JPH04317442A - Method and device for producing hermetically coated optical fiber - Google Patents

Abstract

PURPOSE:To produce a high-quality optical fiber by on-line detecting the electrical resistance value of a conductive film such as a hermetic coat formed on an optical fiber using an eddy current and using the value for the formation of the coat. CONSTITUTION:This device for producing a hermetically coated optical fiber of this invention has an eddy current generating and detecting coil 20 set close to a traveling optical fiber 2B to be hermetically coated and the electrical resistance value measuring device 21 for impressing a high-frequency current to generate an eddy current in the hermetic coat 2c in the optical fiber 2B on the coil 20 and calculating the resistance value from the eddy current generated by the coil 20. The resistance value is specified as the phase angle of a complex impedance calculated from the eddy current. The resistance value calculated by the device 21 is outputted to a process controller 22, and the flow rate of C2H2 gas as the raw gas is controlled by the process controller 22 through a mass flow controller 24 so that the resistance value of the hermetic coat is controlled to a specified fixed value.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention evaluates the state of the hermetic coating of an optical fiber having a conductive hermetic coating such as amorphous carbon on-line, and then evaluates the hermetic coating based on the evaluation results. The present invention relates to a method for manufacturing a hermetic coated optical fiber and an apparatus therefor.

0002

[Prior art] Generally, optical fiber core wire (cable) is
It is manufactured by providing a protective plastic coating on the surface of an optical fiber consisting of a core and cladding spun from a quartz optical fiber preform. Optical fiber cores having such plastic coatings have the property that transmission loss of optical signals increases over time due to penetration of hydrogen and moisture in the atmosphere into the core. In order to eliminate these drawbacks of optical fibers, a hermetic coating made of an inorganic material such as amorphous carbon with a dense structure is provided on the surface of the optical fiber, that is, on the outer surface of the cladding, to prevent hydrogen molecules. Hermetically coated optical fibers have been proposed that have a structure that prevents water molecules from permeating into the core.

[0003] Such a hermetic coated optical fiber core wire is produced by bringing an optical fiber having a core and a cladding immediately after spinning from an optical fiber preform into contact with a raw material gas for forming a hermetic coating in a reaction tube, and then exposing the optical fiber to the outside of the reaction tube. By using the heat from the provided heater and the heat of the optical fiber itself immediately after spinning, the raw material gas is subjected to a thermal decomposition reaction to form a hermetic coating such as amorphous carbon on the outer surface of the cladding. after that,
A protective coating such as a plastic coating is applied to the outer surface of the hermetic coating to form an optical fiber core. Due to the above-mentioned characteristics of the hermetic coating, the hermetic coated optical fiber core having such a structure prevents hydrogen and moisture from penetrating into the core of the optical fiber and does not increase the transmission loss of optical signals over a long period of time. Furthermore, it has the effect of mechanically protecting the outer surface of the optical fiber and increasing the mechanical strength of the optical fiber.

[0004] In such a hermetic coated optical fiber, the stability of the hermetic coat in the longitudinal direction of the cable is important, and if the film quality or film thickness varies even in one place, hydrogen molecules and Water molecules invade the core of the optical fiber, leading to an increase in transmission loss. Therefore,
It is necessary to ensure that the hermetic coating is applied uniformly over the entire length of the optical fiber. Hermetic coatings such as amorphous carbon typically have a
It is also a conductor with a film thickness of 00 Å and an electrical resistance value of several to several tens of kilohms/cm. Therefore, it is effective to measure the electrical resistance value as one method for evaluating the state of film formation of the hermetic coating. The conventional method for evaluating the state of the hermetic coating is to remove the plastic coating formed on the outer surface of the hermetic coating and measure the electrical resistance of the exposed hermetic coating using a tester. This is an offline and destructive evaluation method.

