JPS63501711A - Optical fiber manufacturing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] optical fiber manufacturing The present invention is suitable for the transmission of optical radiation, i.e. radiation of ultraviolet, visible and infrared wavelengths. Concerning the manufacture of suitable fibers.

Small amounts of impurity dopants, e.g. rare earth ions, in the core and cladding of optical fibers It is advantageous for many reasons to be able to add transition metal ions.

Optical fibers can be fabricated using, for example, neodymium or erbium as impurity dopants. Amplifiers and optical fiber lasers can be manufactured. neodymium fiber An example of a user is described in our co-pending UK application no. 8520301.

For example, the incorporation of terbium ions (Tb3+) into a quartz glass matrix It is well known that this increases the Werde constant of silica glass, and this This is useful for fiber devices and sensors that interact with magnetic fields.

The sold temperature sensor uses a rare earth metal to indicate the temperature of the medium surrounding the fiber. on and transition metal ions, e.g. 3+ The temperature in either the absorption spectrum or fluorescence decay time of Nd or Cr3+ 411I can be made using dependent changes.

For example, adding Nb3+ ions to a silica glass matrix It is known to increase both the effect and the nonlinear optical coefficient of silica glass. It is.

Adding ions, such as cerium, to silica glass increases the transmission through the fiber. It allows the optical signal to carry incident high-energy molecules to form a counter.

In one or both of the core glass or cladding glass of the optical fiber, we Light containing a controllable small amount (<1wt%) of one or more impurity dopant ions A novel manufacturing technique has been devised that allows the fabrication of fibers. The technique is light Starter temperature at temperatures commonly encountered in reactant delivery systems for fiber production. materials, such as rare earth halides, exhibit very low vapor pressures and therefore have a melting point, thus allowing their use where previously they could not be used. This humidity is Typically, P is used in the rotating seal connecting the deposition tube to the reactant delivery system described above. The temperature is limited to approximately 250° C., which is the temperature at which the TFE member begins to deform. Also, we The process is also applicable to liquids with low vapor pressure at low temperatures (<250°C).

Using the above technique, the impurity dopant added into the above glass is they themselves cause the difference in refractive index required in the fiber to guide the be able to. Further, the difference in the above rates is, for example, boron oxide, fluorine, and germania.

Commonly used fiber optic dopants such as phosphorous pentoxide and titania What can be achieved by working together.

The above technique effectively exploits the low loss characteristics of communication blade fibers at other wavelengths. For example, rare earth ions with relatively high absorption in the visible/near infrared region The above technique is unique as it allows the fabrication of long lengths of fiber containing Ru.

According to the invention, a preprocessor for the production of optical fibers incorporating doped glass A method of producing a foam, including depositing a dopant material in a dopant-receiving container. , heating the dopant in the container to vaporize the dopant at a predetermined rate. The raw material gas is passed through about two storage containers to combine the raw material and the dopant. mixing materials, mixing solid components from a mixture of said raw materials and said dopant materials; Depositing a compound and forming a doped glass for the preform comprising successive steps of melting said solid component to A method for manufacturing a preform is provided.

The above method is (i) depositing one or more dopant materials into one or more dopant storage containers; to do, (ii) In order to purify the dopant and in the case of solid dopants. , in a dry atmosphere before fusing the dopant to the walls of the container. heating the container; (iii) Pass the raw material gas through the storage container to combine the raw material and the dopant. to vaporize the dopant at a predetermined rate while mixing with the substance; (iv) heating the dopant in the container; (iv) the raw material and the dopant; depositing a mixture of solid components from a mixture of substances; (V) In order to purify the metal objects each time they are deposited, the deposits are processed under a dry atmosphere. heating the loaded mixture; (vi) melting the solid components to form a deposited glass; (vii) crushing the hollow tube until it becomes a solid rod; (viii) optical fiber delineating the zero point to form a ridge; Preferably including successive steps.

Steps (+) and (ii) above involve installing the tube on a preform manufacturing lathe. This can be accomplished either before or after the tube is mounted on the lathe. can. Steps (iii) and (iv) always include the steps (iii) and (iv) in which the deposition tube is It will be installed and carried out. In steps (V) to (vii), the tube is The fiber drawing process (step (viii) )) can be accomplished either.

The present invention Figure 1 shows a chemical vapor deposition I apparatus used for manufacturing optical fibers. Figure 2 shows the absorption spectrum of a fiber containing 30 ppm Nd"+, Figure 3 shows the fluorescence spectrum of a fiber containing 300 ppm Nd3+, Figure 4(a) shows the local attenuation of a Nd3+ doped single mode fiber. and Figure 4(b) shows the corresponding absorption of the reference fiber, and Figure 5 shows the hydroxyl ion absorption. is an absorption spectrum showing the loss for, and 3+ Figure 6 shows a single core in which both Tb ions and E,3+ ions are doped. shows the absorption spectrum of the mode fiber, It will be explained with reference to the corrected drawings.

