JP3027149B1 - Optical fiber preform refractive index distribution measuring device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To measure the refractive index distribution of an optical fiber preform equipped with a device for quickly, simply and safely removing oil adhering to an optical fiber preform whose refractive index distribution has been measured by immersion in a matching oil in a cell. Provide equipment. SOLUTION: The refractive index distribution measuring device of the present invention comprises: a light irradiating section for injecting a laser beam into an optical fiber preform; a cell filled with matching oil and immersing the optical fiber preform therein; It comprises a light detection unit for measuring the angle of refraction of the refracted light, and a matching oil removing device disposed immediately above the cell. The matching oil removing device is a member provided on the inner peripheral surface of the annular member 11. At 12, the matching oil adhering to the outer peripheral surface of the optical fiber preform 1 passing through the annular member 11 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refractive index distribution measuring device used for measuring the refractive index distribution of an ingot in an optical fiber manufacturing process.

[0002]

2. Description of the Related Art In an optical fiber manufacturing process, first, a VAD
An ingot is produced by dehydrating and sintering soot manufactured by the method (gas phase shafting method).
Since this ingot has a large outer diameter of 120 to 180 mm, it is difficult to draw the optical fiber with the drawing apparatus as it is. Therefore, the ingot is primarily drawn into a preform having an outer diameter of 40 to 100 mm by a drawing device, and the preform is drawn to produce an optical fiber.

Whether the optical transmission characteristics required for the optical fiber satisfies the target characteristics, or whether adjustment before drawing such as cladding thickness adjustment is necessary to satisfy the target characteristics. Is determined in advance at the stage of the optical fiber preform.

Conventionally, the refractive index distribution of an optical fiber preform has been measured at the stage of a primary stretched preform. Recently, however, since the outside diameter can be controlled precisely by a stretching device, the ingot of an ingot is measured. It is being done in stages. The refractive index distribution measurement of the optical fiber preform is performed by immersing the optical fiber preform in a cell filled with a matching oil having a refractive index substantially matching the refractive index, irradiating the optical fiber preform with laser light, The light refracted inside the optical fiber preform is received by the light detection unit, and the angle is measured.

[0005]

The optical fiber preform whose refractive index distribution has been measured is an ingot, which is taken out of the cell and sent to the next step of primary stretching. Matching oil is attached to the surface of the base material, and this oil drips during transportation to the next process, contaminating the floor, and evaporates or burns when heated in the primary stretching or drawing process. Thus, the inside and surroundings of the furnace are contaminated, and there are problems such as generation of offensive odor.

Conventionally, in order to remove the matching oil adhering to the optical fiber preform, a work of wiping with a waste cloth is generally performed. However, when the optical fiber preform is an ingot, this work includes a dummy portion. Since the length of the ingot was 2.5 m or more and the weight exceeded 50 kg, there was a problem in safety. Another way to remove the matching oil is to hold the optical fiber preform suspended and wait for the oil to drip, which is the safest and easiest way to remove the matching oil. In order to sufficiently remove the oil, it was necessary to leave the oil for a long time of 50 to 80 minutes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an apparatus for quickly, simply, and safely removing a matching oil adhering to an optical fiber preform whose refractive index distribution has been measured. It is an object of the present invention to provide an apparatus for measuring a refractive index distribution of an optical fiber preform.

[0008]

The apparatus for measuring the refractive index distribution of an optical fiber preform according to the present invention has a technical feature in that the apparatus has a matching oil removing device. A light irradiator that irradiates laser light into the optical fiber preform, a cell that is filled with oil and immerses the optical fiber preform inside, and a light detector that measures the refraction angle of light refracted inside the optical fiber preform And a matching oil removing device arranged above the cell.

Further, the matching oil removing device is
The optical fiber preform pulled up from the cell is made of an annular member, and is passed through the inner hole of the annular member to remove the matching oil attached to the outer peripheral surface of the optical fiber preform, and the removed oil is returned to the cell. is there. The optical fiber preform, especially in the state of the ingot, needs to remove the matching oil along the surface shape of the ingot because there are periodic irregularities on the surface and portions where the outer diameter changes in the longitudinal direction. is there.

For this reason, in the matching oil removing device according to the present invention, a brush extending toward the center is implanted on the inner peripheral surface of the annular member. A configuration in which a nozzle is formed,
A configuration in which a plate-like rubber material extending toward the center is attached to the inner peripheral surface of the annular member, or a cloth material extending from the inner peripheral surface of the annular member toward the center, and provided near the tip of the cloth material It is preferable to use a ring-shaped rubber or a ring-shaped spring material.

