Showing papers on "Optical fiber published in 1971"

Weakly guiding fibers.

Abstract: Thin glass fibers imbedded into a glass cladding of slightly lower refractive index represent a promising medium for optical communication. This article presents simple formulas and functions for the fiber parameters as a help for practical design work. It considers the propagation constant, mode delay, the cladding field depth, and the power distribution in the fiber cross section. Plots vs frequency of these parameters are given for 70 modes

Dispersion in Weakly Guiding Fibers

Abstract: Optical signals transmitted through cladded glass fibers are subject to delay distortion because of (1) dispersion in the material, (2) dispersion caused by the waveguide characteristic, and (3) delay differences between modes. We isolate these effects and evaluate their significance for cases of practical interest. These concern fibers in which the refractive index of the cladding is only slightly lower than that of the core.

The coupling of degenerate modes in two parallel dielectric waveguides

Abstract: Two parallel dielectric waveguides can exchange energy if the field carried by one guide reaches the other guide. We consider only the case of coupling between degenerate modes of dielectric waveguides (optical fibers, etc). Degenerate modes have equal phase velocities, but their transverse field distributions need not be identical. The coupling theory presented in this paper applies to dielectric waveguides of arbitrary shape and arbitrary distribution of refractive index. The dielectric media of the guides as well as the surrounding medium are allowed to be lossy. The coupling coefficient is obtained by means of perturbation theory. It is shown that whereas lossless degenerate modes can exchange their power completely, lossy modes tend to equalize their power. The theory is applied to the problem of crosstalk between cladded dielectric slab waveguides and cladded optical fibers embedded in a lossy medium. Since a lossy surrounding medium also causes an increase in the loss of the guided modes, formulas for this additional loss are presented. It is shown that additional mode loss results even for a lossless surrounding medium if n 3 k > β. (n 3 = index of surrounding medium, k = free space propagation constant, β = propagation constant of guided mode.)

Fiber optic pressure detector

Abstract: A differential sensor unit precisely monitors ambient pressure within a confined space, such as intracranial pressure of a human patient, utilizing fiber optic light guides. Three light guides pass within a pneumatic line into a flexible envelope which is implanted in the skull. Of the external ends of the guides, one faces a light source and each of the others faces a light detector. Within the envelope the guide ends are so arranged with respect to light beam modulating mechanism responsive to envelope distortion due to change in relative pressure that motion of the mechanism relative to the internal ends varies the light transmitted from the first light guide internal end to each remaining light guide internal end, and consequently varies the light intensity sensed by each of the detectors. The detectors can be arranged to actuate pressure display means and pneumatic controls acting through the pneumatic line to adjust the internal pressure of the envelope.

Optical fiber joining technique

Abstract: This paper describes a method of thermally fusing clad glass fibers, end to end, to obtain a good mechanical joint with low transmission loss. Methods of preparing fiber ends and aligning them for joining are discussed. Two sizes of fibers were joined (10.8-μm core and 20-μm core clad fibers with outside diameters of 75 μm and 150 μm respectively).∗

Effect of Thermal Stress on Refractive Index in Clad Fibers

Abstract: i.e., for a very thin fiber (a = λ) with n = 1.5 the index difference may be as large as 0.05, whereas in a macroscopic single-mode waveguide (2a = 100λ)with n = 1.5 the limiting Δn = 2 × 10 5 . In the manufacture of a cladded fiber, core and cladding are fused together at an elevated temperature. During the subsequent cooling to room temperature thermal stresses develop. Under these stresses, core and cladding will become optically anisotropic. If the thermal expansivity of the core is larger than that of the cladding, the principal indices of the core will be lowered and those of the cladding will be raised. For large changes the single-mode condition may be upset, and if n2 becomes larger than n1 even the total reflectivity will be lost. To find the magnitude of the effect we determine first the thermal stress configuration and evaluate subsequently the changes of the refractive indices for silicate glass. where 1 designates the inner and 2 the outer cylinder. Further B1 = 0 to keep the stress in the core finite. With ζ = b/a the solution becomes:

Measurements of loss due to offsets and end separations of optical fibers

Abstract: If fibers are to be coupled together by means of detachable connectors, there is a need to know how much light will be lost by misalignment or axial separation of the fiber ends. Measurements were made of coupling efficiency from one fiber to another versus offset and end separation with and without index-matching liquid between the ends for a single-mode and a multimode fiber at λ = 0.6328 μm. Graphs are presented for offsets as great as 3 radii and for end separations up to 127 μm. Maximum coupling efficiency of 97 percent was obtained, and about 50 percent was obtained with an offset of 1 radius.

