JP2008089893A - Lens-attached fiber with condensing function, and method of manufacturing lens-attached fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus of manufacturing a lens-attached fiber, which has an acute tip end curvature capable of convergently emit light rays to a minute area ≤5 μm. <P>SOLUTION: The lens-attached fiber having a curvature at the tip end of an optical fiber is manufactured by steps of: heating a prescribed position of the optical fiber with a heating means; drawing this optical fiber left and right uniformly in the longitudinal direction and separating completely, with the heating temporarily suspended if the optical fiber is in a heating or fully heated state; immersing in an etching liquid and dissolving the tip end of the optical fiber acutely formed by the separating stage; and processing this acute tip end of the optical fiber to form the curvature using the heating means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tip spherical fiber having a light collecting function and a method of manufacturing the tip spherical fiber for condensing and irradiating light on a minute region.

  With the widespread use of optical communication networks, development of high functional and miniaturized optical functional devices is progressing. Such downsizing reduces the light capturing area of the optical functional device, while the mode diameter of the light propagating through the optical communication network is larger than the light capturing area, so the optical coupling efficiency between the two is low. There's a problem. In response to such a current situation, development for expanding the light capturing area provided on the device side, development for reducing the irradiation spot size on the fiber side that emits light, etc., for spot size converters (SSC) Market demands are increasing.

Among these, various methods for manufacturing an optical fiber in which the tip of the optical fiber is sharpened have been proposed as a method for reducing the irradiation spot size on the fiber side. As an example, Patent Document 1 discloses a tip sphere in which an optical fiber is separated by heating / melting and stretching an arbitrary point of a long optical fiber, and a tapered portion that continuously decreases in the radial direction of the optical fiber is provided at the tip of the optical fiber. A method of manufacturing a structured optical fiber is disclosed. Patent Document 2 discloses an optical fiber with a lens that forms a lens at the tip by sharpening the end of the optical fiber with a polishing machine, melting the tip with a burner or the like, and making the tip curved. A processing method is disclosed.
JP-A-1-270011 JP 2004-177826 A

  By the way, since the manufacturing method described in Patent Document 1 separates an optical fiber by melt drawing, the diameter of the tip portion after separation depends on the drawing method and conditions, and can output a small diameter spot of several μm level. It is difficult to always make a spherical fiber.

  On the other hand, although the processing method described in Patent Document 2 can produce a tip portion of an optical fiber that outputs a constant small-diameter spot, even though it can be produced because sharpening using a polishing machine has a processing limit. The spot diameter is limited to about 5 μm to 10 μm.

  The present invention has been made in view of the above problems, and its object is to produce a tip-spherical fiber having a sharp tip curved surface capable of condensing and irradiating light on a minute region of 5 μm or less. To provide an apparatus.

  There is also a problem in that the propagating optical signal is attenuated because the tip of the tip spherical fiber is covered with a clad material. Furthermore, in the case of a polarization-maintaining fiber having a stress applying portion, there is a problem that a uniform taper is not formed because the stress applying portion protrudes on the surface during melt drawing.

  In order to solve the above-mentioned problems, the present invention according to claim 1 includes a step of heating and softening and melting a predetermined portion of the optical fiber, and a stretching separation for stretching and separating the softening and melting portion of the optical fiber in the major axis direction. And a step of immersing the tip of the optical fiber obtained in the stretching and separating step in an etching solution to dissolve the clad material of the tip and forming a sharpened tip of the core, and a sharpened And a tip sphering step in which the tip of the core is heated and melted to make the tip spherical.

  A second aspect of the present invention is a method for producing a tip-spherical fiber according to the first aspect, wherein the optical fiber is a single mode optical fiber.

  In the third aspect of the present invention, a different type of optical fiber is fused and connected to the rear end of a predetermined length of the front-end fiber obtained by the method of manufacturing a front-end fiber according to any one of claims 1 and 2. It is characterized by that.

  The present invention according to claim 4 is characterized in that the different types of optical fibers are constant polarization optical fibers.

  According to the present invention, by providing a method for manufacturing a tip-spherical fiber having a sharp tip curved surface portion, light is collected in a minute region of 5 μm or less, more preferably 3 μm or less, which has heretofore been difficult to irradiate with light. Light can be irradiated. As a result, the optical coupling efficiency between the propagating light and the high-performance optical device can be improved as compared with the prior art.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 and FIG. 2 are manufacturing process diagrams for explaining a method for manufacturing a tip-spherical fiber according to the first embodiment of the present invention.

  An optical fiber used as a processing target in the present embodiment is a single mode optical fiber (hereinafter referred to as SMF) 1. As a heating means for heating the optical fiber, a heating means such as a gas burner can be mentioned. Specifically, in this embodiment, an optical fiber fusion splicer is used.

