Two opposing fingers of a robot hand are each provided with an array of optical devices which are capable of being in optical communication with one another through the gap between the fingers. One finger is provided with an array of light emitters and the other is provided with an array of light recepetors. By taking advantage of the motion of the robot hand and the small size of the optical devices, the shape of an object between the fingers can be detected by using at least one linear set, and preferably at least two linear sets, of devices in each array. Illustratively, the linear sets form a T-shaped array or a U-shaped array and are disposed along the edges of the fingers. In one embodiment the emitters are GRIN rod lenses coupled through a fiber cable to a light source, and the receptors are also GRIN rod lenses coupled through a fiber cable to a camera system. A manufacturing method utilizing such a sensor to identify the shape of objects is also described.