Abstract: A sintered dense glass, alumina-doped optical fiber preform is stretched and is then heated to a temperature of 1490-1495° C. to remove bubbles without causing crystallization. Thereafter, the stretched glass body is either drawn directly into an optical fiber or overclad and then drawn into a fiber.

Abstract: The invention relates to a process for treating a machined glass surface for improving the adhesive attachment of an optical fiber to this surface, characterized in that machined surface is attacked by an aqueous solution of hydrofluoric acid, then the attacked surface is treated with a bifunctional hydrolyzable silane adhesion promoter or the product of its hydrolysis and partial condensation.

Abstract: An apparatus and method for coating an optical wave guide fiber with a liquid polymer coating includes pressurizing a chamber with a process fluid and venting the process fluid along, and in a direction opposite the direction of travel of, the incoming fiber, to strip particles from the incoming fiber before the particles enter the die assembly.

Abstract: In the process of drawing optical fibers, a protective plastic coating is applied to the fiber by applying a curable liquid coating material thereto and the subsequently curing the liquid coating to a protective plastic layer. At high fiber draw speeds, air entrained with the fiber enters the liquid coating material and causes bubbles in the cured coating. The incidence of bubbles in the coating is reduced by replacing air adjacent the fiber surface with helium.

Abstract: A method and apparatus are provided for removing protective coating material from a fiber optic cable including one or more optical fibers. A stream of hot inert gas is directed onto the cable to soften the protective coating material and blow it from the cable. The stream can be moved relative to the cable until the desired length of coating material has been removed.

Abstract: Disclosed is a method of making an optical fiber preform having at least one annular region of depressed refractive index. A tube of silica doped with fluorine and/or boron is overclad with silica soot. A core rod is inserted into the overclad tube and the resultant assembly is heated while chlorine flows between the tube and the core rod to clean the adjacent surfaces. When the soot sinters, the tube collapses onto and fuses to the rod. The resultant tubular structure is formed into an optical fiber which exhibits low attenuation as a result of the low seed count at the interface between the inner core and the region that is doped with fluorine and/or boron.

Abstract: Improved single-mode optical waveguide fibers comprising a central core region, surrounded by an inner cladding region through which light at a chosen signal wavelength will propagate to an appreciable degree along with propagation of same in the central core region, the inner core region further surrounded by an outer cladding region, the improvement comprising germanium dioxide in the inner cladding region at a concentration within the range of about 0.005 percent by weight to about 1 percent by weight of said inner cladding region, effective to significantly reduce the concentration of oxygen atoms in the inner cladding region which are available to form defects that cause hydrogen-induced attenuation. Also provided are core preforms, overclad preforms, and processes for making the fibers, core preforms and overclad preforms.

Abstract: A method of making 1.times.2 or 2.times.2 overclad couplers, switches and the like such that the process is more reproducible and loss characteristics are improved. Such couplers are typically made by inserting the stripped portions of two active optical fibers into a tube, heating the tube midregion to collapse it onto the fibers and stretching the central portion of the collapsed midregion to achieve the desired coupling characteristics. The improvement involves the insertion of one or two spacer fibers into the tube bore along with the active fibers to take up empty space that had been present in tube bore and to prevent an active fiber from sagging and crossing over the other fiber when the tube is heated during the tube collapse step.

Abstract: A compact monolithic interferometric switch such as a Mach-Zehnder switch is formed such that one of the waveguide paths between the input and output couplers contains a material having exhibits a resonant nonlinearity, whereby its refractive index changes when pump power propagates through it. Each of the waveguide paths has a different propagation constant whereby signal light is subjected to a different delay in each path when no pump power is propagating through the rare nonlinear path. An input signal applied to the input of the switch appears at a first output terminal when the pump power does not propagate through the nonlinear path, and it appears at a second output terminal when the pump power is applied to the nonlinear path. Switching occurs at relatively low levels of pump power.

Abstract: A unitary fiber optic coupling device in which N fibers (N.gtoreq.3) extend in a parallel array having two coupling regions of reduced cross-sectional area. At least one of the fibers is formed of two sections that are situated end-to-end, an active core-containing fiber section that is situated in the first coupling region and a dummy fiber section that is situated in the second coupling region. The coupler also contains at least second and third fibers that are active core-containing fibers throughout their lengths. The second and third fibers couple to one another in the first coupling region but remain uncoupled to one another in the second coupling region. This configuration enables a unitary coupling device to posess multifunction capability. Two fibers that couple in the first coupling region do not couple in the second coupling region, thus avoiding resonance effects.

Abstract: The invention relates to a method of drying and sintering porous optical fiber preforms, especially those consisting of a solid glass core cane surrounded by a layer of cladding soot. After it is dried in a dehydrating atmosphere, the porous preform is heated to a presinter temperature just below that at which it would begin to rapidly densify. The various temperature holds and ramp rates are such that the preform is consolidated in a relatively short time without becoming cloudy or exhibiting other defects that would adversely affect the optical fiber drawn from the consolidated draw blank.

