Showing papers on "Fiber optic sensor published in 1969"

Apparatus for controlling the propagation characteristics of coherent light within an optical fiber

Abstract: A device useful in processing information comprising an optical fiber for transmitting coherent light in a low-order mode of propagation, means for controlling characteristics, including polarity and phase, of the coherent light as it is transmitting through the fiber.

or Optical Fiber

Abstract: An optical ber consists of cylindrical dielectric material surrounded by another cylindrical dielectric material with a lower index of refraction. Figure 1.1 shows that the transistion between the core and the cladding region can either be a discrete transistion (Step Index) or a gradual transistion (Graded Index). n 1 n 2 n 2 step index graded index index index a a n 1 Figure 1.1: End cross-section of an optical ber. First let's look and the step index optical ber, where the core has an index of refaction of n 1 and the cladding has an index of n 2 , where n 1 > n 2. We will initial look at the light traveling in the optical ber as a propagating ray. Even those this is not technically accurate, it provides some intuitive feel for what is going on. Figure 1.2 shows a cross-sectional view of a step index optical ber. If the propagation angle is greater than the critical angle then the ray will bounce of the surface and will be connned to the core region.

Electron imaging device utilizing a fiber optic input window

Abstract: AN ELECTRON IMAGING DEVICE IN WHICH RADIATION IS DIRECTED THROUGH A FIBER OPTIC INPUT WINDOW ONTO A PHOTOELECTRIC SURFACE. THE FIBER OPTIC WINDOW INCLUDES A PLURALITY OF FIBER OPTIC MEMBER IN WHICH EACH OF THE FIBER OPTICS IS PROVIDED WITH A NON-PLANAR INNER SURFACE ON WHICH THE PHOTOELECTRIC LAYER IS DEPOSITED. IN THIS MANNER, A GREATER PHOTOELECTRIC RESPONSE IS OBTAINED TO A GIVEN INSERT OVER A PLANAR SURFACE.

Applications of Fiber Optics

Abstract: The image evaluation of fiber optics arrays are discussed in terms of the modulation transfer function. Emphasis is placed on the removal of the intrinsic spatial invariance from the fiber optics bundle by means of dynamic and static image enhancement techniques. Experimental results are presented and compared with theoretical expectations. An analysis is made of a dynamically scanned system to demonstrate the conditions under which spatial variance may be removed from a fiber bundle. Eventual applications are discussed in terms of systems needs and some possible uses of fiber optics components are given.

Fiber Optic Laser Devices

Abstract: This presentation reviews the unique properties of fiber optics and of lasers and gives ways in which they can be combined to provide possible solutions to some interesting problems. A well-known consequence of Snell’s law is that light traveling in a medium of refractive index nl will be totally reflected from the interface with a medium of refractive index n2 provided n2 < n, and the sine of the angle of incidence exceeds n2/nl or the ratio of low refractive index to the high refractive index. If the media consist of a high refractive index optical glass rod inside a low refractive index glass tubing all fused together, then the light will travel the length of the rod by making many total internal reflections from the rod-tubing interface. The rod-tubing combination can be drawn into a long, thin flexible fiber by the judicious selection of the glasses for the rod and tubing, by controlling the temperature during the drawing process, and by carefully controlling the rates at which the rod-tubing combination is fed into the furnace and the rate at which the fiber is drawn out. The fiber will consist of a central core of high refractive index glass surrounded by a cladding of low refractive index glass. Because of the fiber’s small diameter the light must make many reflections as it propagates down the fiber. Thus, any defect in the core’s optical surface will perturb the conditions for total internal reflection and result in a large loss of transmitted light. The cladding serves to protect the optical surface of the core from contaminants and abrasions that might cause such defects. If the diameter is reduced to a size on the order of a wavelength of light and if the difference in refractive indices between the core and the cladding is small, the fiber will behave as a dielectric waveguide. That is, it will propagate only certain discrete configurations of the optical field, called modes. FIGURE 1 shows the intensity distribution from the end of a fiber dielectric wave guide. This is the so-called TMo2 mode.’ In 1962, Dr. Elias Snitzer, an early worker in studying wave-guide modes in fibers and the inventor of the neodymium glass laser, showed that if the core glass in an optical fiber is Nd-doped laser glass then the fiber can be made to lase.2 The resonant cavity conditions for the laser are easily met by polishing the ends of the fiber and using just the Fresnel reflections. This so-called fiber laser is pumped directly with a flashlamp and because of its flexibility the fiber can be coupled to the flashlamp by a variety of configurations that permit pumping long fiber lengths with relatively short flashlamps. FIGURE 2 shows one such possible configuration: a rigid fiber was coiled into a helix and inserted into a reflecting cylinder with a coaxial flashlamp, whereby a 7.6 cm flashlamp pumped a 1:m fiber. A principal advantage of the fiber configuration for a laser is that the problems associated with nonuniform pumping and with temperature gradients in the lasing medium are minimized; nearly every active ion can be excited to the upper energy level of the laser transition. This permits the maximum use of the energy storage capability of each active ion. Taking advantage of this fact, Dr. Charles Koester investigated the optical