  First, as shown in FIG. 1A, the SMF 1 is fixed to the fiber fixing means (not shown) of the optical fiber fusion splicer. Then, a pair of discharge electrodes 10 are arranged at positions facing each other across the SMF 1 and discharge / heating is started.

  Next, as shown in FIG. 1B, the SMF 1 is stretched equally in the left-right direction in the major axis direction with the heating stopped or when the heating has been sufficiently performed. At this time, in order to extend the left and right evenly, the fixing method of the SMF 1 may be arranged on the rail in advance, and an appropriate stretching method may be devised so that the SMF 1 is evenly extended to the left and right.

  Finally, SMF1 is completely separated by the above stretching. FIG. 1C shows an image diagram of the SMF 1 after stretching and separation. The tip of the SMF 1 after stretching and separation has a sharpened diameter-reduced shape, and the core 1a at the tip is covered with a thin layer made of the clad 1b.

  Therefore, as shown in FIG. 2A, etching is performed by immersing the tip of the SMF 1 using an etching solution in order to remove the cladding 1b. This etching liquid is a mixture of ammonium fluoride 40% aqueous solution, hydrofluoric acid, and water in a ratio of 1.7: 1: 1. While maintaining this at a temperature of 30 ° C., the tip of the SMF 1 after stretching and separation is immersed for 4 to 6 minutes. The mixing ratio, temperature, and immersion time of the etching solution are appropriately changed depending on the type of fiber and the state of the tip after processing, and are not limited to the above conditions.

  As shown in FIG. 2B, the above-described etching process dissolves the clad 1b covering the core 1a at the tip and exposes the core 1a. That is, by immersing in the etchant, the clad is uniformly melted from the outside of the clad 1b, while the tip of the core 1a exposed by the melt of the clad 1b starts to be melted at the same time, as shown in FIG. In addition, sharpening is performed in which the entire tip has an acute angle.

  Here, as shown in FIG. 2C, the tip portion etched by using the optical fiber fusion splicer is again heated, and the core tip is curved.

When the tip part of the tip spherical fiber 11 produced by the above production conditions and production steps was measured, the radius of curvature of the tip part was 3 μm. Further, light having a wavelength of 1550 nm was made incident from the other end (the end opposite to the sharpened side) of this pointed fiber, and the light emitted from the tip portion was measured. As a result, a near field pattern (at a point 6 μm from the fiber end ( Near Field Pattern, 1 / e ² ) 2.5 μm could be obtained.

  From the above results, it is possible to manufacture a tip-spherical fiber having a sharp tip curved surface portion capable of irradiating light to a minute region of 5 μm or less, and further sharply capable of irradiating light to a minute region of 3 μm or less. A tip-spherical fiber with a curved surface at the tip could be fabricated.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The tip spherical fiber of the present invention is manufactured using only SMF 1 in the first embodiment, whereas SMF 1 is connected to the end of a polarization-maintaining fiber (hereinafter referred to as PMF), and the end of this SMF 1 The point which forms a front-end | tip part in a part is different.

  When the processing of the first embodiment is performed on the PMF, the stress applying portion protrudes during the melt drawing, and there is a problem that the sharp shape is not formed. The second embodiment of the present invention can solve this problem.

  FIG. 3 and FIG. 4 are production process diagrams for explaining a production method of a tip-spherical fiber formed by connecting SMF 1 and PMF 2 according to the present embodiment.

  First, SMF1 and PMF2 are prepared as processing target fibers. After SMF1 and PMF2 are cleave-cut, they are fused using an optical fiber fuser.

  Next, as shown in FIG. 3 (b), the two fusion-spliced fibers are fixed to the optical fiber fusion splicer, and a pair of discharge electrodes 10 are arranged at opposite positions across the desired heating position. To do. In the present embodiment, a position 2 to 3 mm away from the fusion point of SMF1 and PMF2 is defined as a heating position. Then, as shown in FIG. 3C, when the heating position is heated or when the heating is sufficiently performed, the heating is stopped once, and the end of PMF2 and the end of SMF1 are equally left and right in the major axis direction. Stretch to. At this time, the above-described fixing brackets and rails may be used in order to extend the left and right evenly.

  The SMF 1 is completely separated by the stretching. The image figure after extending | stretching separation is shown to Fig.4 (a). Hereinafter, FIGS. 4B to 4D are the same processing method as the tip processing of the SMF 1 described in FIGS. 2A to 2C of the first embodiment. That is, since the core tip after stretching and separation is covered with the clad 1b, the clad 1b is removed by being immersed in an etching solution. The etching solution is an aqueous solution in which a 40% ammonium fluoride aqueous solution, hydrofluoric acid, and water are mixed at a ratio of 1.7: 1: 1. While maintaining the temperature at 30 ° C., the tip of SMF 1 was immersed for 4 to 6 minutes. As a result, an optical fiber having a sharpened tip as shown in FIG. 4C was obtained. The tip portion thus formed was subjected to discharge heating as shown in FIG.

