JPH063491B2 - Optical fiber cord and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical fiber curl cord used as an optical fiber transmission line connecting a moving optical communication terminal device and a fixed-side optical terminal device, and a manufacturing method thereof. .

(Background of the Invention) An optical fiber curl cord containing an optical fiber is used as an optical fiber transmission line connecting a moving optical communication terminal device and a stationary optical terminal device. FIG. 1 is an external view of the optical fiber curl cord (A) (FIG. 1A) and an explanatory view of the optical fiber cord (1) constituting the curl cord. (2) is an optical fiber, (3) is a plastic resin, etc. Is a protective coating layer.

An essential problem in the optical transmission of such an optical fiber curl cord is that the expansion and contraction of the curl cord causes a change in the bending diameter due to the curl shape of the optical fiber and a change in the twist, which causes a change in the optical transmission loss. . This change depends on the material of the optical fiber, the size, the structure of the protective coating, etc., but basically as shown in FIG. 2, when the curl cord is stretched, the curl bending diameter increases and the loss decreases. Although it changes (b in the same figure), at the same time, the twist generated in the optical fiber increases and the loss increases (a in the same figure). These effects are remarkable in the plastic fiber having a large optical fiber core diameter according to the trial study by the inventors of the present application. According to the experimental result, the loss change due to bending as shown in FIG. The change in loss due to twisting (Figure A) is larger than that in the figure, and eventually the loss increases by the amount shown in Figure C.

However, the inventors of the present application pay attention to the fact that the loss change directions are opposite to the elongation of the curl cord from the result of the above-mentioned trial production, and the change amount due to the twist (the increase direction) is changed by the bending amount (the increase amount). It has been found that the loss change can be almost zero with respect to the elongation of the curl cord by making the decreasing directions) substantially equal.

DISCLOSURE OF THE INVENTION The present invention provides an optical fiber curl cord having an extremely small loss change and a method for manufacturing the same, from the above viewpoint.

FIG. 3 is an explanatory view showing a method for manufacturing an optical fiber curl cord according to the present invention, in which a normal core (4) is provided with an optical fiber cord.
After winding (7) on (2), heat it as it is at high temperature to protect the optical fiber (2). (3) Thermoset the material (usually plastic resin) to protect the curled shape as a curl cord. However, in such a manufacturing process, when the winding core (4) is rotated in the direction of the arrow and the optical fiber cord (2) is unwound from the supply reel (5) and wound, for example, the supply reel (5 ) Is rotated in the opposite direction (right side in the figure) with respect to the winding direction (left side in the figure), and twist (6) is applied to the optical fiber cord (2). When the optical fiber curl cord in which the imparted twist is left on the optical fiber in the curl cord is extended, the twist imparted to the optical fiber in advance is accompanied by the extension of the curl cord as shown in FIG. Since the direction is opposite to the twist, the loss changes in a decreasing direction (Fig. 4D), and the change in the loss due to the twist is larger than that when the optical fiber is not twisted in advance. The absolute value decreases and the absolute value of the change in loss due to bending (Fig. 2B) is approximately equal, and the signs are opposite, so they cancel each other out, resulting in Fig. 4 ( As shown in (c), the change in loss due to expansion and contraction of the curl cord is almost zero.

In the manufacture of curl cords, there is a case where after heat processing and thermosetting, the positions of adjacent curls are all reversed to increase the curl contracting force, but in this case the curl winding direction is reversed. In addition, since the direction in which the twist is applied when the curl is extended is also reversed, it is necessary to determine the twist direction to be applied in advance in consideration of these. Further, by reversing the position of the curl, the twist of the optical fiber when the curl cord is contracted also changes in the opposite direction by the amount of twist determined by the outer diameter of the cord and the winding diameter of the curl, but this magnitude is not so large. Therefore, the relationship between the direction of twist applied when the curl cord is stretched and the direction of twist given in advance may be mainly considered.

FIG. 5 is an explanatory view of another embodiment of a method of imparting a twist to an optical fiber cord in advance during manufacturing. The coil is formed into a coil shape (8) corresponding to the size and direction of the twist required when processed into a curl shape. The wound optical fiber cord (2) is pulled out from its axis (9) and supplied to a curl processing point to impart a twist (6), which is effective as one of methods for producing a short curl cord.

(Effects of the Invention) According to the above-described optical fiber curl cord of the present invention and the method of manufacturing the same, the optical fiber curl cord is changed so that the change in the optical transmission loss due to the change in the twisting and bending diameter of the optical fiber caused by the expansion and contraction of the curl cord cancels each other. Since the fiber is pre-twisted, the change in loss due to the expansion and contraction of the curl cord is almost zero, and an extremely stable optical fiber curl cord can be obtained.

[Brief description of drawings]

FIG. 1 is an external view of the optical fiber curl cord (FIG. 1A) and an explanatory diagram of the optical fiber cord, FIG. 2 is a relationship diagram of expansion and contraction and loss change of the conventional optical fiber curl cord, and FIG. FIG. 4 is an explanatory view of the manufacturing method, FIG. 4 is a relationship diagram of expansion and contraction and loss change of the optical fiber curl cord of the present invention, and FIG. 5 is an explanatory view of another embodiment of the manufacturing method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Optical fiber cord, 2 ... Optical fiber, 3 ... Protective coating layer, 4 ... Core 5, 5 ... Supply reel of optical fiber cord, 6
… Twisting direction.

Claims (4)

[Claims] 1. A light for canceling a change in optical transmission loss due to a change in twist of an optical fiber caused by expansion and contraction of a curl cord, by a change in optical transmission loss due to a change in bending diameter of an optical fiber caused by expansion and contraction of a curl cord. An optical fiber curl cord characterized in that the fiber is pre-twisted. 2. A change in optical transmission loss due to a change in twist of an optical fiber caused by expansion and contraction of a curl cord is canceled by a change in optical transmission loss due to a change in bending diameter of an optical fiber caused by expansion and contraction of a curl cord. A method for producing an optical fiber curl cord, characterized in that the optical fiber cord is rotated in a direction opposite to the winding direction of the winding core to wind the optical fiber cord on the winding core to impart a twist. 3. The light according to claim 2, wherein the optical fiber cord is twisted by rotating the supply reel of the optical fiber cord in a direction opposite to the winding direction around the winding core. Fiber curl cord manufacturing method. 4. An optical fiber cord wound in a coil shape corresponding to the size and direction of the twist required when curling is drawn so that the twist remains and wound around the core. The method for manufacturing an optical fiber curl cord according to claim 2, which is characterized in that.