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

It has a melting point higher than 250°C, i.e. it becomes solid at temperatures below the melting point of PTFE. ) and should be mixed into the core of the single mode fiber, Allows the use of single starting dopants.

Before deposition, the deposition tube is stationary 1; heated to a dry atmosphere using a heat source, e.g. burner 2; after heating, including gas, for example either chlorine gas or fluorine gas. In the dopant storage container 1, the required dopant is purified by prepared by introducing. This step also includes the above dopants. forming bubbles in the subsequently deposited glass, preventing the particles from flowing downstream in the tube. fusing the dopant material to the walls of the container. Next, the deposition tube 4 is The inside contains fluorine to remove any dopants deposited during the drying process compounds, such as sulfur hexafluoride (SF) or CG 12 F2. Fluorine, which is generated by thermally decomposing halogen-containing carbon compounds, is used. It is then cleaned by vapor phase etching and then a cladding glass 5 is deposited.

During subsequent core deposition, the dopant containing vessel contains the solid impurity dopant. sublimes or occurs typically at 900-1200°C. It is heated to any temperature at which it becomes a liquid with the partial vapor pressure of silver. this produces a small amount of impurity vapor that is carried downstream by the reactant stream, which oxidized in the hot zone 6 formed by other core-forming materials, e.g. ba5i02. At low temperatures (typically <1600°C), the They are deposited so that they do not fuse with each other. Next, the porous glass layer is made of clear, small pores. After being melted to form a thick layer, it is heated in a dry atmosphere. Then it dries even more. The tube is then crushed to form a solid rod. , drawn into fiber.

Other embodiments of the invention include doping, for example neodymium ions Nd3+, in the core region. Manufacture of single-mode optical fiber and multi-mode optical fiber. Ru.

Next, referring to FIGS. 2 through 4, the source of the dopant vapor is hydrated neodymium trichloride. The above deposition step is NdC1.6H0 (99.9% pure, melting point = 758°C). But first, general information.

It was conducted in the same manner as described above. This is done under a chlorine atmosphere. is dried and purified by heating the inside of the tube, and then the tube is hexafluorinated. Cleaning by gas phase etching using fluorine decomposition steam such as sulfur <5F6). Purified. Then, the cladding diameter in the crushed preform is greater than 7:1. Some low loss crund layer was deposited sufficient to provide a core diameter to core diameter ratio.

This is the region of the fiber where there is substantial field penetration by the guided modes. For the entry of OH− ions and other impurity ions from the base tube into It was necessary to prevent losses. Next, the fiber core is The NdCl3 vapor generated in the container is converted to Nd20 in the hot zone. When the dopant containing container is heated as described above so that the dopant is oxidized to Yes, it was deposited without being fused. After that, the core layer is exposed to a chlorine atmosphere. and calcined before crushing the tube into a solid rod.

Absorption measurements on mono-mode and multi-mode fibers It is believed that Jim is mixed into the glass matrix as trivalent Nd3+ ions. (corresponding to dopant levels of Nd3+ from 0.3 to 300 ppm) absorption varying from 30 dB/Km (at 590 nm) to 30.0 OO dB/Km A fiber having an absorption peak is produced. Dopant levels up to 3 oppm Absorbing space for a 500 m length of neodymium doped fiber with The vector is shown in FIG. 2(a). Visible range up to 3000dB/km and very high absorption levels in the near-infrared region can be clearly seen. . Despite this high loss, 950nm and 135nm less than 2dB/km There is a low loss window between 0 nm and the shape observed in conventional fibers. It should be noted that the current situation is not very different from that of the previous model. 1390n The low OH-absorption peak at demonstrates the success of the technique used to dry the compound.

The fluorescence spectrum of Nd3+ doped fiber up to 3ooppm is 94 Obvious fluorescent bands with peak wavelengths of 0nm, 11080n, and 1370nm It is shown in FIG. 3 where it can be clearly seen. high silica host glass As a result, the above bands are made of compound glass used for conventional lasers. wavelengths are shifted to slightly longer wavelengths than the corresponding bands in the spectrum. 590nm The 1/e fluorescence field measurements used are 940nm transition and 1081080n! transfer Moving up and down the wavelength gives a figure of 450 μs for both. In addition, the fiber The dopant concentration along the length of the fiber using the 0TDR technique is It was determined by measuring the local attenuation along the length. Achieves manageable attenuation To achieve this, the source wavelength of 620 nm lies above the tail of the 590 nm absorption band. selected so that The results are shown in Figure 4, where the length of the fiber It shows good uniformity of dopant incorporation along and therefore a high degree of This shows the control of

In another embodiment of the above technique, we add Nd3+ ions to the core region. A highly birefringent single polarizing fiber was fabricated containing: These are patent application No. 8 As stated in No. Known gas phase etchants for producing "Bow-Tie" fibers Due to the incorporation of impurity dopants into the fiber core, It was obtained by combining the techniques used. More than 200 ppm Nd Fibers with beat lengths as short as 2 mm combined with dopant levels of 3+ was obtained using this method.

