JP6402471B2 - Optical fiber manufacturing method - Google Patents

Description

  The present invention relates to an optical fiber manufacturing method.

  When drawing the optical fiber, the characteristics of the optical fiber to be drawn are confirmed in advance, so the optical fiber characteristics are measured at the drawing start end of the optical fiber glass preform, and the drawn optical fiber is good thereafter. In order to draw the optical fiber so that the optical fiber is good, there is known an optical fiber manufacturing method in which the remaining part is drawn by changing the drawing condition according to the measurement result (see, for example, Patent Documents 1 to 3). . It is also known that a transmission furnace for gradually cooling the drawn optical fiber is provided after the drawing furnace, and the transmission loss of the optical fiber can be reduced by slowing the cooling rate (see, for example, Patent Document 4).

JP 2001-215344 A JP 2005-170770 A JP 2004-107190 A JP 2000-335934 A

  By the way, when manufacturing the optical fiber glass base material, the core is made of pure silica, the clad is made of fluorine-added glass, the core part which becomes the core and the pipe which becomes a part of the clad are separately produced, and the core part is made of pipe. It may be integrated by collapsing and putting in.

  Each of the optical fiber glass preforms manufactured as described above is usually drawn under the same conditions, and the transmission loss is often measured in the inspection process after the drawing is completed. If it deviates from the above, it is necessary to change and adjust the drawing conditions in the subsequent drawing. However, since the above inspection process is usually performed after drawing, through processes such as deuterium treatment and division / screening, it takes days until the inspection result is obtained after drawing. Therefore, as described above, when the inspection is performed after the drawing is completed, there is a possibility that a large amount of optical fibers whose transmission loss is out of the standard may be produced.

As described in Patent Documents 1 to 3, the characteristics of the optical fiber are measured at the drawing start end of each optical fiber glass base material, and the drawing conditions are changed according to the measurement results, and each optical fiber is changed. If the remaining part of the glass base material is drawn, it is possible to adjust the transmission loss of the optical fiber drawn from the remaining part so that it falls within the standard.
However, since it is necessary to draw under the same conditions until the measurement result of the transmission loss at the start end is obtained, there is a possibility that the optical fiber drawn during that time is out of the standard. Further, simply checking whether or not the transmission loss is within the standard may cause the transmission loss value to vary within the standard.

  Therefore, an object of the present invention is to provide an optical fiber manufacturing method capable of manufacturing an optical fiber without manufacturing a transmission loss from a target value when manufacturing an optical fiber having a cladding doped with fluorine. .

The method for producing an optical fiber of the present invention that can solve the above-described problem is that a silica glass tube to which fluorine is added is divided, and a core glass preform is put into each of the divided silica glass tubes to integrate them. A process for producing a glass preform for optical fiber,
A step of heating and melting a plurality of glass base materials for an optical fiber in order in a heating furnace, and drawing while keeping the temperature in a heat-reducing furnace for slow cooling,
Among the plurality of optical fiber glass preforms, first measuring the transmission loss of the optical fiber drawn from the optical fiber glass preform,
Based on the measurement result of the transmission loss, the temperature of the slow cooling incubator or the gradual temperature is adjusted so that the transmission loss of the optical fiber drawn from the plurality of glass preforms for optical fiber thereafter becomes a target value. A step of adjusting at least one of the speeds of the optical fibers passing through the cold insulation furnace.

  According to the present invention, when manufacturing an optical fiber having a clad doped with fluorine, the optical fiber can be manufactured without the transmission loss varying from the target value.

It is a graph explaining the transmission loss of the optical fiber by the glass preform | base_material for optical fibers manufactured from the different silica glass tube. It is a graph explaining the transmission loss of the optical fiber drawn from the glass preform | base_material for optical fibers using each silica glass tube divided | segmented from the same silica glass tube. It is a schematic block diagram of the drawing apparatus used for the manufacturing method of the optical fiber which concerns on embodiment of this invention. It is a graph which shows the transmission loss of the optical fiber obtained by an example of embodiment of this invention.

