Abstract: An apparatus and method for measuring the thickness of a film having top and bottom surfaces. The apparatus includes low coherence light source that generates a probe light signal. The film is positioned against a roller having a partially reflecting surface that is positioned at a fixed distance from the film. The probe light signal is applied to the film and is then reflected back through the film by the partially reflecting surface. The light leaving the film is collected to form the input to a receiver that determines the time delay between light reflected from the top and bottom surfaces of the film. The receiver output may also be used to determine the thickness of the various layers in a multi-layer film.

Abstract: An apparatus and method for measuring the thickness of a film having top and bottom surfaces. The apparatus includes low coherence light source that generates a probe light signal. The film is positioned between first and second reference reflectors, the first reference reflector being partially reflecting. The probe light signal is applied to the film after passing through the first reference reflector. Part of the portion of the probe light signal leaving the film is reflected back toward the first reference reflector by the second reference reflector. The light exiting through the first reference reflector is collected to form the input to a receiver that determines the time delay between light reflected from the top and bottom surfaces of the film as well as the change in optical path length between said first and second reflectors resulting from the introduction of said film between said first and second reflectors.

Abstract: An apparatus and method for measuring the thickness of a film. The film is illuminated with a low coherence light signal that is preferably generated from a source including two or more LEDs. The light reflected from the surfaces of the film is collected and coupled to an interferometer. The slope of the Fourier transform of the output of the signal from the interferometer is measured to provide a determination of the thickness of the film. In the preferred embodiment of the present invention, the interferometer output is sampled at fewer than two points per cycle of the low coherence light signal.

Abstract: An instrument includes a polarized optical source for producing three sequential predetermined states of polarization of a light beam and an optical polarization meter for measuring the polarization of a portion of the light beam transmitted by or reflected from an optical network by splitting it into four beams, passing three of the beams through optical elements, measuring the transmitted intensity of all four beams, and calculating Stokes parameters. The light beam enters the optical polarization meter through a single-mode optical fiber that acts as a spatial filter for controlling the position and alignment of the beam with respect to the optical elements. The distortion of the light beam polarization caused by this optical fiber is corrected by introducing two different linearly polarized light beams and measuring Stokes parameters which are used to construct a calibration matrix that is inverted and multiplied times measured Stokes parameters of subsequent measurements to yield true Stokes parameters.

Abstract: A method and an apparatus to re-calibrate a polarimeter without a standard source with known polarization. An input electromagnetic wave is sequentially transformed into many electromagnetic waves, all having substantially the same degree of polarization and at least three of the electromagnetic waves having different states of polarization. All the electromagnetic waves are measured by the polarimeter. The method then calculates a calibration factor which, when applied to the measured signals, generates substantially the same calculated degree of polarization for all the electromagnetic waves. A birefringent material, such as a wave-plate, can be used to generate the electromagnetic waves from the input electromagnetic wave. If the input electromagnetic wave is an optical wave, then loops of optical fibers or an electro-optic material, such as a LiNbO.sub.3 crystal, is used as the birefringent material.

Abstract: An instrument includes a polarized optical source for producing three sequential predetermined states of polarization of a light beam at each of at least two wavelengths, as well as an optical polarization meter for measuring the polarization of a portion of the light beam at each wavelength transmitted by or reflected from an optical network by splitting it into four beams, passing three of the beams through optical elements, measuring the transmitted intensity of all four beams, and calculating Stokes parameters. The three sequential predetermined states of polarization at each wavelength yield three corresponding Jones input vectors at each wavelength, and the Stokes parameters for the responses of the optical network are converted to three Jones output vectors at each wavelength. A Jones matrix for the optical network to within a complex constant is then computed from the Jones input and output vectors at each wavelength.

Abstract: An optical coherence-domain reflectometry system provides an interferometer driven by a broadband incoherent light source with the device under test connected to one arm of the interferometer and a movable scanning mirror in the other arm providing a reference signal. The mirror moves at a controlled velocity to produce a Doppler shift in the reference signal frequency. The reference signal arm also includes a piezoelectric transducer which modulates the phase of the reference signal at a given frequency, causing a further shift in the reference signal frequency. The interference signal is detected and measured by a polarization diversity receiver. A linear polarizer in the reference signal arm is adjusted to produce equal reference signal powers in each arm of the polarization diversity receiver in the absence of a reflection signal from the test arm. The measured reflectometry signal is substantially independent of the state of polarization of the reflected signal from the device under test.

Abstract: An acousto-optica converter fabricated on x-cut (LiNbO.sub.3 and having an optical waveguide extending along the y-direction. An interdigital transducer is oriented at 5.degree. with respect to the y-direction in order to compensate for the acoustic walk-off on such an orientation. Such as integrated acousto-optical converter allows multiple stages of such converters so as to provide for (1) two-stage zero-frequency shifted converters and filters, (2) lasers using an acousto-optic filter as a tuning element, (3) polarization-independent converters in which the modes are divided, separately polarization converted, and recobined according to frequency, (4) and wavelength division multiplexing routing switches capable of simultaneously switching multiple channels.

Abstract: A Bragg cell device for use as a tap in optical systems. In one embodiment an acoustic transducer is secured to a surface of an acoustic transmission medium, which is adjustably secured in hertzian contact with a surface of a waveguide. Bulk acoustic waves at frequencies above about 1 GHz are transmitted from the transducer through the transmission medium into the waveguide along a propagation path wherein the acoustic wavefronts intersect a light path in the waveguide at an angle which satisfies Bragg conditions, producing deflection of light out of the light path. Preferably, the transmission medium is also an optical conductor and is oriented upon the waveguide to receive the deflected light and transmit it to a polished optical window on the transmission medium. A grating transducer is secured on the transmission medium to detect acoustic signals reflected in the transmission medium.