JP4818856B2 - Optical fiber sensor head and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical fiber sensor head using a double-coated multi-core plastic optical fiber cable and a manufacturing method thereof.

  When an optical fiber (bare wire) or an optical fiber cable in which a multi-core optical fiber is coated with a single coating is used for an optical fiber sensor head, it is described in, for example, Japanese Patent Application Laid-Open No. 6-288825 (Patent Document 1). As shown in the figure, after the outer cover (covering material) of the tip portion of the optical fiber cable (optical fiber cord) is peeled off, and the cylindrical head cap is fitted and fixed thereto, the end face of the optical fiber exposed from the head cap is fixed. In general, an optical fiber sensor head is obtained by polishing to a mirror surface.

  By the way, in order to improve the heat resistance of the multicore plastic optical fiber, for example, as described in JP-A-11-95048 (Patent Document 2) or JP-A-11-237513 (Patent Document 3), It is known that a multi-core plastic optical fiber having a sea-island structure is double-coated to form a double-coated multi-core plastic optical fiber cable.

Even when such a double-coated multi-core plastic optical fiber cable is used for an optical fiber sensor head, an optical fiber is provided by attaching a head cap to the tip of the multi-core plastic optical fiber cable and mirror-finishing the end face of the optical fiber. Although it is necessary to obtain a sensor head, its specific manufacturing method is not known.
JP-A-6-288825 Japanese Patent Laid-Open No. 11-95048 Japanese Patent Laid-Open No. 11-237513

  When an optical fiber sensor head is manufactured using a double-coated multi-core plastic optical fiber cable, the optical characteristics of the obtained optical fiber sensor head are deteriorated, for example, compared with the case where a single-coated optical fiber cable is used. Increase in attenuation and deterioration of mechanical characteristics, such as misalignment (protrusion or retraction) of the end face of the multi-core plastic optical fiber with respect to the head cap, are likely to occur.

  Accordingly, an object of the present invention is to provide an optical fiber sensor head excellent in optical characteristics and mechanical characteristics using a double-coated multi-core plastic optical fiber cable.

According to the present invention, as a solution to the above problems,
A double-coated multi-core plastic optical fiber cable in which a first coating and a second coating are applied in this order to the outer peripheral surface of the multi-core plastic optical fiber; and a head cap bonded to the double-coated multi-core plastic optical fiber cable; The multi-core plastic optical fiber has a length of 0.3 mm to 2 mm in an end region where the first coating and the second coating are peeled off, and the head cap is An optical fiber sensor head bonded to an end of the double-coated multi-core plastic optical fiber cable including the end region;
Is provided.

  In one aspect of the present invention, the second coating is peeled in an end adjacent region having a length of 2 mm to 6 mm adjacent to the end region.

Further, according to the present invention, as a solution to the above problems,
An annealing step for annealing a double-coated multi-core plastic optical fiber cable in which a first coating and a second coating are applied in this order on the outer peripheral surface of the multi-core plastic optical fiber, and an end region of the multi-core plastic optical fiber And a coating stripping process for stripping the first coating and the second coating, and head cap bonding for bonding the head cap to the end of the double-coated multi-core plastic optical fiber cable including the end region. And a polishing step of polishing an end surface of the multi-core plastic optical fiber of the double-coated multi-core plastic optical fiber cable to which the head cap is bonded, wherein the coating peeling step and the polishing are performed. The process is performed so that the length of the end region of the multi-core plastic optical fiber after the polishing is 0.3 mm to 2 mm. The symptom, method for producing the optical fiber sensor head,
Is provided.

  In one embodiment of the present invention, the annealing treatment is performed within a temperature range of 80 ° C. to 120 ° C. within a time range of 0.5 hours to 6 hours. In one aspect of the present invention, in the coating stripping step, following the stripping of the first coating and the second coating in the end region, a length of 2 mm to 6 mm adjacent to the end region is further provided. The second coating is peeled off at the end adjacent region.

  According to the present invention, even in a heat-resistant environment of 100 ° C. using a double-coated multi-core plastic optical fiber cable, there is no significant attenuation of the light amount and no significant displacement of the end face of the multi-core plastic optical fiber with respect to the head cap. A heat-resistant optical fiber sensor head can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a first embodiment of an optical fiber sensor head obtained by the manufacturing method of the present invention. FIG. 2 is a second embodiment of an optical fiber sensor head obtained by the manufacturing method of the present invention. FIG. FIG. 3 is a schematic cross-sectional view of a double-coated multi-core plastic optical fiber cable used for manufacturing these optical fiber sensor heads.

