JP2006163194A - Optical fiber, manufacturing method thereof and resin for covering optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber which easily diffuses and penetrates deuterium into the optical fiber at a low cost and has a high hydrogen-proof performance, and also to provide a manufacturing method of the optical fiber, and a resin used for covering the optical fiber. <P>SOLUTION: The optical fiber is covered with the resin which releases deuterium. As such a resin, the resin in which deuterium is dissolved is cited. By force-feeding resin with a gas including deuterium, deuterium may be also dissolved into the resin. As the gas including deuterium, pure deuterium, mixture gas between deuterium and nitrogen or the like is cited. In such a case, the resin in which deuterium is preliminarily dissolved may be also used. Further, the optical fiber is doubly covered with resin and is set so that the secondary cover on the outer side has a lower diffusion coefficient than the primary cover on the inner side. As the secondary cover, the resin or metal which initially does not include deuterium may be used. A chemical reaction may be caused by ultraviolet irradiation etc. so that deuterium is released from the resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber having high hydrogen resistance, and more particularly to an optical fiber in which deuterium is diffused and penetrated, a manufacturing method thereof, and an optical fiber coating resin.

  Currently, communication optical fibers that are widely used are manufactured by drawing a rod-shaped glass rod called a preform by heating and melting at a high temperature. The preform is made of quartz glass, to which germanium or fluorine is added.

  The optical fiber manufacturing process is shown in FIG. The drawing of the optical fiber is performed by heating the preform 1 to about 1900 to 2300 ° C. in the heating furnace 2 to be softened and drawing it with the lower capstan 3. The obtained optical fiber 4 is wound up by a winding device (not shown).

  The drawn optical fiber 4 is coated with a resin to maintain its strength. Usually, the resin coating is performed by passing the optical fiber through the primary coating die 5 and the secondary coating die 6, and the surface is coated with the primary resin coating and the secondary resin coating with an ultraviolet curable resin. These resins are cured by the ultraviolet irradiation devices 7 and 8. The primary coating resin and the secondary coating resin are pressurized with pressurized gas supplied from the pressurization ports 11 and 12 of the primary and secondary coating resin tanks 9 and 10, respectively. Are respectively supplied to the primary coating die 5 and the secondary coating die 6 and applied to the optical fiber. Usually, air, nitrogen, or the like is used as the pressurized gas.

  In general, there are defects in an optical fiber that easily react with hydrogen. When hydrogen diffuses into the optical fiber glass, the hydrogen reacts with defects in the glass to form OH groups, increasing the OH absorption loss observed near the wavelength of 1385 nm.

  As countermeasures, attempts have been made to improve the hydrogen resistance of optical fibers. For example, Patent Documents 1 and 2 propose a method of exposing a drawn optical fiber to deuterium. In this method, by exposing the optical fiber to deuterium, OD groups are generated by reacting deuterium with defects in advance, so that even if hydrogen diffuses after OD groups are generated, Since the defect has already been converted to OD group by deuterium, no new OH group is generated. Since the generated OD group exhibits an absorption loss at a wavelength different from that of the OH group, the optical loss generally observed in the vicinity of 1300 to 1600 nm, which is a wavelength band used for optical communication, hardly changes.

GB2,149,392 Japanese Unexamined Patent Publication No. 2000-148450

However, the methods according to Patent Documents 1 and 2 require a long period of 3 to 10 days to react deuterium and defects, and also require a special processing vessel for this purpose, resulting in high costs. It was.
The present invention has been made in view of the above circumstances, and can easily and inexpensively diffuse and infiltrate deuterium into an optical fiber, and has a high hydrogen resistance property, a manufacturing method thereof, and an optical fiber coating resin. The purpose is to provide.

According to the optical fiber and the manufacturing method thereof of the present invention, the optical fiber is covered with a resin that releases deuterium. Examples of such a resin include a resin in which deuterium is dissolved.
Deuterium can be dissolved in the resin by pumping the resin with a gas containing deuterium. Examples of the gas containing deuterium include pure deuterium or a mixed gas of deuterium and nitrogen. In this case, a resin in which deuterium is dissolved in advance can also be used.
It is also possible to set the optical fiber so that the diffusion coefficient of deuterium is lower in the outer secondary coating than in the inner primary coating. Note that a resin or metal that does not initially contain deuterium may be used for the secondary coating. When using a metal, it is preferable to use a low melting point metal that melts at a temperature lower than the heat resistance temperature of the primary coating. The reason for using metal is that it is generally harder for gas to permeate than resin, and the metal barrier layer reduces the rate at which deuterium released from the primary coating diffuses and disappears, making deuterium efficient. This is because it can reach the core well.
Furthermore, a deuterium can be released from the resin by causing a chemical reaction by ultraviolet irradiation or the like.

  The resin for coating an optical fiber of the present invention is a resin used for coating an optical fiber, and is characterized by releasing deuterium by causing a chemical reaction. This chemical reaction can be induced by ultraviolet irradiation.

