JP3126307B2 - Optical fiber resin coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating an optical fiber with a resin, which minimizes variations in the outer diameter of the optical fiber when the resin is coated on the surface of the optical fiber, and which does not contain bubbles in the resin coating. It is.

[0002]

2. Description of the Related Art A coated optical fiber is manufactured as shown in FIG. That is, the optical fiber 13 is drawn from the optical fiber preform 11 heated in the drawing furnace 12, the outer diameter of the optical fiber is measured by an outer diameter measuring device 14, then cooled by a cooling pipe 15, and the resin coating device is used. The optical fiber is coated with the liquid coating resin by the 16 pressing dies 20, the coating material is cured by the UV irradiation device 18 through the eccentricity monitor 17, and the coated optical fiber obtained in this manner is We take and take up on drum. The outer diameter of the optical fiber is controlled by the take-up speed of the capstan 21. FIG. 3 shows a pressure die of the optical fiber resin coating apparatus. Pressing die is holder 27
A conical die 22 is disposed at the bottom of the nipple, and a conical nipple 23 is disposed above the conical die 22. The resin pressure-fed from the resin tank through the resin supply pipe at a pressure higher than the atmospheric pressure is supplied from the resin supply hole 24 in the center of the holder to the resin attachment portion 25 formed between the die 22 and the nipple 23, and the traveling optical fiber 3 is coated with a resin, and the coated optical fiber emerges from the tip nozzle 26.

[0003]

When the bare optical fiber diameter does not change, the coating outer diameter of the optical fiber is set to the coating resin pressure.
It changes depending on the holding temperature of the coating resin and the drawing speed. In particular, since the viscosity of the coating resin greatly changes depending on the holding temperature, it is necessary to control the viscosity to a required temperature. Variations in the outer diameter of the coating of the optical fiber increase the microbending loss, thereby worsening the transmission loss of the optical fiber. Also, depending on the drawing conditions, especially the pressure of the coating resin, air bubbles are mixed in the resin coating, which also has a problem that transmission loss is deteriorated. SUMMARY OF THE INVENTION An object of the present invention is to provide a resin coating method for an optical fiber having excellent transmission characteristics that minimizes variation in the coating outer diameter of the optical fiber and does not cause air bubbles to enter the resin coating in view of the above problems. Is provided.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a vehicle which travels in a pressing die supplied with a coating resin having a pressure higher than the atmospheric pressure .
Coating resin on optical fiber surface drawn from tip nozzle
In the resin coating process of optical fibers, the coating outer diameter of the optical fiber is proportional to 0.6 square of the coating resin pressure, inversely proportional to the coating resin viscosity, based on the inversely related to the 0.7 power of the drawing speed, the coating Adjust resin pressure and / or coating resin viscosity
The gist of the present invention is to provide a resin coating method for an optical fiber, wherein the outer diameter of the coating of the optical fiber is controlled by adjusting the diameter. In the present invention, all coating resin pressures are gauge pressures (true pressure minus atmospheric pressure).
In shall be I table.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a resin coating method for an optical fiber using a pressing die, factors controlling the coating outer diameter Dc of the optical fiber include a coating resin pressure P, a coating resin viscosity μ, and a drawing speed Vf. . So it was examined a relationship between the coating outer diameter Dc of the three factors and the optical fiber, 0.6 of the coating outside diameter Dc of the optical fiber ([mu] m) of the coating resin pressure P (kg / cm ²⁾
It was found to be proportional to the power, inversely proportional to the coating resin viscosity μ (poise), and inversely proportional to the drawing speed Vf (m / min) to the 0.7th power. Then, when the relationship between the coating outer diameter Dc and P ^0.6 / μVf ^0.7 was examined for an optical fiber having an outer diameter of 125 μm, the results shown in FIG. 2 (indicated by dots in the figure) were obtained, and an approximate line (solid line) was obtained from these values. The following equation (1) was obtained when an equation for calculating the coating outer diameter Dc of the optical fiber was obtained. ^{Dc = k (P 0.6 / μVf} 0.7) + C (k, C represents a constant) ... (1) where, k, C each k = 0.012 in FIG. 2, C = 1
89.

