Abstract: A method for drawing a mother ingot into a preform for optical fibers comprises providing a mother ingot, subjecting the mother ingot to measurement of a distribution of refractive index along radial directions thereof to determine a ratio of a core diameter to a clad diameter, and comparing the thus determined ratio with a predetermined ratio between the core diameter and the ingot diameter which ensures intended optical transmission characteristics, under which if the determined ratio is insufficient for the intended light transmission characteristics, the mother ingot is further processed until the predetermined ratio is substantially attained, and the resultant ingot is drawn to a preform, or if the determined ratio is acceptable on comparison with the predetermined ratio, the mother ingot is finally drawn.

Abstract: An excellent quartz glass optical member having stable laser beam resistance, can be obtained by preparing quartz glass in a process having:a first step of subjecting a starting material obtained from silicon halide, alkoxysilane, alkylalkoxysilane, etc. to an oxidizing heat treatment in a temperature range between 600 and 1,500.degree. C., to decrease the hydrogen concentration to 5.times.10.sup.16 molecules/cm.sup.3 or less and at the same time eliminate reducing defects;a second step of subsequently holding the quartz in a hydrogen-containing atmosphere in a temperature range between 200 and 600.degree. C., to establish a hydrogen concentration in the glass of 1.times.10.sup.17 molecules/cm.sup.3 ; anda third step of carrying out a treatment of making the hydrogen concentration of the resultant quartz glass uniform in an atmosphere of air, inert gas, hydrogen, a mixture of hydrogen and inert gas, or a mixture of air and inert gas in a temperature range between 300 and 800.degree. C.

Abstract: The present invention provides a process for substantially extending the useful life of fused silica elements used in high energy ultraviolet optical systems. The fused silica bulk material is pre-compacted by illuminating it with radiation prior to final mechanical fabrication and polishing to the required final surface figure. When the optical element is subsequently used in a high energy ultraviolet environment, it will continue to be compacted but at a lower effective rate. As a result, the useful life of fused silica optical elements can be increased substantially.In preferred embodiments the fused silica material is precompacted with multiple passes of short-pulse ultraviolet radiation. Multiple passes can reduce precompaction time. In one example useful life of the fused silica is increased from about 150 days to 3.8 years by about 5 days of precompaction.

Abstract: Applicants have discovered that exposing optical fiber to an electrical arc produces a perturbation in its refractive index and that gratings can be made by exposing fiber to arcs at a series of locations along its length. In a first variation of the process, the fiber is exposed under tension to a high current arc (>15 mA) for a prolonged period of time (>2 s). Using this method, long period gratings can be successfully fabricated from fiber without the use of special dopants. In a second variation, the fiber is doped and the tension is reduced. The resulting grating is optically weaker but mechanically stronger. A third variation uses hydrogen-sensitized fibers and reduced currents and times. The resulting grating is optically and mechanically strong.

Abstract: The invention relates to coated optical fibers which are coated with a particular radiation-cured primary coating layer composition. The fibers which are coated comprises a glass core and a glass cladding layer. The core, for example may comprises silica doped with oxides of germanium or phosphorous and the cladding, a pure or doped silicate such as fluorosilicate. Alternatively, the fibers may comprises a polymerclad silica glass core. Examples of such claddings include organosiloxanes such as polydimethylsiloxane or a fluorinated acrylic polymer.

Abstract: Disclosed is a process of producing an optical fiber preform having a step of charging a feedstock gas in an oxygen-hydrogen burner via an electrode and hydrolyzing the same in an oxygen-hydrogen flame to produce particulates containing charged glass particulates and a step of blowing the charged particulates onto a target comprised of a seed rod or a soot body formed on the seed rod so as to cause them to deposit on the target and build up as a soot body. Preferably, the process includes the further step of reducing the magnitude of the charge of the particulates in the burner along with an increase of the diameter of the target which is formed. More preferably, the process also includes the further step of making the position facing the burner across the target an opposite polarity from the charging polarity of the particulates ejected from the burner so as to electrically attract the particulates ejected from the burner.

Abstract: A method of producing an optical waveguide grating by exposure to light. An optical waveguide having a core composed of a material wherein the refractive index changes due to exposure to UV light is formed into an optical waveguide grating by applying a grating portion formation step wherein a grating portion is formed by irradiation with UV light at a predetermined spacing, and an overall exposure step after formation of the grating portion wherein the entire grating portion is irradiated with UV light. As a result, the effective refractive index of the grating portion is changed so as to allow the central wavelength to be adjusted without changing the rejection. Consequently, the grating properties can be precisely and easily controlled.

