James William Fleming

Optimum index profile of the perfluorinated polymer-based GI polymer optical fiber and its dispersion properties

The significant advantages in bandwidth and low material dispersion of perfluorinated (PF) polymer-based graded-index polymer optical fiber (GI POF) are theoretically and experimentally reported for the first time. It is confirmed that the low attenuation and low material dispersion of the PF polymer enables 1 Gb/s km and 10 Gb/s km transmission at 0.85-/spl mu/m and 1.3-/spl mu/m wavelengths, respectively. The PF polymer-based CI POF has very low material dispersion (0.0055 ns/nm/spl middot/km at 0.85 /spl mu/m), compared with those of the conventional PMMA-based POF and of multimode silica fiber (0.0084 ns/nm km at 0.85 /spl mu/m). Since the PF polymer-based GI POF has low attenuation from the visible to near infrared region, not only the 0.65-/spl mu/m wavelength which is in the low attenuation window of the PMMA-based GI POF, but other wavelengths such as 0.85-/spl mu/m or 1.3-/spl mu/m etc. can be adopted for the transmission wavelength. It is clarified in this paper that the wavelength dependence of the optimum index profile shape of the PF polymer-based GI POF is very small, compared to the optimum index profile shape of the silica-based multimode fiber. As a result, the PF polymer-based GI POF has greater tolerance in index profile variation for higher speed transmission than multimode silica fiber. The impulse response function of the PF polymer-based GI POF was accurately analyzed from the measured refractive index profile using a Wentzel, Kramers, Brillouin (WKB) numerical computation method. By considering all dispersion factors involving the profile dispersion, predicted bandwidth characteristic of the PF polymer-based GI POF agreed well with that experimentally measured.

Optical fibers by a hybrid process using sol–gel silica overcladding tubes

Abstract We have successfully developed a sol–gel process to produce large silica glass bodies to be used as optical fiber preform overcladding tubes which meet the demands of optical fiber. We have made and tested tubes weighing approximately 4.5 kg, which comprise about 90% of the eventual fibers mass. This sol–gel process uses colloidal silica dispersed in high pH water. The sol is cast, gelled by reducing the pH and dried to a porous tube. The dried body is heat treated to remove organics, to dehydrate and to purify by removing both refractory oxide particles and transition metal ions to the parts/billion range and then sintered to transparency in He. These tubes are competitive with vapor deposited synthetic silica tubes and produce fiber meeting current commercial standards. Net shape formation of large precision glass bodies by gel casting is demonstrated.

A high coherence supercontinuum source at 1550 nm

We present a low noise supercontinuum source based on a femtosecond fiber laser. Varying the dispersion along the fiber length generates a flat, symmetrically broadened continuum. No degradation in coherence is observed.

Nanosecond pulse amplification in a higher-order mode erbium-doped fiber amplifier

The nonlinear properties of a nanosecond pulse in a higher-order-mode, Er-doped-fiber amplifier with 2440 μm² effective area are compared to a conventional 880 μm2 area fiber. Both 1480 nm pump and 1554 nm signal propagate in the LP₀₉ mode.

Anomalous refractive index changes in optical fibers resulting from frozen-in viscoelastic strain

Important, yet previously overlooked, anomalous optical fiber refractive index changes result from frozen-in viscoelastic strains, which are distinct from residual elastic strains. These index changes affect fiber design, measurement, and splicing, and can be harnessed to serve as the basis for novel fiber devices.

Characterization of dispersion in higher order mode fibers using electrical spectrum measurements

We present a technique for measuring the chromatic dispersion of the higher order modes in kilometer lengths of fiber. The LP/sub 02/ dispersion is measured for several different fibers, and accuracies better than 1% are achieved.

The impact of nonlinearity during femtosecond pulse compression in fibers on continuum coherence

Amplified erbium-fiber-laser pulses compressed in large-mode-area fiber show significantly reduced nonlinearity compared to standard-single-mode fiber. Consequently, supercontinuum generated with the pulses compressed in large-mode-area fiber show a 10 dB increase in cross-coherence fringe visibility.