FI82315C - FOERFARANDE FOER NYBELAEGGNING AV SKARVSTAELLE VID EN OPTISK FIBER. - Google Patents

Description

l 82315

A method for recoating an optical fiber splice

The invention relates to a method for recoating an extension of an optical fiber, the method comprising pulling the extension of the fiber through a space containing an ultraviolet-curable flowable coating material and then out of it through a via hole having diameters substantially the same or slightly larger than the end. curing the coating material remaining on the surface of the fiber drawn through the via hole by ultraviolet radiation.

Optical fiber recoating is required when the total length of the fiber is increased by joining together shorter fiber portions. The overall length may be increased in this way, e.g. in submarine cables, where it is desired to minimize the number of cable splices to be performed in the field. In order to continue, the fiber must be uncoated on both sides of the joint and the exposed area thus formed must be protected with a new coating after extension. It is important for the cabling of the long fiber thus formed that the thickness of the coated splice is as close as possible to the thickness of the original coated fiber.

Ultraviolet curable epoxy acrylate is commonly used as a coating in the recoating, and the coating is performed either by casting into a mold or by drawing the fiber through a crucible containing such epoxy acrylate.

In the mold process, the area to be coated is placed inside a mold that is permeable to ultraviolet radiation, usually formed in two parts.

The mold is filled with epoxy acrylate, which is cured by ultraviolet radiation through the mold.

35 The difficulty with the mold method is to avoid 2 82315 air bubbles remaining inside the mold. Adhesion of the acrylate to the mold must also be prevented in some way.

In the crucible method, the fiber is placed vertically from top to bottom through a crucible filled with an ultraviolet curable epoxy acrylate. The area to be coated is drawn through the crucible and exits the crucible through a through-hole in the bottom of the crucible. The diameter of the via hole is approximately the same as the diameter of the coated fiber, so that it prevents the formation of portions thicker than the original fiber. The coated fiber is cured immediately by an ultraviolet radiation source below the crucible.

However, in the crucible process, it is difficult to make the coating uniform in strength, as the epoxy acrylate tends to shrink at the first point of discontinuity, i.e., moving from the original coated area of the fiber to the uncoated extension area. There is a step between the coated area and the thinner uncoated extension area which, when encountered through the via hole, causes local thinning in the recoating. However, this problem does not occur with the second stage, which moves from a thin extension area to a thicker coated area.

The constriction created in the crucible method is corrected by pulling the fiber again from top to bottom through the crucible, but now the other way around. However, this is a laborious operation that requires e.g. removing and inverting the fiber to be coated.

It is an object of the present invention to provide a method of recoating a fiber splice 30 which avoids the above problems.

This is achieved by a method of the type described in the introduction, which according to the invention is characterized in that the fiber is drawn in a horizontal position through said space 35 through two through-holes on opposite sides.

3 8231 S

through first in one direction and then after reversing the direction of drawing of the fiber in the opposite direction.

The basic idea of the invention is that the fiber is treated in a horizontal position and 5 crucibles are used in the coating, through which the fiber can be drawn in both directions as a continuous process without removing the fastenings in between. In this case, the above-mentioned contraction is avoided.

The invention will be explained in more detail by means of an exemplary embodiment with reference to the accompanying drawing, in which Figures 1a and Ib show a crucible structure suitable for use in the method according to the invention, and Figures 2-7 show different steps of the coating method according to the invention.

In general, any crucible structure having a cavity or a recess in the upper surface which serves as a storage space for an ultraviolet-curable fluid coating can be used in the method according to the invention, as well as through-openings on opposite sides through which the fiber to be coated can be drawn. The diameters of the via openings are preferably equal to or slightly larger than the diameter of the coated portion of the fiber.

Figures 1a and Ib show a side and top view of a suitable crucible structure. The crucible consists of an elongate narrow lower part 1 and an elongate narrow upper part 2 releasably placed on the lower part 1. A vertical cylindrical recess 3 is formed in the upper surface of the lower part. from above. The width and height of the grooves are preferably substantially the same as the diameter of the coated fiber. The upper part 2 further has an opening 6 concentric with the recess 3 and the size 6.

4 82315 Despite the U-shaped grooves or via holes 4 and 5, the coated fiber portion has a circular cross-section because the surface tension spreads the coating evenly over the surface of the fiber.

