JP2002072004A - Method for heating and shrinking heat shrinkable tube for reinforcing optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for heating and shrinking an optical fiber reinforcing heat shrinkable tube so that air does not remain within the optical fiber reinforcing heat shrinkable tube when the optical fiber reinforcing heat shrinkable tube for reinforcing the connecting part of the optical fiber or the bare part of the optical fiber is heated and shrunk. SOLUTION: In the method for heating and shrinking the optical fiber reinforcing heat shrinkable tube, the optical fiber reinforcing heat shrinkable tube is positioned on the optical fiber part to be reinforced, first a part of the tube is heated and shrunk by a heater having such a length as not including air in the initial stage wherein the optical fiber reinforcing heat shrinkable tube is heated and shrunk, the heater is moved left and right from the shrunk part and the optical fiber reinforcing heat shrinkable tube is heated and shrunk while discharging air in the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber reinforcing heat-shrinkable tube for reinforcing an optical fiber connection portion, wherein the heat-shrinkable tube is thermally shrunk so that no air remains in the heat-shrinkable optical fiber tube. The present invention relates to a method for heat shrinking a heat shrinkable tube.

[0002]

2. Description of the Related Art When connecting optical fiber cores or strands (hereinafter referred to as optical fiber cores), the coating layer of the optical fiber cores to be connected is removed with a stripper, and stripped optical fibers (hereinafter referred to as "optical fibers"). The end portion of the optical fiber is simply cut with an optical fiber cutter so that the end surface becomes a mirror surface,
The end faces of the two optical fibers cut into a mirror surface are abutted to each other, and the abutted portion is fusion-spliced by a fusion splicer to connect the two optical fibers.

The optical fiber connection portion thus connected is exposed when the optical fiber is bare, that is, since the connection portion is exposed to the outside air in a glass state, the deterioration of the glass proceeds at an early stage. It is necessary to cover and cover the bare glass part.

FIG. 7 is a schematic explanatory view showing an optical fiber connecting portion 10. As shown in the figure, a connecting portion of an optical fiber core 2 is covered with a heat shrinkable tube 1 for reinforcing an optical fiber, and is thermally shrunk to cover and reinforce. I have. In the drawing, reference numeral 3 denotes an optical fiber, 4 denotes a coating layer of an optical fiber core wire, and 5 denotes a fusion spliced portion of the optical fibers 3. Covered and reinforced with heat shrinkable tube 1. A heat-shrinkable tube 1 for reinforcing an optical fiber as shown as an example in FIG. The heat shrinkable tube for reinforcing the optical fiber 1
Is an outer tube 11, a hot-melt adhesive 12 provided on the inner surface of the outer tube 11, an inner tube 14 inserted inside the outer tube 11, and an optical fiber connecting portion reinforcing inside the outer tube 11. The hot melt adhesive 12 comprises a splint 13 and the outer tube 1
1 for tightly fixing the optical fiber coating layer 4, the optical fiber 3, and the optical fiber fusion spliced portion 5.

In order to connect the optical fiber cores, first, the coating layer 4 of both optical fiber core ends is removed with a stripper to expose the optical fiber 3, and the exposed end of the optical fiber 3 is connected to an optical fiber cutter. And cut to a mirror surface. Next, the heat-shrinkable tube 1 for reinforcing an optical fiber is passed through the coating layer 4 of one of the optical fibers. Thereafter, the two optical fibers are connected by a fusion splicer, and the heat-shrinkable tube 1 for reinforcing the optical fiber is returned to the fusion splicing portion 5 and heat-shrinked to complete the connection of the two optical fibers.

Conventional heat shrinkable tube 1 for reinforcing optical fiber
As shown in FIGS. 9 (a) to 9 (d), a flat type heater 31 which is longer than the heat-shrinkable tube 1 for reinforcing an optical fiber and has a flat cross section is used.
, A U-shaped heater 32, a V-shaped heater 33, a chevron-shaped heater 34, and the like. In order to heat-shrink the heat-shrinkable optical fiber tube 1 with these heaters, first, a coating layer 4 of an optical fiber core is overlapped with a predetermined length inside the both ends of the heat-shrinkable optical fiber tube 1. (The fusion spliced portion 5 is accommodated in the heat shrinkable tube 1 for reinforcing the optical fiber by this arrangement), and then the heat shrinkable tube 1 for reinforcing the optical fiber is set in the heater. Heats and shrinks.