  As shown in FIG. 3, the multi-core plastic optical fiber 1 constituting the double-coated multi-core plastic optical fiber cable has a sea-island structure, and a large number of islands (cores) 11 and seas ( (Sheath part) 12. It is preferable that the number of the core parts 11 is in the range of 50 to 400, and the cross-sectional shape of each core part 11 is substantially circular, substantially elliptical, or substantially hexagonal. The core part 11 is an optical transmission line and is made of a highly transparent resin. Moreover, as resin which comprises the sheath part 12, what has a refractive index lower than resin which comprises the core part 11 is used. Although not shown in the figure, on the outer periphery of the multi-core plastic optical fiber 1, mainly for the purpose of protecting the optical fiber transmission performance, and for improving various characteristics including mechanical characteristics and protecting the multi-core plastic optical fiber 1, It is also possible to form a protective layer made of a thin cladding layer.

  The resin constituting the core part 11 and the sheath part 12 of the multi-core plastic optical fiber 1 has high transparency such as polymethacrylate resin, polystyrene resin, polycarbonate resin, fluorine resin, amorphous polyolefin resin, etc. Examples of the resin include polymethacrylate resins that are particularly excellent in transparency and processability.

  As shown in FIGS. 1 to 3, the first coating (first coating layer) 2 and the second coating (second coating layer) 3 are formed in this order on the outer periphery of the multi-core plastic optical fiber 1. Has been. The first and second coating layers 2 and 3 facilitate handling of the multicore plastic optical fiber 1 and mainly protect the multicore plastic optical fiber 1 from external pressure and damage the multicore plastic optical fiber 1. It plays a role of not. The covering layers 2 and 3 are generally made of a resin having flexibility and low resistance to bending stress. For example, polyolefin resins such as vinyl chloride resin and polyethylene, polyurethane resin, polyamide What consists of resin etc. is used. These resins can be used alone or in admixture of two or more. Due to the double coating with the two coating layers 2 and 3, good characteristics can be maintained even in applications used in a heat resistant environment of 100 ° C.

  1 and 2, reference numerals 4 and 5 denote head caps. The material and shape of the head caps 4 and 5 are not particularly limited. For example, the head caps 4 and 5 are made of stainless steel, aluminum, brass or heat-resistant resin, and those having a cylindrical shape are exemplified.

  The head cap 5 shown in FIG. 1 has a through-hole, which has a large-diameter portion on the insertion port side (left side in FIG. 1) and a small-diameter portion on the tip end side (right side in FIG. 1). Consists of. The length L1 of the small diameter portion is preferably 0.3 mm to 2 mm as will be described later.

  The head cap 4 shown in FIG. 2 has a through hole. The through hole has a large-diameter portion on the insertion port side (left side in FIG. 1) and a small-diameter portion on the tip end side (right side in FIG. 1). It consists of a medium diameter part between these. As described later, the length L1 of the small diameter portion is preferably 0.3 mm to 2 mm, and the length L2 of the medium diameter portion is preferably 2 mm to 6 mm. Corresponding to the fact that only the second covering layer 3 is peeled in the end adjacent region adjacent to the end region where both the first and second covering layers 2 and 3 are peeled off, the head cap 4 Has a small outer diameter at the tip. Thus, by making the multi-core plastic optical fiber 1, the first coating layer 2 and the second coating layer 3 into a multi-stage shape, the tip portion of the head cap 4 can be made to have a small outer diameter, There are advantages in handling such as easy wiring in narrow spaces.

  Although not shown, an adhesive for adhering them is interposed between the through holes of the head caps 4 and 5 and the outer peripheral surface of the double-coated multi-core plastic optical fiber cable.

  Hereinafter, the manufacturing method of the optical fiber sensor head of the above embodiment will be described.

  4 to 7 are schematic cross-sectional views for explaining the manufacturing process of the optical fiber sensor head according to the first embodiment shown in FIG.

