Abstract: The specification describes methods for the manufacture of very large optical fiber preforms wherein the core material is produced by MCVD. Previous limitations on preform size inherent in having the MCVD starting tube as part of the preform process are eliminated by removing the MCVD starting tube material from the collapsed MCVD rod by etching or mechanical grinding. Doped overcladding tubes are used to provide the outer segments of the refractive index profile thus making most effective use of the MCVD produced glass and allowing the production of significantly larger MCVD preforms than previously possible.

Abstract: The specification describes methods for the manufacture of very large optical fiber preforms wherein the core material is produced by MCVD. Previous limitations on preform size inherent in having the MCVD starting tube as part of the preform process are eliminated by removing the MCVD starting tube material from the collapsed MCVD rod by etching or mechanical grinding. Doped overcladding tubes are used to provide the outer segments of the refractive index profile thus making most effective use of the MCVD produced glass and allowing the production of significantly larger MCVD preforms than previously possible.

Abstract: Early stage detection of engine liquid cooling problems is provided with temperature, pressure and other sensors and associated logic circuits configured for detecting alarm conditions including below normal static coolant pressure coupled with an elevated coolant temperature, above normal static coolant pressure, below normal coolant pump pressure condition, coolant voids due to coolant loss or boiling, and external steam or liquid leakage from the cooling system. A gauge displays the difference between coolant pump output pressure and static coolant pressure.

Abstract: Applicants have discovered the existence of loss peaks in optical fiber transmission systems using wavelengths in the E-band and the L-band. Specifically, they have discovered the existence of narrow loss peaks at 1440 nm, 1583 nm and 1614 nm. Because the peaks are relatively narrow, they cannot be easily removed by conventional gain equalizers in long haul transmission systems, and although the peaks are relatively small, they can nonetheless cause transmission channels to drop out in amplified DWDM transmission systems. Applicants have further discovered that these loss peaks are due to carbon contamination of the transmission fiber. Thus optical fibers should be fabricated essentially free of carbon contamination. This means eliminating carbon-containing reagents in preform and tube-making processes.

Abstract: The specification describes methods for the manufacture of very large optical fiber preforms wherein the core material is produced by MCVD. Previous limitations on preform size inherent in having the MCVD starting tube as part of the preform process are eliminated by removing the MCVD starting tube material from the collapsed MCVD rod by etching or mechanical grinding. Doped overcladding tubes are used to provide the outer segments of the refractive index profile thus making most effective use of the MCVD produced glass and allowing the production of significantly larger MCVD preforms than previously possible.

Abstract: Applicants have discovered the existence of loss peaks in optical fiber transmission systems using wavelengths in the E-band and the L-band. Specifically, they have discovered the existence of narrow loss peaks at 1440 nm, 1583 nm and 1614 nm. Because the peaks are relatively narrow, they cannot be easily removed by conventional gain equalizers in long haul transmission systems, and although the peaks are relatively small, they can nonetheless cause transmission channels to drop out in amplified DWDM transmission systems. Applicants have further discovered that these loss peaks are due to carbon contamination of the transmission fiber. Thus optical fibers should be fabricated essentially free of carbon contamination. This means eliminating carbon-containing reagents in preform and tube-making processes.

Abstract: The reproducibility of preforms made by solution doping is significantly improved by adding an internal heat source, such as N2O, as a processing gas during the soot deposition process. The addition of the internal heat source gas results in forming a surface soot layer which exhibits a relatively uniform and consistent morphology. The improvement in the soot surface morphology results in improving the uniformity of the amount of solution dopant retained in the soot layer from preform to preform.

Abstract: A cooling system for conversion of air cooled aircraft engines to liquid cooling, including replacement cylinders, light weight, flex tolerant coolant manifolds and cooling system instrumentation for monitoring coolant temperature and pressure. The replacement cylinders have internal gating of coolant flow between a cylinder jacket and cylinder head exhaust port cooling passages for continuous high power operation of the engine.