FIGS. 10 (b) and 10 (c) show the temperature distribution of the flat type heater 31 among the above heaters. As shown in the figure, the heater 31 has a gradient distribution such that the temperature is higher toward the center and lower as the distance from the center increases. Therefore, the center of the heater 31 having such a temperature distribution is located at the center of the heat-shrinkable tube 1 for reinforcing the optical fiber as shown in FIG.
When the heater 31 is placed as shown in (a), the temperature distribution of the heater 31 is set so as to become higher toward the center, so that the heat-shrinkable tube 1 for reinforcing the optical fiber shrinks from the center, and FIG. As shown in ()), heat shrinkage proceeds toward both ends.

Accordingly, as shown in FIG. 11A, the heat-shrinkable tube 1 for reinforcing the optical fiber undergoes the shrinkage 25 from the central portion toward both ends as the heat-shrinkage progresses. Is extruded toward both ends of the optical fiber reinforcing heat shrinkable tube 1, and the extruded air is exhausted from both ends of the optical fiber reinforcing heat shrinkable tube 1 to complete the shrinkage without leaving any bubbles.

[0009]

However, in the conventional heater (for example, flat type 31), since the entire length of the heat-shrinkable tube for reinforcement 1 needs to be heat-shrinked, the entire surface of the heater is heat-shrinkable for reinforcing the optical fiber. Is set to a high enough temperature to cause heat shrinkage. For this reason, if the heat shrink condition of the optical fiber reinforcing heat shrink tube 1 is slightly different due to thickness variation and radial unevenness of the optical fiber reinforcing heat shrink tube, or the position of the splint 13,
As shown in FIG. 11 (b), thermal contraction starts simultaneously from a plurality of locations (two locations in the illustrated example) as shown in the progress of thermal contraction, and air is confined in the thermal contraction tube 1 for reinforcing the optical fiber, thereby reinforcing the optical fiber. Bubbles 26 in the heat shrinkable tube 1
May result. When the air bubbles 26 stay in the heat-shrinkable tube 1 for reinforcing the optical fiber, the volume of the air bubbles repeats expansion and contraction in the heat cycle, and this force repeatedly acts on the optical fiber as a small bending stress. There is a problem that the reliability is lost and the optical fiber is finally broken.

Generally, as a method for heat shrinking the heat-shrinkable tube, there is a method using a high-temperature liquid such as hot water, or a method using a heated gas to shrink the heat-shrinkable tube from one side to the other. If the method using gas is adopted as the heat shrinking means of the heat shrinkable tube for reinforcing the optical fiber in the optical fiber connection portion, water or gas enters from the joint between the heat shrinkable tube for reinforcing the optical fiber and the coating of the optical fiber, and this water Gas and gas increase the connection loss of the optical fiber connection portion, and have not been adopted yet. The present invention solves the above-mentioned problems and provides a heat shrinking method that does not trap air in a heat shrinkable tube for reinforcing an optical fiber.

[0011]

According to the present invention, a heat-shrinkable tube for reinforcing an optical fiber is positioned on an optical fiber reinforced portion, and air is not entrained in an initial stage of heat-shrinking the heat-shrinkable tube for reinforcing an optical fiber. First, a part of the heat is shrunk by a heater having a length, and the heater is moved to the left or right from the shrunk part to perform heat shrink while removing air in the heat shrink tube for reinforcing the optical fiber. This is a method for heat shrinking a heat shrinkable tube for reinforcing an optical fiber.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Note that the same parts as those described above are denoted by the same reference numerals, and description thereof will be omitted. 1 and 2 show an embodiment of the present invention, wherein 1 is a heat-shrinkable tube for reinforcing an optical fiber, 20 is a cylindrical heater, and the heater 20 is a heat-shrinkable optical fiber before heat shrinkage. It is made of a cylindrical ceramic having an inner diameter larger than the outer diameter of the shrinkable tube 1 and provided with a slit 21 having a width through which the optical fiber core wire 2 can pass. As shown in a perspective view in FIG. 22 is embedded. 23 is a lead wire. FIG. 3 shows the heat generation temperature distribution of the heater 20, wherein the temperature distribution is provided so that the temperature becomes higher toward the center, for example, by considering the density of the heat generation lines.

