Method of processing terminus of optical fiber and terminus processing tool

Provides a method and a terminus processing tool whereby terminus processing for the purpose of connection to another optical fiber may be carried out simply. The terminus processing method entails cutting an optical fiber 20 composed of a glass fiber 21 and a coating 24; and with the optical fiber 20 positioned relative to a terminus processing tool that is disposed contacting the coating at the end surface of the optical fiber 20 and that has a protruded-into space for accommodating inward protrusion of the glass fiber 21, and with the cut end surface of the glass fiber 21 facing the protruded-into space, pushing the optical fiber 20 to thereby strip the coating 24 from the glass fiber 21.

TECHNICAL FIELD

The present invention relates to a method for stripping a coating from the terminus of an optical fiber composed of a glass fiber and a coating, and to a terminus processing tool used in the method.

BACKGROUND ART

When connecting an optical fiber composed of a glass fiber and a coating to another optical fiber, it is known to strip a prescribed length of the coating of the terminus in order to expose the glass fiber. The operation of stripping the coating is carried out using a mechanical stripper, for example (see Japanese Unexamined Patent Application 60-79306).

FIG. 7is a perspective view showing a conventional stripper100. The stripper100is composed of an upper member101and a lower member102that are pivoted at one edge. Clamps105,106are respectively disposed within core guide portions103,104which are provided to the upper member101and the lower member102. A pair of core guide claws107,107are disposed on the lower member102, and slots (not shown in the drawing) that mate with the core guide claws107are provided in the upper member101. Blades108,109situated in opposition to one another are disposed on the upper member101and the lower member102.

When the stopper100is used to strip the coating from an optical fiber, the optical fiber is guided by the core guide claws107and positioned at the location of the clamps105,106. In this state, the upper member101and the lower member102are urged into relative proximity with one another, whereby the blades108,109slice into the coating that is to be stripped from the optical fiber, producing a cut. The coating is then stripped by moving the stripper100relative to the optical fiber.

According to this method, the coating is stripped by pressing the blades108,109against the coating of the optical fiber, followed by relative motion of the stripper100towards the end of the optical fiber. For this reason, coating residue may be left adhering to the end of the optical fiber. Because cutting cannot be carried out in consistent fashion with coating residue adhering to the end of the optical fiber, it was necessary to either cut off the end or clean it with alcohol or the like, resulting in a complicated procedure.Patent Citation 1: Japanese Unexamined Patent Application 60-79306

DISCLOSURE OF THE INVENTION

Technical Problems

It is an object of the present invention to provide a method whereby terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly, as well as a terminus processing tool for use in the method.

Means Used to Solve the Above-Mentioned Problems

The method of processing a terminus of an optical fiber according to the present invention includes: (1) cutting an optical fiber composed of a glass fiber and a coating; and (2) pushing the optical fiber against a terminus processing tool and thereby removing the coating from the glass fiber, the terminus processing tool being adapted to contact the coating at an end surface of the optical fiber, and having a space into which the glass fiber is inserting; and the coating being removed in a state wherein the cut end of the optical fiber is inserted-into the space.

Optionally, the space to which the glass fiber is inserting is a hole with diameter larger than an outside diameter of the glass fiber and smaller than an outside diameter of the coating. In this case, it is preferable for the inside distal end portion of the hole to be chamfered. Where the coating is composed of two or more layers, it is preferable for the inside distal end diameter of the hole to be smaller than the outside diameter of the coating of the innermost layer of the coating of two or more layers. Additionally, it is preferable for the inside diameter of the hole to be progressively smaller in a direction in which the optical fiber is inserted.

In preferred practice, an initial flaw is formed, between the cutting step and the stripping step, in the outside peripheral portion of the coating. In this case, optionally, a plurality of initial flaws are formed in the circumferential direction on an outside peripheral face of the coating.

Optionally, the space is a concave portion with diameter larger than the outside diameter of the glass fiber and smaller than the outside diameter of the coating.

The terminus processing tool according to the present invention is adapted to contact a coating at an end surface of an optical fiber composed of a glass fiber and the coating, and having a space into which the glass fiber is inserting.

Advantageous Effect of the Invention

According to the present invention, it is possible to prevent coating residue from adhering to the end surface of a glass fiber when the coating is stripped by blades traveling towards the end of the optical fiber as practiced in the prior art, thereby obviating the need for a cleaning procedure in a step subsequent to stripping the coating. Consequently, terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention are described below with reference to the drawings. The drawings are intended for illustrative purposes, and are not limiting of the invention. In the drawings, in order to avoid redundant description, like symbols indicate like components. Dimensional proportions in the drawings are not necessarily accurate.