[0005]

[Problem to be Solved by the Invention] In the conventional off-line and destructive electrical resistance measurement method, measurement is carried out after the product has been completed with a hermetic coating and a protective coating such as a plastic coating. Even if a defect is detected in the film formation state of the hermetic coating, the result is fed back to the manufacturing process online at the hermetic coating formation stage to maintain the specified quality of the hermetic coating that is subsequently formed. cannot be used effectively. In addition, with the conventional destructive electrical resistance measurement method, only a partial sampling test is required, and the plastic coating cannot be removed over the entire length of the optical fiber. It is not possible to inspect the state of film formation. Therefore, the inspection results cannot be effectively fed back to the hermetic coating formation. It is desirable to prevent the formation of defective hermetic coatings during the hermetic coating formation stage, but as is clear from the above, in the conventional electrical resistance measurement method, it is necessary to prevent the formation of defective hermetic coatings during the hermetic coating formation stage. cannot perform quality control. In addition, as other conventional methods,
A contact electrical resistance measurement method in which a probe for electrical resistance measurement is brought into direct contact with the hermetic sheathing before forming the protective coating is considered, but if the probe etc. is brought into direct contact with the moving hermetic sheathing, the hermetic sheathing may be damaged. This may cause a decrease in the strength of the optical fiber.
The conventional method cannot be adopted.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have discovered that the electrical resistance value of a conductive hermetic coating can be measured non-contact and online using an eddy current detection method. According to the present invention, in an optical fiber manufacturing method in which a conductive hermetic coating is formed on an optical fiber having a core and a cladding, the electrical resistance value of the hermetic coating is measured non-contact and online based on an eddy current testing method. , there is provided a method for manufacturing a hermetic coated optical fiber, characterized in that hermetic coating forming conditions are adjusted online based on the measured electrical resistance value. Preferably, the eddy current testing method comprises:
A high-frequency current sufficient to generate an eddy current is varied at a frequency sufficiently lower than that frequency, and the average intensity is varied. Further, according to the present invention, there is provided an apparatus for carrying out the above method for manufacturing a hermetic coated optical fiber, that is, an eddy current generation and detection coil disposed near the moving path of the optical fiber on which the conductive hermetic coat is formed; to the coil,
A means for applying a high frequency current whose average intensity changes and generates an eddy current in the hermetic coating, and an electrical resistance value of the hermetic coating is calculated from a detected eddy current value obtained by detecting the eddy current generated in the hermetic coating by the coil. There is provided a hermetic coated optical fiber manufacturing apparatus having process control means for controlling the hermetic coating forming apparatus based on the calculated electrical resistance value.

[0007]

[Operation] In the eddy current inspection method, when a conductor is placed in an alternating magnetic field, an eddy current flows within the conductor in a direction that cancels out the magnetic field.
It is based on the principle of measuring the electrical resistance value of a hermetic coating by utilizing changes caused by internal defects. In other words, in the eddy current inspection method, the magnetic field generated by the eddy current changes the impedance of the eddy current generation/detection coil through mutual induction, and this change in impedance is detected as a change in voltage value or phase. In particular, in the present invention, the electrical resistance value is detected as a phase angle in a complex impedance plane. Preferably, by changing the average intensity of the hermetic coating for generating eddy currents by varying a high-frequency current sufficient to generate eddy currents at a frequency sufficiently lower than that frequency, it is possible to obtain a phase angle that is not affected by drift or the like. Two specified points can be obtained and the electrical resistance value can be measured accurately. Once the electrical resistance value of the hermetic coating is measured using the eddy current testing method, the state of the film thickness of the hermetic coating is evaluated from the electrical resistance value. This evaluation result is fed back to the hermetic coating forming apparatus.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a hermetic coated optical fiber manufacturing apparatus according to a first embodiment of the present invention. This hermetic coated optical fiber manufacturing apparatus includes a drawing furnace (not shown) equipped with a heater 5 for drawing (spinning) an optical fiber preform 1, a reaction tube 6, a laser fiber outer diameter It has a measuring device 9, a resin coating die 10, a capstan roller 11, a dancer roller 12, and a winding drum 13. The hermetic coated optical fiber manufacturing apparatus also includes a nitrogen gas cylinder 14 filled with an inert gas (in this example, nitrogen (N2) gas) used as a sealing gas and a diluent gas, and a raw material gas for forming the hermetic coating (in this example, acetylene (N2) gas). It has an acetylene gas cylinder 15 filled with C2H2) gas, and mass flow controllers (MFC) 23 to 26 that control the supply amount thereof. Furthermore, the hermetic coated optical fiber manufacturing equipment
An eddy current generation/detection coil 20, an electrical resistance measuring device 21 that supplies a high frequency current to the coil 20 and measures the electrical resistance of the hermetic coating, and a process control device 2
It has 2.

