Sumitomo Electric Industries, Limited

Kazuya Kuwahara

Katsuya Nagayama

Ichiro Tsuchiya

Eisuke Sasaoka

Tetsuya Nakanishi

Masashi Onishi

Tatsuya Konishi

Toshiki Taru

Katsuyuki Tsuneishi

Yuichi Ohga

Makoto Shimizu

Kohei Kobayashi

Takayuki Shimazu

Yasuo Matsuda

Kaoru Okuno

Yuji Kubo

Hiroaki Ohta

Hideo Miyaki

Yasuhiro Naganuma

An inexpensive low-attenuation optical fibersuitable for use as an optical transmission line in an optical access network is a silica based glass optical fiber and includes a coreincluding the center axis, an optical claddingsurrounding the core, and a jacketsurrounding the optical cladding. The core contains GeOand has a relative refractive index difference &#x394;core, based on the optical cladding, greater than or equal to 0.35% and less than or equal to 0.50% and has a refractive index volume v greater than or equal to 0.045 &#x3bc;mand less than or equal to 0.095 &#x3bc;m. The jacket has a relative refractive index difference &#x394;J greater than or equal to 0.03% and less than or equal to 0.20%. Glass constituting the core has a fictive temperature higher than or equal to 1400&#xb0; C. and lower than or equal to 1590&#xb0; C. Residual stress in the core is compressive stress that has an absolute value greater than or equal to 5 MPa.

Optical fiber

Optical fiber and optical transmission system

Provided is an inexpensive low-loss optical fiber suitably used in an optical transmission network. An optical fiber includes a core, an optical cladding, and a jacket. The core has a relative refractive index difference between 0.2% and 0.32% and has a refractive index volume between 9%&#xb7;&#x3bc;mand 18%&#xb7;&#x3bc;m. The jacket has a relative refractive index difference between 0.03% and 0.20%. Glass constituting the core has a fictive temperature between 1400&#xb0; C. and 1560&#xb0; C. Stress remaining in the core is compressive stress. A cutoff wavelength measured on a fiber having a length of 2 m is 1300 nm or more and a cutoff wavelength measured on a fiber having a length of 100 m is 1500 nm or less. An effective area at a wavelength of 1550 nm is 110 &#x3bc;mor more. A attenuation at a wavelength of 1550 nm is 0.19 dB/km or less.

Optical fiber, optical transmission system, and method of making optical fiber

The present invention relates to an optical communications system that allows improving OSNR while suppressing the power increase of pumping light for distributed Raman amplification. In the optical communications system, an optical fiber is laid in a transmission section between a transmitter station (or repeater station) and a receiver station (or repeater station), and optical signals are transmitted from the transmitter station to the receiver station via the optical fiber. In the optical communications system, pumping light for Raman amplification, outputted by a pumping light source provided in the receiver station, is fed into the optical fiber via an optical coupler, and the optical signals are distributed-Raman-amplified in the optical fiber. The transmission loss and the effective area of the optical fiber satisfy, at the wavelength of 1550 nm, a predetermined relationship.

Optical communications system

The method of manufacturing an optical fiber in accordance with the present invention comprises a step of yielding an optical fiber by drawing an optical fiber preform softened upon heating, wherein a temperature at which the optical fiber preform is softened is at least 1800&#xb0; C., whereas the optical fiber preform or optical fiber has a glass cooling rate of 4000&#xb0; C./sec or less when attaining a temperature of 1800&#xb0; C.

Method of manufacturing optical fiber

A drawing apparatuscomprises a drawing furnace, a protecting tube, and a resin curing unit. A buffer chamberis disposed between the drawing furnaceand the protecting tube, and has a length Lin the drawing direction of the optical fiber. The buffer chamberis constituted by a first buffer celland a second buffer cell. In the space within the buffer chamber, an He gas, which is an atmosphere gas within the drawing furnace, and the air, which is an atmosphere gas within the protecting tube, exist in a mixed state. The optical fiberdrawn upon heating in the drawing furnaceis fed to the protecting tube, and a predetermined part of the optical fiberis annealed at a predetermined cooling rate. Thereafter, a coating diecoats the optical fiberwith a UV resin solution, and the resin curing unitcures the UV resin, whereby a coated optical fiberis obtained.