FIG. 1is a cross sectional view showing part of an optical fiber terminus processing tool10according to a first embodiment of the invention, together with an optical fiber20being processed. The processing tool10includes a cylindrically shaped outer wall14, a conically shaped wall34with a recessed portion35. An aperture or gap11extends through the processing tool10and the recessed portion35. The gap11has a diameter D1and the recessed portion35has an inner diameter D1′ that is larger than the diameter D1. In the terminus processing method using the terminus processing tool10, first, the optical fiber20, which is composed of a glass fiber21and a coating24, is cut with the coating24still attached. Next, the end surface24aof the coating24at the cut end surface20aof the optical fiber20is pressed against the terminus processing tool10. By so doing, the coating24is peeled and stripped from the glass fiber21.

The optical fiber20has an overall outside diameter d1. The coating24includes a first coating layer22with an outer diameter d2, and a second coating layer23. The glass fiber21has an outer diameter d3. In the optical fiber20, the outside diameter d3of the glass fiber21is, e.g., 125 μm; and the outside diameter d1of the coating24is, e.g., 250 μm. The glass fiber21is a glass fiber having a core and one or more cladding layers, and it is also possible to employ glass fibers of any refractive index distribution, such as single mode fibers or multi-mode fibers.

The first coating layer22of the coating24contacts the glass fiber21, and the second coating layer23serves as a sheath covering the exterior of first coating layer22; however, the coating24is not limited to this arrangement, and configurations having a single layer or more than two layers are also possible. A tinted layer may be provided as the outermost layer. The resin constituting the coating24is a UV curing type resin such as urethane acrylate, and using additives is imparted with properties such as appropriate elasticity. For example, the first coating layer22which contacts the glass fiber21has lower elasticity (i.e., softness) than the second coating layer23.

The terminus processing tool10is adapted to contact the end surface24aof the coating24. The gap11serves as a space for accommodating inward protrusion of the glass fiber21when the optical fiber20is pressed against the conically shaped wall34within the outer wall14of the terminus processing tool10. By forming an outer wall14of round tubular shape at the end of the terminus processing tool10, it is possible to support the optical fiber20during insertion, thereby minimizing the likelihood of buckling when the optical fiber20is inserted into the gap11, to afford insertion of the optical fiber20into the gap11in an easy and reliable manner. The outer wall14defines a hollow space that includes an inner surface14aand a fiber entering end14bthat is contiguous with the inner surface14a. The conically shaped wall34is located within the hollow space facing a portion of the inner surface14aand includes a large diameter end34aand a small diameter end11a(also referred to as a distal end portion11a). The conically shaped wall34has a truncated conically shaped surface located entirely within the hollow space defined within the outer wall14. The conically shaped wall34further defines the hollow space. The conically shaped wall34and the inner surface14aare continuous with one another (uninterrupted). The small diameter end11ais closer to the fiber entering end14bof the outer wall14than the large diameter end34a. More specifically, the small diameter end11ais spaced apart from the fiber entering end14bof the end wall14by a distance L1. The large diameter end34aof the conically shaped wall34intersects the inner surface14aof the outer wall14at a location that is spaced apart from the fiber entering end14bof the outer wall14by a distance L2measured parallel to the distance L1. The distance L2is greater than L1. Further, the outer wall14and the conically shaped wall34are fixed to one another. For example, the outer wall14and the conically shaped wall34can be unitarily formed as a single, monolithic element.

It is possible, for example, for the gap11to be a circular gap, a square gap, or a regular polygon shaped gap, or a gap having serrated contours at its perimeter; here, a circular gap is described as a preferred example. With a circular gap, forces tend to act uniformly in the circumferential direction of the optical fiber20. It is good for stripping of the coating. The inside diameter D1of the gap11is larger than the outside diameter d3of the glass fiber21, and smaller than the outside diameter d1of the coating24(i.e., the outside diameter of the optical fiber20). When the end surface20aof the optical fiber20is pressed against the conically shaped wall34with the glass fiber21aligned with the recessed portion35(the perimeter of the gap11of the terminus processing tool10), the distal end portion11aof the recessed portion contacts the end surface24aof the coating24, but does not contact the glass fiber21.

Preferably, the inside diameter D1′ of the recessed portion35at the distal end portion11aof the gap11is smaller than the outside diameter d2of the first coating layer22that makes up the coating24. Further, the inside diameter D1′ is greater than the outside diameter d3of the glass fiber21. Consequently, the distal end portion11aserves as a coating removing edge. When the optical fiber20is pressed against the distal end portion11aof the terminus processing tool10, force can act directly on the first coating layer22, and the coating24can be completely stripped from the glass fiber21due to the coating removing edge (the distal end portion11aof the gap11). Further, a taper angle θ1of the conically shaped wall34at the distal end portion11a(the angle to the center axis of the gap11) is preferably from 30° to 90°. The coating24can be easily peeled away from the glass fiber21towards the outer wall14.

