Showing papers on "Single-mode optical fiber published in 1989"

Tensile strain dependence of Brillouin frequency shift in silica optical fibers

Abstract: Brillouin frequency shift in a single-mode optical fiber has been measured as a function of tensile strain. The strain coefficient of normalized Brillouin frequency shift C identical to (dv/sub B//d epsilon )/v/sub B/ is found to be 4.4 for silica fibers. This result shows the potential of Brillouin spectroscopy to evaluate tensile strain in the fiber with the strain resolution of about 2*10/sup -4/. The origin of the large strain coefficient is discussed. >

BOTDA-nondestructive measurement of single-mode optical fiber attenuation characteristics using Brillouin interaction: theory

Abstract: A theoretical investigation of Brillouin optical-fiber time-domain analysis (BOTDA) is described. BOTDA uses Brillouin interaction in optical fibers to analyze the attenuation characteristics of the optical fibers nondestructively. The dynamic range performance of BOTDA is approximately 10-dB greater than that of conventional optical time-domain reflectometry. >

Amplification of spontaneous emission in erbium-doped single-mode fibers

Abstract: Amplification of spontaneous emission (ASE) in erbium-doped single-mode fiber amplifiers operating at lambda =1.53 mu m is studied theoretically and experimentally. The ASE noise spectra obtained from the theory are found to be in excellent quantitative agreement with the experimental data. The observed changes in ASE spectral shapes under different population inversion conditions are also explained. The model may be used to evaluate the performance of erbium-doped fiber lasers as well as to assess the noise characteristics of erbium-doped fiber amplifiers as applied to wavelength-division multiplexing optical communications. >

Room-temperature continuous wave lasing characteristics of a GaAs vertical cavity surface-emitting laser

Abstract: Room‐temperature continuous wave (cw) operation of a GaAs vertical microcavity surface‐emitting laser has been achieved. An ultrashort cavity device with a cavity length of ∼5.5 μm was grown by metalorganic chemical vapor deposition. cw lasing characteristics such as mode properties and temperature characteristics were examined. Single longitudinal mode operation with a side mode suppression ratio of 35 dB was obtained. The temperature range for single mode operation was more than 50 K.

Soliton trapping in birefringent optical fibers

Abstract: We show experimentally the trapping of orthogonally polarized solitons in birefringent optical fibers with polarization dispersions as high as 90 psec/km. Solitons along two axes of a fiber compensate for the polarization dispersion by shifting their frequencies, and we observe frequency splitting up to 1.03 THz for a polarization dispersion of 80 psec/km. For a 20-m fiber the energy required to compensate for the polarization dispersion is ~84 pJ, and for a 76-m fiber the energy required reduces to ~64 pJ.

Apparatus and method for reducing phase errors in an interferometer

Abstract: A fiber optic rotation sensor comprises a fiber optic interferometer loop formed from a highly birefringent optical fiber, and a short coherence length source for introducing light into the inteferometer loop to provide a pair of waves which counter-propogate therethrough. A detector is included to detect the phase difference between the waves after they have traversed the loop to provide an indication of the loop rotation rate, in accordance with the Sagnac effect. Phase errors are reduced by selecting the coherence length of the source and the birefringence of the fiber, so that the loop is comprised of plural fiber coherence lengths. The term "fiber coherence length" should be distinguished from source coherence length. Fiber coherence length is the length of fiber required for the optical path length difference between the two polarization modes of a single mode fiber to equal one coherence length of the light source. In addition, phase errors are reduced by providing a birefringent waveguide between the source and the loop such that light propagates from the source to the loop in an optical path having a path length difference which is at least equal to a coherence length of the source. Phase errors are further reduced by positioning the detector to intercept the optical output signal from the loop such that light wave components in orthogonal modes are spatially averaged.

Single mode bend insensitive fiber for use in fiber optic guidance applications

Abstract: A double-clad single mode optical fiber with a depressed inner cladding exhibits increased resistance to attenuation increases resulting from small radius bends and lower attenuation sensitivity to temperature changes when the mode field diameter is less than 7 um and the ratio of the radius of the inner cladding to the radius of the core is at least 6.5 to one.

