JPS58208639A - Proof test method for optical fiber - Google Patents

Abstract

PURPOSE:To minimize the deterioration of the strength of an optical fiber by reducing a tensile load immediately while marking a defective part for removing the same when the defective part whose scattered light exceeds the prescribed limit of intensity is detected in a measuring device through which the optical fiber is passed. CONSTITUTION:A heating furnace 1' for a preform 1 which is a material of an optical fiber 2, an integrating sphere 3 which is a device for measuring the intensity of scattered light, and a control device 4 which detects a measured value obtained by the sphere and gives an instruction to a marker 8 and a capstan and proof test device 9, are provided. Since the preform 1 is heated to a temperature of about 2,000 deg.C by the furnace 1', the light thereof is propagated constantly into the optical fiber 2. When the integrating sphere 3 detects a part of the fiber whose scattered light exceeds a set value in its intensity, the device 4 gives an instruction to the device 9 to reduce a tensile load, while counting a time of delay from the distance from the integrating sphere 3 to the marker 8 and from the speed of the optical fiber 2, and said defective part is marked by the marker 8.

Description

DETAILED DESCRIPTION OF THE INVENTION In particular, the present invention relates to an optical fiber pull test method in which a tensile load is applied uniformly to the optical fiber immediately after drawing.

The strength of optical fibers can be dramatically improved by completely covering the surface of the optical fiber with a material such as C plastic or gold (called precoating) at the same time as drawing.

However, bubbles, foreign matter, surface scratches, etc. inherent in the optical fiber base material itself remain as they are even after the optical fiber is drawn and stretched, and stress concentration occurs in those parts, creating a weak part.

For this reason, optical fibers intended for long-term use are subjected to a Bruf test in which a certain tensile load is applied to the optical fibers, and weak parts are cut in advance so that those parts are not used.

Usually, this bruising test is carried out at the same time as the wire drawing or after the plastic or the like is extruded coated after the wire drawing, but these methods have the following inconveniences.

(1) If a blue test method is used at the same time as wire drawing, if a failure occurs in a low-strength part, the work will be temporarily interrupted and work efficiency will be reduced.

(2) The method of extrusion-breaking plastic ropes, etc. is not only inconvenient due to the addition of a bruf test step, but also can cause major deterioration due to the bruf test depending on the environmental conditions. It was also the cause.

Incidentally, the bottle present on the fiber surface increases due to the action of water vapor under the tensile stress of a normal atmosphere, and the extent of this increase is, for example, at a tensile load three times the installation stress, '
It is expected that an application time of several seconds to several tens of seconds will cause deterioration equivalent to 30 years of installation stress.

However, the rate of increase in surface flaws varies greatly depending on the atmosphere. For example, in an atmosphere with no water vapor, or
The increase stops in an extremely low temperature atmosphere, about the temperature of liquid nitrogen.

The present invention has been made in view of the above, and its purpose is to solve the inconveniences of the conventional optical fiber and to minimize the deterioration of the optical fiber by one degree of Bruf test without deteriorating the workability. The objective is to provide a bruch test method.

The present invention provides an optical fiber bruch test method in which a tensile load is continuously applied to an optical fiber immediately after a tug-of-war, in which the optical fiber is passed through a scattered light intensity measuring device, and the scattered light intensity is constant. If a defective portion exceeding a limit is detected, the tensile load is immediately reduced, and a mark is placed on the defective portion to facilitate removal.

Hereinafter, one embodiment of the present invention will be described based on the drawings. The figure is a system diagram of an optical fiber bruch test device that implements the present invention, and 1 is the material of the optical fiber 2. Preform, 1' is a heating furnace, 3 is an integrating sphere which is a measuring device for scattered light intensity, 4 is a control device that detects the measured value and instructs a marker 8 and a Bruf test device 9 which also serves as a capstan, 5 is a device for measuring the outer diameter of the optical fiber 2, 6 is a precoat breaking device, 7 is a baking furnace thereof, 8 is a marker for making marks, and 9 is a capstan and brush test device that continuously applies a tensile load to the optical fiber 2. , 10 is optical fiber 2
Ticket R (is 4).

Next, the optical fiber proof testing method of this embodiment will be explained in detail.

Since the preform 1 is heated to around 2000° C. by the heating furnace 1', the light is constantly propagating into the optical fiber 2. The intensity of scattered light caused by air bubbles or foreign matter contained in the optical fiber 2 or scratches on the surface is measured by an integrating sphere 3. This integrating sphere 3 is composed of a sphere with a diameter of 8 Crn and a photodiode. The scattered light intensity is closely related to the strength of the optical fiber 2, and when the scattered light intensity is below a certain level, it is assumed that there are almost no fiber defects and high intensity is maintained. When a scattered light intensity part of setting 1 or more is detected in the integrating sphere 3, the control device 4 immediately sends the capstan and proof test device 9
At the same time, a delay time is calculated from the distance from the integrating sphere 3 to the marker 8 and the speed of the optical fiber 2, and a mark is placed on the detected defective part using the marker 8. After the marked defective portion passes through a capstan and bruch test device 9, the defective portion is cut and removed, and only the high-strength optical fiber 2 is spliced into a winder 10.
It is wound up.

In this case, the tensile load applied to the optical fiber 2 was approximately 500 g to 2 K9, and there were no breakage accidents of the optical fiber 2.

Note that this method uses an atmosphere that does not contain water vapor or a liquid! The experiment was carried out in an atmosphere kept at an extremely low temperature, which is the same as the elemental temperature. Considerable effects were obtained even when it was carried out in this state.

As explained above, according to the present invention, the workability is good because it can be carried out with one extra step to remove dust from the optical fiber.
A practical effect can be achieved in that strength deterioration due to Bruf test can be prevented.

[Brief explanation of the drawing]

The figure is a system diagram of an apparatus for carrying out an optical fiber brunch test method according to an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. In an optical fiber bruch test method in which a tensile load is continuously applied to an optical fiber of @pull ci+, the optical fiber is passed through @Dennai for measurement of scattered light intensity, An optical fiber characterized in that when a defective portion where the scattered light intensity exceeds a limit is detected, the tensile load is immediately reduced, and a mark is placed on the defective portion to facilitate removal. Bruch test method. 2. The optical fiber Bruf test method according to claim 1, wherein the inside of the scattered light intensity measuring device is maintained in an atmosphere that does not contain water vapor or an atmosphere that is cooled to a cryogenic temperature of liquid nitrogen temperature.