Showing papers on "Optical fiber published in 1979"

Fiber Optic Communication Systems

Abstract: Industrial manufacturing of low loss optical fiber cables and their specific splicing toolings, together with recent developments of optoelectronic components will lead to real systems installations in the 1980’s. The requirements for these new systems are related to some of the fiber characteristics: protection against electromagnetic perturbations radiation leakage small size low weight electrical isolation high bandwidth low attenuation low cost expectation Understanding fiber optic transmission systems requires a knowledge of the characteristics of optoelectronic transmitters and receivers, which do not differ much from traditional copper pairs (choice of analog to digital modulation, total attenuation, etc.). Therefore, throughout this course we will limit our effort to descriptions of specific elements, essentially those whose parameters are directly connected to system performance.

Optical Fiber Telecommunications

Abstract: S.E. Miller, Overview and Summary of Progress. P. Kaiser and D.B. Keck, Fiber Types and Their Status. D. Marcuse, Selected Topics in the Theory of Telecommunications Fibers. S.R. Nagel, Fiber Materials and Fabrication Methods. C.H. Gartside III, P.D. Patel, and M.R. Santana, Optical Fiber Cables. S.C. Mettler and C.M. Miller, Optical Fiber Splicing. W.C. Young and D.R. Frey, Fiber Connectors. D.L. Philen and W.T. Anderson, Optical Fiber Transmission Evaluation. W.J. Tomlinson and S.K. Korotky, Integrated Optics: Basic Concepts and Techniques. W.J. Tomlinson, Passive and Low-Speed Active Optical Components for Fiber Systems. S.K. Korotky and R.C. Alferness, Waveguide Electrooptic Devices for Optical Communication. T.P. Lee, C.A. Burrus, Jr., and R.H. Saul, Light-Emitting Diodes for Telecommunication. J.E. Bowers and M.A. Pollack, Semiconductor Lasers for Telecommunications. S.R. Forrest, Optical Detectors for Lightwave Communication. K. Kobayashi, Integrated Optical and Electronic Devices. J.A. Long, R.A. Logan, and R.F. Karlicek, Jr., Epitaxial Growth Methods for Lightwave Devices. N.K. Dutta and C.L. Zipfel, Reliability of Lasers and LEDs. B.L. Kasper, Receiver Design. P.W. Shumate, Lightwave Transmitters. R.G. Swartz, High Performance Integrated Circuits for Lightwave Systems. P.S. Henry, R.A. Linke, and A.H. Gnauck, Introduction to Lightwave Systems. S.S. Cheng and E.H. Angell, Interoffice Transmission Systems. D.C. Gloge and I. Jacobs, Terrestrial Intercity Transmission Systems. P.K. Runge and N.S. Bergano, Undersea Cable Transmission Systems. P.E. White and L.S. Smoot, Optical Fibers in Loop Distribution Systems. I.P. Kaminow, Photonic Local Networks.

Polarization optics of twisted single-mode fibers

Abstract: In twisted single-mode optical fibers the polarization of light is affected by an elastooptically induced optical activity and by a modification of any linear birefringence present. These effects are discussed theoretically and demonstrated experimentally. The activity/twist ratio is α/τ ≃ 0.13 … 0.16 universally in weakly guiding silica fibers. Twisted fibers may be used as polarization rotators. A fiber with a ±68° double twist operates as a fast/slow mode interchanger, suitable for delay equalization.

Fiber-optic sensing of pressure and temperature

Abstract: The use of a fiber-optic Mach-Zehnder interferometer to measure differences in temperature or pressure between two single-mode fiber arms is described. Temperature or pressure changes are observed as a motion of an optical interference fringe pattern. Values are calculated for the pressure and temperature dependence of the fringe motion. Pressure and temperature measurements are made with the interferometer, and the experimental values for sensitivity are in good agreement with those calculated.

Light emitting fabric

Abstract: A light emitting fabric (10) in which optical fibers (12, 28, 46, 48) are part of the weave, replacing some of the threaded fibers (27), whereby the fabric is uniformly illuminated and, accordingly, decorated. The individual optical fibers are gathered into a bundle (15) at one end of the fabric and illuminated by a light source (17). Light traveling through the fibers is emitted in small amounts throughout the lengths thereof through small scratches (14) that pierce the outer coating. Uniformity and intensity of light are enhanced by providing a reflective coating (13) on the non-illuminated ends of the optical fibers. This fabric is usable in clothing; such as costumes, high visibility safety clothing, suntan suits (21); rugs, draperies, theater curtains, architectural panels (23), fiberglass boat hulls, and the like.

Polarization effects in fiber Raman and Brillouin lasers

Abstract: Raman and Brillouin gains in fibers are a factor of 2 higher if linear polarization is maintained. Birefringent single-mode fibers are used to demonstrate this gain difference. Threshold powers of 200 mW have been achieved in Raman oscillators.

