Showing papers on "Fiber optic sensor published in 1975"

Transducer for converting acoustic energy directly into optical energy

Abstract: A transducer is disclosed in which energy received from either mechanical or acoustic sources is converted into modulated optical power. The transducer is comprised of three basic components, an input optical fiber, an output optical fiber and a means for varying the optical coupling coefficient between the two fibers in response to information containing energy received from a mechanical or acoustic source. The input optical fiber carries a steady state optical signal which may be either continuous or pulsed. The means operates to control the coupling of the steady state optical signal into the output optical fiber. An intensity modulated output signal is then carried by the output optical fiber away from the transducer. The intensity modulated output signal may be either detected and thereby converted to electrical energy for transmission or may be transmitted in an optical form if optical communications facilities are available.

Keyboard using optical switching

Abstract: The invention relates to keyboard devices using optical switching and includes novel light distribution means to multiple fiber optics, switching means between fiber optics, and collection means from multiple fiber optics to a single point.

System for locating breaks in fiber optic filaments

Abstract: A system for locating breaks in fiber optic filaments employs light energyulses which are controlled to be emitted at determinable times and directed along the light path of the fiber optic filaments under test. A pulse detector is positioned to receive any reflected pulse light energy from the fiber optic filaments and an indicator is responsive for indicating the elapsed time between the emission of the pulses and the reception of the reflected pulse light energy, preferably calibrated in terms of distance to establish the location of breaks in the fiber optics line.

Shuttle pulse measurements of pulse spreading in an optical fiber.

Abstract: Partially transparent mirrors were pressed against fiber ends so that the length dependence of pulse spreading could be determined without cutting the fiber into pieces. Measurements were made by comparing the widths of laser pulses (λ = 0.9 μm) through the output end mirror, which returned from 9½ successive round trips (2014-m extrapolated length) along a 106-m multimode fiber. Mode mixing was significant in this fiber (fabricated by Corning Glass Works), and a square root of length pulse width dependence was observed. However, some of the mode-mixing effects on pulse width were caused by the way in which the fiber was wound on a drum.

New Slitless Optical Fiber Laser-Raman Spectrometer

Abstract: A new slitless optical fiber laser-Raman spectrometer has been developed in which long, thin, low loss optical fibers, either liquid filled or solid core, act simultaneously as the sample and entrance aperature. The fiber end is placed at the focus of the collimator lens, and the resultant parallel radiation is dispersed by three large triangular Steinheil prisms in series. The dispersed radiation is then focussed by the camera lens to a series of points in the focal plane. The Raman points are detected photoelectrically by scanning with either an exit pinhole or slit, and a photomultiplier whose photocathode surface can be as small as the fiber end. Because of the long fiber lengths employed and of the high transmission efficiency of the spectrometer, very large Raman signals result. For example, the extremely weak Raman intensity maximum from fused silica at Δν- ≈ 2165 cm−1 is readily detected visually in the focal plane using a fiber length of 85 m and a few hundred milliwatts of 476.5 nm excitation. The new spectrometer will be of considerable use in Raman studies of pure and doped glasses in fiber form, and of a wide range of liquids and mixtures where small sample amounts are involved. It may also be possible eventually to extend this slitless method to studies of water, aqueous solutions, and gases by employing straight dielectric waveguide techniques.

Data distribution using fiber optics.

Abstract: This paper reviews some considerations that need to be addressed in applying fiber optic transmission lines to the distribution of data to a number of remote terminals. Considerations are given to system components such as sources, receivers, and connectors as well as distribution formats.

Mode coupling in an optical fiber with core distortions

Abstract: The variations in the geometry of a step-index optical fiber are determined as functions of position along the axis of the fiber by an analysis of the backscattered light produced when a beam from a cw laser is incident perpendicular to the fiber axis. The power spectrum computed from this distortion function is then utilized with coupled-mode theory to predict the mode coupling, the reduction in pulse dispersion, and the accompanying increased radiation loss of the fiber. The theoretical calculations support experimental observations and account for a partial reduction in the multimode pulse dispersion.

