Abstract: A ferroelectric material 44 is selectively poled using laser light 14 capable of being absorbed by the material 44, a shutter 18 for turning the light on and off, a variable attenuator 28, with a beam splitter 31 and an optical detector 31a, to set the laser power level, a lens 32 to provide focused laser light 14d, a mirror 36 driven by a motor 40 (mirror-scanner) to direct the light to the regions to be poled, and an electric field applied by electrodes 68, 70. A computer 24 provides automatic control over selective poling of the material 44 by controlling the shutter 18, variable attenuator 28, mirror 36 position, and the direction of the applied electric field. A temperature sensor 52 provides temperature feedback to ensure proper laser power and dwell time. In the alternative, the material 44 is covered with a mask 604 and scanned with the laser to provide selective pole reversal.

Abstract: A system for correcting nonlinear distortion in fiber optic systems including communication systems by means of light modulation provided by interferometric modulators such as the Mach-Zehnder. The present invention involves the addition of a correction signal which contains error canceling information. The additive correction signal optical beam is frequency shifted or phase scrambled through the use of a phase or frequency modulator. This insures the corrective light signal adds incoherently or quasi-incoherently within the signal bandwidth of interest. Furthermore, the present system requires only a single light source and can be made independent of wavelength and is easily optimized with active servo devices. A system provided by the present invention also provides improvement over the state of the art because of its high degree of correction and independence from link length using ordinary single mode fibers.

Abstract: An electro-optic modulator includes a closed loop bias control system for maintaining the modulator at its half-power point by modulating a time varying signal on and off at a modulation frequency f.sub.m. The modulation frequency f.sub.m is much lower than the frequency components within the spectrum of the time varying signal, such that, energy within the time varying signal spectrum is recovered at the modulation frequency when the modulator is not operating at the half-power point. A phase sensitive demodulator operating at the modulation frequency f.sub.m demodulates a signal indicative of the modulator optical output signal to provide a DC voltage signal value indicative of the half-power point bias error value. The time varying voltage signal may be a dither noise signal or any other time varying signal such as a signal with a single frequency component (e.g. a sine or cosine) or a signal with a plurality of frequency components (e.g., a square wave).

Abstract: A feed-forward predistortion circuit to provide improved linear response in optic modulators. The circuit includes a non-linear element, an amplifier/delay means and a power combiner. The non-linear element generates a first signal sin(X), where (X) is the input signal. The amplifier/delay means generates a second signal 2(X). The first and second signals are combined in the power combiner to produce a modulating signal 2(X)-sin(X) which is fed to an optic modulator. The modulating signal 2(X)-sin(X) compensates for the transfer function of the optic modulator which has a transfer function sin(X), thereby producing a linear output.

Abstract: An optic intensity modulator includes a substrate of an optic material that is conductive to light and acoustic waves and has both electrooptic and piezoelectric properties. A pair of associated elongated light waveguides is formed in the substrate, with the waveguides extending substantially coextensively with one another, and being separated from one another by a transverse distance that gradually varies along the courses of the waveguides. Each of two portions of light of substantially identical properties is launched into one of the waveguides for propagation longitudinally thereof, and different phase shifts are induced in the light portions as they propagate in the waveguides by imposing different variable electric fields onto each of the waveguides. The light portions are combined with one another subsequently to their emergence from the waveguides with attendant amplitude modulation of the combined output light due to interference between such phase-shifted light portions.

Abstract: A pair of interferometers, such as Mach-Zehnders, are disposed in a series arrangement in which a signal fed to an input of the first Mach-Zehnder is modulated by an optic modulator, the modulated signal is fed to an input of the second Mach-Zehnder and is modulated by a second optic modulator, the two optic modulators effectively being connected in a series or cascade arrangement. The phase offset of both modulators and the contrast of one modulator are adjusted to minimize both second and third order harmonics inherently generated by the modulation process of each modulator, thereby providing an improved linear response in the output signal of the second Mach-Zehnder.

Abstract: The present invention can be utilized for altering the optical characteristics (e.g. refractive index) of selected regions of planar and channel waveguide structures fabricated by the Proton Exchange (PE) process from materials such as LiNbO.sub.3 or LiTaO.sub.3. The present invention employs localized surface heating from the absorption of optical radiation in an annealing process.