SC-type single-mode optical fiber connectors

Abstract: SC-type single-mode optical fiber connectors specifically developed for subscriber loop networks are discussed. The properties and design of precision zirconia ceramic ferrules which have been found to be ideal for high-performance, low-cost single-mode optical fiber connectors are described. A design approach featuring a plastic-molded rectangular connector housing using a push-pull coupling mechanism which has also been found to be suitable for durable, compact, and low-cost connectors is presented. SC connectors used with 10/125 single-mode fibers exhibit insertion loss of 0.06 dB and return loss of 38.6 dB, with no degradation during and after mechanical and environmental tests. To realize higher packaging density, duplex-ferrule connectors, quadruple-ferrule connectors and optical attenuators have also been developed on the basis of the SC connector design. >

Resistance of solitons to the effects of polarization dispersion in optical fibers.

Abstract: Using numerical simulation, we show that solitons of any pulse width can avoid splitting or excessive broadening in response to birefringence of randomly varying orientation as long as the fiber’s polarization-dispersion parameter (in psec/km1/2) is less than ~0.3D1/2, where D is the dispersion parameter (in psec nm−1 km−1). Nevertheless, we also find that polarization dispersion tends to produce a significant amount of dispersive wave radiation from the soliton.

Mode field diameter measurements in single-mode optical fibers

Abstract: The role of the mode field diameter in the characterization of single-mode fibers is examined. The most relevant definitions of this parameter are reviewed, and a comparative analysis of methods for its measurement is performed. All the discussed measurement methods have reached a repeatability and reproducibility which are quite satisfying. Emphasis is given to the requirements posed by the new fiber designs, such as the polarization-maintaining structures. Most of the discussed techniques have been industrialized, and a number of instruments based on them are commercially available; however, it is predicted that the evolution of fiber design will impose new requirements on some of these instruments. >

Longitudinal acoustic modes and Brillouin-gain spectra for GeO 2 -doped-core single-mode fibers

Abstract: Guided longitudinal-acoustic modes, which give rise to Brillouin gain, are theoretically clarified for a single-mode fiber with a GeO2-doped core and pure-silica cladding. Longitudinal-acoustic L0m modes are found from the theoretical analysis to interact with the electromagnetic field of the HE11 mode. Brillouin-gain spectra are measured for clarifying the theory. A few gain peaks in the Brillouin-gain spectra are successfully explained by taking account of the phase-velocity characteristics of the L01, L02 and L03 modes guided in the GeO2-doped core region. Furthermore, Brillouin frequency shifts per unit dopant concentration for GeO2 and F are experimentally obtained to confirm the dispersion characteristics of the guided acoustic modes. The evaluated frequency shifts per unit dopant concentration are 107 and 356 MHz/mol% for GeO2 and F, respectively, at a wavelength of 1550 nm.

Measurement of polarization-mode dispersion in single-mode fibers with random mode coupling.

Abstract: A simple frequency-domain technique for measuring polarization-mode dispersion in single-mode fibers with random mode coupling is used to give what is to my knowledge the first direct experimental demonstration of the transition of the dispersion from a linear length dependence to a square-root-of-length dependence. Sensitivity to external perturbations is demonstrated by an order-of-magnitude increase in dispersion when the fiber is removed from a conventional spool and placed on a large-diameter drum. An expression for the length-dependent probability density function that describes the dispersion for highly coherent sources is also presented and confirmed experimentally.

DOUBLE CLAD HIGH BRIGHTNESS Nd FIBER LASER PUMPED BY GaAlAs PHASED ARRAY

Abstract: We report on the most recent improved version of the double clad configuration for efficient pumping of a single mode fiber laser with a multi-mode pump1 In the earlier report, the first and second claddings were substantially fused slica and the core containing Nd was offset from the center of the fiber axis, as shown in Fig. (1,a).