If the relationship of the formula (1) is used, for example, when the coating outer diameter fluctuates due to a change in the temperature of the coating resin or the drawing speed, it depends on the viscosity at that temperature or the amount of change in the drawing speed. The coating resin pressure is calculated from equation (1), and the coating outer diameter can be maintained at a predetermined value by adjusting the pressure. In the actual drawing step, the coating outer diameter of the optical fiber is measured by an outer diameter measuring device, and an appropriate coating resin pressure is calculated by equation (1) based on a difference amount with respect to a predetermined coating outer diameter. The coating resin pressure is controlled by the pressure control unit, and the coating outer diameter is maintained at a predetermined diameter. Further, by controlling the coating resin viscosity or the coating resin pressure and the coating resin viscosity with respect to the fluctuation of the coating outer diameter of the optical fiber according to the equation (1), the coating outer diameter is controlled to be maintained at a predetermined diameter. .
By adjusting the pressure applied to the coating resin in the pressing die so as to satisfy Equation (1) in this manner, even if the drawing speed of the optical fiber is high or low, or if the temperature of the coating resin is high, Since the coating diameter for coating the optical fiber can be controlled to a predetermined diameter even if it is low, the present invention is supplied into the pressure die regardless of the drawing speed of the optical fiber or the viscosity of the coating resin whatever the value. By adjusting the coating resin pressure, the outer diameter of the coated optical fiber can be maintained at a predetermined value.

[0007] In the present invention, the coating resin pressure is set at 1.
If the pressure is 7 to 5 times, no air bubbles are mixed into the resin coating, so that an optical fiber free of air bubbles can be manufactured. The coating resin pressure is 1.7 times the pressure at which the resin is depleted.
If the pressure is less than twice, there is a problem of air bubbles in the resin coating. If the pressure exceeds five times the pressure at which the resin is depleted, the coating resin overflows from the upper portion of the nipple of the pressing die.

FIG. 1 is a configuration diagram of a drawing apparatus according to an embodiment of the present invention. First, the optical fiber preform 1 is inserted into an electric furnace 2, heated and melted, and drawn into an optical fiber 3.
The drawn optical fiber passes through a cooling pipe 5 and a resin coating device 6.
3 and a press die 10 having a conical inside as shown in FIG.
The resin-coated optical fiber passing through the inside is cured by an UV irradiation device 8 through an eccentricity monitor 7 and wound up by a drum (not shown). At this time, the outer diameter of the optical fiber and the outer diameter of the coating of the optical fiber are measured by the optical fiber outer diameter measuring device 4 and the coating outer diameter measuring device 9, respectively. In addition, the coating resin temperature and the drawing speed Vf are respectively the temperature measurement unit,
It is measured by the drawing speed measuring unit. Here, the measurement data of the coating outer diameter Dc of the optical fiber is sent to the calculation unit, and at the same time, the measurement data of the coating resin temperature (converted to coating resin viscosity μ) and the drawing speed Vf are also sent to the calculation unit. The coating resin pressure P is calculated so that the difference between the coating outer diameter Dc of the optical fiber and the set coating diameter becomes zero, and is fed back to the pressing force controller. This coated optical fiber diameter Dc, viscosity μ,
An appropriate coating resin pressure is calculated based on the measurement data of the drawing speed Vf, and the coating resin pressure P is adjusted by the pressing force control unit. When the coating outer diameter of the optical fiber reaches the set diameter, the coating resin pressure is maintained. Therefore, even if the drawing speed of the optical fiber fluctuates or the temperature (viscosity) of the coating material fluctuates, the coating outer diameter of the optical fiber always corresponds to the drawing speed and viscosity at that time. The coating resin pressure is adjusted so that

[0009]

