RESUMEN
A novel optical fiber fabrication technique was developed by converting the symmetry of the silica substrate into the germanosilicate ring core to efficiently introduce geometric birefringence in an elliptical hollow optical fiber. Due to high ellipticity in the hollow ring core, the fiber provides an extremely high group birefringence of 2.35 x 10(-3) at 1550 nm. Single-mode single-polarization guidance was also experimentally confirmed, with a bandwidth of approximately 35 nm. The generic adiabatic mode conversion capability in the taper also provided a stable fusion splice to conventional single-mode fiber with low loss and high tensile strength.
RESUMEN
A new method of measuring optical nonlinearity for resonant nonlinear optical fibers is proposed. A long-period fiber grating (LPG) pair was used to measure the nonlinear refractive index n(2) of a Yb(3+)/Al (3+) codoped optical fiber, which was spliced between the two LPGs, as the fiber was pumped with a laser diode. The nonlinear refractive index of the Yb(3+)/Al (3+) codoped fiber near 1580 nm depended on the pump power. As the pump power increased, the nonlinear refractive index decreased. At launched pump powers of 2-8 mW, the nonlinear refractive index of the Yb(3+)/Al (3+) codoped fiber near 1580 nm was ~7.5x10(-15)m (2)/W .
RESUMEN
We report experimental results on the development of residual stress due to OH impurity in optical fibers. The effect of OH impurity on residual stress is demonstrated by direct residual stress measurement. The residual stress at the outer-cladding/jacketing-tube boundary of the fiber drawn at 3.48 N was found to be -61 MPa . The residual compressive stress is attributed to the viscosity decrease induced by a significant OH impurity at the boundary, as measured by a Fourier transform infrared microscope.
RESUMEN
By using the diffracted field of the LP(11) mode of a hollow-core optical fiber, we have produced a micrometer-sized, focused dark laser spot in the near field of the fiber. The minimum half-width of the dark spot is less than 1 mum . In particular, by masking the hollow core and metal coating the cladding with a microsphere, we blocked the light propagating in the cladding and obtained a clean dark spot, which may be useful in atom-optical experiments such as with atomic lenses, atom traps, and atom switches.
RESUMEN
We observed residual stress relaxation by CO(2) laser irradiation in the cores of optical fibers by direct stress measurement. It was demonstrated that the mechanical stress was fully relaxed by CO(2) laser irradiation and that the remaining stress in the core was thermal stress that was due to a mismatch of the thermal expansion coefficients of the fiber core and cladding. The net core stresses after relaxation were 17, 68, and 203 MPa in Ge-B-codoped fibers drawn at 0.53, 1.38, and 3.48 N, respectively. Changes in the refractive indices of the cores as a result of residual stress relaxation were also estimated.
RESUMEN
A Sm(+2)/Sm(+3) codoped aluminosilicate glass optical fiber was fabricated by use of modified chemical-vapor deposition in conjunction with an aerosol-delivery technique. A permanent index change of 7.6 x 10(-5) was induced in the fiber by irradiation of 1 W of multiline output from an Ar-ion laser. Bleaching of a broad absorption band of Sm(+2) in the visible range was also observed, and it is believed that photoionization of Sm(+2)? Sm(+3)+e plays an important role in the induced photorefractivity.
RESUMEN
The timing restrictions for soliton-dragging logic gates can be relaxed by asymmetrizing the interaction between the orthogonally polarized control and signal pulses. In particular, by prechirping the signal pulse in a normal group-velocity dispersion fiber, we find experimentally that the timing restriction can be loosened from less than 2 pulse widths to over 3.3 pulse widths. For this passive prechirper arrangement the timing restrictions are loosened at the expense of increased minimum switching energy. Soliton-dragging logic gates with a signal prechirper can provide timing restoration as well as logic-level restoration, so that two inverter gates can be cascaded to implement an ultrafast, all-optical pulse regenerator.
RESUMEN
Statistically significant correlations have been established between certain fabrication parameters of matched clad, single-mode optical fiber waveguides and their response to an ionizing radiation dose of 2000 rad. The reCOVE:ry data measured at -35 degrees C following exposure have been fit to nth-order kinetic behavior where the adjustable parameters are the initial and permanent incremental losses (A(o) and A(f), respectively), the half-life of attenuation tau, and the order of kinetics n. The set of fibers chosen for analysis had Ge-doped silica cores. In fibers with Ge-F-doped silica clads, A(o) correlates with the concentration of Ge-doped into the fiber core; A(f) correlates with the ratio of oxygen to reagents used during core deposition; and tau and n correlate with a two-way interaction of core oxygen and fiber draw speed. In P-F-doped clad fibers, the P concentration has been found to correlate with the order of the kinetics of recovery.
