JP2006227250A - Optical fiber with ferrule and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferrule-attached optical fiber which makes the core of the hard polymer clad fiber situated unprotrusively from the tip end of the ferrule regardless of external conditions and which greatly simplifies the assembly as well as reducing the cost, and also to provide its manufacturing method. <P>SOLUTION: In a ferrule 1 having an inserting hole 1B for fixedly holding a secondary coated optical fiber and a through hole 1A for fixedly holding a primary coated optical fiber, there is provided a core holding section 1D between the tip end 1C of the ferrule 1 and the through hole 1A. In the same ferrule 1 with a step section 1E formed between the core holding section 1D and the through hole 1A, the hard polymer clad fiber 2 is inserted. Then, a difference in level is formed between the core 3 and a clad layer 4, wherein the core 3 is exposed by removing the clad layer 4 at the end of the fiber, and the difference in level is brought into contact with the step section 1E of the ferrule 1 and engaged therewith. The tip end 3A of the exposed core 3 is situated inside the core holding section 1D that is inward from the tip end 1C of the ferrule 1. Thereafter, the primary and the secondary coated optical fibers are fixed using an adhesive. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber with a ferrule using a hard polymer clad fiber (hereinafter abbreviated as HPCF) and a method for manufacturing the same.

  Conventionally, as an optical fiber, a single mode fiber and a multimode fiber are generally used. The fiber of the optical fiber is formed of a clad layer that prevents leakage of light passing through the core around the core around the core, and the core diameter is generally several μ to several tens μ. As a material, both the core and the clad layer are mainly glass components such as quartz. By further covering the strand with this strand, an optical fiber core wire having an outer diameter of 125 μm is obtained. Ferrules used for these optical fiber terminals have extremely high accuracy because the diameter of the core of the optical fiber is extremely small and the application is for communication. In other words, the terminal structure is that the optical fiber strand is held and fixed in the through hole of the ferrule with an adhesive or the like, then the optical fiber protruding from the ferrule tip is cut, and then the end face is polished to become a mirror surface. The outer diameter accuracy of the ferrule and the accuracy of the through-hole are extremely high, such as submicron order, and strict conditions are required for the end face shape and the like (see Patent Document 1).

  Apart from the above directions, the demand for optical fibers for general civilian use is increasing for short-distance use among aircraft and vehicles, factories, and medical use. In this case, it is required that the cost be low. Therefore, a plastic fiber having a core and a clad layer made of resin is used as the optical fiber. The terminal structure of plastic fiber can be used sufficiently for medium and short distances, although the accuracy is significantly lower than that of single mode fiber or multimode fiber. However, in the future, even in applications in this field, there is a high possibility that the plastic fiber having a low speed and a limited transmission capacity cannot be transmitted due to the large capacity and high speed of information.

Then, HPCF is examined instead of plastic fiber. The HPCF has a core made of a glass component having an outer diameter of the order of 200 to 700 μm and a resin clad layer covering the core with a thickness of about 15 to 25 μm to form a strand. Since HPCF uses a glass component as a core, it has a feature that it can transmit high-capacity information at a higher speed than plastic fiber, and it does not require high accuracy and can be assembled at a relatively low cost. It has been studied to insert and fix to the above-mentioned conventionally known ferrule.
JP 2001-174668 A

  However, when HPCF is fixed in the through-hole of the ferrule, the core is a glass component and the clad layer is a resin. There exists a problem that it will move to around [mu] to several tens of [mu] and protrude from the tip end surface of the polished ferrule. For this reason, as a means for solving this problem, when polishing the tip of the ferrule, only the end face of the optical fiber at the center is particularly deeply polished and the tip of the core is positioned inside the through hole so that the core moves forward. However, there is a known method for preventing the protrusion from protruding from the ferrule tip. However, the above configuration requires precise polishing conditions and labor, and increases costs. Further, depending on the situation, it is not completely possible to avoid protruding from the tip. In view of this, the present invention has been studied to solve the above-described problems by using an HPCF in which the core of an arbitrary length is exposed by removing the end cladding layer.

