Showing papers by "E. J. Friebele published in 1991"

Modal evolution of induced second-harmonic light in an optical fiber.

Abstract: We show how the mode of the photoinduced second-harmonic light in an optical fiber changes with preparation time. We also discuss what type of nonlinear interaction can be causing the induced second-harmonic light and give experimental evidence that the initial second-harmonic light is a core–cladding interface effect.

Noncontact measurement of optical fiber draw tension

Abstract: A simple technique for measuring the tension on an optical fiber during the draw process without contacting the fiber surface is reported. It is based on detecting the resonant vibrational frequency of the fiber during draw using the position output of the fiber diameter monitor and requires no specialized circuitry. The tension, determined from the fundamental resonant frequency of the length of fiber between the neckdown region in the furnace and the coating cup, is accurate to within 1% and repeatable to >

Computer-simulation analysis of the ESR spectra of V-type centers in irradiated heavy-metal fluoride glasses

Abstract: Computer line-shape simulations were carried out on the electron-spin-resonance spectra of several heavy-metal fluoride glasses following exposure to ioniziong radiation at cryogenic temperatures. The primary objects of this study were certain spectra circumstantially attributable to holes trapped on a cluster of two or more inequivalent fluoride or foreign halide ions. The earlier attribution of certain spectral features to ${\mathrm{FCl}}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{FBr}}^{\mathrm{\ensuremath{-}}}$ species was confirmed in Cl- and Br-doped glasses, respectively, although the simulations show that ${\mathrm{FCl}}^{\mathrm{\ensuremath{-}}}$ in the glasses has a structure quite different from the same species in mixed alkali halide crystals. Two other spectra---universally observed in irradiated glasses composed of ${\mathrm{ZrF}}_{4}$ (or ${\mathrm{HfF}}_{4}$), ${\mathrm{BaF}}_{2}$, and virtually any number of other fluoride constituents---were also examined in detail. The previous assignment of one of these spectral components to ${\mathrm{F}}_{2}^{\mathrm{\ensuremath{-}}}$ molecular ions is sustained, although the specific nature of these defects is now argued to be interstitial fluorine atoms in configurations analogous to ${\mathit{V}}_{\mathit{K}\mathit{A}}$ and ${\mathit{V}}_{\mathit{H}}$ centers (rather than ${\mathit{V}}_{\mathit{K}}$ centers) in the alkaline-earth fluorides. The second ubiquitous component, which was previously ascribed to ``interstitial ${\mathit{F}}^{0}$,'' is demonstrated to arise from an ${\mathrm{F}}_{3}^{2\mathrm{\ensuremath{-}}}$ species similar to the ${\mathit{V}}_{\mathit{t}}$ center in LiF. The ${\mathrm{F}}_{2}^{\mathrm{\ensuremath{-}}}$ and ${\mathrm{F}}_{3}^{2\mathrm{\ensuremath{-}}}$ can be thought of as ``on-center'' and ``off-center'' configurations of the interstitial fluorine atom, and it appears that the former may undergo a thermal transmutation into the latter.

Cooperative implementation of a high temperature acoustic sensor

Abstract: The current status and results of a cooperative program aimed at the implementation of a high-temperature acoustic/strain sensor onto metallic structures are reported. The sensor systems that are to be implemented under this program will measure thermal expansion, maneuver loads, aircraft buffet, sonic fatigue, and acoustic emissions in environments that approach 1800 F. The discussion covers fiber development, fabrication of an extrinsic Fabry-Perot interferometer acoustic sensor, sensor mounting/integration, and results of an evaluation of the sensor capabilities.

Pulse Energy Dependence of Defect Generation in Bragg Grating Optical Fiber Materials

Abstract: Ge-associated defect centers induced by 5 eV (~ 245 nm) photons of various intensities in Ge-doped silica were studied using electron spin resonance (ESR). We found that Ge E’ centers observed in Bragg grating Ge-doped silica core fibers are induced and bleached by one- and two-photon absorption processes, respectively. The observation that Ge E’s are the only paramagnetic centers induced by low intensity 5 eV photons supports the proposal that the Ge E’ center is responsible for the photoinduced structures observed in both Bragg grating and second-harmonic-generation (SHG) fibers.

Radiation effects in high NA single mode optical fibers

Abstract: The sensitivity of high NA single mode optical fibers to both steady state and transient radiation environments over the -55 to 80 C temperature range has been evaluated. In accord with prediction, the initial incremental losses are equal to or less than that in comparable telecommunications fibers. >