JPS6215491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention reduces the area of optically unnecessary portions and increases the ratio of effective portions in the end face portions of optical fiber bundles produced by the acid elution method. The present invention relates to a method for manufacturing optical fiber bundles.

Generally, optical fiber bundles used in endoscopes etc.
It is effective to reduce unnecessary parts and make it as thin as possible. An acid elution method is used as one method for manufacturing this optical fiber bundle. This method will be explained below.

As shown in FIG. 1, there is an optical guide core 1 made of glass with a relatively high refractive index, an acid-resistant coating glass 2 with a relatively low refractive index surrounding it, and an acid-soluble coating glass surrounding it. 3 and optical single fiber 4
as shown in FIG. 2, is densely packed into an acid-soluble jacket tube 5, and stretched while heating with a heating heater 6 to form a fused optical fiber bundle 7 as shown in FIG. Create. Next, as shown in FIG. 4, both ends of the fused optical fiber bundle 7 are protected with acid-resistant coatings 8, 8' so as to cover the end faces, and the whole is immersed in an acid solution 9. The acid-soluble glasses 3 and 5 (between the acid-resistant coatings 8 and 8') are eluted. A flexible optical fiber bundle thus produced, with the acid-resistant coatings 8, 8' removed, is shown in FIG. As is clear from FIG. 3 or 5, the end face part has
Acid-soluble mantle 5 having the same wall thickness as the stretched acid-soluble mantle 5 used in FIG.
part remains. This acid-soluble jacket tube 5 is completely unnecessary for the function of the optical fiber bundle, and needs to be made as thin as possible, especially when used in an endoscope or the like. In order to make this part thinner, it is sufficient to reduce the wall thickness of the acid-soluble mantle 5 used in FIG.
The maximum thickness is 3 mm, and even in the heated and drawn state shown in FIG. 3, the thickness of this portion is about 10 to 20 times the diameter of the optical single fiber.

Alternatively, as disclosed in Japanese Patent Publication No. 56-13283, in the state shown in Fig. 5 with the intermediate soluble glass removed, the end face of the intermediate part is coated with an acid-resistant material. There is also a method of removing the acid-soluble mantle 5 by immersing it in acid again. However, this method requires an additional step of coating the end face with an acid-resistant material, and a more serious drawback is that in the state shown in Figure 5, the boundary between the flexible part and the hard part The fibers are very easy to break, and immersing them in an acid solution again in this state risks increasing the number of breaks due to handling.

The object of the present invention is to create an optical fiber bundle in which the acid-soluble jacket tube 5 used in FIG. It provides a manufacturing method.

The present invention will be explained below using figures. The steps up to manufacturing the fused optical fiber bundle 7 are the same as the method described above. Next, the entire fused optical fiber bundle 7 is immersed in an acid solution 9 without any protection, as shown in FIG. 6, to reduce the thickness of the acid-soluble jacket tube 5. The change in the wall thickness of the acid-soluble mantle 5 due to this elution has a linear relationship as shown in FIG. 7, and it is fully possible to achieve a predetermined thickness by controlling the immersion time. Under the conditions shown in FIG. 7, the acid-soluble mantle tube 5 having a wall thickness of 0.2 mm can be made thinner to 0.02 mm. Further, during this step, the acid-soluble coated glass 3 elutes from the end face by about 0.5 mm, but this portion is cut and removed before proceeding to the next step. In the subsequent steps, both ends are protected with acid-resistant coatings 8 and 8'.
It is immersed in an acid solution 9 to elute the acid-soluble glass 3 and 5 in the middle portion, and is taken out and coated with an acid-resistant coating 8.
8' is removed to produce a flexible optical fiber bundle.

As described above, it is possible to easily manufacture a flexible optical fiber bundle in which the thickness of the acid-soluble mantle is reduced by very simple means and the ratio of the effective portion of the end face of the optical fiber bundle is increased. I can do it.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a single fiber, Figure 2 is a diagram showing a large number of single fibers bundled and heated and drawn, Figure 3 is a diagram showing a bundle of fused optical fibers that has been heated and drawn, and Figure 4 is a conventional example. FIG. 5 is a perspective view of a flexible optical fiber bundle manufactured by the conventional acid elution method, and FIG. 6 shows an embodiment of the present invention. FIG. 7 is a diagram illustrating the relationship between the elution time and the elution thickness of the mantle. 1: Optical core, 2: Acid-resistant coated glass, 3: Acid-soluble coated glass, 4: Optical single fiber, 5: Acid-soluble jacket tube, 6: Heater, 7: Fused optical fiber bundle, 8, 8' : Acid-resistant coating, 9: Acid solution.

Claims (1)

[Claims] 1. In a method for manufacturing an optical fiber bundle by an acid elution method, the thickness of the acid-soluble mantle tube on the outer periphery of the optical fiber bundle is reduced by immersing the entire heat-drawn fused optical fiber bundle in an acid. Then, by cutting both ends leaving a predetermined length, and then protecting both ends with an acid-resistant coating and removing the acid-leached glass in the middle, the ratio of the effective part of the end face portion is increased. A method for manufacturing flexible optical fiber bundles featuring: