Showing papers on "Fiber optic sensor published in 1976"

Fiber waveguides: a novel technique for investigating attenuation characteristics

Abstract: Light from a pulsed GaAs injection laser is coupled into a glass fiber via a taper coupler. The time dependence of the light backscattered within the fiber as the pulse travels down the waveguide is recorded. From these data the total loss may be determined, as well as an estimate of the scattering and mode mixing characteristics of the fiber.

Fiber optic laser illuminators

Abstract: An object-illuminating and imaging system utilizing, in combination, a laser beam as a light source and an optical fiber as a light transmitter. Light-focusing means are provided and the focused laser beam is, in a preferred embodiment of the invention, directed to impinge upon a single, small-diameter optical fiber. Sensing means such as film or a television-type camera may be used visually to reproduce and/or display the illuminated object. A light-flow-disruptive means such as a vibrator, acting upon a collimated line of illumination, serves to reduce objectionable speckle effects ordinarily present in coherent light beams, thus providing enhanced clarity as viewed and in imaged reproductions.

Direct transmission of pictorial information in multimode optical fibers

Abstract: The problem of coherent image transmission through a single multimode optical fiber is discussed. A scheme is presented for recovering the transmitted image after distortions brought about by the fiber modes dispersion. Realization of this scheme by holographic techniques and with lens systems is proposed, and its limitations pointed out. The application of this scheme in canceling out temporal signal dispersion in a multimode fiber transmission line is also discussed briefly.

Fiber optics access coupler

Abstract: There is disclosed a fiber optic coupler for use in single strand fiber systems comprising a device to allow optical access to a single fiber by means of a second fiber which has been attached to it by fusing the glass cladding of the two fibers as by application of heat by a laser. The resulting access coupler provides for coupling both into and out of a single strand of fiber optic waveguide. That is to say, an input optical signal to one single fiber strand can be read out at more than one point on the single fiber or more than one input can be read out at a single point. The coupler is sufficiently low loss to make control systems utilizing single fiber lines rather than bundles a realistic possibility.

Refractive-index profile of an optical fiber: its measurement by the scattering-pattern method.

Abstract: This paper describes a new method (the scattering-pattern method) for determining the refractive-index profile in an optical fiber from its scattering pattern for a normally incident laser beam. The proposed method is applicable to an arbitrary profile and is nondestructive. The spatial resolution is high, and the accuracy is good when the fiber diameter and the refractive-index variation are relatively small. The drawback is that a large number of data are required; however, this difficulty has been overcome by using the automated measuring system described in this paper. The profile obtained shows good agreement with design data.

Fiber optic multiplex optical transmission system

Abstract: A multiplex optical transmission system for simultaneously transmitting and receiving a plurality of signals while minimizing external interference. The system includes a plurality of subgroup mixers wherein video signals, digital data signals, and audio signals are supplied to the respective subgroup mixers for being blocked into respective frequency ranges. The output of the subgroup mixers are, in turn, fed to a master mixer that produces a composite electrical signal therefrom. An optical transmitter is connected to the master mixer for converting the composite signal into an optical signal and transmitting the optical signal over a fiber optic cable. An optical receiver is connected to the other end of the fiber optic cable for receiving the optical signal and converting such back into a composite electrical signal. A de-multiplexer is coupled to the output of the optical receiver for separating the composite signal back into a composite video, data, and audio signals. A programmable optical patch board is interposed in the fiber optic cables for selectively connecting the optical signals to various receivers and transmitters.

Method for using on line optic fiber loss monitor

Abstract: A method and means is disclosed for continuously monitoring an optical fiber's attenuation or loss as it is being formed, which includes: a light source, which may be the heated fiber itself during drawing operations or an external source; passing the light through the fiber being produced; positioning the end of the fiber in a holder adjacent to a light detector, for example a photodiode with or without passing the transmitted light through a filter; detecting the light transmitted by the fiber from the light source; converting the detected light into an electrical equivalent signal; amplifying the signal if necessary and recording or observing the changes in the signal to determine an objective measure of the optical fiber's attenuating characteristic.