Single-mode optical waveguides.

Abstract: An efficient and powerful technique has been developed to treat the problem of wave propagation along arbitrarily shaped single-mode dielectric waveguides with inhomogeneous index variations in the cross-sectional plane. This technique is based on a modified finite-element method. Illustrative examples were given for the following guides: (a) the triangular fiber guide; (b) the elliptical fiber guide; (c) the single material fiber guide; (d) the rectangular fiber guide; (e) the embossed integrated optics guide; (f) the diffused channel guide; (g) the optical stripline guide.

Preservation of polarisation in optical-fibre waveguides with elliptical cores

Abstract: Elliptically cored fibres with large index differences have been drawn and shown to hold polarisation well, the modal beat length being less than 1 mm. An analysis of the propagation characteristics shows that there is a point below the higher-mode cutoff where the difference in group velocities between the two fundamental modes is zero but where there is a large enough difference in the phase velocities to preserve polarisation.

Fiber optic lever displacement transducer.

Abstract: Intrinsic performance limits of noncontacting fiber lever displacement measuring systems are quantitatively described. Generalized relationships linking displacement detection limit, frequency response, dynamic range, linearity, and working distance to fiber diameter, illumination irradiance and coupling angle, photo-detector characteristics, and reflection and transmission losses were obtained by analysis and confirmed by measurement. Both procedures showed performance limits to be functions of the square root of the flux density coupled into the target-illuminating fiber(s) by the electroluminescent source. Displacement detection and bandwidth limits achievable with tungsten or LED sources were in the 2 × 10−11 to 2×10-12m/Hz and MHz, range respectively. A basis for optimizing levers for different applications and determination of intrinsic performance limits is provided.

Magneto‐optic current sensing with birefringent fibers

Abstract: To measure currents on high‐voltage lines, the Faraday rotation is used in a single‐mode optical fiber encircling the conductor. Disturbing linear birefringence is suppressed by twisting the fiber. With ∼10 m of fiber, coiled with a 3‐cm radius, we obtain 0.25 mrad/A polarization rotation, permitting measurement of currents of 0.2–2000 A.

Optical fibers for transmission

Abstract: Provides a broad and easily assimilated introduction to fiber communications, requiring no more mathematical knowledge than needed for a bachelor's degree in physics, chemistry, or engineering. Reviews necessary mathematics, introducing electromagnetic theory and dielectric waveguides; presents underlying theories of propagation in multimode step index and graded index fibers, emphasizing physical models in practical situations. Covers mode coupling, the performance of joint sections, and mode and material dispersion. Includes detailed discussions of techniques for the preparation of optical fibers, factors, controlling their loss and bandwidth, and techniques for measuring, jointing, and splicing. Also includes optical fiber cables, their design, materials used in their construction, and special strength properties. Closes by examining the optical receiver and the special properties that it shows as a result of the photon or shot noise associated with the optical signal, followed by some simple modelling to see how fibers interact and can be optimized within an optical fiber system.

Practical application of the refracted near-field technique for the measurement of optical fibre refractive index profiles

Abstract: Both the theoretical basis and experimental realization of the refracted near-field technique for the direct measurement of optical fibre profiles are presented. The technique requires minimal sample preparation, no computation and is applicable to both single and multimode fibres. Both the core and the cladding are profiled. After outlining the problems associated with other techniques, the use of this method for the measurement of fibre profile, numerical aperture and geometry is discussed. Leaky mode rejection and resolution are treated in detail. A fitting procedure for determining theα-value of a profile is given. The experimental apparatus is fully discussed. Results are presented to illustrate both the applicability of the technique to single and multimode fibres and also the rejection of leaky modes. The experimental sensitivity is shown sufficient to reveal an index fluctuation having a wavelength < 1μm and an amplitude of < 0.0001.

Optical Fiber Waveguides In Radiation Environments

Abstract: A review of the behavior of state-of-the-art low loss optical fiber waveguides in both pulsed and steady state radiation environments is given. The influence on radiation-induced transmission loss due to experimental parameters such as total dose, dose rate, time after irradiation, temperature, wavelength, injection conditions, light intensity and radiation history, and materials parameters such as OH and impurity content and dopant type and concentration is described. Data are reported for both step and graded index doped silica core fibers and glass clad and polymer clad silica core fibers. Candidate fibers for deployment in certain specific, limited nuclear environments are identified.

Fiber-ring interferometer: polarization analysis.

Abstract: In a rotation-sensing fiber-optical Sagnac interferometer, temperature fluctuations and mechanical vibrations affect the birefringence of the fiber and may cause phase shifts like those resulting from rotation. Insertion of polarizing elements, acting at both ends of the fiber, yields a stable phase.