[Description of Embodiment of Present Invention]
An optical fiber manufacturing method according to an embodiment of the present invention is as follows.
(1) dividing a silica glass tube to which fluorine has been added, and integrating a core glass preform into each of the divided silica glass tubes to produce a plurality of glass preforms for optical fibers;
A step of heating and melting a plurality of glass base materials for an optical fiber in order in a heating furnace, and drawing while keeping the temperature in a heat-reducing furnace for slow cooling,
Among the plurality of optical fiber glass preforms, first measuring the transmission loss of the optical fiber drawn from the optical fiber glass preform,
Based on the measurement result of the transmission loss, the temperature of the slow cooling incubator or the gradual temperature is adjusted so that the transmission loss of the optical fiber drawn from the plurality of glass preforms for optical fiber thereafter becomes a target value. A step of adjusting at least one of the speeds of the optical fibers passing through the cold insulation furnace.
When a silica glass tube to which fluorine is added is divided and a small core glass base material is put in each divided silica glass tube and integrated to manufacture a plurality of glass base materials for optical fibers, the core glass base material Is small, it is difficult to cause a variation in transmission loss, and the variation in transmission loss is mainly caused by a silica glass tube. For this reason, if a plurality of glass preforms for optical fibers are manufactured using a silica glass tube divided from the same silica glass tube to which fluorine is added, the first glass preform for optical fibers is included. As a result of the transmission loss of the optical fiber drawn from the wire, at least one of the temperature of the slow cooling incubator or the speed of the optical fiber passing through the slow cooling incubator is adjusted. By drawing the optical fiber glass preform using each of the other divided silica glass tubes under the conditions adjusted as described above, the transmission loss can be adjusted to the target value.
Thereby, when manufacturing the optical fiber by drawing a plurality of base materials using the divided silica glass tube, the optical fiber can be manufactured without the transmission loss varying from the target value.

(2) The adjustment of the temperature of the annealing furnace and the speed of the optical fiber passing through the annealing furnace includes an adjustment to increase transmission loss.
In general, the lower the transmission loss, the better. Therefore, if the transmission loss of the optical fiber drawn from the first optical fiber glass preform is smaller than the target value, there is no need to adjust the conditions of the slow cooling incubator. Although it is conceivable, there is a possibility that the dispersion of transmission loss becomes large. For this reason, when the transmission loss is smaller than the target value, an optical fiber obtained by drawing an optical fiber glass preform using each of the other divided silica glass tubes by adjusting to increase the transmission loss. The transmission loss variation can be suppressed near the target value.

(3) Based on the measurement result of the transmission loss of the optical fiber drawn at the drawing start end of the first optical fiber glass preform, the transmission of the optical fiber drawn from the remaining portion of the first optical fiber glass preform. Adjust at least one of the temperature of the slow cooling incubator or the speed of the optical fiber passing through the slow cooling incubator so that the loss becomes a target value, and the first optical fiber glass preform A step of drawing the remainder.
Adjust at least one of the temperature of the slow cooling incubator or the speed of the optical fiber passing through the slow cooling incubator as a result of the transmission loss of the optical fiber drawn at the first drawing end of the glass preform for the optical fiber. To do. By adjusting the conditions in this way, it is possible to suppress variation in transmission loss even with respect to the remainder of the first optical fiber glass preform among the plurality of optical fiber glass preforms.

An optical fiber manufacturing method according to an embodiment of the present invention is based on the knowledge found by the present inventor and will be described below.
The inventors of the present application piped the fluorinated glass to produce a plurality of silica glass tubes. Then, the plurality of silica glass tubes were divided into predetermined lengths, respectively, and collapsed and integrated with the core base material to produce a plurality of optical fiber glass base materials.
And the optical fiber is manufactured by drawing the plurality of glass base materials for optical fibers under the same drawing conditions (slow cooling temperature, drawing speed), and all the optical fibers manufactured from a plurality of different silica glass tubes are used. Transmission loss was measured. The measurement results are shown in FIG.