  According to the optical fiber and the manufacturing method thereof of the present invention, deuterium can be diffused and penetrated into the optical fiber without passing through the step of exposing the optical fiber to deuterium gas, and the hydrogen resistance property is easy and low cost. An excellent optical fiber can be obtained.

  The optical fiber and the manufacturing method thereof according to the present invention are characterized in that the optical fiber is coated with a resin that releases deuterium. This can be accomplished by coating the optical fiber with a resin in which deuterium is dissolved, or by coating the optical fiber with a resin that releases deuterium during the curing process by a chemical reaction induced by ultraviolet irradiation or the like. Can be mentioned.

  For this reason, deuterium diffuses and penetrates into the optical fiber glass and reacts with defects in the glass without exposing the optical fiber to deuterium using a special processing vessel in the subsequent process. Generate a group. As a result, even if the optical fiber is exposed to hydrogen later, the optical fiber has excellent hydrogen resistance without increasing OH absorption loss.

In order to make the optical fiber coating resin contain deuterium, the deuterium is dissolved in the resin by pumping the resin with a gas containing deuterium, for example, pure deuterium or a mixed gas of deuterium and nitrogen. be able to.
When the gas to be pumped is pure deuterium, the solubility of deuterium in the resin is increased. When a mixed gas of deuterium and nitrogen is used, the concentration of deuterium in the mixed gas depends on the solubility of deuterium in the resin, the diffusion coefficient of deuterium in the resin, the thickness of the coating resin, and the defects in the optical fiber. It is necessary to set in consideration of various factors such as concentration. When the production conditions are constant, the required deuterium concentration is almost constant, so replacing part of the deuterium with nitrogen can reduce the consumption of expensive deuterium, and in terms of cost preferable.

  When the resin is pumped with a gas containing deuterium, a resin containing deuterium in advance can also be used. For example, by supplying a gas containing deuterium from at least one of the pressure ports 11 and 12 in FIG. 1, deuterium can be dissolved in the resin being pumped. By dissolving deuterium in advance before pumping in this way, a sufficient amount of deuterium can be contained in the resin from the beginning of the drawing.

  In the optical fiber of the present invention, the resin is coated twice on the optical fiber, and the material is selected so that the deuterium diffusion coefficient of the outer secondary coating is lower than the inner primary coating, More deuterium can be diffused and penetrated into the optical fiber glass, and the total amount of deuterium used can be reduced. Further, when the diffusion coefficient of deuterium in the secondary coating is sufficiently low, a resin that does not contain initial deuterium in the secondary coating can also be used. In this case, even if the secondary coating resin does not release deuterium, the hydrogen resistance characteristics can be sufficiently improved.

  The optical fiber obtained by the present invention depends on processing conditions such as the type of resin used and the concentration of deuterium, but after drawing, deuterium diffuses and penetrates into the optical fiber glass in about 1 to 10 days. Since it reacts with defects in the glass to generate OD groups, even if hydrogen diffuses later, OH groups are not generated, and optical loss does not increase in the wavelength band of 1300 to 1600 nm.

  In the methods described in Patent Documents 1 and 2, the optical fiber cannot be shipped or processed into a cable while deuterium is diffused by placing the optical fiber in the processing container. Then, it can be used as it is for the next process such as shipping and cable processing, and during that time, deuterium diffusion proceeds into the optical fiber glass. For this reason, it is possible to manufacture an optical fiber excellent in hydrogen resistance property at low cost without installing special equipment for deuterium treatment or taking time for the treatment.

Example 1
Using the apparatus shown in FIG. 1, the preform 1 was heated and melted to 2270 ° C. in a heating furnace 2 and drawn at a drawing speed of 1200 m / min to produce an optical fiber.
For the primary and secondary coatings, UV curable resins are used, and these resins are pre-pressurized with 100% deuterium at 0.2 MPa for 24 hours to dissolve deuterium. Using. The primary coating resin and the secondary coating resin in the resin tanks 9 and 10 are pumped to the dies 5 and 6 with 100% deuterium supplied from the pressurization ports 11 and 12, respectively, applied to the optical fiber, and irradiated with ultraviolet rays. Cured while passing through apparatus 7,8. The optical fiber 4 was taken up by the capstan 3 and taken up by a bobbin by a take-up device (not shown).

(Example 2)
Preform 1 was heated and melted to 2270 ° C. in heating furnace 2 and drawn at a drawing speed of 1200 m / min to produce an optical fiber. An ultraviolet curable resin was used as the resin for the primary coating and the secondary coating. These resins were pressurized in advance at 0.2 MPa for 24 hours using a mixed gas composed of 3% deuterium and 97% nitrogen to previously dissolve deuterium. The primary coating resin and the secondary coating resin in the resin tanks 9 and 10 are respectively fed to the dies 5 and 6 by the air supplied from the pressure ports 11 and 12 and applied to the optical fiber, and the ultraviolet irradiation devices 7 and 8 are applied. Cured with. The obtained optical fiber was designated as Sample B.

