Abstract: A method for manufacturing hollow core optical fibers is disclosed comprising continuously feeding a glass rod of the desired cladding composition into a high temperature furnace with the rod in line contact with the inner surface of the glass tube. The glass transition temperature of the rod is substantially lower than the glass transition temperature of the glass tube. The glass rod composition is uniformly distributed on the glass tube inner wall as it enters the furnace hot zone. The ratio of the rod diameter to the glass tube inner diameter and the drawing temperature determine the coating thickness of the glass cladding on the inner surface of the glass tube. As the coated tube is passed through the furnace hot zone peak, the optical fiber is drawn. The rod and tube feed rate, the drawing temperature of the rod and glass tube and the drawing rate of the coated glass tube are selected to yield a hollow core optical fiber, with preselected interior and exterior diameters.

Abstract: An apparatus for determining the rotational position of a shaft comprises opposed first and second disks mounted for relative rotation about a predefined axis, with one of the disks being mounted to the shaft for rotation therewith and the other of the disks being maintained in a reference position. First and second rows of spaced apertures are provided on each disk, which lie in concentric paths of different radial distance from the predefined axis, the first rows being at the same radial distance from the axis and second rows being at the same radial distance from the axis. These apertures are positioned so that apertures of the first rows move into alignment while apertures of the second rows move out of alignment as the disks are rotated relative to each other.

Abstract: An apparatus is disclosed for sensing rotational or angular position of a shaft. The apparatus incorporates two light transmission paths, each having a separate photodetector providing an electrical signal in response to the intensity of received light. The electrical signals from the photodetectors are differentially processed to obtain a signal representative of rotational position. Devices are provided in each of the light transmission paths to vary the intensity of light transmitted in the path, and these devices are mechanically coupled to the shaft so that the variations in the respective light paths are opposite. The differentially processed photodetector signals are therefore unaffected by the absolute position of the shaft but are responsive only to deviations from a reference position. Futhermore, this differentially processed signal exhibits a higher degree of linearity was heretofor obtainable. Various embodiments are disclosed for achieving this opposite variation in the respective light paths.

Abstract: A sensor element for a liquid level sensor of the "light prism" type is constructed so as to have a gradually tapering frusto-conical shape and a sensing surface at its lower tip. Such a shape has a tendency to collomate the light transmitted within it and to concentrate all critical reflections in the lower tip of the sensor element, thereby defining a relatively concentrated sensing area. At the same time, the sensor element is shaped and dimensioned in the vicinity of the sensing surface so that the surface tension of the droplet causes the droplet to be lifted upwardly and away from the sensing surface. Any deliterious effect of the droplet on the sensing ability of the sensor is thereby avoided.

Abstract: A utility meter has a plurality of rotating shafts which have angular positions corresponding to the digits of a consumption reading. A cam is attached to that shaft which is associated with the least significant digit. The cam has a light reflecting track. Light from a light source is reflected off the track to a photodetector along an optical path which varies in length in accordance with angular cam position. Electronic circuitry is connected to the light source and photodetector and produces an output signal in digital form which has a frequency related to intensity of light incident upon the photodetector.

Abstract: A process for making an optical fiber includes the steps of inserting a rod of the core glass composition into a closed tube made of the cladding glass. The diameter of the rod is substantially less than the inner diameter of the tube. The glass transition temperature of the core glass must be substantially lower than the glass transition temperature of the cladding and the rod is placed in contact with the tube along its entire length. When heat is applied to the lower portion of the rod and tube, the rod melts and forms a thin film on the inner surface of the tube which can rapidly be fined to a relatively pure glass. This melted glass forms a melt pool in the bottom of the tube, and the tube and pool can then be drawn into a fiber with the desired characteristics. A process for making a graded optical fiber utilizing a modified chemical vapor deposition process is also disclosed wherein a cladding glass is entrained on the inner surface of a tube substrate.

Abstract: A method is provided for making an optical fiber by melting and cladding a multi-component core glass without adding the contamination that is normally associated with these processes. As an initial step, a pure multi-component glass is melted in a high purity silica crucible. The temperature of the glass in the crucible and the temperature of the orifice thereof are controlled so that a cane of glass is drawn from the bottom of the crucible. This cane of glass is fed into a silica or borosilicate tube which is being drawn into a fiber. This results in an optical fiber in which the multi-component glass forms the core while the tube forms the cladding.

Abstract: A process is disclosed for making an optical fiber having a graded index glass core enveloped by a cladding material. The ingredients from which the core glass is to be formed are dropped into a closed tube of the cladding material which is more refractory than the core glass. The ingredients are melted to form a glassy liquid which is fined within the tube. Fining takes place at a temperature sufficiently high to cause a relatively fast reaction between the core glass and cladding, resulting in a partial mixing of the cladding and core glasses. The mixed glasses have an index of refraction intermediate that of the core and cladding at the interface. The temperature is then elevated further and the tube and glassy liquid drawn into a fiber.

Abstract: A process is disclosed for manufacturing an optical fiber comprising a silica cladding and multi-component glass core wherein a tube made of the cladding material serves as a crucible in which the core glass is melted and fined. The core glass includes silicon dioxide, boron oxide, barium oxide or lead oxide (or a combination of both, and an alkali oxide). The materials are selected to provide a high numerical aperture, rapid melting and stability at the high temperatures required to draw the fiber. In accordance with a further feature of the invention, the batch material for the core is actually melted as it is falling to the bottom of the silica tube, thereby increasing the speed of melting and further facilitating outgassing of effluents.