Broadband tunable raman-effect devices in optical fibers

Abstract: STIMULATED RAMAN EMISSION IN THE VISIBLE HAS BEEN OBSERVED IN GLASS-FIBER OPTICAL WAVEGUIDES. EVEN THROUGH THE RAMAN CROSS SECTION IS QUITE SMALL, RELATIVELY LOW THRESHOLD FOR RAMAN EMISSION CAN BE ACHIEVED BECAUSE HIGH OPTICAL POWER DENSITIES ARE MAINTAINED OVER LONG LENGTHS OF WAVEGUIDE. THE BROAD STIMULATED GAIN BRANDWIDTHS AVAILABLE IN GLASS SHOULD PERMIT THE CONSTRUCTION OF WIDEBAND FIBER AMPLIFERS AND RAMAN OSCILLATORS TURNABLE OVER A RANGE OF ABOUT 100 ANGSTROMS.

Group delay in glass-fibre waveguide

Abstract: The group delay in a single-mode glass fibre appears to be dominated by the glass dispersion but could, in principle, be reduced considerably by using glass with a certain index/frequency characteristic. In a fibre communication system, with a GaAs laser as transmitter, the large frequency spread of the present-day laser is the most serious factor limiting the bandwidth.

Sizing composition and glass fibers sized therewith

Abstract: A sizing composition for glass fibers is provided, comprising polyvinyl acetate, water dispersible epoxy resin and numerous lubricants, wherein the sized glass fibers are used in fiber optics for the transmission of light or images from one point to another, which sizing enables further processing of the glass fibers without substantial loss in transmission.

Air clad optical fiber waveguide

Abstract: An air clad optical fiber is described comprising a low-loss dielectric core, having a polygonal cross section disposed within a circular jacket. Because of its shape, the core is, in effect, totally surrounded by air, contacting the outer jacket at only its corners. To further minimize the number of contacting regions, and increase the spacing between core and jacket, the latter is made oversized.

Fiber optic device having some fibers clad with absorbing glasses

Abstract: Disclosed is a fiber optic device of the type having a plurality of light-conducting optical fibers secured together in side-byside relation so that corresponding opposite ends of the fibers cooperate to define first and second faces. Some of the fibers have a single cladding of light absorbing material, the remainder of the fibers having a single cladding of non-absorbing material. The combined effect of this combination of fibers results in image transfer devices capable of transferring an image with high resolution and only a moderate loss in light transmission and image storage devices capable of providing high resolution images having moderately high contrast.

Modular optical apparatus

Abstract: This is modular keyboard utilizing fiber optics for signalling. Each keyboard module includes a common light source for illuminating a group of optical fibers. One optical fiber is provided for each key, and transmission of light by the fiber is permitted only when the corresponding key is depressed, withdrawing a shutter element from a gap in the fiber. The coherent light outputs are furnished to a housing mounted in a ceramic module which couples the light outputs to respective photodetecting elements on a semiconductor chip which is also mounted on the ceramic module. The keyboard modules and individual keys are also replaceable, thus providing low out-ofoperation time and character versatility.

Photometric analyzer employing fiber optic light transmitting means

Abstract: Photometric analyzer having a reaction chamber for exciting samples by thermal, chemical or other energy to emit characteristic light, the reaction chamber usually being operated at elevated temperature. A photometric light sensor is located remotely from the chamber away from the influence of heat therefrom. Characteristic light is transmitted from the chamber to the photometric light sensor by a fiber optic bundle.

Efficient small-area GaAs-Ga 1-x Al x As heterostructure electroluminescent diodes coupled to optical fibers

Abstract: A GaAs-Ga 1-x Al x As heterostructure prepared by liquid-phase epitaxy has been employed in the fabrication of efficient small-area (50-µm diameter) electroluminescent diodes, and the light output has been coupled into optical fibers. The light output through a short fiber was about 1 mW at a wavelength of 0.9 µm for a bias current of 200 mA dc. By comparison, the output from the most efficient diffused GaAs diodes of similar geometry was about 0.4 mW at this current.