(Comparative Example 1)
Preform 1 was heated and melted to 2270 ° C. in heating furnace 2 and drawn at a drawing speed of 1200 m / min to produce an optical fiber. Although UV curable resin was used as the resin for the primary coating and the secondary coating, deuterium was not previously dissolved in these resins. The primary coating resin and the secondary coating resin in the resin tanks 9 and 10 are respectively fed to the dies 5 and 6 by the air supplied from the pressure ports 11 and 12 and applied to the optical fiber, and the ultraviolet irradiation devices 7 and 8 are applied. Cured with. The obtained optical fiber was designated as Sample C.

Samples A, B, and C were all left at room temperature for 4 days after drawing. Then, it exposed to the atmospheric pressure hydrogen containing atmosphere which consists of 1% hydrogen and 99% nitrogen for 4 days in an airtight container. Before and after hydrogen exposure, optical signal transmission loss at a wavelength of 1393 nm was measured using the cutback method. The transmission loss at 1393 nm before hydrogen exposure was 0.28 dB / km for all of Samples A, B, and C. The transmission loss at 1393 nm after exposure to hydrogen was 0.28 dB / km for samples A and B, but no change was observed, but the transmission loss of sample C increased to 0.35 dB / km.
In all samples, after hydrogen exposure, the transmission loss at 1240 nm, which indicates the vibrational absorption of hydrogen molecules, increased, and it was confirmed that hydrogen had sufficiently reached the inside of the glass.

  According to the present invention, it is possible to supply an optical fiber that is low in cost and excellent in hydrogen resistance.

It is a schematic sectional drawing explaining the drawing process of an optical fiber.

Explanation of symbols

1 ...... Preform,
2 …… Heating furnace,
3 …… Capstan,
4 ... optical fiber,
5 …… Primary coating die,
6 …… Secondary coating dies,
7, 8 ...... UV irradiation device,
9: Resin tank for primary coating,
10 …… Resin tank for secondary coating,
11, 12 …… Pressurizing port,
13, 14 …… Piping.

Claims (24)

An optical fiber which is coated with a resin that releases deuterium. The optical fiber according to claim 1, wherein the resin is a resin in which deuterium is dissolved. The optical fiber according to claim 1 or 2, wherein deuterium is dissolved in the resin by pumping the resin with a gas containing deuterium. The optical fiber according to claim 3, wherein the gas containing deuterium is pure deuterium. The optical fiber according to claim 3, wherein the gas containing deuterium is a mixed gas of deuterium and nitrogen. The optical fiber according to claim 1, wherein deuterium is dissolved in the resin in advance. The optical fiber according to any one of claims 1 to 6, wherein the resin is doubly coated, and the outer secondary coating is set to have a lower deuterium diffusion coefficient than the inner primary coating. . The optical fiber according to claim 7, wherein the secondary coating is initially coated with a material not containing deuterium. The optical fiber according to any one of claims 1 to 6, wherein a primary coating made of resin is provided on the inner side, and a secondary coating is provided on the outer side with a metal to coat the optical fiber doubly. The optical fiber according to claim 1 or 2, wherein deuterium is released from the resin by causing a chemical reaction. The optical fiber according to claim 10, wherein the chemical reaction is induced by ultraviolet irradiation. An optical fiber manufacturing method comprising coating an optical fiber with a resin that releases deuterium. The optical fiber manufacturing method according to claim 12, wherein the resin dissolves deuterium. The method of manufacturing an optical fiber according to claim 12 or 13, wherein the resin is pumped with a gas containing deuterium to dissolve the deuterium in the resin. The method for producing an optical fiber according to claim 14, wherein the gas containing deuterium is pure deuterium. The method for producing an optical fiber according to claim 14, wherein the gas containing deuterium is a mixed gas of deuterium and nitrogen. The method for producing an optical fiber according to claim 12, wherein deuterium is previously dissolved in the resin. 13. A resin in which deuterium is dissolved in an optical fiber is coated twice, and an outer secondary coating is set to have a lower deuterium diffusion coefficient than an inner primary coating. 18. A method for manufacturing an optical fiber according to any one of items 17 to 17. The optical fiber manufacturing method according to claim 18, wherein the secondary coating is initially coated with a material not containing deuterium. 18. The method of manufacturing an optical fiber according to claim 12, wherein the optical fiber is doubly coated by providing a primary coating with a resin on the inner side and a secondary coating with a metal on the outer side. The method of manufacturing an optical fiber according to claim 12 or 13, wherein the optical fiber is coated with a resin that releases deuterium by causing a chemical reaction. The method for producing an optical fiber according to claim 21, wherein the chemical reaction is induced by ultraviolet irradiation. A resin for coating optical fibers, which is a resin used for coating optical fibers and releases deuterium by causing a chemical reaction. The optical fiber coating resin according to claim 23, wherein the chemical reaction is induced by ultraviolet irradiation.

Images