The reaction tube 6 has an upper seal gas inlet 6A for sealing N2 gas from the nitrogen gas cylinder 14 in the upper seal zone, and a lower seal gas inlet 6C for sealing N2 gas in the lower seal zone. . The MFCs 23 and 26 control the mass of these seal gases. A raw material gas inlet 6B is provided at the bottom of the upper seal gas inlet 6A, and the raw material gas C2 H2 gas and the diluent gas N2 are separated by the MFC24 and MFC25.
Gas is introduced into the reaction section 6E. The used gas is discharged from the exhaust port 6D by the exhaust pump 8. Internal space 6 between upper seal gas inlet 6A and lower seal gas inlet 6C
E is a reaction part that forms a hermetic coating. A pressure sensor 7 is provided to measure the pressure in the reaction section 6E.

The preform 1 is drawn in a drawing furnace to form an optical fiber 2 having, for example, a core with a diameter of 10 μm and a cladding with an outer diameter of 125 μm formed on the outside of this core.
is formed. This optical fiber 2 is heated by the heat of the optical fiber 2 itself immediately after being introduced into the reaction tube 6 and led out from the drawing furnace.
Alternatively, due to this heat and heat from a heater (not shown) disposed outside the reaction tube 6, the C2H2 gas introduced into the reaction section 6B reacts by heating, and carbon is deposited on the surface of the cladding. An amorphous carbon hermetic coating having a thickness of 500 to 1000 Å is formed, and the bare optical fiber strand 2A is drawn out from the reaction tube 6. Midfielder
C24 and 25 are coated so that a hermetic coating is formed.
Appropriately control the mass (flow rate) of C2 H2 gas and N2 gas. When the bare optical fiber strand 2A passes through a laser outer diameter measuring device 9, its outer diameter is measured. The optical fiber 2A that has passed through the laser outer diameter measuring device 9 is coated with plastic resin as a protective coating in a resin coating die 10, and becomes a hermetic coated optical fiber strand 2B. FIG. 2 shows a cross section of the hermetically coated optical fiber strand 2B manufactured by the above manufacturing process. A core 2a, a cladding 2b, an amorphous carbon hermetic coating 2c, and a plastic coating 2d are formed from the inside to the outside, and each has the thickness described above. This hermetic coated optical fiber strand 2B is connected to the capstan roller 11.
, and is conveyed via dancer rollers 12 and wound up by a winding drum 13.

In this embodiment, an eddy current generation/detection coil 20 is disposed between the capstan roller 11 and the dancer roller 12 in close proximity to the moving hermetic coated optical fiber strand 2B. 2d
The electrical resistance value of the hermetic coating 2c is measured online in a non-contact manner from the outside. As shown in FIG. 3, the eddy current generation/detection coil 20 is formed by solidifying a cylindrical coil 201 within an air-core resin 202. As shown in FIG. FIG. 3 also shows an electric resistance that supplies a high frequency current sufficient to generate an eddy current in the hermetic coated optical fiber strand 2B to the eddy current generation/detection coil 20, and inputs the detected eddy current value from this coil 20. The configuration of the measuring device 21 is shown. The electrical resistance measuring device 21 measures a high frequency current sufficient to generate an eddy current in the hermetic coated optical fiber strand 2B, for example, the amplitude A1 is 5 mA in effective value and the frequency f1 = 2 to 3 MHZ.
, a bias power source 212 that generates a DC current of bias current D1=500 mA, a current addition circuit 214, a control circuit 215, and a switching circuit 216.

FIG. 4 shows the waveform of the test current applied to the eddy current generation/detection coil 20 by the electrical resistance measuring device 21. The control circuit 215 selects a frequency f2 that is sufficiently lower than the high frequency f1, for example, 10 of the frequency f1.
By turning on and off the switching circuit 216 at a frequency f2 = 200 Hz, which is 1/0, a high frequency current biased by the bias current D1 is intermittently applied to the eddy current generation/detection coil 20. In this example, the high frequency detection current was intermittently turned on and off at a frequency of 200 Hz, which is sufficiently lower than the high frequency of 2 MHZ, as shown in FIG. 4, showing the average intensity of the detection current. The frequency of the current at the on timing is a high frequency of 2 MHZ, but its amplitude is sufficiently smaller than the amplitude at the time of turning on and off. The reason for turning on and off in this manner is to detect the eddy current when on and the eddy current when off, and to accurately measure the phase angle of the complex impedance vector defined by these two points.

