Abstract: In an information recording method, a voltage is applied to an information recording medium comprising a semiconductor layer and a layer of a ferroelectric substance overlaid on the semiconductor layer, and information is thereby recorded on the information recording medium by means of directions of polarization of the ferroelectric substance. The value of the applied voltage is set at a value such that a voltage not lower than avalanche breakdown voltage may be applied to depletion layers, which occur in the semiconductor layer. Information is thus recorded quickly.

Abstract: A method of manufacturing a radiation-resistant optical fiber includes steps of a) heating a bare optical fiber to remove residual hydrogen gas present in the bare optical fiber and b) forming a coating layer consisting of a substance which does not allow permeation of hydrogen gas on the surface of the bare optical fiber from which the residual hydrogen gas has been removed.

Abstract: An image fiber preform for use in an image fiber according to the present invention includes a plurality of optical fiber strands, each optical fiber strand including a silica glass core which contains a dopant for increasing a refractive index of the core and a silica glass cladding surrounding the silica glass core, the silica glass cladding containing a fluorine dopant for decreasing a refractive index of the cladding, the cladding having an outer peripheral surface, and a quartz tube in which the optical fibers are closely arranged, wherein the cladding has a concentration of the fluorine dopant which decreases radially outward toward the outer peripheral surface of the cladding. in the present invention, an image fiber prepared from the image fiber preform and fabrication processes for the image fiber preform and the image fiber are provided.

Abstract: An image-transmitting fiber includes at least one first fiber element for transmitting light power therethrough, and a plurality of second fiber elements disposed around and extending along the first fiber element. The second fiber elements cooperates with one another for transmitting an image of an object therethrough. The first fiber element is greater in diameter than each of the second fiber elements.

Abstract: An optical fiber includes light-transmitting means comprising at least one optical fiber element, and a heat-resistant and radiation-resistant coating formed around the light-transmitting means. The coating comprises an inner buffer layer formed around the light-transmitting means and an outer layer of polyether ether ketone formed around the inner layer.

Abstract: A fiberscope has a light source and a light guide for leading light emitted from the source onto an object disposed in liquid helium. A transmission system for transmitting the image of the object has an image guide. A body tube is fixed to one end of the image guide and faces the object. Objective lenses are disposed in the body tube to project the image of the object onto the one end face of the image guide. An eyepiece is fixed to the other end of the image guide, through which the image of the object is viewed. The interior of the body tube is kept under vacuum.

Abstract: An optical fiber of a silica-based material includes a coating of cured silicone rubber covering an outer surface thereof. The cured silicone rubber coating, when subjected to an infrared spectroscopic measurement, has a transmissivity of not less than 70% at a wave number of 2100 to 2200 cm.sup.-1 at a coating thickness of 0.1 mm due to the infrared absorption due to the stretching and vibration of SiH. The coating of cured silicone rubber contains a neglibible amount of SiH so that the transmission loss of the optical fiber can be prevented from increasing over a long period of time.

Abstract: An apparatus for producing a multi-component glass fiber preform includes a multi-conduit burner 31 having five concentric conduits 31a-31e, the center three conduits (a), (b) and (c) being flush with each other at their ends, the fourth conduit d, interposed between the third (c) and outermost conduit (e) extends axially beyond the first three. The burner has a flange 33 to direct the flame onto a substrate.In operation glass raw material is fed through the inner-most conduit (a) by a carrier gas. The material emitted from conduits (a -d) is mixed in a mixing area 32. Glass raw material and a nebulized dopant salt solution are emitted and burned with hydrogen gas depositing particulate glass material or soot on an adjacent substrate to produce a multi-component glass fiber preform.

Abstract: A method for producing a multi-component glass fiber preform which comprises the steps of nebulizing an aqueous solution of at least one metal salt, and reacting the nebulized solution and a gaseous glass raw material with oxygen gas at a high temperature to produce particulate glass material deposited on a substrate. Apparatus for producing such a preform is also disclosed.

Abstract: A microwave melter in which a material charged in a crucible is heated and melted by irradiation of microwaves, the melter including a melting furnace having an upper furnace body fixedly mounted on a support structure and a lower furnace body detachably connectable with the upper furnace body, a waveguide for guiding microwaves from a microwave generator toward the furnace, a crucible received rotatably and in a suspended state in the lower furnace body, and a feed pipe for feeding untreated material to the crucible.