Optical fiber producing method

The drawing method of the present invention uses a drawing furnace comprising a furnace muffle tube, a furnace body and a heater. According to the method, an optical fiber preform is inserted from the inlet of the furnace muffle tube, the optical fiber preform is melted by means of a heater, under a specified gas atmosphere, and is drawn toward the outlet of the furnace muffle tube by means of a specified drawing tension. The optical fiber preform and the drawing furnace used in this method both satisfy the condition of below-indicated formula (1):&#x2267;8&#x2003;&#x2003;(1)wherein L indicates the length of the furnace body in the drawing direction and D indicates the diameter of the optical fiber preform. Through this method, even for the case of drawing optical fibers having a large relative index difference between the central core and the cladding, optical fibers wherein residual amounts of lattice defects are sufficiently reduced and degradation of characteristics under a hydrogen atmosphere is sufficiently suppressed can be obtained efficiently and at low cost.

Drawing method of optical fiber and drawing furnace

The present invention relates to an optical fiber comprising a structure enabling WDM transmissions by utilizing the whole wavelength range of 1300 nm to 1625 nm as a signal wavelength band. In the optical fiber according to the present invention, the transmission loss is 0.4 dB/km or less at a wavelength of 1310 nm, 0.4 dB/km or less at a wavelength of 1383 nm, and 0.3 dB/km or less at a wavelength of 1550 nm. The chromatic dispersion is 0.1 ps/nm/km or more but 5.5 ps/nm/km or less at a wavelength of 1383 nm, and 0.1 ps/nm/km or more but 16.5 ps/nm/km or less in the wavelength range of 1530 nm to 1565 nm. The cut off wavelength at a length of 22 m is 1300 nm or less, and the absolute value of dispersion slope in the wavelength range of 1300 nm to 1625 nm is 0.1 ps/nm/km or less.

A furnace for drawing an optical fiber provided with a muffle tube ( ) and inner tubes ( &prime;) connected to the upper end of the core tube, wherein a preform ( ) supported by a dummy rod ( ) at the upper part thereof is disposed inside the muffle tube ( ) and inner tubes ( &prime;) so as to be movable downward together with dummy rod ( ), the preform ( ) is heated and melted by a heater ( ) from the outside of the muffle tube ( ) and an optical fiber ( ) is pulled out from the lower end of the preform ( ); the furnace is further provided with one or a plurality of sets of separating plates ( ) adapted to partition a space in the inner tubes ( &prime;) above the preform ( ) into a plurality of portions in the advance direction of the preform and disposed in the space, and with gas blowing inlets ( ) disposed in the parts of wall surfaces of the inner tubes ( &prime;) which are below the separating plates ( ) and adapted to blow an inert gas into the inner tubes ( &prime;) and the muffle tube ( ), thereby preventing variations in diameter of the optical fiber ( ).

Method of controlling an upper portion of an optical fiber draw furnace

A fiber drawing method according to the present invention is a drawing method of optical fiber for drawing an optical fiber from one end of a fiber preform by softening with heat, wherein the fiber preform is set in a semi-closed space opening in part at a lower end in a fiber drawing furnace, the fiber preform is heated by a heater disposed on the lower end side of this semi-closed space and fiber drawing is carried out with adjusting a quantity of heat dissipation from the upper portion of this semi-closed space.

Optical fiber drawing method and drawing furnace

Optical fiber drawing furnace having adjustable partitions

The present invention provides an optical fiber and the like comprising a structure making it possible to realize optical communications with a higher speed and a larger capacity as compared with conventional optical transmission systems. The optical fiber according to the present invention is an optical fiber in which at least one first portion having a positive chromatic dispersion at a predetermined wavelength within a wavelength band in use and at least one second portion having a negative chromatic dispersion at the predetermined wavelength are arranged adjacent each other along the longitudinal direction thereof. In particular, the optical fiber comprises a polarization coupling structure for inducing coupling between polarization modes of propagating light. This polarization coupling structure randomly causes coupling between polarization modes of the propagating light, whereby polarization mode dispersion decreases at the predetermined wavelength. As a consequence, transmission characteristics are effectively restrained from deteriorating due to polarization mode dispersion. Specifically, the polarization coupling structure is a twist applied to the optical fiber.

Optical fiber, method of making the same, and optical transmission system including the same

There is provided an optical fiber drawing furnace capable of drawing an optical fiber having small non circularity, which drawing furnace includes a muffle tube, in which an optical fiber preform is supplied, a heater surrounding the muffle tube, a plurality of electrode connecting portion extending from the heater, a plurality of electrodes connected to electrode connecting portions, and in conjunction therewith to an electric power source, and unifying means for unifying the temperature distribution along the circumferential direction.

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Yokohama, Japan

Kazuya Kuwahara