Abstract: A predistortion circuit (102) includes a signal splitter (114), a diode network (118) and a signal combiner (116). The signal splitter (114) is splits an input signal into two portions. One of the signal portions is passed through the diode network (118) and combined with the other portion of the input signal in the signal combiner (116). The diode network (118) includes a plurality of diode circuits (204,206), each including two diode branches (208-214) coupled to an electrical ground (220). The resulting predistorted signal at the output (106) of the signal combiner is amplified, amplitude adjusted and injected into the nonlinear device (112). The input signal is predistorted such that distortion due to nonlinear characteristics of the nonlinear device (112) is reduced.

Abstract: A pilot signal is generated and injected into the input (108) of a signal modulator (104). The harmonic signal of a pilot signal produced at the output (110) and due to the non-linear transfer function of the signal modulator (104) is coherently sampled in the time domain to produce a plurality of digital samples defining a digital sample signal. The digital sample signal is cross-correlated with a reference signal having a phase based on the pilot signal to produce a cross-correlation signal. The bias voltage at which the signal modulator (104) is biased is adjusted to minimize the difference between the phase of the correlation signal and an optimum phase value corresponding to a linear mode of operation of the signal modulator 104.

Abstract: A narrowband twisted optical fiber wavelength division multiplexer ("WDM") and a method for fabricating the WDM. The WDM includes a twisted pair of first and second optical fibers that are fused together, each of the first and second fibers having a first and second end. In the WDM, when a first and second light are applied to the first end of the first fiber, they will appear on the second end of the first fiber and the second end of the second fiber, respectively. When the first light enters the second end of the first fiber, and the second light is applied to the second end of the second fiber, they will both appear on the first end of the first fiber.

Abstract: An input signal is split into two signals, one of which is provided to a distortion generator and a the other of which is provided to a three-way combiner. The distortion generator comprises a single composite amplifier stage having two nonlinear amplifiers and two 180 degree splitters. The amplifiers produce signals having both odd and even-order distortion components because the amplifiers exhibit non-linear behavior. The distortion generator produces two output signals, one of which consists of the fundamental signal and odd-order distortion components, and the other of which consists only of even-order distortion components. The three-way combiner combines these two signals with a portion of input signal at a phasing that produces a resultant output having both the odd and even-order distortions suppressed. Equalizers may be used to provide phase and/or amplitude compensation for the two signals produced by the distortion generator before providing them to the three-way combiner.

Abstract: An optical fiber coupler and its method of use are disclosed. In the coupler a centrally located lens is disposed between the ends of the source and outlet optical fibers, the fibers themselves are formed into the most spacing filling configuration at their ends adjacent the lens, and the lens and fiber ends are secured with an adhesive. The lens, fibers and adhesive will all have substantially equivalent indices of refraction so that there is no excessive light attenuation through the lens and adhesive layers. The optical fibers may be glass or polymer, be single or multiple mode, and have uniform, step or graded refractive indices. A wide variety of combinations of fiber bundles, from single fibers to bundles of up to 128 or more fibers, can be coupled through this device. In its method of use aspect, the received fibers are inserted into the sleeve and adhered to the lens with the adhesive, while venting trapped air and excess adhesive.

Abstract: The second-order predistorter comprises two RF amplifiers and three 180.degree. hybrid combiner/splitters. The RF sinusoidal input is split into two separate signals which have equal amplitudes but are 180.degree. out of phase. Each of these signals is fed into separate moderately linear amplifiers, the output of each being composed only of the amplified input signal and second-order distortion components produced by the amplifiers' nonlinearities. The output signal from each amplifier is combined with the other in a second combiner/splitter to produce two different outputs consisting of the sum and difference of the amplified signals. The difference signal consists only of the desired signal, and the sum signal consists of only the second-order distortion terms. The sum and difference signals are recombined in a third combiner/splitter to form a composite signal which is input into the device to be linearized.

Abstract: An optical modulator or laser source has a detector for detecting its output signal and for producing a corresponding output signal. A tapping device is connected to tap off a portion of the input modulation signal as a reference signal. The reference signal is compared and subtracted from the detector output signal by a subtraction unit in order to produce an error output signal which will be proportional to the laser noise/distortion components. This error signal is amplified and connected to an external modulator linked to the laser optical output and intensity modulates the laser output signal by the error signal in order to reduce or cancel the noise and distortion components in the signal.

Abstract: An array of diode lasers selected to emit at certain fixed wavelengths is assembled to temperature stabilzed Bragg reflectors to assure maintenance of the selected wavelength within 1 .ANG.. One laser is included in the array for each wavelength at which absorption will occur within a photochemically active optical storage medium. Each temperature stabilized laser is focussed by a lens onto an optical storage medium containing photoactive chemical components containing guest and hose molecules, as is known in the art. Light emitted by each laser will be used to burn a pit for each bit of data at the locations of the storage medium. One or more photodetectors located on the opposite side of the sotrage medium to detect the presence or absence of a hole with respect to the selected wavelength with which the hole was initially burned. A similar device is available with a temperature stabilized tunable laser which accurately controls the selected wavelength withing 1 .ANG..

Abstract: An integral waveguide is formed in the epitaxial layers as a continuation of a diode laser. The waveguide runs away from the laser active region. Light is coupled out of the laser and its integral waveguide into a dielectric waveguide which runs parallel and adjacent to the integral waveguide. Processing to form the temperature-stabilized Bragg grating, therefore, need not be performed on the laser substrate directly adjacent to the active area, but can be done some distance away to avoid damage to the laser's active area.

