Fujikura Limited

Manabu Saitou

Shoichiro Matsuo

Kazuhiko Aikawa

Akira Wada

Takaaki Suzuki

Takashi Suzuki

Koichi Harada

Naritoshi Yamada

Shunichirou Hirafune

Masahiro Horikoshi

Ryozo Yamauchi

Kumi Onodera

A method for manufacturing an optical fiber preform and an optical fiber preform apparatus are provided which can reduce hydroxyl groups in an optical fiber preform to a sufficient level without requiring any special equipment or operating conditions. When an optical fiber preform is manufactured by the vapor-phase deposition method, the dehydrating treatment is performed on a porous core preform that is obtained by depositing glass microparticles. In this treatment, a dehydrating agent is supplied to a dehydration apparatus through a feeding pipe and a main feeding pipe made of a material having a water permeance factor of 1.0&#xd7;10g&#xb7;cm/cm&#xb7;s&#xb7;cmHg or less, thereby manufacturing an optical fiber preform.

Method for manufacturing optical fiber preform and optical fiber preform apparatus

A method for manufacturing an optical fiber preform and an optical fiber preform apparatus are provided which can reduce hydroxyl groups in an optical fiber preform to a sufficient level without requiring any special equipment or operating conditions. When an optical fiber preform is manufactured by the vapor-phase deposition method, the dehydrating treatment is performed on a porous core preform that is obtained by deposing glass microparticles. In this treatment, a dehydrating agent is supplied to a dehydration apparatus through a feeding pipe and a main feeding pipe made of a material having a water permeance factor of 1.0&#xd7;10g&#xb7;cm/cm&#xb7;s&#xb7;cmHg or less, thereby manufacturing an optical fiber preform.

A dehydration-sintering furnace for dehydrating and/or sintering an optical fiber preform for use in production of an optical fiber includes a muffle for accommodating the optical fiber preform, a heater for heating the muffle, and a pressure fluctuation absorbing apparatus connected to the muffle. Since the pressure fluctuation absorbing apparatus is thermally insulated from a room temperature atmosphere or heated, vapor produced in a dehydration-sintering process is prevented from condensing (liquefying) in a pressure fluctuation absorbing apparatus, thereby preventing reduced dehydration effectiveness in the muffle and reduced quality of the optical fiber preform.

Dehydration-sintering furnace, a manufacturing method of an optical fiber preform utilizing the furnace and an optical fiber preform manufactured by the method

A dehydration-sintering furnace includes a core tube configured to dehydrate and sinter a porous base material in fabrication of an optical fiber and having an outlet configured to discharge a vapor. The furnace includes a pressure-variation damper connected to the outlet of the core tube. The furnace includes a trap between the core tube and the pressure-variation damper for collecting the vapor.

Dehydration-sintering furnace

This invention provides a method for manufacturing an optical glass in order to prevent the deterioration of the burner used in the synthesis of glass particles that form the optical glass, and to obtain a stable quality optical glass. In this invention, the number of residual bubbles with a diameter of 0.3 mm and more is 0.005/cmor less per unit volume of the optical glass. Such optical glass is obtained by controlling the temperature of an end face of the burner for glass synthesis during the deposition of the glass particles by regulating the relationship of the flow velocity or the flow volume between an inflammable gas and a combustion-supporting gas.

Method for producing optical glass

The present invention provides an optical fiber preform manufacturing method and a burner apparatus employed for this method. In this manufacturing method, when glass particles are synthesized in an oxy-hydrogen flame emitted from a burner to form a porous optical fiber preform by depositing glass particles in the radial direction of a starting member, the relationship between the flow rate vm (m/sec) of a source material gas or a mixed gas of the source material gas and an additive gas discharged from the burner, and the flow rate vs (m/sec) of an inert gas is such that &#x2212;0.06 vm+1.4&#x2266;vs&#x2266;&#x2212;0.02 vm+1.8, and vs&#x2267;0.40, while the relationship between the flow volume Vm (1/min) of the source material gas discharged from the burner and the flow volume Vs (1/min) of the inert gas is such that Vs/Vm&#x2266;0.2.