In FIG. 1, for all the optical fibers manufactured as described above, the deviation (horizontal axis) of transmission loss from the target value 0 is divided into 0.001 dB / km, and the ratio is plotted on the vertical axis. It is what I took.
As shown in FIG. 1, the optical fiber manufactured as described above has a large variation in deviation from the target value of transmission loss (where the horizontal axis is 0), and the standard (for example, where the target value is 0). Many optical fibers deviated from (within ± 0.002 dB / km).

  Next, this inventor measured the transmission loss of the optical fiber by the several glass preform | base_material for optical fibers manufactured using only the pipe divided | segmented from the same silica glass tube. 2, as in FIG. 1, the deviation (horizontal axis) of the transmission loss from the target value 0 is divided into different ones by 0.001 dB / km, and the ratio is plotted on the vertical axis. As shown in FIG. 2, the variation in the transmission loss is smaller than that in the above-described FIG. Even when the other silica glass tubes were measured, similarly, the dispersion of the transmission loss was smaller than that of the above-described FIG.

  However, since the median transmission loss of each optical fiber of each silica glass tube may deviate from the target value, the optical fiber manufactured from each silica glass tube may have a transmission loss that deviates from the target value. Come out. In the measurement result of FIG. 2 above, since the median value of transmission loss is shifted by 0.002 dB / km from the target value, there is an optical fiber that deviates from the standard (for example, within ± 0.002 dB / km from the position of the target value 0). Has occurred.

  Based on the above measurement and knowledge, the present inventors measured the transmission loss of the optical fiber obtained by drawing the first glass preform for the optical fiber for each silica glass tube, and the value is the target. By adjusting the drawing conditions (slow cooling temperature, drawing speed) of the optical fiber glass preform made of the same silica glass tube so that the value is reduced, the optical fiber transmission loss can be manufactured without variation from the target value. I found that I can do it.

[Details of the embodiment of the present invention]
Specific examples of the optical fiber manufacturing method according to the embodiment of the present invention will be described below with reference to the drawings.
In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

FIG. 3 is a schematic configuration diagram of a drawing apparatus used in the optical fiber manufacturing method according to the embodiment of the present invention.
As shown in FIG. 3, the wire drawing device 1 includes a base material supply device 2, a wire drawing furnace 3, an annealing furnace 5, a thermometer 7, a control unit 8, a guide roller 9, a capstan device 10, and a winding device 11. It has. The drawing furnace 3 is provided with a drawing furnace heater 4, and the annealing furnace 5 is provided with an annealing furnace heater 6.

In the drawing process by the drawing apparatus 1, the optical fiber glass preform 12 held by the preform supply apparatus 2 is supplied to the drawing furnace 3, and the lower end of the optical fiber glass preform 12 is heated and softened by the drawing furnace heater 4. The optical fiber 13 is pulled out from the lower part of the drawing furnace 3.
The drawn optical fiber 13 is sent to the warming furnace 5 for slow cooling. The inside of the annealing furnace 5 is adjusted to a predetermined temperature by the annealing furnace heater 6.
The optical fiber 13 that has passed through the annealing furnace 5 is wound on the winding device 11 through the guide roller 9 and the capstan device 10 after the coating layer is formed (illustration of the configuration is omitted). . An optical fiber is manufactured by such a drawing process.

Further, the wire drawing device 1 is provided with a thermometer 7 for measuring the temperature of the annealing furnace 5 for slow cooling, and the measured temperature value of the heating furnace 5 for slow cooling is transmitted to the control unit 8. .
The control unit 8 adjusts the temperature of the slow cooling warming furnace 5 by controlling the slow cooling warming furnace heater 6 according to the measured value of the temperature of the slow cooling warming furnace 5, and the capstan device 10. Is controlled to adjust the speed of the optical fiber 13 passing through the annealing furnace 5 for slow cooling.