Material dispersion in optical fibers.

Abstract: A three-parameter description of optical fiber material dispersion is proposed which fits the available data and reveals the key roles played by bond length, lattice structure, chemical valence, average energy gap, and atomic mass. Using broadly applicable trends in electronic and phonon oscillator strengths, simple expressions are deduced for material dispersion including the zero crossover wavelength λc. These results impose severe constraints on fiber design which essentially limit the possibilities for significantly improving on pure silica to sulfates (particularly Li2SO4) and to BeF2. The predicted value of λc for the latter material is 1.05 μm.

Solar lighting system

Abstract: Light energy from the sun is directed by a solar collector device onto the end of a bundle of optical fibers. Means which may comprise a tracking system is provided to maintain the collector device directed toward the sun throughout the day so that a maximum amount of light energy is collected thereby. The optical fiber bundle is run into a building or other place where the light energy is to be utilized where the bundle may be split off to provide light in various areas through various utilization devices, such as lamps, indicator devices, signs, etc.

Phase-nulling fiber-optic laser gyro

Abstract: A fiber-optic gyro is described that employs closed-loop phase compensation. Preliminary experimental results are reported of the sensing of rotation rates down to 0.5 degrees /sec for a 135-mm-radius, 100-m-length fiber coil.

Single-mode fiber-optical power divider: encapsulated etching technique

Abstract: A straightforward and dependable method to fabricate a low-loss single-mode fiber-to-fiber coupler is reported, in which two twisted single-mode fibers are etched by an HF:NH4F solution in an elongated container with four ports, two ports for fiber passage and the other two ports for etchant filling and draining. Coupling efficiency was controllable anywhere between zero and unity simply by manipulating a threaded cap attached on top of the container. Throughput losses of 2 dB were routinely achieved.

Measurement of sensitivity of optical fibers for acoustic detection

Abstract: Acoustically induced optical phase modulation has been measured in single-mode fibers over the acoustic frequency range of 100–1400 Hz. These results are compared to the predictions of a simple strain-optical model. An order of magnitude increase in sensitivity was found for plastic coated fibers.

Illuminated urethral catheter

Abstract: A urethral catheter includes a flexible transparent catheter tube, a drainage adapter having a major aperature secured to the proximal end of the catheter tube, a minor aperature axially aligned with the major aperature and a drainage funnel located between the aperatures and a fiber optic member having means on one end for attachment to a light source and a flexible fiber optic strand on the other end thereof extending through the minor and major aperatures and through the interior lumen of the tube with the distal end located adjacent the distal end of the tube. An end portion of the fiber optic within the tube is abraded to provide circumferential illumination extending outwardly of the fiber optic end through the transparent tube. The fiber optic may be axially adjusted within the tube by means of the sliding fit with the minor aperature of the drainage adapter.

Calculation of bandwidth from index profiles of optical fibers. 1: Theory

Abstract: This paper describes a method for calculating the impulse response and bandwidth of multimode optical fibers from measured refractive-index profiles obtained either from the fiber itself or from its preform. The computational method is based on the WKB solution of the guided-mode problem. First, the pulse delay time of each mode is calculated. The different arrival times of impulses carried by the modes are then used to construct the shape of the impulse response curve whose Fourier transform may be used to predict the signal bandwidth of the multimode fiber. By omitting mode groups or weighting the power distribution among the modes, the influence of certain mode groups on pulse distortion can be studied separately. Dispersion of the host material and of one dopant can be taken into account. The method has been used to study the effects of deviations from the desired perfect index profile and the influence of a central dip. The practical value of the computer program is its ability to predict fiber performance from index measurements made on preforms even before the fiber is drawn.

Pressure sensitivity of a clad optical fiber

Abstract: Experiments carried out by Bucaro et al. demonstrate that an optical-fiber acoustic wave detector with a plastic coating several times its diameter exhibits greatly increased sensitivity compared with an uncoated fiber. In this paper we show that this effect should be expected because the plastic is much more compressible than the glass fiber. With a very thick coating of a Teflonlike plastic, the calculated longitudinal strain produced in the fiber by hydrostatic pressure is thirteen times larger than for an uncoated fiber. The effective phase change is increased by the much larger factor of 38 because the coated fiber expands laterally instead of contracting.

Coupled communications fibers

Abstract: A coupling structure for coupling light intelligence between fiber optic elements. Both abuttment and lateral coupling structures are presented.