  The optical fiber with a ferrule of the present invention removes the clad layer at the end, and holds the hard polymer clad fiber in which a step is formed between the exposed core and the clad layer, and the hard polymer clad fiber strand A core holding part that holds the through hole and the core, and a ferrule configured by a step part provided therebetween, and the step of the hard polymer clad fiber is brought into contact with and locked to the step part of the ferrule, and the inside of the core holding part The first gist is that the tip of the core is positioned inward from the tip of the ferrule.

  Also, as a method of manufacturing an optical fiber with a ferrule, the hard polymer clad fiber is cut to remove the clad layer at the end and expose the core to form a step between the core and the clad layer. A fiber is inserted into the ferrule, the hard polymer clad fiber strand is disposed in the through hole of the ferrule, and the exposed core is disposed in the core holding portion, and a step provided between the through hole and the core holding portion. The second aspect is that the hard polymer clad fiber is fixed after the step of the hard polymer clad fiber is brought into contact with and locked to the portion, and the tip of the core is positioned inward from the tip of the ferrule in the core holding portion. And

  Further, as a method of manufacturing an optical fiber with a ferrule, a hard polymer clad fiber is cut by a laser processing method to remove the clad layer at the end and expose the core, thereby forming a step between the core and the clad layer. This is the third gist.

  In the optical fiber with a ferrule of the present invention, the core of the HPCF does not protrude from the tip of the ferrule due to external conditions, and it is not necessary to polish the end surface of the ferrule. Therefore, it is possible to produce an optical fiber terminal structure that can be manufactured by a simple operation and is always stable at low cost.

  The optical fiber with a ferrule of the present invention realizes the object of positioning the core inward by a predetermined amount from the tip of the ferrule to prevent the core from protruding.

  FIG. 1 is a cross-sectional view showing an optical fiber with a ferrule of the present invention. FIG. 2 is a front view showing the HPCF with the core layer exposed by removing the cladding layer at the end, and FIG. 3 is a sectional view showing the ferrule used in the optical fiber with a ferrule of the present invention. The left side of the drawing is the front and the right side is the rear.

  The ferrule-equipped optical fiber of the present invention includes a ferrule 1 and an HPCF 2 fixed to the ferrule 1 as shown in FIG. As shown in FIG. 2, the HPCF 2 used in the present invention comprises a core 3 having an outer diameter of 200 μm made of a glass component and a cladding layer 4 having a film thickness of about 15 μm. A step is formed between the two. Here, the distance between the tip 3A of the core 3 and the step can be arbitrarily set within a specific range depending on the cutting conditions and the type of HPCF. The core 3 and the clad layer 4 form an HPCF strand, and an outer sheath 5 is coated on the outer periphery of the HPCF strand to form an HPCF core.

  The ferrule 1 of the present invention is made of resin and has a through hole 1A for holding the HPCF strand as shown in FIG. 3, and a core wire insertion hole 1B for holding the HPCF core wire is formed behind the through hole 1A. ing. A core holding portion 1D is formed between the through hole 1A of the ferrule 1 and the tip 1C of the ferrule 1, and a step portion 1E is provided between the through hole 1A and the core holding portion 1D. The diameter of the core holding portion 1D is formed slightly larger than the core diameter, and holds the core 3. Therefore, the height of the stepped portion 1E is set to be approximately the same as or slightly larger than the thickness of the cladding layer 4. Further, the length of the core holding portion 1D is such that the tip 3A of the core 3 is positioned inward from the tip 1C of the ferrule 1 in the core holding portion 1D, and the core 3 that moves back and forth due to external conditions is The tip 1C is set to a length that does not protrude. That is, the step portion 1E is provided at a position that is appropriately set in consideration of the cutting conditions of the HPCF 2, the expansion rates of the core 3 and the cladding layer 4, and the like. The ferrule 1 is made of resin, but metals other than resin, ceramic, glass, and the like can also be used.

  As shown in FIG. 1, the optical fiber with a ferrule of the present invention is composed of a ferrule 1 and an HPCF 2 fixed to the ferrule 1, and the step of the HPCF 2 is brought into contact with the step 1E of the ferrule 1 of FIG. The tip 3A of the core 3 is positioned inward of the tip 1C of the ferrule 1 in the core holding part 1D. Here, the HPCF wire is fixed in the through hole 1A, and the HPCF core wire is fixed in the core wire insertion hole 1B. By adopting this structure, the position of the tip 3A of the core 3 can be easily and reliably set, and a good ferrule-attached optical fiber can be prevented from protruding from the tip 1C of the ferrule 1 due to external conditions.