The above-mentioned plate-like rubber material or cloth material provided on the inner peripheral surface of the annular member and extending toward the center is made to penetrate the optical fiber preform in contact with the front end thereof, and is divided into a plurality of sectors. The side edges may be formed so as to be in close contact with each other, or a single rubber material or cloth material may be formed so as to have a hole at the center for inserting the optical fiber preform. Also,
In the matching oil removing device according to the present invention, the shape of the outer periphery of the annular member may be any shape such as a circle, an ellipse, and a square.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In the following description, an example in which an ingot is used as an optical fiber preform as an object to be measured will be described. However, it is needless to say that the present invention can also be used when the optical fiber preform is a preform. FIG.
FIG. 2 is a front view of a pulling device to which the optical fiber preform refractive index distribution measuring device of the present invention is attached, and FIG. 2 is a main part of an optical measuring unit in the optical fiber preform refractive index distribution measuring device of the present invention. FIG. FIGS. 3 to 6 are perspective views of a main part showing a specific modification of the matching oil removing device in the optical fiber preform refractive index distribution measuring device of the present invention.

In the pulling device shown in FIG.
Is driven up and down while being supported by the suspending unit 2, and
Is immersed in the matching oil 3 filled therein. An optical measuring unit 5 is attached to the side of the cell 4, and a matching oil removing device 10 is installed above the cell 4. The matching oil 3 has a refractive index substantially matching the refractive index of the optical fiber preform.

As shown in FIG. 2, on one side of the cell 4 there is a light irradiator 7 for emitting a laser beam 6 for measuring the refractive index distribution. A transparent cell window 8, 8 'is provided on one side and the opposite side, and a laser transmitted through the ingot 1 via the cell windows 8, 8' and the matching oil 3 is provided on the other side. A light detection unit 9 that receives the light 6 is provided.

From the angle data of the laser beam 6 received by the light detecting section 9, the refractive index distribution of the ingot 1 is determined,
From the results, the optical characteristics of the manufactured optical fiber are estimated. Judge whether the adjustment of the clad thickness is necessary using the estimation result, and when it is judged that the clad thickness adjustment is necessary, including the shaving allowance for removing the outer peripheral portion, it is stretched to the preform. The stretching diameter is calculated and set in the stretching apparatus in the next step.

Immediately above the cell 4, a matching oil removing device 10 is provided as shown in FIG. When the ingot 1 is passed through the inner hole of the annular member 11, the matching oil removing device 10 makes the wiping member provided on the peripheral surface of the inner hole contact the peripheral surface of the ingot 1,
By blowing gas such as compressed air to the ingot 1,
The matching oil adhering to the surface of the ingot 1 is removed and dropped into the cell 4.

3 to 6 show modifications of the matching oil removing device 10. The matching oil removing device 10 shown in FIG. 3 has a brush 12 extending to the center on the inner peripheral surface of the annular member 11. When the ingot 1 passes through the inner hole of the annular member 11, the brush 12
The matching oil adhering to the outer peripheral surface of the optical fiber preform 1 is scraped downward at the tip of the optical fiber preform 1. In the matching oil removing device shown in FIG. 4, a plurality of gas ejection nozzles 13 are formed on the inner peripheral surface of the annular member 11. The matching oil attached to the outer peripheral surface of the base material 1 is blown off and falls.

The matching oil removing device shown in FIG. 5 has a structure in which a plurality of elastic fan-shaped plate-like rubber members 21 extending toward the center are closely attached to the inner peripheral surface of the annular member 11. The tip side of the plate-like rubber material 21 comes into contact with the outer peripheral surface of the optical fiber preform 1 so that the matching oil adhering to the surface of the optical fiber preform drops.

In the matching oil removing device shown in FIG. 6, a plurality of fan-shaped cloth materials 22 extending toward the center are provided on the inner peripheral surface of the annular member 11 in close contact with each other. A ring-shaped rubber or a ring-shaped spring material 23 is attached so that the fiber 22 is in a stretched state, and the tip side of the cloth material 22 comes into contact with the outer peripheral surface of the optical fiber preform 1, and Matching oil adhering to the surface falls down.

As shown in FIG. 1, the refractive index distribution measuring apparatus of the present invention suspends an ingot 1 whose refractive index distribution is to be measured from a suspending unit 2 and moves the suspending unit 2 downward to move the ingot 1 down. Is allowed to stand still in the cell 4 and the light irradiation unit 7 and the light detection unit 9 are scanned in the vertical direction (horizontal direction) in FIG. 2 while the laser light 6 from the light irradiation unit 7 is detected by the light detection unit 9. By moving the suspension unit 2 shown in FIG. 1 up and down, the refractive index distribution is measured at an arbitrary position in the vertical direction of the ingot.

After the measurement is completed, the hanging unit 2 is moved upward, whereby the ingot 1 is pulled up from the cell 4 through the matching oil removing device 10, and at the same time, the matching oil on the surface is removed. . The removed matching oil is returned to the lower cell 4.