Length dependence of pulse dispersion in a long multimode optical fiber.

Abstract: Shuttle pulse measurements performed on a 1280-m long multimode optical fiber were used to determine pulse dispersion along a 6400-m extrapolated length. The fiber's steady-state mode coupling length was determined without breaking the fiber. The impulse responses for one, three, and five trips through the fiber were recorded and Fourier transformed to yield the corresponding baseband frequency responses. It was concluded that the coupling length was approximately 840 m, and that the impulse response became increasingly more symmetrical for fiber lengths beyond this coupling length. This agrees with theory.

Measurement of very short optical delays in multimode fibers

Abstract: We describe a new method for measuring group‐delay differences between the modes of an optical fiber of the order of 1 psec. This is accomplished by Fourier analyzing the intensity output of the fiber, which is fed with a quasimonochromatic signal whose frequency is linearly modulated in time. We present the results of an experiment, in which time delays of the order of 10 psec have been measured. This confirms the potential of the method for measuring dispersion in optical fibers.

Radius of uncladded optical fiber from back-scattered radiation pattern*

Abstract: The back-scattered pattern produced by a plane-polarized beam incident normally on a large uncladded optical fiber can be used to determine the refractive index and the radius of the fiber. The geometric-optics method is used to analyze the pattern. A new procedure to find the radius of the fiber is proposed. The procedure can make use of nearly the whole of the back-scattered pattern, without need to measure exactly the positions of all of the individual fringes. Special attention is given to the limits of accuracy.

Fiber-optic laser illumination

Abstract: Multiple-wavelength light from an ion laser was transmitted through a 85-µm optical fiber to provide illumination for viewing and color photography. Also adequate black-and-white TV display and photography were obtained using red light from an He-Ne laser transmitted through the same optical fiber.

Woven fiber optics.

Abstract: In this paper we describe how the art of weaving can be applied to fiber optics in order to produce precisely controlled reproducible image guides and image dissectors. As examples of the types of device for which woven fiber optics are applicable, we describe a 3:1 interleaver for use with a cathode-ray tube to produce color images, and a high speed alpha numeric output device. The techniques of weaving fiber optics are discussed in sufficient detail in order to allow for further work. Although, in principle, one might be able to weave glass optical fibers, all the work described here made use of plastic optical fibers 0.25 mm in diameter.

Method of connecting light fiber

Abstract: PURPOSE:By monitoring the maximum output of a light fiber to be connected, connection of the light fiber is optimized.

Plastic optical fiber displacement sensor for study of the dynamic response of a solid exposed to an intense pulsed electron beam

Abstract: The principle of the branched fiber bundle sensor has been known for many years. The apparatus which is described in this paper is distinguished by simple fabrication, low cost, high sensitivity, and a fast response time. It is used for measuring the velocity of the back surface of an irradiated aluminum target. In spite of intense consecutive bremsstrahlung, the plastic fiber probe gives good results, whereas with glass fiber a large scintillation impulse appears which covers the signal.