Hand probe for manually operated optical scanning system

Abstract: A low-cost hand held probe for scanning retrospective pulse modulation bar coding documents of high density comprises a bundle of many discrete optical image fibers which is optically divided into a pair of light carrying conduits by means of an aperture plate having two contiguous apertures therein. One aperture transmits light from a source of illumination down one optical conduit to a paper document. The light emanating from the document end of the bundle travels horizontally through the fibers of the paper to the optical fibers forming the other optical conduit. This light is transmitted up through the bundle to a photosensitive device coupled to circuitry for determining the degree of reflected light. The optical bundle is preferably tapered and is drawn in a unit which eliminates critical alignment problems and reduces the number of operations for manufacture. The apertures are parts of a circle whereby orientation of the probe is virtually unnecessary in most applications. Where orientation is desired, the tip is faced at an angle normal to and at an angle away from normal to the longitudinal axis of the probe in one alternate embodiment and the fiber optic bundle is bent in another alternate arrangement. These structures assist the operator in orienting the light apertures with respect to the document being scanned.

Optical fiber equalizer

Abstract: BECAUSE OF IMPERFECTIONS IN OPTICAL FIBERS, LIGHT PROPAGATING THEREALONG IS CONTINUOUSLY BEING SCATTERED AND RESCATTERED. SOME OF THIS SCATTERED ENERGY IS TRAPPED WITHIN THE FIBER IN A PROPAGATING MODE AND ULTIMATELY REACHES THE OUTPUT OF THE FIBER DELAYED RELATIVE TO THE INPUT SIGNAL. IT IS SHOWN THAT THE DOUBLE-REVERSE SCATTERING RESPONSE OF A FIBER IS VERY NEARLY THE SAME AS THE RESPONSE OF AN R-C INTEGRATOR FOR THE SAME INPUT. ACCORDINGLY, THE EFFECTS OF DOUBLE-REVERSE SCATTERING INTERFERENCE CAN BE SUBSTANTIALLY REDUCED BY PASSING A PORTION OF THE RECEIVED SIGNAL THROUGH AN R-C INTEGRATOR AND INJECTING THE INTEGRATED SIGNAL THUS PRODUCED BACK INTO THE MAIN SIGNAL PATH IN TIME COINCIDENCE WITH THE SIGNAL SO AS TO CANCEL THE INTERFERENCE COMPONENT.

Optical distance and thickness converter

Abstract: In accordance with an illustrative embodiment of the invention, an apparatus is provided which comprises a fiber optic bundle for transmitting light to an emitting end thereof to illuminate a front and rear surfaces of a transparent body opposite this emitting end. At least two fiber optic receiver bundles each having at least one receiving end for picking up light reflected by a respective one of said surfaces are provided for transmitting a luminous flux to produce a respective signal linearly related to the relative distance between the respective surface and the emitting end. The difference of the signals gives an indication of the spacing between the two surfaces, i. e., the thickness of the body. A third fiber optic bundle is provided to obtain a third signal related to the distance of the rear surface according to a desired relationship. The third signal is used to provide a compensated indication of the thickness.

Absorption and Scattering Losses in Glasses and Fibers for Light Guidance

Abstract: Fiber optics for telecommunications applications require very high purity glass. Light loss in glass results primarily from absorption and scattering. Transition metal ions and OH ions cause most of the absorption, whereas scattering is caused by microheterogeneity. Scattering losses vary from 1 to 4 dB/km at 850 nm; absorption losses are high near 630 nm, because of Cr3+ and Ni2+ impurities, but are lower near 850 nm, making this a preferred wavelength region. Flint glass with a total loss of 50 dB/km at 850 nm, prepared using pure material and special techniques, was used as the core of thin-clad optical fibers 70 μm in diameter; these fibers had an internal loss at 850 nm of ∼450 dB/km.

Fiber optics decorative ornament

Abstract: A decorative structure comprising a hollow body enclosing an electric lamp and carrying a spray of optical fibers laterally thereof. The hollow body is formed of separate but matinglyengageable anterior and posterior members, each defining opposing coincident annular surfaces, an opening being formed through the coincident surfaces at the juncture of the anterior and posterior members to receive the bundled ends of an optical fiber spray. In one embodiment, the anterior member is coniform. In another embodiment the anterior member is spheriform and the structure incorporates a plurality of optical fiber sprays.