The optical fiber manufacturing method according to this embodiment will be described below.
(Process 1: Base material manufacturing process)
The silica glass tube to which fluorine is added is divided into a plurality of pieces (hereinafter described as four examples) with a predetermined length. A core glass base material is put in each of the divided silica glass tubes and integrated by rod in collapse. Thereby, the four glass preforms 12 for optical fibers are manufactured.

(Process 2: Drawing process)
The above four optical fiber glass preforms 12 manufactured in the above step 1 are heated and melted in sequence using the drawing apparatus 1 shown in FIG. This step 2 includes the following procedures (steps 2-1 to 2-3).
(Step 2-1)
Of the four optical fiber glass preforms 12 manufactured in the above step 1, the transmission loss of the optical fiber drawn from the first optical fiber glass preform 12 to be drawn is measured.
(Process 2-2)
Based on the result of the transmission loss of the optical fiber measured in the above step 2-1, the transmission loss of the optical fiber 13 drawn from the second to fourth optical fiber glass preforms 12 becomes a target value. Thus, at least one of the temperature (slow cooling temperature) of the warming furnace 5 for slow cooling and the speed (drawing speed) of the optical fiber 13 passing through the warming furnace 5 for slow cooling is adjusted.

The adjustment of the slow cooling temperature or the drawing speed in the step 2-2 is performed as follows, for example.
The slow cooling temperature is adjusted by controlling the slow cooling warming furnace heater 6 by the control unit 8 and adjusting the temperature of the slow cooling warming furnace 5 so as to reach a target temperature. For example, in order to reduce the transmission loss of the optical fiber 13 by the above adjustment, the temperature of the warming furnace 5 for slow cooling is adjusted to be high.

  For adjusting the drawing speed, the control unit 8 controls the capstan device 10 to adjust the speed of the optical fiber 13 passing through the warming furnace 5 for slow cooling. For example, in order to reduce the transmission loss of the optical fiber 13 by the adjustment described above, the speed of the optical fiber 13 passing through the slow cooling incubator 5 is adjusted to be slow.

Note that both the temperature of the annealing furnace 5 and the speed of the optical fiber 13 passing through the annealing furnace 5 may be adjusted.
As described above, the drawing conditions (slow cooling temperature and drawing speed) are set such that the transmission loss of the optical fiber 13 drawn from the second to fourth glass preforms 12 is a target value. The

(Step 2-3)
Drawing is performed on the second to fourth optical fiber glass preforms 12 under the drawing conditions (slow cooling temperature and drawing speed) set in Step 2-2.

  In the optical fiber manufacturing method according to the present embodiment described in detail above, the optical fiber glass preform 12 using each of the other divided silica glass tubes is drawn under the conditions adjusted in the step 2-2. For example, since the dispersion of transmission loss is small when the optical fiber glass preform 12 using the same silica glass tube is drawn, the transmission of the optical fiber 13 drawn from the second to fourth optical fiber glass preforms 12 is performed. The loss can be adjusted near the target value. Thereby, when the optical fiber 13 is manufactured by drawing a plurality of glass base materials 12 for optical fibers using the divided silica glass tubes, the optical fiber 13 can be manufactured without the transmission loss varying from the target value. .

  Further, the adjustment of the temperature of the annealing furnace 5 and the speed of the optical fiber 13 passing through the annealing furnace 5 in the above step 2-2 may include adjustment for increasing transmission loss. The adjustment for increasing the transmission loss is performed, for example, so that the temperature of the annealing furnace 5 for slow cooling is lowered. Or it adjusts so that the speed of the optical fiber 13 which passes the heat retention furnace 5 for slow cooling, for example may be made quick. Alternatively, the transmission loss may be increased by adjusting both the temperature of the annealing furnace 5 and the speed of the optical fiber 13 passing through the annealing furnace 5.