Abstract: A method of making modular micro-optical systems of great flexibility and adaptability. A substrate is formed with a relief pattern, optical components such as optical fibers are added, another relief pattern is formed, partially through the optical components, and additional components are added, some coupling with the first components. A third relief pattern is formed, further modifying the substrate surface and the optical components already mounted, and further optical components are added, whereby optical signals can be coupled, modulated, transmitted, detected and switched, among others. The method can be employed to form tactile sensors which may be used with robotic manipulators.

Abstract: A fiber-optic bandpass filter comprising a resonant cavity formed in an optical waveguide is coupled to a fiber-optic bus which carries a large number of frequency multiplexed channels. The fiber-optic bandpass filter is selected to be one-half the modulation wavelength of the desired center frequency within a range of frequencies carried on the same transmission. The creation of a resonant cavity at the desired center frequency provides a filter which reduces the intensity of signals at surrounding frequencies so that an overall reduced output power is provided, resulting in less cross-talk between a large number of frequency multiplexed signals which, unfiltered, would all have equal power. The filter is broad enough that many adjacent channels are not significantly attenuated. The optical waveguide of which the filter is formed may be in the form of an optical fiber segment or a planar waveguide.

Abstract: A dielectric film is deposited on a glass substrate which is transparent to the emission wavelength of a grating coupled surface emitting laser. The dielectric film has a continuously varying refractive index with thickness, usually in the form of a sine wave. The rugate filter is assembled to overlie the second order grating of the laser so that a peak wavelength .lambda..sub.p is reflected back into the second order grating which couples the light into the laser. By reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within the same narrow band which can be set to any wavelength by choosing the rugate filter's grating period.

Abstract: A glass film is deposited over the second order grating of a grating coupled surface emitting laser. The glass film has a continuously varying refractive index with thickness, usually in the form of or similar to a sine wave. The rugate filter is assembled to overlie the second order grating of the laser so that a peak wavelength .lambda..sub.p is reflected back into the second order grating which couples the light into the laser. Be reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within the same narrow band. The use of a surface emitting laser facilitates summing of the output light of several adjacent lasers within a monolithic array to provide high power output.

Abstract: An optical transmitter, appropriate for transmitting analog signals in fiber optic systems, having an adjustable distortion device which distorts the input to a light emitter device so as to linearize the overall input-to-output response of the optical transmitter. The optical transmitter further has a feedback circuit optically coupled at its input to the output of the light emitter device and electrically coupled at a plurality of its outputs to a corresponding plurality of inputs of the adjustable distortion device, for altering the degree and kind of distortion in response to the output of the light emitter device in order to adaptively compensating the nonlinearities of the overall system.

Abstract: This invention concerns devices for optical measurement of torsion of a rotating shaft. The measurement system can readily be installed to monitor existing equipment because it requires only that a band consisting of alternating high and low reflectivity regions be placed on the shaft at the locations to be measured. The band may be applied as an adhesive tape, among other possibilities. One sensor head is located to correspond to each band. Each sensor head projects light onto the corresponding band, then collects the light reflected by the high reflectivity region(s) of the band. The phase displacement between the intensities of the reflected light at two or more sensor heads may be used to determine torsion on the rotating shaft.

Abstract: Apparatus for mounting optical and electro-optical components and the like to a substrate to obtain physical mounting and electrical connections, along with heat dissipation. A relief pattern of precisely dimensioned grooves is formed on a substrate surface and the components are mounted in those grooves. The grooves may be partially lined with electrode material to facilitate electrical interconnection between the components and the substrate. The invention also relates to the method of mounting and interconnection.

Abstract: An optical coupling apparatus employing two spherical lenses between the optical signal source and the target. Each lens is positioned at its respective focal length from its associated optical element and is adjustable along a single axis. The lens adjustment axes are mutually perpendicular and both are perpendicular to the optical axis between the source and the target. The source may be a laser diode and the target is typically an optical fiber. This structure permits less than precise coaxial alignment between the source and target while maintaining desired optical coupling efficiency.

Abstract: A micro-optical building block system for optical processing of light signals and method for making the components used in the system. The basic system includes a master substrate on which is mounted at least one building block. Typically, there are a multiplicity of pre-defined positions at which the building blocks will mate with the master substrate. Building blocks can be positioned adjacent to each other on the master substrate in such a way as to allow light signals to be transferred between them. Mating relief patterns are formed on both the master substrate and the building block substrates, the relief pattern areas on the master substrate being adjacent and repetitive, or alternatively, different patterns. The mating relief patterns enable self alignment of the building blocks at predetermined positions on the master substrate. The relief pattern on the building blocks is adapted to be employed to embody a variety of optical components as integral or constituent parts of the relief pattern.

Abstract: A fiber-optic system for measuring a desired environmental parameter, such as temperature, is disclosed. The system includes a fiber-optic sensing head that alters light of a prescribed frequency as a function of the environmental parameter to be measured. Light not of the prescribed frequency is not so altered. In a preferred embodiment of the fiber-optic sensing head, a semiconductor material is positioned between two substantially parallel optical fibers at a distal end of the fibers. One fiber serves as in input channel and the other fiber serves as an output channel. Both fibers approach the semiconductor material from the same direction. Light channeled to the semiconductor material is reflected at the distal end of the input fiber so as to pass through the semiconductor material, and then is reflected again at the distal end of the output fiber so as to pass back out the output fiber. The semiconductor material absorbs the light of the prescribed frequency as a function of temperature.