JPH06171986A - Method of aligning fiber in focus of hardening lamp - Google Patents

Abstract

PURPOSE: To execute efficient irradiation by measuring the intensity of the radiation for irradiating an optical fiber and changing the position of a radiation source with this intensity as a reference at the time of curing a polymer applied on the optical fiber by the radiation.

CONSTITUTION: The fiber 1 is drawn from a preform 2 and is taken up on a reel 5 via a curing lamp 3 and a light shield 4. The lamp 3 has a discharge tube 6 radiating, for example, UV rays and an internally reflective cylinder 7 of an elliptic shape. This discharge tube 6 exists on the first focus of the cylinder 7 and the fiber 1 is pulled via a second focus. The fiber 1 travels through the light shield 4. A photodetector 11 which responds with the UV rays is set at the wall of the light shield 4 and observes the fiber 1. A meter 14 is connected to the photodetector 11 and applies a reading proportional to the observed UV intensity. This intensity is proportional to the intensity of the incident light on the fiber 1 in the lamp 3. The orientation state and finest position of the lamp 3 for maximizing the intensity are determined by using the same.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for curing coated fibers such as optical fibers.

[0002]

BACKGROUND OF THE INVENTION Standard optical fibers consist of a core of fused silica with a temporary coating and, if necessary, a secondary coating. These coatings are usually polymers that are cured by UV light.

These coatings are applied to the optical fiber as it is drawn from the preform. When the fiber is withdrawn, it is run through an upright cup containing the coating material and having a small hole in its bottom. As the fiber travels through the small holes, a coating of the desired thickness is symmetrically deposited on the fiber. Further downstream with respect to the direction of movement of the fiber, there is arranged at least one UV lamp, which radiates UV-radially equalizing fibers on the fiber carrying the coating in order to cure the coating. Is configured accordingly. It is possible to use a plurality of coating cups in series and a UV lamp to apply a continuous coating.

Since the fiber has a small diameter,
The optics of the UV lamp used must focus the light generated by its light source onto a small area to be occupied by the fiber during operation. This is necessary in order to increase the intensity of light incident on the fiber without wasting light. The higher the intensity of the light, the higher the speed at which the fiber can travel through the lamp, and at such a high speed it is possible to completely cure the coating carried by the fiber.

US Pat. No. 4,849,640 (Kru
discloses a lamp and optics for curing the coating on the optical fiber,
In that case, the light from the compact arc lamp is
It is directed onto the optical fiber by using several reflectors.

US Pat. No. 4,710,638 (Woo
d) discloses another system for curing the coating on the optical fiber, in which case
The light from the linear bulb is focused onto the fiber.

When using the device as disclosed in the above-mentioned prior art, a focusing problem occurs.
Due to the small diameter of the fiber, it is necessary to focus the light on a small area and therefore the fiber must be precisely positioned to be located in the focused light area. If the fiber is not in the far cass region, the intensity of light incident on the fiber will be significantly reduced.

For example, in a DRF-10 type radiator or irradiator manufactured and sold by Fusion Systems Corporation, a linear light valve is positioned and cured on one focus of a reflective elliptical cylinder. The fiber carrying the coating to be moved is moved along another focus of this elliptical cylinder. Due to the geometry of this system, the light from the bulb is
It is not perfect, but it is focused on the focal point through which the fiber passes. However, 2 from this second focus
The UV rays may be reduced by about 30% even if the distance is only mm.

In order to maintain the fiber at the focal point of the above-mentioned illuminator optics of the Fusion Systems Corporation, the illuminator must be precisely positioned in two directions perpendicular to the fiber and with respect to the fiber. It must have an appropriate orientation state with respect to two virtual axes that are orthogonal to each other.

Accurately positioning the UV fiber curing lamp so that it travels past the focal point of the fiber lamp is difficult. The intensity of the lamp is very high,
It is not possible to directly observe the bulb or its reflected light. This eliminates the possibility of viewing the fiber while adjusting the position of the lamp. Although such a method is safe, it is very small on the fiber and the radiation from the bulb is very bright, making it difficult to determine if the fiber is actually in focus.