【Example】

Example Using the drawing apparatus shown in FIG. 1, the pressure nozzle of FIG. 3 was made to have a tip nozzle diameter of 0.25 mm, and an acrylic / urethane UV curing resin was used as a coating resin, and the viscosity was set to 15 poise (40 ° C.). The coated wire was drawn at a drawing speed of 120 m / min. Coating resin pressure was performed by setting 1.7 times the 0.5 kg / cm ² gauge pressure in the pressure 0.3 kg / cm ² where the resin at the time of lowering the coating resin pressure becomes depleted. At this time, the outer diameter of the optical fiber was 125 μ
m, the outer diameter of the coating was set to 200 μm, and the pressure of the coating resin was controlled by equation (1) to draw 10 km. The dispersion of the outer diameter of the obtained coated optical fiber is ± 0.24 μm, and the transmission loss is 0.34 dB / km (wavelength 1.3 μm) and 0.20 dB / km (wavelength 1.55 μm), which are extremely good values. No air bubbles were mixed during the coating. As a comparative example, the drawing speed was determined using the conventional drawing apparatus shown in FIG.
When a 10 km line was drawn at 100 m / min, the variation in coating outer diameter was ± 1.0 μm.

[0010]

According to the present invention, since the outer diameter of the coated optical fiber is always adjusted to a constant value, variations in the coated diameter due to fluctuations in drawing speed and viscosity can be minimized. Therefore, it is possible to manufacture a high-quality coated optical fiber having no microbending loss due to the variation in the coating outer diameter of the optical fiber and free of bubbles.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a drawing apparatus according to the present invention.

FIG. 2 is a diagram showing the relationship between coating outer diameter, coating resin pressure, coating resin viscosity, and drawing speed at an optical fiber outer diameter of 125 μm in the present invention.

FIG. 3 is an explanatory view of a pressing die.

FIG. 4 is a configuration diagram of a drawing apparatus according to a conventional method.

[Explanation of symbols]

 1, 11: Optical fiber preform 2, 12, Electric furnace 3, 13, Optical fiber 4, 14, Optical fiber outer diameter measuring device 5, 15, Cooling pipe 6, 16, Resin coating device 7, 17 ... Eccentric monitor 8 , 18… UV irradiation device 9,19… Coating outer diameter measuring machine 10,20… Pressure die 21… Capstan 22… Die 23… Nipple 24… Resin supply hole 25… Resin adhesion part 26… Tip nozzle 27… Holder

Continuation of the front page (56) References JP-A-59-131417 (JP, A) JP-A-2-51218 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6 / 00-6/54

Claims (3)

(57) [Claims] 1. A vehicle travels in a pressure die to which a coating resin having a pressure higher than the atmospheric pressure is supplied, and is drawn out from a tip nozzle.
In a resin coating method for an optical fiber in which a resin is coated on the surface of an optical fiber, the outer diameter of the coating of the optical fiber is determined by the pressure of the coating resin.
It is proportional to the 0.6 power, inversely proportional to the coating resin viscosity,
Based on the relationship inversely proportional to the power of 0.7 , the coating resin pressure and
And / or adjusting the coating resin viscosity to control the coating outer diameter of the optical fiber. 2. Coating resin pressure P (kg / cm ² ) , optical fiber drawing speed Vf (m / min.) , Coating resin viscosity μ (pois
For e) , the coating outer diameter Dc (μm ) of the optical fiber is (1)
Formula: Dc = k (P ^0.6 / μVf ^0.7 ) + C (k and C represent constants) (1) In order to satisfy the relationship, the drawing speed Vf and the variation of the coating resin viscosity μ are always satisfied. 2. The resin coating method for an optical fiber according to claim 1, wherein the coating resin pressure P and / or the coating resin viscosity μ are controlled so that the coating outer diameter of the optical fiber is maintained at a predetermined diameter. 3. The optical fiber resin coating method according to claim 1, wherein the coating resin pressure is 1.7 to 5 times the pressure when the coating resin pressure is reduced and the resin is depleted.