[0022]

EXAMPLES [Examples] The refractive index distribution of an ingot was measured using the pulling apparatus shown in FIG. 1 to which the refractive index distribution measuring apparatus of the present invention was attached. External diameter φ16 for hanging part 2
Attach the ingot 1 of 0 mm (the length of the ingot including the dummy part is 3,000 mm), move it down,
After passing through the matching oil removing device 10 and immersing in the matching oil 3 filled in the cell 4, after 10 minutes required for measuring the refractive index distribution have passed, the speed is 1,500 m
m / min through the oil removing device 10 and the ingot 1
Was raised. As the matching oil removing device 10, all of those shown in FIGS. 3 to 6 were tested. In any case, the matching oil hardly adhered to the ingot 1 immediately after being lifted, and the next time without any waiting time. To the stretching step. Also, in the stretching step, there was no generation of contamination or off-odor in the furnace due to evaporation and combustion of oil.

COMPARATIVE EXAMPLE After measuring the mass of an ingot 1 having an outer diameter of 160 mm, the ingot was set in a hanging portion 2 of a refractive index distribution measuring device, and was immersed in a matching oil 3 in a cell 4. After 10 minutes, the oil removal device 1
While measuring the change in weight by lifting the ingot 1 without passing through 0, the time required for the matching oil adhering to the surface to drop naturally and be removed was measured. It took 50 minutes.

[0023]

According to the apparatus for measuring the refractive index distribution of an optical fiber preform of the present invention, the operation can be shifted to the next stretching step without waiting time after the measurement is completed, so that the operation time can be greatly reduced. In addition, since the degree of matching oil removal can substantially achieve the desired target, the moving factory /
It is possible to prevent contamination in the facility and the generation of contamination in the furnace and generation of an odor due to evaporation and combustion of oil in a stretching step using the furnace.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a pulling device to which an optical fiber preform refractive index distribution measuring device of the present invention is attached.

FIG. 2 is a schematic plan view showing a main part of an optical measuring section of the optical fiber preform refractive index distribution measuring device of the present invention.

FIG. 3 is a perspective view of an essential part showing one embodiment of a matching oil removing device in the optical fiber preform refractive index distribution measuring device of the present invention.

FIG. 4 is a perspective view of a main part showing another embodiment of an oil removing device to be matched in the optical fiber preform refractive index distribution measuring device of the present invention.

FIG. 5 is a perspective view of an essential part showing another embodiment of the matching oil removing device in the optical fiber preform refractive index distribution measuring device of the present invention.

FIG. 6 is a perspective view of a main part showing another embodiment of the matching oil removing device in the optical fiber preform refractive index distribution measuring device of the present invention.

[Description of Signs] 1 Ingot (optical fiber preform) 10 Matching oil removing device 2 Hanging unit 11 Ring member 3 Matching oil 12 Brush 4 Cell 13 Nozzle 5 Optical measuring unit 14 Oil tank 6 Laser beam 21 Plate rubber material 7 Light irradiation unit 22 Cloth material 8 8 'Cell window 23 Ring rubber or ring spring material 9 Light detection unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideo Hirasawa 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Research Laboratories (56) References JP 8-297707 (JP) , A) JP-A-7-55799 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 11/00-11/02 G01N 21/41 Patent file (PATOLIS)

Claims (6)

(57) [Claims] 1. An apparatus for measuring the refractive index distribution of an optical fiber preform, wherein the apparatus for measuring the refractive index distribution of the optical fiber preform comprises a matching oil removing device. 2. A light irradiator for injecting laser light into an optical fiber preform, a cell filled with matching oil and immersed in the optical fiber preform, and a refraction angle of light refracted inside the optical fiber preform. The optical fiber preform refractive index distribution measuring device according to claim 1, comprising a light detecting unit for measuring the refractive index, and a matching oil removing device disposed above the cell. 3. The apparatus for measuring the refractive index distribution of an optical fiber preform according to claim 1, wherein the matching oil removing device is provided with a brush extending toward the center on the inner peripheral surface of the annular member. 4. The optical fiber preform refractive index distribution measuring device according to claim 1, wherein the matching oil removing device has a plurality of gas ejection nozzles formed on an inner peripheral surface of the annular member. 5. The refractive index distribution of an optical fiber preform according to claim 1, wherein the matching oil removing device has a configuration in which a plate-like rubber material extending to the center is attached to the inner peripheral surface of the annular member. measuring device. 6. A matching oil removing device comprising: a cloth material extending from an inner peripheral surface of an annular member to a center; and a ring-shaped rubber or a ring-shaped spring material provided in the vicinity of a tip portion of the cloth member. Item 3. The optical fiber preform refractive index distribution measuring device according to item 1 or 2.