  First, as shown in FIG. 4, a double-coated multi-core plastic optical fiber cable having a required length (in FIG. 4, the second coating layer 3 is shown) is prepared. Annealing treatment is performed. This annealing treatment is performed in order to relieve the residual stress due to stretching during spinning of the multi-core plastic optical fiber 1 and to improve the adhesion between the multi-core plastic optical fiber 1 and the double-coated cable jackets 2 and 3.

  In the annealing process, if the temperature is too low or the time is too short, there may be inconveniences such as insufficient adhesion between the multi-core plastic optical fiber and the double-coated cable jacket. If the time is too high or the time is too long, the release of residual stress due to stretching of the multi-core plastic optical fiber will progress at once, causing inconveniences such as eccentricity of the multi-core plastic optical fiber and weakness of the multi-core plastic optical fiber. There is. For this reason, the annealing treatment is preferably performed within a temperature range of 80 ° C. to 120 ° C. within a time range of 0.5 hours to 6 hours. The heating method in the annealing treatment is not particularly limited, and may be performed using, for example, a hot air drying furnace.

  Next, as shown in FIG. 5, in the end region of the multicore plastic optical fiber cable 1, the outer peripheral surface of the multicore plastic optical fiber 1 is exposed by peeling off the double coating layers 2 and 3. . If the length of the end region where the double coating is peeled off (the dimension in the length direction of the multi-core plastic optical fiber) is too long, the resulting optical fiber sensor head has a large amount due to the influence of heat from the side surface through the head cap. The core plastic optical fiber 1 may be significantly deteriorated and its life may be extremely shortened. For this reason, it is preferable that the length of the end region where the double coating is peeled is 2 mm or less after the polishing step described later. In addition, the lower limit of the length of the end region where the double coating is peeled is 0.3 mm or more after the polishing step described later from the viewpoint of maintaining the adhesive strength between the multicore plastic optical fiber 1 and the head cap 5. Is preferable.

  Next, as shown in FIG. 6, a multi-core plastic optical fiber cable is inserted from the insertion port of the head cap 5, and the end surfaces of the first coating and the second coating adjacent to the cable end are passed through the head cap. Butt against the inner step of the hole. In this state, the tip of the multi-core plastic optical fiber 1 slightly protrudes from the tip of the head cap 5.

  Prior to the insertion of the multicore plastic optical fiber cable into the through hole of the head cap 5, an adhesive is applied to the inner surface of the through hole of the head cap 5 and / or the outer peripheral surface of the corresponding end of the multicore plastic optical fiber cable. Keep it. As an adhesive used for bonding and fixing the head cap 5 and the multi-core plastic optical fiber cable, a heat-resistant adhesive that does not cause cracks or the like causing deterioration in the multi-core plastic optical fiber 1 is used. For example, epoxy, silicon, and acrylic adhesives are exemplified.

  The adhesive cures at room temperature, but in applications where the optical fiber sensor is used in a heat-resistant environment of 100 ° C., it is preferable to perform heat curing for about 2 hours at 100 ° C. after the adhesive is cured at room temperature. , The reaction of the unreacted part of the adhesive is promoted to realize stronger adhesion and fixation.

  Next, as shown in FIG. 7, the extra length of the multi-core plastic optical fiber 1 protruding from the tip end of the head cap 5 is removed by polishing using a polishing means such as water-resistant paper 10. By this polishing, the tip surface of the multi-core plastic optical fiber 1 is finished in a mirror shape. Thus, an optical fiber sensor head is obtained.

  FIGS. 8-10 is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 2nd Embodiment shown by the said FIG.

  First, in the same manner as in the first embodiment, an annealing process is performed on a double-coated multi-core plastic optical fiber cable having a required length.

  Next, as shown in FIG. 8, in the same manner as in the first embodiment, the double coating layers 2 and 3 are peeled off at the end region of the multi-core plastic optical fiber cable 1. Then, the multi-core plastic optical fiber 1 is exposed. Following this, in the end adjacent region adjacent to the end region of the multicore plastic optical fiber cable 1, only the second cover layer 3 is peeled to expose the first cover layer 2. Thus, the multi-core plastic optical fiber 1, the first coating layer 2, and the second coating layer 3 are formed in a multistage shape.

  Next, as shown in FIG. 9, a multi-core plastic optical fiber cable is inserted from the insertion port of the head cap 4, and the end surfaces of the first coating and the second coating adjacent to the cable end are passed through the head cap. It hits the multi-step part inside the hole. In this state, the tip of the multi-core plastic optical fiber 1 slightly protrudes from the tip end of the head cap 4.