Abstract: A method of manufacturing an optical fiber having a core portion doped with a dopant and a surrounding optical cladding portion is disclosed. The method comprises the steps of drawing a fiber from a molten extremity of a silica preform and moving the fiber along towards a device for coating it with a protective sheath. Prior to the coating step, the moving fiber is irradiated with irregularly modulated actinic radiation, thereby causing corresponding irregular variations in the refractive index of its core portion as a function of longitudinal position. The resulting fiber demonstrates a significantly reduced polarisation mode dispersion.

Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: A method of forming a mirror in a waveguide, including the steps of forming a layer constituting a waveguide in a substrate and forming a mirror-finished surface at a boundary between a portion irradiated with radiation and a non-irradiated portion by obliquely irradiating a layer constituting the waveguide with radiation. The waveguide may be composed of a photosensitive material, and either the irradiated area on the non-irradiated area may be removed by solvent. The waveguide may be composed of a refractive index imaging material in which a refractive index distribution is formed by irradiation with radiation or the refractive index may be increased by heating the irradiated portion. The refractive index imaging material may include a catalyzer to assist in increasing the refractive index distribution of the irradiated area.

Abstract: An improved method of coating an optical fiber is disclosed. A transducer is submerged in a container of liquid coating material and activated so that it causes the formation of a wave of coating material within the container. The optical fiber is then drawn through the container and through the wave, the wave counterbalancing the negative meniscus produced by drawing the fiber through the container. A curved housing also may be placed in the container and surrounding the transducer for controlling the size, amplitude, shape, or direction of the wave. A plurality of transducers also advantageously may be used.

Abstract: The method of making an optical fiber refractive index grating comprises writing the grating through the fiber coating. The method involves providing optical fiber of significantly higher photosensitivity than conventional fiber, such that the grating can be written before unacceptable darkening of the coating occurs. Such fiber is H.sub.2 and/or D.sub.2 -loaded silica-based fiber having a Ge-doped core, the fiber selected to have a germanium-oxygen deficiency center content that provides the fiber with a photosensitivity that is at least twice as large as that of an otherwise identical, conventionally prepared, optical fiber. The fiber typically is drawn from a preform, at least a portion of which was exposed to a reducing atmosphere at an elevated temperature.

Abstract: Apparatus for forming a refractive index grating in a waveguide in accordance with the invention includes a waveguide formed from a material that changes its index of refraction when exposed to a beam of optical radiation, a source of coherent optical radiation for forming a beam of radiation, a mirror arranged to intercept a first part of a beam and to reflect the first part of the beam through an angle, and a phase delay plate arranged to intercept a second part of the beam for delaying the second part of the beam propagating through the plate, in which the mirror and the phase delay plate are arranged so that the first part of the beam and the second delayed part of the beam form an interference pattern on the waveguide for changing the index of refraction of the waveguide, in a pattern corresponding to the interference pattern for forming an index grating in the waveguide.

Abstract: The present invention is predicated upon the discovery by applicants of a relationship describing thermal decay of radiation-induced index changes and a mechanism which permits stabilization by accelerated aging. Specifically, the induced index change decays in proportion to 1/(1+At.sup..alpha.) where A and .alpha. are functions of temperature, and the decay can be accelerated by heat treatment. As a consequence, the extent of decay can be determined for arbitrary time and temperature and, significantly, an appropriate heat treatment can be scheduled for making a device stable within predeterminable limits.

Abstract: Recognizing the rate-determining nature of the coating removal and recoating steps, applicants have demonstrated that with proper combination of low absorbing polymer, glass and low intensity radiation, UV-induced gratings can be side-written into polymer coated fibers without removing the polymer, thus permitting up the possibility of high speed fabrication of fiber gratings.

Abstract: The invention provides a process for fabricating a fiber optic microcable mposed of materials having properties which facilitate its manufacture. The microcable is comprised of an optical fiber core, a buffer surrounding the core, and a protective sheath surrounding the buffer consisting of an electromagnetic radiation cured resin impregnated with fibers suspended in the resin to enhance the resistance of the microcable to physical damage. The microcable is fabricated by soaking the fibers in an electromagnetic radiation curable resin, placing the wetted fibers around the core and buffer to form a matrix, and then irradiating the matrix with electromagnetic radiation to cure the resin.