The heating element 22 embedded in the cylindrical heater 20 shown in FIG. 2 is constituted by a heating wire of a continuous length that is periodically turned back at the slit portion 21 of the heater 20.
As 2, a tungsten wire, a nichrome wire or the like can be adopted. When the heating element 22 is configured in this manner, it can be designed so that the diameter inside the cylindrical heater is constant, the distribution is isothermal in the circumferential direction, and the temperature distribution is arbitrary in the longitudinal direction. Therefore, FIG.
If the temperature distribution is as shown in the following, and the optical fiber reinforcing heat shrinkable tube 1 is located at the center of the cylindrical heater, the optical fiber reinforcing heat shrinkable tube 1 is uniformly heated in the circumferential direction,
It contracts sequentially in the longitudinal direction.

In the present invention, the effective length of the cylindrical heater 20 is such that the contracted portion does not involve air in the initial stage of contracting the optical fiber reinforcing heat-shrinkable tube 1. Specifically, it differs depending on the type of the heat-shrinkable tube 1 for reinforcing an optical fiber, the heat generation capacity of the heater 20, the temperature distribution, and the like. For example, when the length of the heat-shrinkable tube 1 is 40 mm, the length is 10 mm or less, 60 mm or less. At the time of 1
An appropriate length is about の of the length of the optical fiber reinforcing heat shrinkable tube 1 so as to be 5 mm or less. By setting as described above, for example, the thickness of the heat shrinkable tube 1 for reinforcing the optical fiber varies, or the splint 1
Even if the heat shrinkage is affected by the position 3, the shrinkage of the optical fiber reinforcing heat shrinkable tube 1 does not start from a plurality of places, and there is no danger of air being caught in the initial stage.

In order to shrink the heat-shrinkable tube 1 for reinforcing an optical fiber, first, as shown in FIG. The heat-shrinkable tube 1 is pulled back so that the center of the heat-shrinkable tube 1 is located at the center of the optical fiber connection portion 5 as shown in FIG. At this time, the inner sides of both ends of the heat-shrinkable tube 1 for reinforcing the optical fiber are coated with the coating layers 4 and 4 of the connected optical fiber.
4 and a predetermined length.

A cylindrical heater 2 is provided on the outer periphery of the heat-shrinkable tube 1 for reinforcing the optical fiber disposed on the optical fiber connection portion 5.
In order to install the optical fiber, the optical fiber coating layer 4 is inserted through a slit 21 provided in the cylindrical heater 20 and the tube is first contracted, for example, as shown in FIG. Return to the center of the heat-shrinkable tube 1. It is preferable that the width of the slit 21 be as small as possible because it is necessary to apply heat as uniformly as possible in the circumferential direction of the heat shrinkable tube 1 for reinforcing the optical fiber. Therefore, the width of the slit 21 is set to be slightly larger than the outer diameter of the optical fiber. Then, as described above, it is preferable to insert the optical fiber from the portion of the optical fiber core (the coating layer 4).

FIG. 4D shows the optical fiber reinforcing heat-shrinkable tube 1 positioned at the center of the cylindrical heater 20 in the radial direction.
1 shows an initial stage of heat shrinking. The central portion A first undergoes thermal contraction around the central portion A where the temperature of the heater 20 is high. Next, the heater 20 is moved in the right direction B to shrink the heat-shrinkable tube 1 for reinforcing the optical fiber ((e) in the figure), and the heater 20 is further moved to the left C to thereby shrink the heat-shrinkable tube for the optical fiber. 1 is heat-shrinked to complete the heat-shrinkage of the heat-shrinkable tube 1 for reinforcing an optical fiber (FIG. 1F). At this time, the air in the heat-shrinkable tube 1 for reinforcing the optical fiber moves in the left-right direction, and since the length of the heater 20 is short, heat shrinkage does not occur at a plurality of places at the same time. There is no such thing as air being caught in.