In other embodiments, we provide Er3+ at depths up to 0.25 wt% Er3+. Generates mono-mode and multi-mode fibers containing ions. There is. This is a mono mode doped with up to 2 ppm Er3+ in the core region. - It will be explained with reference to FIG. 5, which shows the absorption spectrum of the fiber.

As mentioned for the Nd3+ doped fiber, the hydrated trisalt Erbium chloride ErC161-103'2 (99,9% pure, melting point = 744°C), the fiber is manufactured with It was done. The remainder of the manufacturing process is performed in the resulting fiber drawn from the preform. , very little low loss, such that the ratio of cladding diameter to core diameter is up to 2=1 Similar to that described above, except that a cladding layer is deposited. death Therefore, as seen in Figure 5, the expected OH- absorption at 1390 nm A slightly restricted field to the fiber core gives a higher loss than the There was penetration of the basal canal by. Fibers containing up to 0.25 wt% Er3+ are between 1 μm and 1.3 μm, despite the absorption band peak being greater than 50 dB/m. manufactured using this technique, giving a loss of less than 40 dB/km in the region of was created.

Yet another embodiment is doped with Erbium Er34- ions in the core region. terbium ion Tb3+. This is trichloride A mixture of terbium and erbium trichloride is used to accommodate the dopant prior to the start of deposition. It is manufactured as described above, except that it is placed in a container. Purif The fiber drawn from the foam has absorptions at 518 nm and 970 nm of l Although this is due to the presence of Er3+ ions, there is a large absorption spectrum at 486 nm. The broad absorption centered at 725 nm indicates the presence of Tb3+ ions. Therefore, the absorption characteristics as shown in FIG. 6 were exhibited. This is because many impurity ions This shows the possibility of co-doping the deposited glass with ions.

The above method can also be used to incorporate other rare earth and transition metals into optical fibers. can be done.

Techniques such as those described above are used in so-called modified chemical vapor deposition (MC). All @ types that can be manufactured by VD), i.e. m single mode fiber (ii) Multimode fiber (i i i) High birefringence single polarizing fiber (iv) Cyclic birefringence (helical type core) fiber (V) multi-core fiber (vi) “Ring core” fiber It should be understood that this can be applied to

Fukumaruhanihigashi 1, 6th Fuiba murmured the work ♂ “allEp” ado 7” and translated the amendment. Document submission (Article 184-3, Paragraph 1 of the Patent Act) February 12, 1986

Claims (11)

[Claims] 1. Manufacture of preforms for the production of optical fibers incorporating doped glass depositing a dopant material in a dopant containing container; heating the dopant to vaporize said dopant at a predetermined rate; The raw material gas is passed through the storage container to mix the raw material and the dopant material. and depositing a mixture of solid components from the mixture of the raw material and the dopant material. and to form a doped glass for the preform. dove, characterized in that it comprises successive steps of melting solid components; A method for producing preform for the production of optical fiber that incorporates glass. 2. The method leaves a dry atmosphere in the dopant container and at the same time Claims further comprising a step for heating the dopant storage container. A method for producing a preform according to paragraph 1. 3. The method includes fusing a solid dopant to the wall of the dopant storage container. The manufacturing of a preform according to claim 1, characterized in that it comprises the step of: Construction method. 4. The dopant is characterized in that it contains a rare earth or transition metal element. A method for producing a preform according to claim 3. 5. Claim 4, wherein the rare earth element is neodymium. A method of manufacturing briform according to Section. 6. Claim No. 1, characterized in that the rare earth element is erbium. A method for producing a preform according to Section 4. 7. Claim No. 1, characterized in that the rare element is terbium. A method for producing a preform according to Section 4. 8. Claims characterized in that the dopant includes a plurality of impurity ions. A method for producing a preform according to any one of Items 1 to 3. 9. The dopants of the claim include terbium and erbium. A method of manufacturing a preform according to scope 8. 10. An optical fiber made according to any one of claims 1 to 9. BRIFORM FOR MANUFACTURING. 11. An optical fiber drawn from a preform according to claim 10.