Wavelength multiplexer/demultiplexer for optical circuits

Abstract: A coupler for wavelength multiplexing or demultiplexing of multimode optical signals in optical circuits. Light introduced through an input/output surface at one end of a planar optical waveguide formed within a glass substrate propagates to a convexly curved second end of the waveguide on which is contiguously mounted a flexible, reflective diffraction grating. The light is diffracted by the diffraction grating and focussed by the curved end back onto the first end of the waveguide. In a multiplexer (beam combiner) embodiment, a plurality of optical signal sources, each having a different wavelength component, is aligned along the first end of the waveguide so that light propagating from each of the sources travels through the waveguide to the reflective diffraction grating, is diffracted by the grating and then brought to a common focus at the first end. An optical fiber abutting the first end is positioned at the common focus to receive the combined beams. Operating in a reverse mode, a demultiplexer (beam splitter) embodiment has an optical fiber abutting the first end surface which transmits a beam having a plurality of wavelength components through the waveguide to the reflective diffraction grating where each wavelength component in the beam is diffracted by the grating into angularly separated beams which are then brought to a focus in the plane of the first end so that each wavelength component forms a spatially separated image. A plurality of detectors or optical fibers abutting the first end surface is positioned to receive a different one of the images.

Wide band multicore optical fiber

Abstract: An optical waveguide having a plurality of cores disposed in a common cladding provides an optical fiber with both a wide bandwidth, by minimizing modal dispersion, and a large aperture to enhance light-carrying capacity. Each of the cores is sized to support only the lowest order mode, HE 11 , and the intercore spacing is selected to achieve a required bandwidth. At the same time, the multiple cores provide a large aperture allowing a relatively large amount of light energy emitted from a noncoherent light source to be coupled into the optical fiber. An array factor A f is given which provides design criteria for the intercore spacing by providing an accurate calculation of the pulse spreading with a large number of cores beginning with a simple twin core fiber.

Edge illuminated photodetector with optical fiber alignment

Abstract: A silicon photodetector capable of long wavelength response which includes means for aligning an optical fiber for edge illumination. The detector is formed in a silicon body (11 and 12) with major surfaces lying in the (110) plane. A groove (23) is etched in the body adjacent the detector to produce sidewalls (24) and an end wall (25) lying in (111) planes. The sidewalls form a v-shaped groove with a depth precisely determined by the width of the groove so that an optical fiber (26) placed in the groove is vertically aligned with the detector. The end wall is perpendicular to the surface of the body so that light from the fiber is not refracted from the plane of the detector.

Fiber optics light switch

Abstract: A light switch for controlling the transmission of optical energy through optical fibers includes a hollow, light-transmitting tube extending transversely across the end of at least one light transmitting fiber. The tube contains one or more masses of light diverting material in a matrix of light-transparent fluid. The masses of light diverting material may be reflective, refractive or absorbent. Means are provided for varying the pressure along the tube to shift the masses relative to the light transmitting fiber so as to divert or pass the light to receiving fibers.

Piezoelectric optical switch

Abstract: A piezoelectric optical switch includes a piezoelectrical element having an optical fiber affixed thereto. A second optical fiber is placed in general proximity to the first optical fiber so that, upon application of a first voltage to the piezoelectric element, the optical fibers are caused to be aligned, and wherein upon application of a different voltage to the element, the optical fibers are caused to be nonaligned. The switch can include a nonpiezoelectric cantilever beam having a fixed end and a free end and adapted to be bent along an axis adjoining the two ends. One optical fiber is affixed to the beam. A plurality of optical fibers, each in general proximity to and each adapted to be selectively aligned with the one optical fiber, is provided. A piezoelectric bending element, having opposite ends coupled to fixed supports, has a medial portion coupled to the cantilever beam near the fixed end. Thus, upon application of a first voltage to the bending element, the first optical fiber is caused to be aligned with a specific one of the plurality of optical fibers. Upon application of a different voltage to the bending element, the first optical fiber is caused to be aligned with a specific different one of the plurality of optical fibers.

Mechanical optical switching device

Abstract: The mechanical optical switching device comprises an input optical fiber with a collimating lens (5) and a first and a second output optical fiber each with a converging lens (6 and 7, respectively) at the respective terminal ends. Further there are provided a movable first optical path-changing means (8) and a fixed second and a fixed third optical path-changing means (12 and 13) associated to the first and second output fiber, the three path-changing means (8, 12 and 13) comprising two reflecting surfaces each. For performing the switching operation the first optical path-changing means (8) may be inserted into the optical axis of the collimating input lens (5) or removed therefrom. In the removed position the input beam is directed towards the second output fiber via the third path-changing means (13) and the second output lens (7), and in the inserted position the input beam is directed towards the first output fiber via the first path-changing means (8), second path-changing means (12) and the first output lens (6) Preferably the first path-changing means (8) is a parallelogram prism with the two reflecting surfaces opposite to each other and the second and third path-changing means (12 and 13, respectively) are triangle prisms.