[0011]

It is an object of the present invention to provide an improved method of aligning coated optical fibers within an optical system to cure the coating on the fibers.

[0012]

SUMMARY OF THE INVENTION In accordance with the present invention, a curing radiation incidentally coupled to a coated fiber during a curing step is directed to a position along its length, i.e. Detachment from the fiber, preferably between the preform and the coating cup or at a location after the curing lamp. The magnitude of the emitted radiation is measured and used as an indicator of the intensity of the radiation incident on the fiber. The position of the curing lamp relative to the fiber can then be adjusted to obtain the maximum total radiation incident on the fiber.

It is believed that the anomalous coupling of radiation into the fiber can be described as Rayleigh scattering. Due to the short wavelength of the curing radiation (typically 250-400 nm), it is scattered by small defects and / or impurities in the fiber coating or core. Peter
K. Cheo "Fibre Optics Devices a"
nd Systems), 1968, Prentice Hall Publishing Co., Section 5.8, describes Rayleigh scattering by impurities in optical fibers, and that longer wavelengths should be selected to avoid scattering. Points out. The present invention utilizes Rayleigh scattering of a short wavelength of curing radiation (irradiation light).

F. A. Jenkins and H .; E. W
hite "Fundamentals of optics (Fundamentals
of Optics), 1957, McGraw-Hill Publishing Co., section 22.8, describes Rayleigh scattering, and states that the intensity of scattered light is proportional to the intensity of incident light.

In the preferred embodiment of the present invention, the non-invasive means for decoupling light from the fiber is used to decouple the light from the fiber without interrupting the normal winding motion. This can be accomplished by using a photodetector that views the fiber from within the enclosure that surrounds the fiber. This technique relies on the spontaneous departure of UV radiation from the fiber due to Rayleigh scattering. On the other hand, it can be achieved by interposing a condensing medium such as oil for refractive index matching between the moving fiber and the stationary photodetector.

[0016]

The preferred embodiment of the method for aligning fibers to one or more curing lamps is carried out when the draw line for producing the fibers is first started under operating conditions. During the alignment procedure, the draw or draw line can be run at a reduced speed to reduce the amount of fiber produced while adjusting the system.

Conventional drawing or drawing and coating means and conventional curing lamps can be used as described above.

The fiber travels from the preform 2 from which it is drawn and unwound via one or more curing lamps 3 (eg, DRF-10 described above) via a coating cup (not shown). It is wound on the reel 5. The position of the fiber is determined by the position of the preform 2 and the position of the take-up reel 5.

The non-invasive light separating means is the curing lamp 3.
And the take-up reel 5 so that light can be decoupled from the section of fiber 1. The light shield 4 and the light decoupling means around the fiber 1 are used to prevent the light sensing means associated with the decoupling means from being affected by direct or ambient light leaking from the curing lamp. It is possible to generate an electrical signal from the emitted light using a UVX-36 photodetector manufactured by Ultra Violet Products.

The lamp 3 appears to be translatable in two directions perpendicular to the fiber path and rotatable about two axes perpendicular to the fiber path. Is attached to. The light representing the intensity of the emitted light is a light detection device, an electric amplification means,
And display means can be used. Each lamp is preferably individually positioned while the others are off.

The signal for the original lamp position is read. Each possible adjustment of angle and position is then repeated until a maximum signal representing the maximum intensity of the decoupled light and a maximum intensity of the light on the fiber are obtained. On the other hand, the alignment according to the invention can be carried out under non-operating conditions. The fiber is drawn from the preform but uncoated. It is possible to operate the lamp at a reduced power level to limit overheating of the fiber.

Referring to the drawings, there is shown one embodiment of the present invention. The fiber 1 is pulled out of the preform 2 and the coating cup (not shown), the curing lamp 3,
It is pulled through the light shield 4 and wound on the winding reel 5.

The lamp 3 has a discharge tube 6 for emitting ultraviolet rays and an elliptic cylinder 7 having internal reflection. The discharge tube 6 can be, for example, a long mercury discharge arc lamp or a microwave non-powered lamp. The discharge vessel 6 is located on the first focus of an elliptical cylinder 7 and the fiber 1 is pulled via the second focus.
The light emitted by the discharge tube 6 is reflected toward the fiber 1 by the elliptic cylinder 7.