With the above production conditions and production steps, it is possible to produce a tip spherical fiber 12 having a sharpened tip portion made of SMF1 at the tip of PMF2. When the tip of the completed pre-spherical fiber 12 was measured, the radius of curvature of the tip was 3 μm. Further, light having a wavelength of 1550 nm was incident from the open end side of the PMF 2 and the light emitted from the tip portion was measured. As a result, a near field pattern (Near Field Pattern, 1 / e ² ) of 2.5 μm was obtained at a point 6 μm from the fiber end. I was able to get it.

  In addition, the extinction ratio of this tip fiber 12 was measured and compared. Specifically, for the measurement, five stages of SMF1 tip lengths different from 1, 2, 3, 4, and 5 mm were prepared, and the extinction ratio of each tip-spherical fiber was measured. As a result, the extinction ratio was -30 dB or less in any of the tip spherical fibers.

  From the above results, the SMF 1 of 5 mm or less is connected to the tip of the PMF 2 and the tip is formed at the end of the SMF 1 to deteriorate the extinction ratio (this is a level that does not usually cause a problem). However, it is possible to produce a pointed fiber having a sharp tip curved surface portion capable of irradiating light to a minute region of 5 μm or less, and further to sharply irradiating light to a minute region of 3 μm or less. A tip-end fiber with a tip curved surface was produced. Furthermore, it has been shown that the tip spherical fiber having the tip curved surface portion of the present invention induces the effect of reducing the conventional extinction ratio of −40 dB to −30 dB.

  As another example of the second embodiment, a tip spherical fiber 13 in which SMF 1 is replaced with a GI type multimode optical fiber (hereinafter referred to as GI type MMF) was manufactured. FIG. 5 shows a cross-sectional view of the tip spherical fiber 13 in which the tip portion made of the GI type MMF 3 is provided in the PMF 2 according to the present embodiment.

  Similar to the effect of the second embodiment, this tip-spherical fiber has a function of condensing and irradiating light on a minute region, although the PMF extinction ratio of −40 dB deteriorates to −25 dB. .

  From the above, according to the present invention, by providing a method for producing a tip-spherical fiber having a sharp tip curved surface portion, it is difficult to irradiate with light up to 5 μm or less, more preferably 3 μm or less. It becomes possible to collect and irradiate the area with light. As a result, the optical coupling efficiency between the propagating light and the high-performance optical device can be improved as compared with the prior art. Furthermore, according to the present invention, the above functions can be provided in both SMF and PMF fibers.

It is a manufacturing process figure (the 1) for demonstrating the manufacturing method of the tip spherical fiber which concerns on the 1st Embodiment of this invention. FIG. 6 is a production process diagram (No. 2) for explaining the production method of the tip-end fiber according to the first embodiment of the invention. It is a manufacturing process figure (the 1) for demonstrating the manufacturing method of the tip spherical fiber which concerns on the 2nd Embodiment of this invention. It is a manufacturing process figure (the 2) for demonstrating the manufacturing method of the tip spherical fiber which concerns on the 2nd Embodiment of this invention. It is a cross-sectional view of a pointed ball fiber according to another example of the second embodiment of the present invention.

Explanation of symbols

1. Single mode optical fiber (SMF)
DESCRIPTION OF SYMBOLS 1a ... Core 1b ... Cladding 2 ... Polarization plane maintenance fiber (PMF)
3. GI type multimode optical fiber (GI type MMF)
10: Discharge electrode 11, 12, 13: Tip ball fiber

Claims (4)

Heating and softening and melting a predetermined portion of the optical fiber;
A stretching and separating step of stretching and separating the softened and melted portion of the optical fiber in the major axis direction;
A step of immersing the tip of the optical fiber obtained in the stretching and separating step in an etching solution to dissolve the clad material of the tip and forming a sharpened tip of the core;
A tip sphering step of heating and melting the tip of the sharpened core to make the tip spherical,
A method of manufacturing a tip-ball fiber characterized by comprising:   2. The method of manufacturing a pointed fiber according to claim 1, wherein the optical fiber is a single mode optical fiber.   A front-end fiber, wherein different types of optical fibers are fusion-bonded to the rear end of a front-end fiber having a predetermined length obtained by the method for manufacturing a front-end fiber according to any one of claims 1 to 2. .   The tip-spherical fiber according to claim 3, wherein the different optical fiber is a constant polarization optical fiber.

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