  Prior to the insertion of the multi-core plastic optical fiber cable into the through hole of the head cap 4, the inner surface of the through hole of the head cap 4 and / or the multi-core plastic corresponding to the same as in the first embodiment. An adhesive is applied to the outer peripheral surface of the end portion of the optical fiber cable.

  Then, the adhesive is cured in the same manner as in the first embodiment.

  Next, as shown in FIG. 10, the excess length portion of the multi-core plastic optical fiber 1 protruding from the tip end of the head cap 4 is the same as in the case of the first embodiment. It removes by performing grinding | polishing using the grinding | polishing means of this, and finishes the front end surface of the multi-core plastic optical fiber 1 in mirror shape by this grinding | polishing. Thus, an optical fiber sensor head is obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[Example 1]
A double-coated multi-core plastic optical fiber cable having an outer diameter of 2.2 mmφ as shown in FIG. 3 was prepared. In this multi-core plastic optical fiber cable, the multi-core plastic optical fiber 1 has an outer diameter of 1 mmφ, the number of core portions 11 is 151, and the cross-sectional shape of the core portion 11 is substantially circular. The resin constituting the core part 11 of the multicore plastic optical fiber 1 was a polymethacrylate resin, and the resin constituting the sheath part 12 was a low refractive index resin containing fluorine. The first coating layer 2 was made of crosslinked polyethylene and had an outer diameter of 1.5 mmφ. The second coating layer 3 was made of a urethane resin and had an outer diameter of 2.2 mmφ.

  The above-mentioned double-coated multi-core plastic optical fiber cable is cut to a length of 2100 mm and annealed in a hot air drying furnace at 100 ° C. for 4 hours to relieve the residual stress of the multi-core plastic optical fiber 1 and The adhesion between the plastic optical fiber 1 and the double-coated cable jackets 2 and 3 is improved.

  Subsequently, the jackets (first coating and second coating) 2 and 3 of the double-coated multi-core plastic optical fiber cable were peeled 2 mm from the tip to expose the outer peripheral surface of the multi-core plastic optical fiber 1.

  Next, as shown in FIG. 1, a double-coated multi-core plastic optical fiber cable has a through-hole for inserting and fixing the end, and the through-hole has a large-diameter portion on the insertion port side. A cylindrical head cap 5 made of stainless steel and made of a small diameter portion on the tip end side was prepared. The length L1 of the small diameter portion was 1.9 mm.

  Next, an epoxy heat resistant adhesive was applied to the inner surface of the through hole of the head cap 5 and the outer peripheral surface of the end portion of the double-coated multi-core plastic optical fiber cable. Then, the end portion of the double-coated multi-core plastic optical fiber cable was inserted from the insertion port of the head cap 5 until the end surfaces of the double-coated cable jackets 2 and 3 abut against the inner hole step portion of the head cap 5. . Thereafter, the adhesive was cured at room temperature and further cured by heating in a hot air drying oven at 100 ° C. for 2 hours.

  Next, the extra length of the fiber protruding 0.1 mm from the head cap 5 is removed by polishing with water-resistant paper 10, thereby finishing the end face of the multi-core plastic optical fiber 1 into a mirror surface, and an optical fiber sensor. Got the head.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat resistant environment of 100 ° C., the light amount was hardly attenuated, and the positional accuracy of the end face of the multi-core plastic optical fiber 1 with respect to the head cap 5 was well maintained.

[Comparative Example 1]
An optical fiber sensor head was obtained in the same manner as in Example 1 except that the annealing treatment was not performed on the double-coated multi-core plastic optical fiber cable.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat-resistant environment of 100 ° C., the amount of light was attenuated, and maintenance of the positional accuracy of the end face of the multicore plastic optical fiber 1 relative to the head cap 5 was insufficient. .

[Comparative Example 2]
Strip the outer sheath (first coating and second coating) 2 and 3 of the double-coated multi-core plastic optical fiber cable 5 mm from the tip to expose the outer peripheral surface of the multi-core plastic optical fiber 1, and further reduce the size of the head cap 5. An optical fiber sensor head was obtained in the same manner as in Example 1 except that a caliber having a length L1 of 4.9 mm was used.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat-resistant environment of 100 ° C., light quantity attenuation was recognized.