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: We have discovered that at least some optical waveguide lasers such as Er-doped fiber lasers are subject to excessive output amplitude fluctuations, including severe fluctuations when the laser is subjected to mechanical shock. We have determined that these highly undesirable fluctuations are due to a resonance phenomenon, and that the fluctuations can be at least substantially reduced by means of a feedback loop that makes the amplitude of the output of the pump laser responsive to the amplitude of the output of the waveguide laser. We have also discovered that the operation of a pump laser/waveguide laser combination is frequently improved if an appropriate non-reciprocal element (e.g., an isolator or a tilted wavelength filter) is placed between the two lasers. An exemplary embodiment of the invention comprises the feedback loop as well as the non-reciprocal element.

Abstract: We have discovered that at least some optical waveguide lasers such as Er-doped fiber lasers are subject to excessive output amplitude fluctuations, including severe fluctuations when the laser is subjected to mechanical shock. We have determined that these highly undesirable fluctuations are due to a resonance phenomenon, and that the fluctuations can be at least substantially reduced by means of a feedback loop that makes the amplitude of the output of the pump laser responsive to the amplitude of the output of the waveguide laser. We have also discovered that the operation of a pump laser/waveguide laser combination is frequently improved if an appropriate non-reciprocal element (e.g., an isolator or a tilted wavelength filter) is placed between the two lasers. An exemplary embodiment of the invention comprises the feedback loop as well as the non-reciprocal element.

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: Unexpectedly large normalized refractive index changes (.DELTA.>10.sup.-5, but possibly even larger than 10.sup.-3) can be obtained in oxide glass, e.g., high-silica glass, by a treatment that comprises exposing at least a portion of the glass at a temperature of at most 250.degree. C. to H.sub.2 or D.sub.2 (partial H.sub.2 or D.sub.2 pressure greater than 1 atmosphere), and irradiating at least a part of the exposed portion with actinic (typically UV) radiation. The method can be used to make optical components that comprise a region (or regions) of raised refractive index, e.g., an in-line refractive index grating in an optical waveguide, a planar optical waveguide, or a phase grating.

Abstract: Unexpectedly large normalized refractive index changes (.DELTA.>10.sup.-5, but possibly even larger than 10.sup.-3) can be obtained in SiO.sub.2 -based optical waveguides (fiber or planar waveguides) by a treatment that comprises exposing at least a portion of the waveguide at a temperature of at most 250.degree. C. to H.sub.2 (partial pressure greater than 1 atmosphere), and irradiating at least a part of the exposed portion with actinic (typically UV) radiation.

Abstract: A method of for manufacturing a coated optical fiber includes depositing a conductive coating on the optical fiber and measuring a value of conductance of that coating. Featured within the manufacturing method is a method for measuring the thickness of the conductive coating on an insulator, e.g., carbon on an optical fiber, including the following steps. An electromagnetic field is established by an input signal. The conductively coated insulator is moved through the energized electromagnetic field. The conductive coating on the insulator is oriented with respect to the electric field so that their interaction increases transmission loss from input to output. An output signal is extracted from the electromagnetic field. From changes in the output signal with respect to a predetermined standard, or reference, the conductance and the thickness of the conductive coating are determined.

Abstract: A process for manufacturing an optical fiber includes the steps of heating and drawing material from a hot optical fiber preform; depositing a conductive coating (especially carbon) on the moving optical fiber; putting a heat curable liquid material on the moving optical fiber; and curing the heat curable liquid material by inductively heating the conductive coating on the moving optical fiber in an electromagnetic field. Heat induced into the conductive coating by energy from the field is conducted from the conductive coating to the heat curable material. The optical fiber continuously moves through the steps of the process without any physical contact.

Abstract: A process for manufacturing an optical fiber includes the steps of heating and drawing material from a hot optical fiber preform; exposing the hot optical fiber to a compound containing carbon for depositing a carbon coating on the moving optical fiber; measuring an electrical property of the carbon coating; and in response to the measured electrical property, changing a parameter of the process for controlling a characteristic of the carbon coating on the moving optical fiber. Featured within the manufacturing method is a method for measuring the thickness of the carbon coating on the moving optical fiber. From the measured thickness of the carbon coating, a control signal is generated for changing one or more of the process parameters for depositing the carbon coating on the optical fiber from a precursor gas. The coated optical fiber continuously moves through the process without any physical contact. No interruption of the production process occurs.