As shown in FIG. 5, the electrical resistance value of the hermetic coated optical fiber strand 2B is defined as the phase angle θ in the complex impedance plane determined from the eddy current detected by the eddy current generation/detection coil 20. . In FIG. 5, the horizontal axis X represents the real part of the complex impedance, and the vertical axis Y represents the imaginary part of the complex impedance. The phase angle θa of the complex impedance vector is based on the measurement results for the three samples a to c below, which actually have different resistance values, that is, the three types of hermetic coating in the hermetic coated optical fiber.
~θc is shown. Resistance value of sample a = 4.6KΩ/c
When m, θa = 21° When resistance value of sample b = 7.0KΩ/cm, θb = 19°
When the resistance value of sample c = 9.3 KΩ/cm, θc = 13°. This measurement result was obtained under the following eddy current generation/detection coil 20 and high frequency current application conditions. Inner diameter of detection coil 201
1.6mmΦ Wire diameter of detection coil 201 0.05mmΦ
Number of turns of detection coil
150 Detection coil length 10mm
Frequency f1 of high frequency current for detection flowing through the detection coil

2MHz
On/off frequency f2 that changes the average intensity of the detection current
200H
z Optical fiber 2
Traveling speed (linear speed) of B: 600m/min

0014
】The above results are based on the sample hermetic coating 2c.
The phase angle θ becomes smaller as the electrical resistance value increases, indicating that the phase angle θ depends on the electrical resistance value of the sample. Therefore, by providing a calculation means such as a microcomputer in the control circuit 215 in the electrical resistance measuring device 21, it is possible to calculate the electrical resistance value of the hermetically coated optical fiber strand 2B from the phase angle θ. In addition, in FIG. 5, the output point at the ON timing when the test current is applied to the eddy current generation/detection coil 20 is not a single point but extends in the phase angle θ direction, which is due to the traveling hermetic coating light. This is due to the vibration of the fiber wire 2B. When the detection current applied to the coil 20 is off, the output is zero and therefore the origin position is reached, so the zero point is corrected every time. Therefore, the influence of the output zero point drifting due to temperature can be eliminated.

FIG. 6 shows changes in the electrical resistance value of the hermetic coating 2c. A curve CV1 in FIG. 6 shows changes when the MFC 24 introduces C2 H2 gas into the raw material gas supply inlet 6B under the same setting conditions. The optical fiber manufacturing conditions at this time are shown below. Drawing furnace temperature
2100°C Drawing speed 6
00m/min Pressure inside reaction tube 6
-30mmAq
Seal gas flow rate
10 liters/min
Raw material gas flow rate
1 liter/min dilution gas flow rate
9 liter/min eddy current generation/detection coil 20
The shape of is the same as above. Normally, the electrical resistance value of the hermetic coating 2c is around 10KΩ/cm, but the curve CV1 shows that even if the MFC24 has the same setting value,
This indicates that the electrical resistance value of the hermetic coating 2c increases, in other words, the film thickness decreases. The reason for this is thought to be that carbon adheres to the inner wall of the reaction section 6E as time passes, the tube diameter becomes smaller and the gas flow rate increases, so the amount of carbon adhered to the outer surface of the cladding 2b decreases.

In order to perform online correction of the film formation status of the hermetic coating 2c, in the present invention, the electrical resistance value of the hermetic coating 2c calculated by the electrical resistance measuring device 21 is output to the process control device 22. The process control device 22 outputs a control command to the MFC 24 so that the electrical resistance value falls within a predetermined range, for example, 10 KΩ/cm. Based on the control command from the process control device 22, the MFC 24 reduces the flow rate of C2H2 gas introduced from the acetylene gas cylinder 15 into the reaction section 6E, and coats the outer surface of the cladding 2b with amorphous carbon to a predetermined thickness. Allow to form. By controlling the flow rate of C2 H2 gas in this way, the curve CV2 in FIG.
As shown in FIG. 2, the electrical resistance value of the hermetic coating 2c is maintained at approximately 10 KΩ/cm, and the film thickness of the hermetic coating 2c is set to a predetermined value, for example, 1000 Å. In this way, by feeding back the electrical resistance value of the hermetic coating 2c formed based on the amount of C2 H2 gas introduced, the thickness of the subsequently formed hermetic coating 2c can be accurately controlled.