Next, the heater 20 is continuously arranged in the right B direction.
Alternatively, the optical fiber reinforcing heat-shrinkable tube 1 is sequentially shrunk by intermittently moving. At this time, if the moving speed of the heater 20 is increased, the heat shrinkage becomes partially insufficient and a gap containing air may be generated. It is necessary to proceed with the contraction work as shown in (c). Right B
When the contraction operation in the direction is completed, the heater 20 is then moved in the left C direction, and the heat contraction section 25 which does not entrap air by gradually contracting the heat contraction tube 1 for reinforcing the optical fiber similarly to the right direction. Can be completed. In FIG. 4, the tensile members are omitted.

FIG. 5 shows an embodiment in which the contraction start point of the tube is set at one end of the tube. First, a heater is set at the end of the tube and the end is thermally contracted. At this time, the heater 20 may be set so that the end of the tube is located at the center in the longitudinal direction of the heater. With this setting, the possibility of air entrapment is greatly reduced. One end of the heat-shrinkable tube 1 for reinforcing the optical fiber is heat-shrinkable as shown by a dotted line.
5, the heater 20 is gradually or continuously intermittently moved to the other end side to thermally shrink the heat-shrinkable tube 1 for reinforcing the optical fiber, and the heat shrinkage without entraining air proceeds as described above. And a connection portion free of air bubbles can be completed.

FIG. 6 is a conceptual diagram of a heat-shrinkable heat-shrinkable tube 40 for reinforcing an optical fiber embodying the present invention. The light sensor array 41 and the light source array 42 are composed of, for example, a photodiode array and an LED array, and constitute a pair of sensors by opposing photodiodes and LEDs. The sensors measure the length of the heat-shrinkable tube 1 for reinforcing an optical fiber. A length measuring sensor, a position confirmation sensor for confirming the position of the heat shrinkable tube 1 for reinforcing the optical fiber, and a cylindrical heating at the shrinkage start point (the initial set position on the left end in the figure) of the confirmed heat shrinkable tube 1 for reinforcing the optical fiber. Each of them operates as a position control sensor for positioning the container 20.

The light sensor array 41 and the light source array 42 operate as sensors by receiving the output light of the LEDs facing each other by the photodiodes facing each other. Where the optical fiber reinforcing heat-shrinkable tube 1 is present, the output light from the LED is cut off by the optical fiber reinforcing heat-shrinkable tube 1, so that the output from the photodiode is reduced and the lower limit is not more than a predetermined value. In the case of, the heat-shrinkable optical fiber reinforcing tube 1 which has not yet been shrunk, the presence of the shrinkable optical fiber heat-shrinkable tube at the intermediate value, and the absence of the heat-shrinkable optical fiber tube at the upper limit or more. Is detected. Therefore, the position and length of the heat-shrinkable tube for reinforcing the optical fiber can be determined.

The heat-shrinkable tube 1 for reinforcing an optical fiber is set on a V-groove-shaped wire netting 48. The cylindrical heater 20 is moved right and left by a slide table 46 mounted on a slide rail 45 provided below a wire netting 48. The slide table 46 on which the cylindrical heater 20 is mounted is driven by a ball screw 44 and a motor 43.

The outline of the operation will be described below. First, various data (for example, heat shrinkage corresponding to the optical fiber reinforcing heat shrinkable tube 1 and the heater 20) corresponding to the type of the heat shrinkable tube 1 for optical fiber reinforcement and the heater 20, which are obtained in advance by an experiment, are supplied to the controller 49. Time). From these input data, the heat shrink tube 1 for reinforcing the optical fiber to be set in the device 40 and the control data of the heater 20 (for example, the time T required for heat shrink, the moving distance L corresponding to the shrink length at the time T, etc.) are operated. Call on panel 47. Next, the heat-shrinkable tube 1 for reinforcing the optical fiber is set at an arbitrary position of the wire netting 48 of the device 40, and the optical sensor array 41 and the light source array 42
To measure the length, position, left end, and the like, and report the measurement result to the control unit 49. The control unit 49 displays information such as the length of the optical fiber reinforcing heat-shrinkable tube 1 on the operation panel 47.