  As a method for manufacturing an optical fiber with a ferrule of the present invention, the HPCF 2 is first cut to remove the cladding layer 4 at the end, the core 3 is exposed, and a step is formed between the core 3 and the cladding layer 4 as shown in FIG. Form. At this time, a step may be provided simultaneously with the cutting of the optical fiber, or the step may be provided by removing the clad layer after cutting. As the cutting means, a laser processing method is preferable, and at the same time as the core 3 is cut, the resin clad layer 4 is scattered due to heat by the laser and recedes backward, and as a result, the clad layer 4 at the end portion is scattered. As a result, the core 3 is exposed, and a step is formed between the core 3 and the cladding layer 4 simultaneously with the cutting. The tip 3A of the core 3 obtained by laser processing has a mirror surface in spite of being unpolished, has optical characteristics comparable to those when polished, has the effects of less labor, and lowers costs. In the present embodiment, the laser processing method is used for cutting the HPCF 2, but it may be cut by another thermal method or a mechanical method to have a predetermined shape.

  The HPCF 2 is inserted into the ferrule 1 of FIG. 3, the HPCF core wire is positioned in the core wire insertion hole 1B, the HPCF strand is positioned in the through hole 1A, and the exposed core 3 is inserted into the core holding portion 1D. When further inserted, the step of the HPCF 2 comes into contact with the step 1E provided between the through hole 1A and the core holding portion 1D, and the HPCF 2 is locked. At this time, the core 3 is held by the core holding portion 1D, and the tip 3A of the core 3 is positioned in the core holding portion 1D that is recessed inward from the tip 1C of the ferrule 1. Next, the HPCF strand is fixed in the through hole 1 </ b> A and the HPCF core wire is fixed in the core wire insertion hole 1 </ b> B by an adhesive, and the HPCF 2 is fixed to the ferrule 1. In addition, as a method of fixing the HPCF 2 to the ferrule 1, in addition to fixing the HPCF wire and the HPCF core wire with an adhesive, the HPCF core wire is not fixed with an adhesive, and the HPCF core wire is bonded with an adhesive, caulking or Although not shown, a mechanical method such as a chuck or a method of fixing in or behind the core wire insertion hole by thermal welding such as a laser may be used. However, it is preferable to fix the HPCF strand with an adhesive because the movement of the core due to expansion is small.

  By the above method, a stable terminal can be obtained at all times, and an optical fiber with a ferrule can be manufactured by a simple operation while the tip 1C of the ferrule 1 is not polished. When the opposing ferrules are abutted in this state, the tips of the cores are separated from each other without contacting each other. However, since the core diameter of HPCF is 200 μm or more and is used for medium and short distances, there is no problem in optical characteristics and accuracy. In addition, in the said structure, it becomes unnecessary to grind | polish the front-end | tip 1C of the ferrule 1, and has a great merit on cost. Further, the stepped portion 1E can prevent the adhesive from protruding to the tip 1C of the ferrule 1. That is, it is possible to fix the HPCF 2 in FIG. 2 in the through hole without a stepped portion. However, in that case, it is difficult to set the position of the core tip, and at the same time, when the HPCF strand is fixed with an adhesive, the adhesive inevitably protrudes from the tip of the core and the tip of the ferrule. You will have to cut the fiber by cutting it out and polishing it.

  FIG. 4 is a cross-sectional view showing another optical fiber with a ferrule of the present invention. The ferrule 6 is composed of two parts, a resin capillary 7 and a resin flange 8, and the capillary 7 is formed by the flange 8. It is supported. The flange portion 8 has a core wire insertion hole 8A for holding and fixing the HPCF core wire, and the capillary 7 has a through hole 7A for holding and fixing the HPCF strand. A core holding part 7C is formed between the through hole 7A of the capillary 7 and the tip 7B of the capillary 7, and a step part 7D is provided between the through hole 7A and the core holding part 7C. By contacting the step formed between the cladding layer 4 of the HPCF 2 and the core 3 with the stepped portion 7D, the tip 3A of the core 3 is positioned in the core holding portion 7C so as not to protrude from the tip 7B of the capillary 7. Let As a material of the capillary 7 and the flange portion 8, any material such as metal, ceramic, glass, etc. may be used in addition to the resin, and a combination of materials of the capillary 7 and the flange portion 8 is also arbitrary.