Investigation of coupling between a fiber and an infinite slab

Abstract: An optical waveguide system consisting of an unclad fiber core suspended at a constant distance parallel to the surface of an infinite extended dielectric slab is investigated. Fiber and slab are both embedded in a homogeneous dielectric medium. The fate of light initially launched into the fiber depends on the relationship between the refractive index values of the slab and fiber. When the refractive index of the fiber is considerably larger than that of the slab, the latter exerts little influence on the wave, so that almost no power is transferred out of the fiber. When the refractive indexes of fiber and slab are more nearly the same, a beating phenomena is observed, that is, light is exchanged periodically between the fiber and the slab. However, after some distance the beating dies out. Some of the light energy remains in the combined system of fiber and slab, which can be regarded as a ridge waveguide, while the remaining light spreads out laterally in the slab. If the refractive index of the slab is considerably larger than that of the fiber, the slab acts as a drain on the light initially launched into the fiber. The light power in the fiber decreases exponentially with the distance along the fiber axis as it is transferred to the slab where it is carried away. >

Single-mode instability in optical bistability.

Abstract: This paper gives a detailed description of the plane-wave Gaussian models of optical bistability and of the experimental investigations of the single-mode instability induced on a beam of sodium atoms in a cavity by an external driving field. Our goal is to provide a careful comparison of the theoretical and experimental results. We focus on the shape of the instability domain, the nature and behavior of the spontaneous output oscillations produced by the instability, and their frequency dependence on the control parameters. We carry out this comparison using both the plane-wave and Gaussian models. Our analysis shows that the latter is in good quantitative agreement with the experimental results. We investigate in detail the main assumption of the Gaussian model, namely, that the internal cavity field retains the same radial profile as the input field.

Optical fiber connector

Abstract: Disclosed is an optical fiber connector that comprises two right capillary cylinders or "plugs", an alignment sleeve that contactingly maintains the plugs in substantially fixed relative relation, and means for maintaining the plugs in substantially fixed relative axial relation. Connectors according to the invention can have very low insertion loss, are easily field-installed, can be easily and relatively inexpensively manufactured, and are useful for single mode as well as for multimode fiber applications. In a preferred embodiment the connector takes the form of the ST® connector.

Frequency doubling polymeric waveguide

Abstract: OF THE DISCLOSURE In one embodiment this invention provides a frequency doubling optical waveguide consisting of a substrate-supported polymeric thin film which exhibits second order nonlinear optical response, and which has a periodic structure for quasi-phase matching of propagating laser wave energy. In a preferred embodiment the waveguide has a two-dimensional channel structure for intensified single mode wave transmission.

An apparatus for optically connecting a single-mode optical fiber to a multi-mode optical fiber

Abstract: An apparatus connects a single-mode optical fiber (2) in a transmitting side to a multi-mode optical fiber (4) in a receiving side without a deterioration of baseband transmission characteristics. The apparatus optically connects the single-mode fiber (2) to the multi-mode fiber (4) with an optical axes displacement therebetween, so that an optical signal to a multi-mode optical fiber (4) from a single mode optical fiber (2) is incident in a steady state mode including not only lower mode, but higher mode. In one embodiment, the optical axes displacement is achieved by axial displacement (d) between the single-mode fiber (2) and multimode fiber (4). In another embodiment, the optical axes displacement is achieved by an angle displacement between the single-mode fiber and multi-mode fiber.

Effects of Microwave Processing on Fiber-matrix Adhesion in Composites

Abstract: Experiments have been done using a single mode (TE111, 2.45 GHz) cylindrial microwave cavity with single fiber composite specimens. After obtaining a cure cycle with microwaves to match that achieved with a conventional thermal cure cycle as measured by tensile tests, dynamic mechanical analysis and differential scanning calorimetry, quantitative measurements of interfacial shear strength and physical properties have been carried out and compared with the results from conventional thermally-cured systems. Under the conditions studied for single fiber specimens, the fiber-matrix interfacial shear strength decreases slightly in both glass-epoxy and aramid-epoxy cases as comapared with thermally-cured specimens. Graphite fiber-epoxy adhesion, on the other hand, increases significantly in these single fiber studies in microwave processed specimens as indicated by an increase in the interfacial shear strength. The failure mode changes from interfacial (thermal curing) to matrix failure.

Stress-induced birefringence fibers designed for single-polarization single-mode operation

Abstract: By a simple numerical method, it is shown that a stress-induced birefringence fiber can be operated as a single-polarized single-mode fiber if absorption loss is introduced in the stress-applying regions and the refractive index of the regions is raised to a level between the effective indices of the two fundamental polarization modes. Numerical results also show that the characteristics of this fiber are sensitive to the refractive index and the location of the stress-applying regions, but rather insensitive to the size of these regions. >

Evaluation of performance parameters of single-mode all-fiber Brillouin ring lasers.