InFIG. 2AandFIG. 2Bare enlarged fragmentary views showing the distal end portion of the gap11in the terminus processing tool10. In preferred practice, the inside distal end portion11aof the gap11is chamfered, instead of including the recessed portion35shown inFIG. 1. For example, a chamfer having an arcuate curving face (rounded chamfer12a) as shown inFIG. 2Amay be provided. Alternatively, a chamfer having a linear flat face (45° chamfer12b) as shown inFIG. 2Bmay be provided. This makes it easy to insert the optical fiber20into the gap11of the terminus processing tool10. The inside diameter D2of a large-diameter end13of the chamfer12at the distal end of the gap11is smaller than the outside diameter d2of the first coating layer22that makes up the coating24, and greater than the outside diameter d3of the glass fiber21. The large-diameter end13defines a coating removing edge.

FIG. 3Ais a cross sectional view of an optical fiber20provided with initial flaws in the coating, andFIG. 3Bis a front view thereof. In preferred practice, the outside peripheral portion at the distal end of the coating24is provided with initial flaws25. The initial flaws25may be formed in the coating24beforehand, or formed during the terminus processing step. Preferably, the initial flaws25are disposed at multiple equidistant locations (four are shown inFIG. 3) on the outside peripheral face of the coating24and are provided with prescribed length which is shorter than the terminus processing length in the axial direction (about 0.5 to 1 mm, for example). The initial flaws25may be given a “V” shaped cross section, for example, or may be provided by simple cuts. This facilitates outward peeling of the coating24, whereby the coating24may be easily stripped.

FIGS. 4A and 4Bare drawings illustrating terminus processing of the optical fiber20provided with initial flaws in the coating, whereinFIG. 4Ais a cross sectional view of the optical fiber prior to processing. An initial flaw26that is continuous in the circumferential direction of the optical fiber20may be disposed at a location a prescribed distance from the end surface20aof the optical fiber20, for example, one equal to the terminus processing length. Optionally, the initial flaw26is a cut that slices inward towards the end of the optical fiber20.FIG. 4Bis a cross sectional view of the optical fiber subsequent to processing. When the optical fiber20is pressed against the gap11of the terminus processing tool10, the coating24bat the end is pressed in the rightward direction in the drawing and spreads outwardly along the initial flaw26, whereby the coating24bcan be easily stripped. Moreover, by setting the location of the initial flaw26to one equal to the terminus processing length from the end surface20a, the desired length of the coating24can be stripped.

FIG. 5is a cross sectional view showing a modification of the terminus processing tool of the first embodiment. The gap11is provided with a tapered portion11bof progressively smaller inside diameter towards the inside from the distal end surface of the terminus processing tool10. The inside diameter of the tapered portion11bat the distal end portion11ais smaller than the outside diameter d1of the optical fiber20and larger than the outside diameter d3of the glass fiber21of the optical fiber20. Also, it is preferable for the inside diameter at the distal end portion11ato be smaller than d2, so that the distal end portion11acontacts the first coating layer22. The taper angle of the tapered portion11b(the angle to the center axis of the gap11) θ2is preferably from 0° to 30°.

When the optical fiber20is pressed against the terminus processing tool10, the end surface24aof the coating24contacts the distal end portion11a, the coating24peels away from the glass fiber21, and the tip of the glass fiber21pushes into the gap11. Because the optical fiber20is inserted along the tapered portion11b, positioning of the distal end of the optical fiber20can be carried out with high accuracy.

According to the optical fiber terminus processing method and terminus processing tool10described above, it is possible to prevent coating residue from adhering to the end surface of the glass fiber21when the coating24is stripped by blades traveling towards the end of the optical fiber20as practiced in the prior art, thereby obviating the need for a cleaning procedure in a step subsequent to stripping the coating24. Consequently, terminus processing for the purpose of connection to another optical fiber may be carried out straightforwardly. The material of the terminus processing tool10is preferably a ceramic such as zirconia, or a resin material such as an epoxy resin or polyphenylene sulfide resin.

FIGS. 6A and 6Bare cross sectional views showing part of an optical fiber terminus processing tool10B according to a second embodiment of the invention, together with the optical fiber being processed, whereinFIG. 6Ashows the state prior to processing. The terminus processing tool10B has a concave portion15of inside diameter larger than the outside diameter d3of the glass fiber21of the optical fiber20, and smaller than the outside diameter d1of the optical fiber20.FIG. 6Bshows the state subsequent to processing. When the end surface of the optical fiber20is pressed against the concave portion15of the terminus processing tool10B, the distal end of the coating24peels away outwardly, and the tip of the glass fiber21protrudes from the coating24and is enclosed within the concave portion15.

The present application claims priority on the basis of a Japanese Patent Application (Japanese Unexamined Patent Application 2007-137171) applied for on 23 May 2007, the content of which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The invention is useful as a terminus processing method and a processing tool prior to securing an optical fiber to an optical connector.