RESUMEN
We show experimentally and numerically that intensity-dependent polarization rotation does not lead to pulseshape distortions for fundamental solitons because the soliton rotates as a unit. We demonstrate an optical limiter based on nonlinear polarization rotation in a standard, single-mode fiber followed by a polarizer. The output pulse shape from the limiter resembles that of the input, although the pulse width may be different.
RESUMEN
The transmission performance of trapezoidal-index profile single-mode fibers that can operate with zero dispersion in the 1.5-microm region has been investigated. The exact numerical calculations of propagation characteristics for these lightguides established a variety of relationships in terms of the parameters of a trapezoidal-index profile. One of the profile parameters that defines the shape of a trapezoid is the aspect ratio S, which ranges between 0 and 1. It was found that as the aspect ratio decreases from 1.0 to 0.3 the optimum core radius of the fiber gradually increases. But when S is <0.3, it approaches a constant equal to the value of the triangular-index profile (S = 0).
RESUMEN
Based on a set of exact vector form solutions to Maxwell's equations for optical waveguides, we studied the parametric effects on propagation characteristics of the HE(11) mode, varying the lightguide parameters (lambda,Delta,a,alpha). In this work a three-term Sellmeier equation was employed to describe accurately the material dispersion of a single-mode fiber doped with GeO(2). The calculated results are compared with the measured values and found to be in good agreement.
RESUMEN
Parametric studies were done on the propagation characteristics of single-mode fiber using measured refractive-index profile data. Two types of profile were considered--a graded-index core with a depressed cladding (Delta' < 0), and a triangular index core with no depressed cladding. The computations employ accurate material dispersion data for the germania-doped silica core and the fluorine-doped silica cladding. The investigation also includes the use of an alpha-index profile as an idealized profile using the same computational method. We find that there is good agreement with the experiments.
RESUMEN
A newly designed 7.3-m high tower is reported that is equipped with a 10-kW curing system capable of coating a fiber with 50-microm thickness of UV curable resin at a speed in excess of 5 m/sec. Performance of fibers coated at two different speeds (V(f) = 1.5 and 5 m/sec) were evaluated. It was found that there were no noticeable differences in the measured values of mechanical and optical properties such as strength, coating thickness, transmission loss, bandwidth.
RESUMEN
The UV flux density required for photopolymerization is calculated, primarily based on an estimation of the overall system efficiency and the activation energy of the photoinitiator added to the prepolymer solution. We found that there is a linear relationship between the flux density and coating speed. The experimental results support the relation. Furthermore, it is noted that full curing has been achieved at speeds >5 m/sec with the 10-kW output power. The 10-kW system delivers 1.5 kW of UV power in the 300-400-nm spectral range.
RESUMEN
A study was made of the use of a CO(2) laser for producing a hemispherical lens at the end of a fiber. When the fiber end is heated to the softening points of the material, it tends to become spherical in shape due to surface tension. A one-dimensional heat conduction model for the fiber can reasonably predict the required laser power for a given pulse length to produce lenses on fibers made of various kinds of materials. A He-Ne laser beam was coupled into a fiber to investigate the properties of the spherical lens. We also observed that such lens can couple light from a source into the fiber, can be used for imaging, and can focus enough laser intensity for machining various materials.
RESUMEN
A high speed framing camera was used to record the sequential steps of the start, development, and cessation of a highly energetic plume of matter caused by a ruby laser pulse of intensity of the order of 10(7) W/cm(2) on alumina ceramic and copper materials. The results of the experiments have established that the laser intensity and a normalized absorption coefficient are the two most important factors to be considered for any material removal process such as hole drilling. This study has provided the experimental support of a theoretical analysis on laser-induced vaporization and explosion of solid material, developed and published previously.
RESUMEN
A system consisting of a cw CO(2) laser and an ellipsoidal reflector was developed in order to draw fused silica fibers from bulk material. The system was used to obtain unclad fused silica fibers (Suprasil 2) having a total transmission loss of less than 100 dB/km at 6328 A. Preforms (rod in tube) have also been drawn to fibers of long lengths with diameters as small as 10 microm and variations within 5%. Analysis of the fiber drawing process established relations that allow determination of the design parameters for fiber drawing systems. Experimental results are given that support these relationships.