[Example 2]
In the same manner as in Example 1, an optical fiber sensor head was obtained. However, after the outer coverings (first covering and second covering) 2 and 3 of the double-coated multi-core plastic optical fiber cable were peeled 2 mm from the tip, only the second covering was further peeled 6 mm. Thereby, the multi-core plastic optical fiber 1, the first coating 2, and the second coating 3 were formed in a multistage shape. Further, as shown in FIG. 2, a multi-stage head cap having a through hole having a large-diameter portion on the insertion port side, a small-diameter portion on the front-end port side, and a medium-diameter portion positioned therebetween as shown in FIG. 4 was used.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat resistant environment of 100 ° C., the light amount was hardly attenuated, and the positional accuracy of the end face of the multi-core plastic optical fiber 1 with respect to the head cap 5 was well maintained.

[Comparative Example 3]
An optical fiber sensor head was obtained in the same manner as in Example 2 except that the annealing treatment was not performed on the double-coated multi-core plastic optical fiber cable.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat-resistant environment of 100 ° C., the amount of light was attenuated, and maintenance of the positional accuracy of the end face of the multicore plastic optical fiber 1 relative to the head cap 5 was insufficient. .

[Comparative Example 4]
Strip the outer sheaths (first and second coatings) 2 and 3 of the double-coated multi-core plastic optical fiber cable 5 mm from the tip to expose the outer peripheral surface of the multi-core plastic optical fiber 1. An optical fiber sensor head was obtained in the same manner as in Example 2 except that a caliber having a length L1 of 4.9 mm was used.

  When the obtained optical fiber sensor head was continuously used and evaluated in a heat-resistant environment of 100 ° C., light quantity attenuation was recognized.

It is typical sectional drawing of 1st Embodiment of the optical fiber sensor head obtained by the manufacturing method of this invention. It is typical sectional drawing of 2nd Embodiment of the optical fiber sensor head obtained by the manufacturing method of this invention. It is a typical sectional view of a double covering multi-core plastic optical fiber cable used for manufacture of an optical fiber sensor head. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 1st Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 1st Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 1st Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 1st Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 2nd Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 2nd Embodiment shown by FIG. It is typical sectional drawing for description of the manufacturing process of the optical fiber sensor head of 2nd Embodiment shown by FIG.

Explanation of symbols

1 Multi-core plastic optical fiber 11 Island (core)
12 Sea (sheath)
2 First coating layer 3 Second coating layer 4 Multi-stage head cap 5 Head cap 10 Water resistant paper

Claims (3)

A double-coated multi-core plastic optical fiber cable in which a first coating and a second coating are applied in this order to the outer peripheral surface of the multi-core plastic optical fiber; and a head cap bonded to the double-coated multi-core plastic optical fiber cable; An optical fiber sensor head comprising:
In the end region of the multicore plastic optical fiber having a length of 0.3 mm to 2 mm , both the first coating and the second coating are peeled off,
In the end adjacent region having a length of 2 mm to 6 mm adjacent to the end region, only the second coating of the first coating and the second coating is peeled off,
The optical fiber sensor head, wherein the head cap is bonded to an end of the double-coated multi-core plastic optical fiber cable including the end region. An annealing step for annealing a double-coated multi-core plastic optical fiber cable obtained by applying a first coating and a second coating in this order to the outer peripheral surface of the multi-core plastic optical fiber;
A coating stripping step of stripping both the first coating and the second coating in an end region of the multi-core plastic optical fiber;
A head cap bonding step of bonding the head cap to the end of the double-coated multi-core plastic optical fiber cable including the end region;
Polishing the end face of the multi-core plastic optical fiber of the double-coated multi-core plastic optical fiber cable to which the head cap is bonded,
Here, the coating peeling step and the polishing step are performed so that the length of the end region of the multi-core plastic optical fiber after the polishing is 0.3 mm to 2 mm ,
In the coating peeling step, following the peeling of both the first coating and the second coating in the end region, in the end adjacent region having a length of 2 mm to 6 mm adjacent to the end region. A method of manufacturing an optical fiber sensor head, wherein only the second coating of the first coating and the second coating is peeled off. 3. The method of manufacturing an optical fiber sensor head according to claim 2 , wherein the annealing treatment is performed in a temperature range of 80 ° C. to 120 ° C. in a time range of 0.5 hours to 6 hours.

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