JPS6045207A - Method for connecting optical fiber - Google Patents

Abstract

PURPOSE:To connect easily optical fibers without requiring the selection of the working site by using an oxyhydrogen flame contg. a halogen compound. CONSTITUTION:Gaseous O2 and gaseous SF6 are fed to an oxyhydrogen burner having a double-tubed structure. Gaseous H2 is fed to the outer tube, the tip of the burner and optical fibers are set at 2mm. interval to preheat the fibers, and the fibers are melted and connected with the gaseous O2 and gaseous SF2. After the connection, surface hydroxyl groups are removed from the connected part and its vicinities by surface treatment. This surface treatment is carried out at a low temp. so as to prevent the corrosion of the surface of the connected fiber with HF produced in the oxyhydrogen flame. The exposed part of the resulting optical fiber including the connected part is coated with epoxy resin which is the coating material of the original optical fibers, and the resin is crosslinked with ultraviolet rays to reinforce the optical fiber. In this method, a gaseous or liq. halogen compound having a hydroxyl group removing effect and high stability at ordinary temp. is added to an oxyhydrogen flame in place of conventional gaseous chlorine having the same effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber splicing method that allows optical fibers to be fused and spliced in good condition using an oxyhydrogen flame without being limited to a work area.

In general, methods using arc discharge and oxyhydrogen flame are known as methods for permanently connecting optical fibers, but if you want to obtain a high-strength connection, add chlorine gas to the oxyhydrogen flame. This method of fusion bonding is considered to be better.

However, since optical fibers can be installed in a variety of locations, the work of connecting optical fibers must be carried out without limiting the work location. To do this, you will need to prepare a chlorine gas cylinder and carry it with you. However, since this chlorine gas is a toxic gas, there are various restrictions and dangers involved in handling the cylinder.Therefore, a method of adding chlorine gas to an oxyhydrogen flame to create a high-strength connection of optical fibers has been implemented. making it difficult.

This invention was made in view of the above circumstances, and its purpose is to provide an optical fiber splicing method that can easily connect optical fibers with high strength using an oxyhydrogen flame without limiting the work area. In particular, gaseous or liquid halogen compounds, which are stable at room temperature and generate halogen gases such as chlorine and fluorine when decomposed in an oxyhydrogen flame, can be used in various ways in place of chlorine gas. This eliminates the need to use chlorine cylinders, which have the above limitations and risks.

The basis of this invention is that, first, chlorine gas, which has the effect of dehydrating and removing hydroxyl groups that adhere to the surface of glass fibers and cause surface scratches, can be converted into chlorine gas in an oxyhydrogen flame. The second reason is that it is not necessary to use a single chlorine gas from the beginning, and the second reason is that other halogens such as fluorine can be used instead of chlorine as a substance that dehydrates and removes hydroxyl groups on the glass surface.

Therefore, in this invention, a gaseous or liquid halogen compound that is stable at room temperature and decomposes in an oxyhydrogen flame to generate halogen gas is added to an oxyhydrogen flame to melt and connect glass fibers. As the above halogen compound,
CF4, SF4, and N are gaseous at room temperature and extremely stable.
There are fluorine compounds such as Fs, and chlorine compounds such as CCe4 and CHzCet, which are liquid at room temperature and stable. In addition, when the halogen compound is liquid, hydrogen gas,
Alternatively, oxygen gas may be used as a carrier gas and contained therein.

The above fluorine compound is decomposed in an oxyhydrogen flame to produce fluorine [F].
] gas or HF gas, and dehydrates and removes the hydroxyl groups attached to the surface of the glass fiber. This hydroxyl group removal reaction using fluorine ions is completely carried out at about 800°C. In addition, the hydroxyl group removal reaction with chlorine gas is 700
The reaction is completely carried out at 950°C to 550°C, and the removal reaction of CCl4 alone is carried out at 550°C to 6 Q O'C.

The fusion splicing of optical fibers according to the method of this invention can easily provide high-strength splicing by following the following steps.

(i) A pretreatment for removing hydroxyl groups is performed by spraying an oxyhydrogen flame containing halogen gas onto the read-out portion of each optical fiber and its nearby surface before connection.

(11) Next, each optical fiber is fused and spliced using an oxyhydrogen flame or an oxyhydrogen flame containing a small amount of halogen gas.