According to the basic idea of the method according to the invention, the horizontal fiber to be recoated is drawn through a space containing an ultraviolet-curable coating material through two through-holes on opposite sides of said space, first in one direction and then in the reverse direction of the fiber.

Figures 2 to 7 illustrate the steps of the method according to the invention when the method is applied in the crucible according to Figures 1a and Ib.

As a preliminary measure, the fiber 7 to be coated is placed in the grooves 4 and 5 in the lower part 1 of the crucible, from which the upper part 2 has been lifted, so that the extension 8 to be coated remains outside the crucible, as illustrated in Fig. 2.

The upper part 2 of the crucible is then placed in place on the lower part 1, whereby from above it delimits the grooves 4 and 5 in the lower part 1, which are hereinafter referred to as through-holes. The purpose of the crucible two-piece is to facilitate the installation and removal of the fiber-25 from before and after coating.

In Fig. 2, an ultraviolet-curable coating agent, preferably epoxy acrylate, is added to the space formed by the recess 3 and the hole 6 so that the coating agent surrounds the fiber 7 in the crucible.

The fiber 7 is then drawn in a horizontal position through the crucible so that the splice 8 passes through the first through hole 4 into the coating-containing space where the coating adheres to the fiber, and then through the through hole 5 into the crucible outside the crucible 5. ultraviolet radiation, as shown in Figures 4 and 5.

When the fiber is drawn in this first direction, the thickness of the coating adhering to the fiber is limited in the tension-5 direction by a second via hole 5. When the first discontinuity point of the fiber 7, i.e. step 9a from the thicker coated portion to the thinner extension portion 8, meets the resultant hole 7 a thinning of the coating, i.e. a constriction 10, as illustrated in the enlarged sub-view 11. At the second stage 9b, i.e. a change from a thin extension to a thicker coated section, no constriction occurs.

The constriction in the first drawing direction is then corrected according to the invention by reversing the drawing direction of the fiber 7 without removing the fasteners and retracting the extension through the crucible in the opposite direction through the second through hole 5 inside the crucible and then through the first through hole 4 outside the crucible 20, where it is immediately cured in ultraviolet 6 and 7 are illustrated. Since the constriction caused by the step 9a now encounters the through hole 4 limiting the thickness of the fiber in the opposite direction, the constriction is filled, as illustrated in the partial view 12.

The fiber 7 can then be easily removed by first removing the top 2 of the crucible.

The method according to the invention is particularly suitable for coating fiber splices 30 in connection with cable manufacturing, providing a fiber of sufficient uniform strength for subsequent cabling.

The figures and the related description are intended to illustrate the present invention only. The details of the method according to the invention may vary within the scope of the appended claims.

Claims (2)

A method for recoating an optical fiber splice, the method comprising pulling a splice (8) of 5 fibers (7) through a space (3, 6) containing an ultraviolet-curable flowable coating material (10) and then exiting the through-hole (5) therefrom. having diameters substantially equal to or slightly larger than the diameter of the coated fiber (7) and curing the coating material remaining on the surface of the fiber (7) drawn through the via hole (5) by ultraviolet radiation, characterized in that the fiber (7) is drawn in a horizontal position (3, 6) through two via holes (4, 5) on opposite sides, first in one direction and then after reversing the drawing direction of the fiber (7) in the opposite direction. Process according to Claim 1, characterized in that the coating agent is an epoxy acrylate which can be cured by ultraviolet radiation. 7 82315 1. A method for the production of an optical fiber, including an optical fiber, 5 drags for an optical fiber (7) for the production of an optical fiber (3, 6) of a single ultraviolet transmission medium, 10% of the intermediate material (10) en genomföringsöppning (5), stem diameters with an average of 10 or more fibers (7) diameter, as well as an ultraviolet ultraviolet field with a crossover material, in which case the genomic fibers (5) 7), känne-t ecknat därav, att 15 fibern (7) dras i horisontalt läge genom nämnda utrymme (3, 6) via tvä pä motstäende sidor befintliga ge-nomföringsöppningar (4, 5) först i en riktning och sedan efter omkastning av fiberns (7) dragriktning i motsatt riktning. 20 2. Förfarande enligt patentkravet 1, känne- t e c k n a t därav, att överdragsmaterialet är ett medelst ultraviolettsträlning härdbart epoxyiakrylat.