  FIG. 5 is a cross-sectional view showing still another optical fiber with a ferrule according to the present invention. A ferrule 9 is composed of a resin inner cylinder 10 and a resin outer cylinder 11 to fix the HPCF 2. The inner cylinder 10 is fixed in the outer cylinder 11 having a flange by press-fitting or an adhesive, and a through hole 10A for holding and fixing the HPCF strand is formed. Further, the through hole 10A and the tip 10B of the inner cylinder 10 are formed. Is formed with a core holding portion 10C, and a step portion 10D is provided between the through hole 10A and the core holding portion 10C. The tip 11A of the outer cylinder 11 and the tip 10B of the inner cylinder 10 are configured on the same plane, and the rear part of the outer cylinder 11 after the inner cylinder 10 is fixed in the outer cylinder 11 holds and fixes the HPCF core wire. It becomes the core wire insertion hole 11B. The step of the HPCF 2 is brought into contact with and locked to the stepped portion 10D, and the tip 3A of the core 3 is positioned in the core holding portion 10C. As a material of the inner cylinder 10 and the outer cylinder 11, any material such as metal, ceramic, glass, etc. may be used in addition to the resin, and a combination of materials of the inner cylinder 10 and the outer cylinder 11 is also arbitrary. With this structure, several types of inner cylinders with different step positions and heights are prepared in advance, and an inner cylinder that matches the tip shape of the cut HPCF is selected and fixed in the outer cylinder. Thus, an optical fiber with a ferrule can be obtained.

  An optical fiber with a ferrule that does not protrude the core at the tip of the ferrule and that can provide stable connection performance can be manufactured, and can be sufficiently applied to the demand for widespread use in the optical communication field.

It is sectional drawing which shows the optical fiber with a ferrule of this invention. Example 1 It is a front view which shows HPCF which removed the cladding layer of the edge part and exposed the core. Example 1 It is sectional drawing which shows the ferrule used for the optical fiber with a ferrule of this invention. Example 1 It is sectional drawing which shows the other optical fiber with a ferrule of this invention. (Example 2) It is sectional drawing which shows the other optical fiber with a ferrule of this invention. Example 3

Explanation of symbols

1 Ferrule 1A Ferrule 1 through hole 1B Ferrule 1 core wire insertion hole 1C Ferrule 1 tip 1D Ferrule 1 core holding part 1E Ferrule 1 step 2 Hard polymer clad fiber 3 Core 3A Core 3 tip 4 Cladding layer 5 Outer skin 6 Ferrule 7 Capillary 7A Through-hole in capillary 7 7B Tip of capillary 7 7C Core holding part of capillary 7 7D Step part of capillary 7 8 Flange part 8A Core wire insertion hole of flange part 9 Ferrule 10 Inner cylinder 10A Through of inner cylinder 10 Hole 10B Tip 10 of inner cylinder 10C Core holding part 10D of inner cylinder 10 Step part of inner cylinder 10 11 Outer cylinder 11A Tip of outer cylinder 11B Core wire insertion hole of outer cylinder 11

Claims (3)

  Hard polymer clad fiber in which a step is formed between the exposed core and the clad layer by removing the cladding layer at the end, a through hole that holds the hard polymer clad fiber strand, and a core holding that holds the core And a step of the hard polymer clad fiber is brought into contact with and locked to the step portion of the ferrule, and the tip of the core in the core holding portion is more than the tip of the ferrule. An optical fiber with a ferrule that is positioned inward.   Cutting the hard polymer clad fiber, removing the cladding layer at the end and exposing the core to form a step between the core and the clad layer, and inserting the hard polymer clad fiber into the ferrule, The hard polymer clad fiber strand is disposed in the through hole, and the exposed core is disposed in the core holding portion, and the step of the hard polymer clad fiber is applied to the step portion provided between the through hole and the core holding portion. A method of manufacturing an optical fiber with a ferrule, characterized in that the hard polymer clad fiber is fixed after the core tip is positioned inward from the tip of the ferrule within the core holding portion.   3. The hard polymer clad fiber is cut by a laser processing method to remove the clad layer at the end and expose the core to form a step between the core and the clad layer. Manufacturing method of optical fiber with ferrule.

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