Abstract: An analytical theory of the operation of all-fiber Brillouin ring lasers that accounts for pump depletion is presented. Expressions for stimulated Brillouin scattering lasing threshold power, output Stokes power, and conversion efficiency are derived. It is shown that the fiber cavity detunes from its resonant value owing to the buildup of the counterpropagating Stokes wave, which can be a limitation in the performance of all-fiber resonator systems. The application of the theory is in the design and optimization of performance parameters of devices using all-fiber ring resonators, particularly Brillouin lasers and gyroscopes.

Polarization fluctuation measurements on installed single-mode optical fiber cables

Abstract: Measurements are reported of the polarization fluctuation observed at 1550 nm on samples of cable that Telecom Australia has installed in its interexchange network. The rate of polarization fluctuations is found to be slow, on the order of hours. The fluctuation in the polarization angle is typically in the range of 2-10 degrees each day, with some changes up to about 25 degrees . The results indicate there are no significant limitations on implementing polarization control in a coherent system receiver. >

Modulation instability-based fiber interferometric switch

Abstract: High incremental gain and ultrafast switching operation are achieved in a fiber interferometer switch by employing a control optical signal in one arm of the interferometer and a pump optical signal split between both arms of the interferometer wherein signal frequencies are in the anomalous group velocity dispersion region of only one arm of the fiber interferometer to cause modulation instability to occur. Net gain in excess of 10 4 has been observed where net gain is the ratio of device output peak power to control signal input power. In a preferred embodiment of the invention, the interferometer is a balanced Mach-Zehnder interferometer utilizing a single mode, dispersion shifted, polarization-preserving optical fiber.

Observation of ultrafast nonlinear polarization switching induced by polarization instability in a birefringent fiber rocking filter

Abstract: Ultrafast all-optical switching between two orthogonal linear polarizations in a periodically twisted fiber filter is discussed. The dependence of the switching characteristics on the input power and operating wavelength is considered. >

Acoustic wave characteristics of lead-free (Bi1/2Na1/2)0.99Ca0.01TiO3piezoelectric ceramic

Abstract: Acoustic wave characteristics of lead-free (Bi1/2Na1/2)0.99Ca0.01TiO3 (BNC-1) piezoelectric ceramic are studied from a viewpoint of a new substrate material group for a surface acoustic wave and/or a bulk acoustic wave. The BNC-1 ceramic, which has high electromechanical coupling factors, k33(=37.6%) and kt(=51.3%), and low free permittivities, e33T/e0(=236) and e11T/e0(=271), along with a high mechanical strength, is favorable to high frequency ultrasonic uses. Two interdigital transducers can excite an SH plate mode wave or a Lamb mode wave whose travelling direction is perpendicular or parallel to the poling axis, respectively. A delay line type oscillator using the SH wave is demonstrated a single mode oscillation of 8.319 MHz.

New formalism for bending losses in coated single-mode optical fibres

Abstract: A new method to estimate the losses in bent weakly guiding optical fibres is described, taking into account the finite dimensions of the fibre cross-section. A comparison between theoretical and experimental results is presented to demonstrate the validity of this theory.

Polarization measurements on single-mode fibers

Abstract: An overview of current measurement techniques on conventional and polarization maintaining single-mode fibers is presented. The various methods are discussed and classified with respect to the relevant polarization parameters. Applicability ranges and resolution are pointed out for different types of fibers. >

Inverse scattering theory applied to the design of single-mode planar optical waveguides

Abstract: An inverse scattering theory is used to design single-mode planar optical waveguides that have wider inhomogeneous cores than those obtained by direct scattering methods. The wave equation for the electric field in the core is transformed into a Schrodinger-type equation whose potential function q(x) is related to the refractive-index profile. The modal structure of the waveguide is characterized by the transverse reflection coefficient r(k); a single discrete propagating mode and continuous radiating modes are considered. The Gel’fand–Levitan–Marchenko inverse scattering theory is used to obtain the unique solution of q(x) from a rational-function representation of r(k).