Method for manufacturing optical fiber preform and burner apparatus for this method for manufacturing optical fiber preform

An optical fiber is fabricated with a refractive index profile having a central core; a middle part provided around the outer periphery of the central core and having a lower refractive index than that of the central core; and a cladding provided around the periphery of the middle part and having a higher refractive index than the middle part and a lower refractive index than the central core. This optical fiber has an effective core area of 120 &#x3bc;mor more in an employed wavelength band selected from the range of 1.53&#x2dc;1.63 &#x3bc;m, and has a cut-off wavelength that is capable of substantially single mode propagation in the aforementioned employed wavelength band. As a result, it is possible to construct an optical transmission system having excellent transmission characteristics in which nonlinearity is decreased.

Optical fiber and optical transmission system

In a wavelength division multiplexed transmission path, the used waveband can be selected from the widest possible waveband among the S-band, C-band, and L-band. The wavelength division multiplexed transmission path has a dispersion-compensating transmission path comprising a dispersion-shifted fiber, which has positive chromatic dispersion throughout a range of wavelengths from 1460 nm to 1630 nm, and one type of dispersion-compensating fiber, or two or more types of dispersion-compensating fiber having different chromatic dispersion having negative chromatic dispersion in a compensation waveband, selected from the abovementioned range; the residual chromatic dispersion of the wavelength division multiplexed transmission path is adjusted so as to be greater than &#x2212;1.0 ps/nm/km or equal to and less than or equal to +1.0 ps/nm/km in a used waveband of the wavelength division multiplexed transmission path, which is selected from the abovementioned range.

Wavelength division multiplexed transmission path and dispersion-compensating fiber used therein

In order to provide a dispersion-compensating optical fiber able to be applied over a broad wavelength band, having a large effective area, and as a result, suppressing the occurrence of non-linear effects, the present invention comprises a dispersion-compensating optical fiber that compensates chromatic dispersion of a 1.3 &#x3bc;m single-mode optical fiber over the entire wavelength range of 1.53-1.63 &#x3bc;m characterized in that, chromatic dispersion at a wavelength of 1.55 &#x3bc;m is &#x2212;50 ps/nm/km or less, the dispersion slope is negative over the entire wavelength range of 1.53-1.63 &#x3bc;m, a cutoff wavelength is provided at which there is substantially single-mode propagation, bending loss is 30 dB/m or less, effective area is 20 &#x3bc;mor more, and the absolute value of chromatic dispersion during compensation of the chromatic dispersion of a 1.3 &#x3bc;m single-mode optical fiber serving as the target of compensation is 0.5 ps/nm/km or less.

Dispersion-compensating optical fiber and hybrid transmission line

In order to provide a dispersion-compensating optical fiber able to be applied over a broad wavelength band, having a large effective area, and as a result, suppressing the occurrence of non-linear effects, the present invention comprises a dispersion-compensating optical fiber that compensates chromatic dispersion of a 1.3 &mgr;m single-mode optical fiber over the entire wavelength range of 1.53-1.63 &mgr;m characterized in that, chromatic dispersion at a wavelength of 1.55 &mgr;m is &minus;50 ps/nm/km or less, the dispersion slope is negative over the entire wavelength range of 1.53-1.63 &mgr;m, a cutoff wavelength is provided at which there is substantially single-mode propagation, bending loss is 30 dB/m or less, effective area is 20 &mgr;m or more, and the absolute value of chromatic dispersion during compensation of the chromatic dispersion of a 1.3 &mgr;m single-mode optical fiber serving as the target of compensation is 0.5 ps/nm/km or less.

A dispersion-compensating fiber is provided that can compensate chromatic dispersion of a DSF in the L-band (wavelength of 1.565 &mgr;m to 1.625 &mgr;m). The dispersion-compensating fiber is provided with a central core segment, an intermediate core segment, a ring core segment, and a clad, which are provided in this sequence concentrically from the inside, and has refractive index profile such that the refractive indices of these segments satisfy the relationship of intermediate core segment<clad&lE;ring core segment<central core segment. When a dispersion-shifted fiber having a zero dispersion wavelength of 1.55 &mgr;m&plusmn;0.05 &mgr;m has been compensating, the residual chromatic dispersion in all or part of the L-band is within &plusmn;1.5 ps/nm/km.

Growing community of inventors

Sakura, Japan

Manabu Saitou