Fiber optics cable strengthening method and means

Abstract: A non-metallic, high strength, high temperature resistant external or internal strengthening for fiber optics cables is provided. The strengthening may be in various forms such as internally deployed filaments, outer woven mesh fibers, segmented cylinders, helical wrap ribbon, etc., and is made from single high-strength crystal fibers preferably of sapphire, i.e. α-Al 2 O 3 . The non-conductive strengthening crystals have a low density, are highly crush resistant and meet severe environmental fiber optic sensor and data transmission requirements.

Fiber optics electro-mechanical light switch

Abstract: An electro-mechanically actuated light switch is provided for transferringight energy into or out of a fiber optic light transmission path. Liquid material contained within the switch provides a continuity between two fiber optic terminals in the fiber optic light transmission path. The liquid material is chosen to have an index of refraction higher than the material which contains it, so that substantially total internal reflection is sustained along the optical axis of the fiber optic light transmission path. A transparent member is movably mounted in a port in the switch and resiliently supported for extension into the liquid material. An electromagnetic-solenoid arrangement is adapted to extend an angularly disposed reflective end of the transparent member into the liquid material for redirecting light energy which it intercepts. Such redirected light energy in the form of light intercepted in the optical path may be detected by a suitable sensor; alternatively light signals from a suitable source such as a light emitting diode may be introduced into the transparent member and reflected to propagate along the optical path.

Optical-fiber impulse-response measurement system

Abstract: This paper describes time-domain instrumentation that was designed to measure impulse response and delay of multimode optical fibers that are being used in an experimental optical communications system at Bell Laboratories. Time-domain data is transformed to frequency-domain by a minicomputer, and the result is displayed as the fiber's baseband frequency response.

Angle selective fiber coupler

Abstract: Angle selective input coupling through the side of a slightly tapered section of Corning highly multimode fiber has been experimentally demonstrated for the first time. This coupling technique allows the possibility of fabricating bidirectional (duplex) couplers for systems employing single strands of multimode, low loss fiber.

Fiber optic position sensing and indicating apparatus for electrical interference sensitive environments

Abstract: Apparatus is disclosed for remotely sensing the mechanical position of oner more objects in an electrical inferference sensitive environment, such as the landing gear of an aircraft of the like in which is utilized a passive, fiber optic transmission system having means for testing the continuity of the system to enhance safety and reliability.

Fiber optic missile guidance and control

Abstract: A fiber optical transmission system for guiding and controlling a missile.he fiber optic link can provide for up and down link transmission that can provide target and reference position information not available to present wire guided missile systems. Fiber optics have an almost unlimited information transfer rate and does not have the electrical interference problems of the wire systems.

Fiber Laser Gyroscopes

Abstract: The application of the optical fiber waveguides to laser gyroscopes is divided into two sections: 1) The ring interferometer and 2) The ring laser. Experiments show that a well defined, stable interference pattern can be obtained using a single mode fiber. This together with the experimentally obtained coupling efficiency of laser radiation into the fiber (-50%) indicate that in addition to a sensitive ring interferometer gyroscope a ring laser gyroscope can be built using a single mode fiber waveguide as the passive part of the laser cavity.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wavelength dependence of frequency-response measurements in multimode optical fibers

Abstract: A newly developed technique for directly measuring fiber dispersion in the frequency domain as a function of wavelength is described Spectrally filtered white light from a xenon arc lamp is sinusoidally modulated in the range 0 to 1 GHz by an electrooptic modulator and injected into a fiber The procedure is to vary the modulation frequency and measure the corresponding sideband output power with a photomultiplier and spectrum analyzer Ratio measurements between the test fiber and a short reference fiber give the baseband frequency response A number of germanium- and boron-doped fibers have been examined The least dispersive borosilicate graded-index fiber has a 1 dB bandwidth of 1 GHz, after 107 km of propagation at λ = 908 nm The width broadens gradually with increasing wavelengths up to λ = 1100 nm

Input and output devices for optical fiber

Abstract: Input and output devices for an optical fiber include an acoustic transducer for generating a planar acoustic wave tilted at an angle with respect to the axis of an optical fiber embraced by a quartz block. The gap between the optical fiber and the quartz block is filled with a liquid, such as water, to obtain acoustic impedance matching. A desired mode of propagating light can be extracted from the fiber or injected therein by reflection under Bragg's condition through a glass block and optical system without cutting or damaging the optical fiber.