The lamp 3 is mounted on a plate 9 so that it can be translated in two respective orthogonal directions XY and can be rotated about two orthogonal axes φ and θ. It is installed. Four degrees of freedom are used to properly align the lamp, so the path the fiber is pulled through corresponds to the second focus. If this lamp is manufactured with high dimensional accuracy such that the elliptical cylinder and the discharge tube are exactly aligned, the degree of freedom in the direction of rotation can be omitted.

This mounting can be provided outside the lamp housing by means of three or four screw holes. The horizontal platform is provided with an enlarged hole through which the bolt 10 (two shown) can be inserted and screwed into the hole in the lamp housing. The latter configuration only provides horizontal freedom unless a shim is provided between the platform and the ramp. If a shim is provided, it can be used to rotate the lamp.

As the fiber line travels, the fiber travels through the light shield 4 located downstream of the lamp. A photodetector 11 responsive to ultraviolet light is set on the wall of the light shield 4, and therefore the photodetector 1
1 observes the fiber 1 inside. Light shield 4
Is composed of two parts integrated along the joint 12. These two parts have a recess along the joint 12, so that when the light shield is integrated it is provided with two opposite holes 13 (only one shown), A fiber can pass through the hole. The photodetector is electrically connected to a meter 14, which provides a reading proportional to the UV intensity observed by the photodetector. As mentioned above, the UV intensity read by the meter is proportional to the light intensity incident on the fiber in the curing lamp 3.
This reading is used to determine the orientation and best position of the lamp for maximum intensity.

If the stray light coming out of the curing lamp is obscured by what is scattered by the fiber, it is possible to rotate the fiber 90 degrees after leaving the curing lamp before it reaches the light shield 4. May be necessary.

According to the invention, when using certain lamps and optics other than those shown in the accompanying drawings,
For example, adjustments may be made in the optical system, such as by changing the distance between the optical elements, in order to obtain some relative value of the intensity of the radiation (illumination) incident on the fiber. The usually desired relative value is maximum radiation. The signal representative of the intensity of the light that is decoupled is used as an indication of the radiation incident on the fiber.

Although specific embodiments of the present invention have been described in detail above, the present invention should not be limited to these specific examples, and various modifications can be made without departing from the technical scope of the present invention. It goes without saying that the above can be modified.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus configured according to an embodiment of the present invention.

[Explanation of symbols]

 2 Preform 3 Curing lamp 4 Light shield 5 Winding reel 6 Ultraviolet emission discharge tube 7 Elliptical cylinder 9 Plate 10 Bolt 12 Joint part 13 Hole 14 Meter

Claims (9)

[Claims] 1. A process of coating an optical fiber with a radiation curable polymer and the resulting coated fiber in a process of providing radiation in an optical curing system comprising a curing lamp, wherein the coated fiber is A method of aligning the fiber within the curing system, wherein the polymer is cured and a portion of the curing radiation is coupled into the interior of the fiber during the step of imparting radiation; Disengage a portion of the radiation that has been coupled into, measure the intensity of the dissociated radiation, and determine the relative position of the curing system and the coated fiber until the desired intensity of the dissociated radiation is reached. Change, A method comprising the above steps. 2. The method of claim 1, wherein the fibers are aligned while the fibers are linearly moved through the curing system. 3. The method of claim 1, wherein the curing radiation comprises ultraviolet light. 4. The method of claim 1, wherein the curing radiation has a wavelength in the range of about 250 to about 400 nanometers. 5. The method of claim 1, wherein the desired intensity is the maximum attainable intensity. 6. The relative position between the coated fiber and the curing system according to claim 1,
A method of changing the position of at least one of the optical members. 7. The relative position of the coated fiber to the curing system according to claim 1, wherein
A method characterized by changing the position of a curing lamp. 8. The method of claim 1, wherein the relative position of the coated fiber and the curing system is changed by adjusting the angular orientation of the lamp. 9. The method of claim 1, wherein the relative position of the coated fiber and the curing system is changed by adjusting the position of the coated fiber.