Fiberscope viewing system with dynamic image enhancer

Abstract: A flexible optical fiber viewing system including a relatively long and thin bundle of optical fibers having image-receiving and image-emitting opposite end faces and a bundle of tapered optical fibers having image-receiving and image-emitting opposite end faces. The image-emitting and image-receiving faces of the bundle of tapered fibers and the flexible fiber bundle respectively are optically interfacially coupled and one is rotated eccentrically relative to the other to effect nutation of images conveyed by the bundle of tapered fibers upon the image-receiving face of the flexible bundle of optical fibers. Rotated synchronously with the bundle of tapered optical fibers, adjacent the image-emitting face of the flexible bundle, is a tilted plate of glass or its equivalent which receives the optical images emitted by the flexible bundle for neutralizing motion imparted to these images at the image-receiving end of the bundle.

Ornamental globe utilizing optical fibers

Abstract: An illuminated globe carrying sprays of optical fibers in which a hollow globular body is formed with openings for receiving the bundled ends of a plurality of optical fiber sprays. An electric lamp within the hollow body illuminates the optical fibers.

Photochromic fiber optic image storage device

Abstract: Disclosed is a fiber optic image storage device of the type having a plurality of light-conducting optical fibers secured together in side-by-side relation so that corresponding opposite ends of the fibers cooperate to define first and second faces. Each of the fibers is characterized in that it comprises a glass core and a layer of photochromic glass formed upon the surface of the core. The layer of photochromic glass may function as a sheath having a refractive index substantially the same as that of the core, or it may have a refractive index lower than that of the core thereby forming with the core a light reflecting interface. The core may consist of a photochromic glass or a nonabsorbing glass.

Crosstalk caused by scattering in slab waveguides

Abstract: Light scattered in one optical fiber can be scattered back into a guided mode in a neighboring optical fiber. This type of scattering crosstalk is investigated in this paper for slab waveguides. However, the results for the slab waveguide case are upper limits on the crosstalk between round optical fibers. Scattering crosstalk is expressed in terms of guided mode radiation loss whose cause is the same scattering mechanism. It is thus not necessary to know the details of the scattering mechanism as long as the scattering loss, which is a measurable quantity, is known. In addition to the total radiation loss the crosstalk depends on the width of the radiation lobe in which the scattered energy escapes from the waveguide. The crosstalk is inversely proportional to the width of the radiation lobe and thus is larger when the radiation lobe is narrow. Scattering crosstalk can become serious if both guides have a systematic sinusoidal imperfection of the same mechanical frequency resulting in a radiation lobe of nearly zero width. In the absence of a systematic sinusoidal imperfection it can be concluded that scattering crosstalk between dielectric waveguides (optical fibers) is negligible if the radiation losses are tolerable. In this case it appears unnecessary to suppress crosstalk by means of a lossy medium between the waveguides.

Display apparatus employing fiber optics

Abstract: A fiber optic display employs a rotating drum having on the periphery thereof a plurality of light sources arranged along a line parallel to the axis of rotation. A row and column array of fiber optic members has one end terminating on a cylindrical surface and the other end terminating at a display surface. As the drum rotates with respect to the cylindrical surface, the line of light sources sequentially couples light on a column by column basis to the end of the fiber optic array associated with the cylindrical surface. By selectively energizing the light sources in synchronism with the rotation of the drum, alphanumeric characters are formed on the display surface.

Method of making fiber optic device

Abstract: A shortened image inverter formed of a plurality of light-conducting fibers arranged in side-by-side relationship with each other as a bundle having opposite image-receiving and image-emitting faces; the bundle being twisted intermediately of its opposite end faces by the amount of 180° and compressed axially for shortening.

Photoelectrically converting optical fiber and method of making the like

Abstract: The peripheral surface of a portion of an optical fiber is roughed and thereon a photoelectrically converting element is provided, so that light transmitted in the optical fiber is converted into electric signals by the photoelectrically converting element. Such a photoelectrically converting optical fiber is made by taking a model or a replica of an optical fiber, forming a photoelectrically converting element on the replica, roughing the peripheral surface of the portion of the optical fiber from which the replica is taken, and interlocking again the replica to the optical fiber so as to transfer the photoelectrically converting element onto the roughed surface portion. Furthermore, electrically conductive coating is provided on the other portion of the optical fiber except for the roughed surface portion so as to provide a terminal, and also lead wire, for the photoelectrically converting element.

Dental illumination device

Abstract: A handpiece for holding dental tools which contains an illuminating system is disclosed. The illuminating system consists of a fiber optic bundle which passes through the handpiece. The fiber optic bundle is connected to a remote light source on one end, with the other end illuminating the region in which the dental tool is to be operated.