Abstract: A method of controlling the polarization properties of a photo-induced device in an optical waveguide and a method of investigating the structure of a light guiding body such as an optical waveguide are disclosed. A device, such as gratings, is written by exposing one side of the optical waveguide to light. The unexposed side is then exposed to an amount of light sufficient to impart the desired birefringence to the written device. The birefringence can be minimized in the written device by exposing the opposite side to light in an amount sufficient to minimize the amount of birefringence. The light guiding body is investigated by cleaving the elongated light guiding body, such as an optical waveguide, to expose its cross-section. The cleaved section is then treated to expose difference between the core and cladding. Treatment may include etching in an acid or base.

Abstract: In accordance with the invention, the index of refraction of a glassy material is increased by treating the material with hydrogen and applying heat. Specifically, the glass is exposed to hydrogen or deuterium at pressure in the range 14-11,000 p.s.i. and a temperature in the range 21.degree.-150.degree. C. for a time sufficient for the hydrogen to diffuse into the glass. The glass is then subjected to heat in excess of about 500.degree. C., as by application of a flame or infrared radiation. The duration of heating can be less than a second. The result is a substantial and long-lived increase in the normalized refractive index. For example, flame heating of H.sub.2 loaded commercial GeO.sub.2 doped optical fibers (AT&T Accutether single mode fiber) has produced normalized index changes .increment.n/n of 4.times.10.sup.-3. This process can be used to make and adjust a variety of optical waveguide devices.

Abstract: In accordance with the invention, the index of refraction of a region of a glass body is selectively increased by treating the material with hydrogen and then simultaneously applying heat and actinic radiation to the region. Preferably the body is heated to a temperature in excess of 150.degree. C. and the heat and radiation are simultaneously applied. The result is a substantial and long-lived increase in excess of 5.times.10.sup.-5 in the refractive index of the irradiated region. This process can be used to make and adjust a variety of optical waveguide devices such as photoinduced Bragg gratings.

Abstract: A method for making a glass preform substantially free of OH impurities is disclosed. The method comprises the steps of introducing a moving stream of a vapor mixture including at least one compound glass-forming precursor together with an oxidizing medium into a tube, while generating a hydrogen-free isothermal plasma on an outer surface of the tube to react the mixture and produce a glassy deposit on an inner surface of the tube. The method uses a plasma torch or a radio frequency furnace.

Abstract: Described is a new method and apparatus for measuring the thickness of a thin conductive coating deposited on a moving elongated dielectric body. Of special use is an application of a carbon coating on an optical fiber. The thickness of the conductive coating is measured by establishing an electromagnetic field in a resonator including an elongated unshielded helix and a pair of coupling loops. The helix is suspended between the coupling loops out of contact with either one of them. An electromagnetic energy is coupled into one loop as an input signal from a source of electromagnetic energy and coupled out from the other loop as an output signal. The difference between the magnitude of energy of an empty helix or of a helix with an uncoated body, and the helix with a coated body, is used for controlling the coating process.

Abstract: A light transmitting body (10), (40) has a longitudinal axis (12), (42), and a light radiating surface (14), (46) extending substantially parallel to the axis (12), (42). Where the body is an optical fiber (10), the light radiating surface is the circumferential surface (14) of the fiber (10). Where the body is a rectangular panel (40), the light radiating surface is a rectangular surface (46) of the panel (40). A plurality of striations (16), (44) are formed in the light radiating surface (14), (46) parallel to the axis (12), (42), which cause light entering the body (10), (40) along the axis (12), (42) to be radiated out of the body (10), (40) through the light radiating surface (14), (46) with substantially uniform intensity along the axis (12), (42). The striations (16), (44) may be formed by molding, cold drawing, heating the body (10), (40) under tension, cutting, or by bundling and fusing a plurality of small optical fibers (90) together.

Abstract: A multi-waveguide cylindrical optical conductor for telecommunications cable, the conductor comprising a plurality of optical fibers, each of which is a unit cylindrical fiber constituted by a core and by cladding, the unit fibers are all connected together by silica after a fiber-drawing operation, wherein said core of said unit cylindrical fiber has a diameter of about 8 .mu.m to 10 .mu.m, wherein said cladding has an outside diameter lying in the range 25 .mu.m to 35 .mu.m, and wherein all of the cores of said unit fibers are either situated regularly on generator lines of a cylinder having the same axis as said conductor, or else are parallel with one another and are coplanar. An optical conductor can thus be obtained having an outside diameter of 125 .mu.m and containing six waveguides each having a diameter of about 25 .mu.m to 35 .mu.m.