(iii) After the connection is completed, oxyhydrogen flame containing halogen gas is sprayed onto the fusion spliced portion of the optical fiber to remove hydroxyl groups that cause surface scratches from the fiber surface.

As described above, the method of the present invention can exhibit similar effects in place of chlorine gas, which has the effect of removing hydroxyl groups, and is added to an oxyhydrogen flame to make high-strength connections of optical fibers. A gaseous or liquid halogen compound that is highly stable at room temperature is added to an oxyhydrogen flame, and the resulting flame is used to weld and re-read optical fibers, so it can be used in various ways in optical fiber splicing work. This eliminates the need to use a chlorine gas cylinder, which has many restrictions and dangers, and allows the above-mentioned connection work to be easily carried out without being limited by the work location.

Next, the present invention will be explained in more detail with reference to Examples.

[Example 1] Two single mode fibers each having an outer diameter of 125 μm and a core diameter of 8 μm were fixed by a V-groove. The double g-structure hydrogen oxide burner used for fusion splicing these optical fibers has an inner tube with an inner diameter of 0.7 mm and an outer diameter of 1.5 mm, and an outer tube with an inner diameter of 2.0 mm and an outer diameter of 3.0 mm. I used something.

First, 1g of the above 202 gas 200CC/9. S
Fa'i gas was flowed at 10 cc/min, H2 gas was flowed at 35 Q:c/min into the outer tube, the distance between the tip of the burner and the optical fiber was maintained at 2 mm, and the tube was preheated for 20 seconds.

Next, the above optical fibers are butted together, and the inner tube is
Crush 25Q: c/min to 5F6-X gas 1c (/min) was flowed, H2 gas was flowed through the outer tube at 40 oCc/min, and the optical fibers were fused and spliced.Heating time at this time was 25 seconds. Ta.

Next, hydroxyl groups on the surface of the fusion spliced part of the optical fiber after splicing and its vicinity were removed from the inner tube using O gas at 150 cc/min.
SF6. ;Gas if): flow c/min, H2 into the above outer tube
It was removed by flowing 300 CC/min of gas.

The surface treatment after this fusion splicing is performed using H
It is important to carry out the process at the lowest possible temperature so that the fiber surface is not eroded by F. This operation was performed for 20 seconds.

Finally, the same plastic boxy resin as the coating material for the optical fiber was applied to the exposed area around the fusion spliced portion of the obtained optical fiber, and this was crosslinked with ultraviolet rays to reinforce the fiber.

The strength of the fusion spliced parts of the optical fibers obtained in this way was 5.41 (rm) on average for 30 fibers, the lowest of which was 31ψ/m. The connection loss was not much different from that of the normal arc method.

[Example 2] First, the tip of a single mode fiber with an outer diameter of 125 μm, a core diameter of 8 μm, and a silicone coat diameter of 420 μm (
The silicone layer on the connecting part) was removed.

Thereafter, the organic matter adhering to the exposed surface of the exposed portion was removed using the same oxyhydrogen flame burner as in Example 1.
02 gas 200cc/min, CF, gas 20cc/min, H
The gas was removed by applying a flame at a flow rate of 200 cc/min for 60 seconds to keep the temperature as low as possible.

Next, 02 gas 25 Dcc 1 minute, CF was added to the burner.

The optical fibers were fused and spliced by flowing gas at 1 cc/min and Hl gas at 400 Cc/min. The heating time at this time was 15 seconds.

Next, 150 cc/min of 0□ gas, 10 cc/min of SFa gas, and 300 cc/min of H2 gas were flowed through the burner to remove hydroxyl groups on the surface of the fusion spliced portion of the optical fiber and its vicinity for 20 seconds.

Finally, the same silicone resin as the coating material of this optical fiber was applied and baked on the exposed portion around the fusion spliced portion to reinforce the fiber.

The strength of the fusion spliced portion of the optical fiber obtained by such G straining was 4.8 kg7 m on average for 20 fibers.
Among these, the lowest was 3.2 kg/m.

Applicant Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] In a method of melt splicing optical fibers using an oxyhydrogen flame, a room temperature-stable gaseous or liquid halogen compound that decomposes in the oxyhydrogen flame to generate halogen gas is added to the oxyhydrogen flame, thereby splicing optical fibers. An optical fiber splicing method characterized by performing fiber fusion splicing.