FIG. 7 shows the configuration of a hermetic coated optical fiber manufacturing apparatus according to a second embodiment of the present invention. In this embodiment, as is clear from a comparison with the configuration of the hermetic coated optical fiber manufacturing apparatus shown in FIG.
The configuration is such that the set values of 7 are changed. That is, in this example, the drawing temperature in the drawing furnace is controlled instead of directly controlling the carbon flow rate as in the first embodiment. The relationship between the electrical resistance value and the drawing temperature is shown in FIGS. 8A to 8C. This figure shows that the electrical resistance values are 10 and 1, respectively.
The drawing temperature and drawing speed at 5 and 20 KΩ/cm are shown. When the drawing temperature is lowered, the diameter of the optical fiber consisting of the core 2a and the cladding 2b becomes thinner, and the drawing speed becomes slower. Thereby, the decomposition temperature of the raw material gas can be effectively lowered. Furthermore, as described with reference to the first embodiment, since the electrical resistance value increases due to changes in the reaction section 6E, it is necessary to set the wire so that the electrical resistance value of the hermetic coating 2c is constant under each setting condition. The draw temperature is gradually raised.

When implementing the present invention, the above-described first embodiment and second embodiment can also be combined. In addition, in Figures 1 and 7, the eddy current generation/detection coil 2
0, resin coating die 10 and capstan roller 11
It may be placed between. Furthermore, in the present invention,
Eddy current generation/detection coil 20 and hermetic coating 2c
Since the laser outer diameter measuring device 9 and the resin coating die 10 do not contact
It is also possible to measure the electrical resistance value of

The high frequency current applied to the eddy current generation/detection coil 20 can have various waveforms in addition to the waveform shown in FIG. 4 described above. FIG. 9 shows the high frequency current waveform. This high frequency current increases the frequency of the detection current flowing through the eddy current generation/detection coil 20 to 3M.
Hz, and the average intensity of the detection current was changed at 50 Hz. That is, in the first embodiment, the high frequency current was turned on and off, but in the second embodiment, it was changed in a sinusoidal manner. In this example, the amplitude A2 of the high frequency current was 3 mA in effective value, the amplitude A3 of the low frequency AC was 10 mA in effective value, and the DC bias current D2 was 20 mA. In this case, as shown in FIG.
and an AC power source 213 with a low frequency f4 = 50 Hz shown by a broken line, for example, a commercial frequency power source, and further,
It has a circuit 214 that adds a 3 MHZ current to a 50 Hz alternating current. This added alternating current is applied to the eddy current generation/detection coil 20. In this example as well, as described above, it is possible to determine the phase angle according to the electrical resistance value of the hermetic coating 2c, and from that phase angle, it is possible to calculate the electrical resistance value of the hermetic coating 2c. By adjusting the output current of the DC bias power supply 212, correction can be made so that the straight line of signal change passes through the zero point when the output point approaches the origin (zero point). Further, even without correction, stable measurement is possible regardless of the drift of the zero point by measuring only the direction of the complex impedance vector, that is, the phase angle θ.

Another embodiment in which the electrical resistance value of the hermetic coating 2c is measured in a non-contact and online manner will be described. FIG. 10 shows a partial view of FIG. 1 or FIG. In this embodiment, an electrical resistance measuring device 21 vibrates a vibration table 28 disposed between a capstan roller 11 and a dancer roller 12 at a frequency of about 200Hz, which is about 1/10 of the high frequency current that generates eddy currents. The coil 20 for generating and detecting eddy current is vibrated at high speed by a number and placed on this mounting table 28.
is vibrated at high speed near the moving hermetic coated optical fiber strand 2B. This oscillation is equivalent to adding the above-mentioned high frequency current to the low frequency current to change the average power. Therefore, with this method as well, it is possible to accurately measure the electrical resistance value of the hermetic coating 2c within the moving hermetically coated optical fiber strand 2B in a non-contact and online manner. Note that the eddy current generation/detection coil 20 may be fixed, and the moving hermetic coated optical fiber strand 2B may be vibrated relative to the eddy current generation/detection coil 20. As is clear from the above, the frequency of the high frequency current for eddy current generation is 1/1 of the frequency between the eddy current generation/detection coil 20 and the hermetic coated optical fiber 2B.
By approaching and separating at a frequency of about 10, the electrical resistance value of the hermetic coating 2c can be measured in the same manner as described above.