  As described above, generally, the lower the transmission loss, the better. Therefore, when the optical fiber 13 drawn from the first (first) optical fiber glass preform 12 is smaller than the target value, the annealing furnace for slow cooling is used. Although it is considered that there is no need to adjust the condition 5 (annealing temperature, drawing speed), there is a possibility that the dispersion of transmission loss becomes large. For this reason, when the transmission loss is smaller than the target value, the optical fiber using each of the other divided silica glass tubes (for example, the second to fourth) is adjusted by adjusting the transmission loss as described above. The dispersion of transmission loss of the optical fiber 13 obtained by drawing the glass base material 12 can be suppressed near the target value.

In addition to the procedure of the above embodiment, the following steps may be performed.
The transmission loss of the optical fiber 13 drawn at the drawing start end of the first (first) optical fiber glass preform 12 is measured (step 2-1a). Based on the measurement result of step 2-1a, for slow cooling, the transmission loss of the optical fiber 13 drawn by the remainder of the first (first) optical fiber glass preform 12 becomes a target value. At least one of the temperature of the heat retaining furnace 5 or the speed of the optical fiber 13 passing through the slow cooling heat retaining furnace 5 is adjusted, and the remainder of the first (first) optical fiber glass preform 12 is drawn (step 2- 1b).

  As a result of the transmission loss of the optical fiber 13 drawn at the drawing start end of the first (first) optical fiber glass preform 12, it passes through the temperature of the annealing furnace 5 and the annealing furnace 5 Since at least one of the speeds of the optical fibers is adjusted, variation in transmission loss can be suppressed even for the remaining portion of the first (first) optical fiber glass preform 12.

  In addition, the division | segmentation number of the silica glass tube to which the fluorine was added at the said process 1 is not limited to the 4 division illustrated above, The glass preform | base_material 12 for optical fibers drawn by the said process 2 is four. It is not limited.

An example of the transmission loss of the optical fiber manufactured by the present embodiment as described above is shown in FIG. 4 (the deviation (horizontal axis) of the transmission loss from the target value 0 is divided into different ones by 0.001 dB / km). The percentage is taken on the vertical axis).
Note that the measurement result of FIG. 4 adjusts both the temperature of the slow cooling heat retention furnace 5 and the speed of the optical fiber 13 passing through the slow cooling heat retention furnace 5 in Step 2-2.
In the example of the optical fiber manufactured by the present embodiment shown in FIG. 4, the center value matches the target value, and σ (standard deviation) representing the variation in transmission loss is ± 0.001 dB / km or less. Therefore, the transmission loss can be suppressed within ± 0.003 dB / km from the target value.

DESCRIPTION OF SYMBOLS 1 Wire drawing apparatus 2 Base material supply apparatus 3 Wire drawing furnace 4 Wire drawing furnace heater 5 Heat retention furnace for slow cooling 6 Heat insulation furnace heater for slow cooling 7 Thermometer 8 Control part 9 Guide roller 10 Capstan apparatus 11 Winding device 12 Glass for optical fibers 12 Base material 13 Optical fiber

Claims (2)

Dividing the silica glass tube to which fluorine has been added, producing a plurality of glass preforms for optical fibers by integrating a core glass preform in each of the divided silica glass tubes;
A step of heating and melting a plurality of glass base materials for an optical fiber in order in a heating furnace, and drawing while keeping the temperature in a heat-reducing furnace for slow cooling,
The plurality of optical fiber glass preforms are manufactured using a silica glass tube divided from the same silica glass tube, and the first optical fiber glass preform is drawn from the plurality of optical fiber glass preforms. Measuring the transmission loss of the measured optical fiber;
Based on the measurement result of the transmission loss, the slow cooling is performed so that the transmission loss of the optical fiber drawn from the plurality of fiber glass preforms after the first optical fiber glass preform becomes a target value. A method for producing an optical fiber, comprising adjusting at least one of a temperature of a heat-retaining furnace or a speed of an optical fiber passing through the slow-cooling heat-retaining furnace.   The method of manufacturing an optical fiber according to claim 1, wherein the adjustment of the temperature of the slow cooling heat-retaining furnace and the speed of the optical fiber passing through the slow cooling heat-retaining furnace includes adjustment for increasing transmission loss.

Images