The control unit 49 controls the motor 43 to move the center of the cylindrical heater 20 in the longitudinal direction to the left end (initial setting position) of the contraction start point of the optical fiber reinforcing heat-shrinkable tube 1 measured by the sensor. To the heater 20
To move. (In the present embodiment, one end is set as the initial position, but the initial position can be arbitrarily selected.) The longitudinal direction of the cylindrical heater 20 is set at the contraction start point of the heat-shrinkable tube 1 for reinforcing the optical fiber. If it is located at the center, it first waits for the heat shrinkage time (T) of that part. When the waiting time is over, the center of the side surface length direction of the cylindrical heater 20 is moved by the length L to the next heat shrinking portion,
At this point, the heating / shrinking time T waits. This intermittent movement, that is, the number of movements by the length L after waiting for the T time is repeated [M / L + 1] times, and the heat shrinkage ends.

[0025]

According to the present invention, there is provided a heater which is shorter than the heat-shrinkable tube for reinforcing an optical fiber, heats a local area of the heat-shrinkable tube for reinforcing an optical fiber, and has a length which does not involve air in the initial stage of heating. First, the initial position of the optical fiber reinforcing heat-shrinkable tube covering the connection portion of the optical fiber core wire is first heat-shrinked, and the heat-shrinkable initial position is sequentially shrunk in the non-shrinkage direction, so that the shrinkage is reduced. The air can be shrunk without remaining in the finished heat shrinkable tube for reinforcing the optical fiber. As a result, it is possible to obtain a reinforced connection part that hardly causes a change in connection loss due to a heat cycle and has no fear of causing disconnection of an optical fiber.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the present invention, and is a perspective view showing a state where it is inserted into an optical fiber core of a cylindrical heater.

FIG. 2 is an explanatory view showing an example of a cylindrical heater of the present invention.

FIG. 3 is a graph showing a temperature distribution of the cylindrical heater of the present invention.

FIG. 4 is an explanatory view showing a state in which the heat-shrinkable tube for reinforcing an optical fiber is in a shrinkage progressing state.

FIG. 5 is an explanatory view showing an initial state of heat shrinkage of the heat shrinkable tube for reinforcing an optical fiber.

FIG. 6 is a conceptual diagram showing a heat shrinking device for a heat shrinkable tube for reinforcing an optical fiber of the present invention.

FIG. 7 is an explanatory diagram of a connection portion that connects optical fiber strands to each other.

FIG. 8 is an explanatory diagram showing an example of a heat-shrinkable tube for reinforcing an optical fiber.

FIG. 9 is an explanatory view showing the shape of a conventional heater that heat-shrinks a heat-shrinkable tube for reinforcing an optical fiber.

FIG. 10 is an explanatory view showing the arrangement of a heat-shrinkable tube for reinforcing an optical fiber and an optical fiber core placed on a heater.

FIG. 11 is an explanatory view showing a heat-shrinkable state of a conventional heat-shrinkable tube for reinforcing an optical fiber.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 heat shrink tube for reinforcing optical fiber 2 optical fiber core wire 3 optical fiber 4 optical fiber coating layer 5 optical fiber fusion splicing part 10 optical fiber connecting part 20 cylindrical heater 21 slit 22 heating element 25 heat shrinking part 40 heat shrink Device 41 Optical sensor array 42 Light source array 43 Motor 44 Ball screw 45 Slide rail 46 Slide table 47 Operation computer panel 47
Operation panel 48 Wire mesh 49 Control unit

Claims (1)

[Claims] 1. A heat-shrinkable tube for reinforcing an optical fiber is positioned on a portion to be reinforced by an optical fiber. Heat shrinking the portion, and moving the heater to the left or right from the shrunk portion to eliminate the air in the heat shrinkable tube for heat shrinking while heat shrinking. Heat shrinkage method of the tube.