An optical-fiber cable fault location method

Abstract: creasing at a rate proportional to J L . Hence, the pulse spread will increase at a rate proportional to f l . There will also be radiative losses. An equilibrium situation will arise when each part of the pulse energy will be carried in a mixture of modes undergoing continuous conversion as it propagates. Before this equilibrium is reached, the pulse shape undergoes complex changes from its initial state when the pulse will have a particular mixture of propagating modes along its duration, through successive stages when the modal delay causes pulse shape changes and pulse broadening. The distance required for equilibrium may vary from fiber to fiber. It is the spectral distribution and the spectral content of the coupling discontinuities which govern the rate and type of equilibrium. For fiber waveguides with imperfections which can cause gross modal conversion distributed along its length, equilibrium may not be established. This paper presents the results of an experimental study of dispersion in long multimode fiber waveguides. The fiber waveguides under study are made by a chemical vapor deposition process. The resulting fibers have a numerical aperture of approximately 0.2. Fibers of various lengths are studied including one of 4 km length. Measurements have been carried out on a dispersion measuring apparatus consisting of a GaAs laser source switched at low repetition rate by a subnanosecond pulse and a fast detector. The optical output has a subnanosecond rise edge and the principal pulse has a duration of 1 ns. The optical output is launched into the fiber with adjustable numerical aperture from 0.1 to 0.2. Various fiber lengths from 2 meters to 1 km are measured for dispersion. A particular fiber is destructively tested by successive reduction of length. This serves to check the consistency between different fibers. A 4 km fiber is also destructively tested to study equilibrium effect. It is then rejoined by couplers of different tolerances. The gross discontinuities are introduced by the couplers. The equilibrium effects are again studied. -

Integrated optical data bus coupler

Abstract: A data bus coupler having a fiber optic bundle input, a separate optical ulator or detector (described in a concurrent disclosure by the same inventors) attached to each fiber of the bundle for adding information to, extracting information from, or detecting the information conducted by the fiber, and an output wherein the fibers are rejoined into a fiber optic bundle. The optical modulator/detectors are double heterojunction semiconductors that are switched "on" by reverse biasing and with large voltages they may act as photoavalanche diodes when detecting incident radiation.

Development of an optical rate sensor

Abstract: : This report documents the results of a feasibility investigation program of optical rate sensing by a unique technique of differential phase shift measurement between counter-traveling light beams forming a closed path. The program involved the design, build, and test of a discrete component research test model of the sensor, and an investigation of the applicability of integrated optics technology to such a sensor. Such a sensor possesses many of the attributes of the ring laser gyro without the problem of frequency lock-in which is characteristic of that device. It also offers the potential advantage of size reduction without performance degradation through the use of multiple turns of fiber optics for an effective area increase and replacement of the gas laser with a solid state source. The purpose of the program was to evaluate a complete sensor using the research test model and to determine how well integrated optics can be applied to the optical rate sensor. The results indicate that fiber optics and the solid state laser can be used to overcome problems encountered in the discrete component model and to achieve performance in the one-half to ten degree per hour bias stability range in a sensor configured for a maximum rate of 400 degrees/second. An optical rate sensor using only integrated optics components, although promising, requires further research developments in the field of integrated optics. (Author)

Coupling of integrated optics systems to fiber light guides

Abstract: An investigation was made of the possibility of efficient coupling of film and fiber light guides on the basis of the tunneling of the optical energy across a dielectric gap.

Wideband Signal Transmission Over Optical Fiber Waveguides

Abstract: Optical fiber waveguides are being employed in several communication systems of moderate bandwidth and length. For example, Nippon Electric Company(I) has reported on a 7.6 Mb/s system operating over 2.3 km using SELFOC fiber waveguide while U. S. Naval Electronics Laboratory Center (2) has installed a 44 MHz closed circuit TV system and a 108 kHz, 6 telephone system both several hundred feet long. GTE Labs(3) reported on a short length T-2 (6. 3 Mb/s) system. Others will be described in this conference. (4) The full potential afforded by the characteristics of optical fiber waveguide transmission such as wide bandwidth, noise immunity, small size and weight has not been reached as yet. More studies of its feasibility in various applications are required, and here the suitability of wide-band signal transmission over optical fiber waveguides is examined.

Light Emitting Diodes And Injection Lasers For Fiber Optic Communication Systems

Abstract: A review of Light Emitting Diodes (LEDs) and Injection Lasers (ILs), which are suited as signal sources in Fiber Optic Communication Systems is presented. LED and IL structures and their important operational characteristics, such as efficiency, power out, radiance,spectral emission, and lifetime are discussed.