Abstract: A method for forming a GeO.sub.2 -doped SiO.sub.2 glass article by depositing glass particles to form a porous preform and then drying and sintering the porous preform. A precursor of SnO.sub.2 is also present in the reactant stream used to form the particles, whereby the reaction produces particles of glass that contain GeO.sub.2, SiO.sub.2 and SnO.sub.2. The presence of SnO.sub.2 in the particles reduces the reaction of GeO.sub.2 with chlorine to form GeCl.sub.4 during the drying step. The GeCl.sub.4 that would have formed would have either escaped from the porous preform or caused GeO.sub.2 to be re-deposited in an undesirable portion of the preform. The retention of GeO.sub.2 in the article is therefore enhanced.

Abstract: Overclad fiber optic couplers are made by inserting the uncoated portions of a plurality of optical fibers into the bore of a glass tube, collapsing the tube midregion onto the fibers and stretching the central portion of the tube midregion. The present method utilizes a glass tube the bore of which includes a circular portion and a recess. A plurality of optical fibers are sequentially inserted into the tube by threading the coated end into the circular bore portion until the uncoated portion of fiber is centered in the tube. The uncoated portion of fiber is then transferred laterally into the bore recess. After all fibers have been threaded into the circular bore portion and transferred to the recess, a filler fiber is inserted into the circular bore portion. The resultant coupler exhibits low excess loss.

Abstract: An integrated optical proximity coupler comprises first and second parallel straight interaction waveguide segments. First and second end segments are connected to the input ends of the first and second straight waveguide segments, respectively, by means including first and second curved segments, respectively. The end segments are both the same predetermined size which is determined by conventional optical fibers to which they are to be connected. To make the device broad banded, one of the straight segments must be narrower than the other. To reduce device excess loss, the first straight segment and at least part of its respective curved segment are made slightly narrower than the end segments, and the second straight segment and at least part of its respective curved segment are made slightly wider than the end segments. Thus, the required .DELTA..beta. can be obtained without making the narrow path too narrow.

Abstract: A single-mode optical fiber suitable for the transmission of solitons has a refractive index profile that changes along the length of the fiber to provide a fiber dispersion that monotonically decreases along the fiber from one end thereof to the other. The fiber includes a core of maximum refractive index n.sub.1 and a radius a, surrounded by cladding material having a refractive index n.sub.2 which is less than n.sub.1. The fiber core includes a central region that extends to the longitudinal axis of the fiber and an outer region, the inner and outer regions being separated by a region of depressed refractive index. The inner radius a.sub.1 of the region of depressed refractive index is greater than zero and the maximum radius a.sub.o of the region of depressed refractive index is less than a.

Abstract: To couple the elliptical mode field light beam of a laser radiation source to a circularly symmetric single-mode optical fiber, the end of the fiber is provided with an anamorphic lens. The double wedge-shaped lens provides high coupling efficiency and is easily constructed. Other anamorphic lenses are also disclosed. A single wedge lens can provide high coupling efficiency if it is formed on the end of a coupling fiber which has a core that is elliptically-shaped in cross-section, the line of intersection of the two surfaces forming the lens being aligned with the major axis of the elliptical fiber core.

Abstract: A package for a high power semiconductor laser comprising a hermetically sealed container filled with a dry gaseous medium containing oxygen. The presence of oxygen in the laser atmosphere is counter to standard practice in the art which teaches the use of an atmosphere of a dry inert gas.

Abstract: A 1.times.N fiber optic switch is disclosed for selectively coupling light from a first fiber to any one of a plurality of output fibers. The switch includes a coupler in which the first optical fiber and the plurality of optical fibers are elongated in a narrowed coupling region. The coupling region can be bent in various directions to cause the radius of curvature of the input fiber to differ from that of at least one of the output fibers, whereby light propagating in the input fiber can be coupled to only one of the output fibers or to more than one of those fibers.

Abstract: A Mach-Zehnder filter includes an input coupler for splitting an input signal into N equal output signals, where N>2, and a signal combining coupler for combining N optical signals into a single output signal. It further includes N optical waveguide fibers for connecting the N outputs from the input coupler to the signal combining coupler. Each of the N optical fibers subjects the light propagating therethrough to a delay that is different from the delay experienced by light propagating through each of the other optical fibers. This Mach-Zehnder filter exhibits greater finesse per stage than previous Mach-Zehnder devices, finesse being the ratio of the wavelength separation between adjacent peaks to the peak widths.

Abstract: An optical system for coupling a laser radiation source to a circularly symmetric single-mode optical fiber. The laser radiation source produces a beam of light having an elliptical mode field. The input end of a coupling fiber, which has a core that is elliptically-shaped in cross-section, is situated in light receiving relationship with respect to the source. The coupling fiber is oriented with respect to the source such that the mode field of the source is aligned with the coupling fiber core to provide the most efficient coupling of light from the source to the fiber. Means such as an evanescent coupler couples light from the output end of the fiber to the circularly symmetric fiber.