Yoichi Ishiguro

Characterization of fluorine'doped silica glasses

Fluorine-doped silica glasses containing up to 2 wt% were prepared by the vapour-phaseaxial-deposition (VAD) sintering process. The characteristics of these glasses were investigated by Raman spectroscopy, vacuum-ultraviolet-ultraviolet (v.u.v-u.v.) spectroscopy, and viscosity measurements. From the Raman spectroscopic investigation, it has been shown that the Si-F bond structure in the fibres is the same as that in bulk glass and is not affected by codoped additives such as B2O3. From the u.v.-v.u.v, spectroscopic investigation, it has been shown that the absorption band at 7.6 eV in high-purity silica glass is removed with the addition of fluorine. This addition produces a silica glass with most excellent transparency in u.v. and v.u.v. regions. Also it was observed that the optimum addition is around 1 wt%. This fact proves that fluorine incorporation in glass prevents the generation of defects related to optical loss in fibres. From the viscosity study, it was found that the viscosity decreases with an increase of the fluorine content in glass and the activation energy also decreases with increasing fluorine content.

High-performance dispersion-compensating fibers

Abstract An optimum fiber structure for a practical dispersion-compensating fiber (DCF) has been explored theoretically and experimentally, taking dispersion, attenuation, bending loss characteristics, polarization mode dispersion, and nonlinear effects into account. A high figure of merit (FOM) of 280 ps/nm/dB has been successfully achieved with a simple matched cladding design. Furthermore, it was confirmed that the optimized structure with enhanced FOM also benefits self-phase modulation (SPM) suppression.

Study of fluorine doping during vapour-phase axial deposition sintering process

The fluorine doping process of pure silica “soot” with various type of fluorine gases in the vapour-phase axial deposition (VAD) sintering process was investigated in detail. This investigation showed that the doping level is proportional to the 1/4 power of the concentration of the fluorine gas, and the achievable reduction of relative refractive index is −0.75% with this process. The kinetic investigation clarified that the fluorine doping process consists of the doping and dissociation reactions; the former reaction obeys the 1/2 power of the SiF4 partial pressure and the latter the two power of fluorine content [SiO1.5F], where SiO1.5F represents a silicon tetrahedron consisting of one fluorine and three bridging oxygen atoms in glass. The fluorine content is proportional to the 1/4 power of the SiF4 partial pressure at an equilibrium where the doping reaction is in competition with the dissociation reaction.

Optical WDM transceiver module using wavelength-selective coupler and WDM-PD for optical access networks

We have proposed a new WDM-transceiver module using a wavelength-selective coupler and a 1.3 /spl mu/m InGaAs WDM p-i-n photodiode and InGaAsP MQW laser diode in order to reduce component number and module size. In this report, we confirmed the fundamental operation of this module assembled with pigtailed components. Evaluation results imply that this WDM transceiver module is promising for application to an optical WDM transceiver/receiver.