Although the above embodiments have exemplified an amorphous carbon coating as a hermetic coating, the method and apparatus of the present invention can be applied to any conductive coating. Thus, for example, the invention can also be used to manufacture cables having conductive coatings such as aluminum.

[0022]

[Effect of the invention] As described above, according to the present invention,
The electrical resistance value of the conductive hermetic coating inside a moving hermetic coated optical fiber can be measured non-contact and online, and the results can be fed back to the hermetic coating formation, making it possible to easily respond to changes in the hermetic coating formation conditions. It is possible to form a hermetic coating that satisfies certain conditions without depending on the method, and it is possible to prevent the occurrence of defective products.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a hermetic coated optical fiber manufacturing apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a hermetically coated optical fiber core manufactured by the hermetic coated optical fiber manufacturing apparatus shown in FIG. 1;

FIG. 3 is a diagram showing the configuration of the electrical resistance measuring device and the eddy current generation/detection coil in FIG. 1;

[Figure 4] Eddy current generation and
FIG. 3 is a current waveform diagram applied to a detection coil.

5 is a graph showing a phase angle measurement result corresponding to the electrical resistance value of the hermetic coating detected by the eddy current generation/detection coil shown in FIG. 4. FIG.

FIG. 6 is a graph showing changes over time in the electrical resistance value of the hermetic coating, which changes over time in the hermetic coating forming process.

FIG. 7 is a diagram showing the configuration of a hermetic coated optical fiber manufacturing apparatus according to a second embodiment of the present invention.

8 is a graph showing the relationship between the electrical resistance value of the hermetic coating, the drawing temperature, and the drawing speed by the hermetic coating optical fiber manufacturing apparatus shown in FIG. 7. FIG.

9 is a diagram showing a modified example of the current waveform applied to the eddy current generation/detection coil by the electrical resistance measuring device shown in FIG. 3; FIG.

FIG. 10: Another method for measuring the electrical resistance value of the hermetic coating in the hermetic coating optical fiber manufacturing apparatus of the present invention is a configuration in which an eddy current generation/detection coil is vibrated with respect to the hermetically coated optical fiber strand. FIG.

[Explanation of symbols]

1... Preform, 2B... Hermetic coating optical fiber strand, 2c... Hermetic coating, 5... Heater of drawing furnace, 6... Reaction tube, 6E... Reaction part, 7... Pressure sensor, 9 ...Laser outer diameter measuring device, 10.. Resin coating die, 11.. Capstan roller, 12.. Dancer roller, 13.. Winding drum, 14.. Nitrogen gas cylinder, 15.. Acetylene gas cylinder, 20.・Eddy current generation/detection coil, 21...Electrical resistance measuring device,
22...Process control device, 23-26...MFC, 2
7. Temperature regulator, 28. Vibration mounting table.

Claims (2)

[Claims] Claim 1. A method for manufacturing an optical fiber in which a conductive hermetic coating is formed on an optical fiber having a core and a cladding, the electrical resistance value of the hermetic coating being measured non-contact and online based on an eddy current testing method,
A method for producing a hermetic coated optical fiber, comprising adjusting hermetic coat forming conditions online based on the measured electrical resistance value. 2. An eddy current generation and detection coil disposed near the moving path of an optical fiber on which a conductive hermetic coating is formed, the average intensity of which changes, and an eddy current generated in the hermetic coating. means for applying a high-frequency current that generates eddy current generated in the hermetic coating by the coil; means for calculating the electrical resistance value of the hermetic coating from the detected eddy current value obtained by detecting the eddy current generated in the hermetic coating by the above-mentioned coil; A hermetic coated optical fiber manufacturing apparatus having a control means for controlling a coating forming apparatus.