Proximal scanning systems: improved resolution using inclined optical fibers.

Abstract: The illumination of a plane beneath the radiating aperture of an inclined multimode optical fiber is calculated. Graphical results are presented that show, for a proximal scanning head made up of fiber triplets composed of a central sensing fiber and two illuminating fibers, inclining the illuminating fibers away from the sensing fiber provides improved illumination of the work surface. The improvement in illumination obtained allows closer spacing of the scanning head to the work surface, thus improving resolution. A simple geometrical formula is presented that enables a prediction to be made of the fiber inclination for optimum illumination. This formula holds for large variations in the shape of the fiber polar sensitivity function.

Evaluation of Cryogenic Temperature Sensors for Use in Electromagnetic Fields

Abstract: The establishment of organ banks for long-term storage could become feasible if rapid, uniform electromagnetic thawing of cryopreserved organs can be accomplished. Internal and external temperature measurements of the organ during thawing will be nec­ essary to provide real-time data on tissue heating rate and distribution. This information will be use­ ful for both optimization of thawing system design and as an input for system power control. But because conventional measurement techniques which are useful at cryogenic temperatures are not suitable for use with EM thawing systems, several alternative methods for making temperature measurements have been inves­ tigated. These alternative methods include techniques where temperature probes are implanted in the bio­ logical tissue and techniques employing non-invasive temperature sensors. From a clinical standpoint, a non-invasive temperature sensor would be the best alternative for measurements in cryopreserved organs. It would minimize introduction of foreign materials into the organ and would also reduce long term costs by eliminating the need to implant separate sensors in each organ. On the other hand, temperature probes can provide localized temperature data which a ■noninvasive measurement technique might not. Also, probes are more nearly feasible in the current measurement technology than are non-invasive techniques. In this paper, the requirements of a cryogenic temperature sensor suitable for use in the presence of an electro­ magnetic field will be discussed and both non-invasive and probe measurement techniques will be considered.

Laser method for transparent fiber geometrical and optical parameter measurements

Abstract: This paper deals with a homogeneous fiber whose surface is an elliptical cylinder. The effect of fiber parameters on the properties of light scattered by the fiber are defined. The method presented makes it possible to determine the transverse dimensions, the degree of cross-section ellipticity, and the refractive index of single-layer fiber.

Optimized Led for Single-Fiber Optical Links.

Abstract: : The power coupled into an N.A. = 0.15, 90-micrometers core, multimode fiber from an edge-emitting, light-emitting diode has been significantly increased by the development of the narrow active region, double-heterojunction (DH) LED. As much as 0.8 mW has been coupled into a single fiber. The new diode structure results in a narrow (approx. 25 deg FWHM) emitted beam (in the direction perpendicular to the junction plane), and leads to optical coupling efficiencies 3 to 5 dB better than previously achieved. The radiance of the emitting facet is greatly increased, to over 1000 W/sq cm--sr, a factor of 10 greater than previously reported. The new structure also results in LEDs that can be modulated at high frequencies (150 MHz). Coupling from the narrow-active-region, DH diodes into the fiber is further enhanced, by about 3 dB, with the use of a microlens melted onto the fiber end. Overall coupling efficiencies of 9 to 11 dB are achieved. With the high modulation speed and coupled power of these diodes, material dispersion effects in the fiber, rather than signal power or diode speed, limit the usable distance-bandwidth product. (Author)