JP2009271108A - Optical combiner, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an optical combiner by an easy method. <P>SOLUTION: The optical combiner 100 is composed of one optical fiber 121 for signal light and a plurality of optical fibers 131 for excitation and is integrated by arranging the plurality of optical fibers 131 for excitation around the optical fiber 121 for signal light, and the one optical fiber 121 for signal light and each of the plurality of optical fibers 131 for excitation are formed of a double core optical fiber 30. The double core optical fiber 30 includes: a single mode core 30a; a multi mode core 30b provided so as to cover the single mode core 30a, and formed of a material having a refractive index lower than that of the single mode core 30a; and a clad 30c provided to cover the multi mode core 30b, and formed of a material having a refractive index lower than that of the multi mode core 30b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is composed of a single optical fiber for signal light and a plurality of optical fibers for excitation light, and a plurality of excitation lights are encircled around the optical fiber for signal light at the tip thereof. The present invention relates to an optical combiner in which an optical fiber for use is integrated and a manufacturing method thereof.

  In an optical apparatus such as a fiber laser or an optical amplifier, a double clad fiber is widely used as an optical amplification element.

  The double-clad fiber has a core at the center of the fiber doped with a rare earth element or the like as an optical amplification component, a first clad having a lower refractive index provided around the core, and a lower core provided around the first clad. And a second clad having a refractive index. In such a double-clad fiber, the excitation light incident on the first cladding propagates through a region surrounded by the second cladding while repeating reflection at the interface between the first cladding and the second cladding, and the excitation light. When passing through the core, the rare earth element doped in the core is turned into an inverted distribution state excited by the outermost electrons, and the signal light propagating through the core is amplified by the stimulated emission.

  In such a double clad fiber, a method using an optical combiner is known as a method of making signal light enter the core and pump light incident on the first clad.

The optical combiner has, for example, a close-packed structure of one optical fiber for signal light at the center and six optical fibers for pumping light surrounding the optical fiber, and has a structure in which they are fused and integrated at the tip portion ( Patent Document 1). When the optical combiner is connected to the double clad fiber, the core of the signal light optical fiber is connected corresponding to the core of the double clad fiber, and the core of the pump light optical fiber is connected to the first clad of the double clad fiber. Correspondingly connected.
JP 2007-163650 A

  The optical combiner uses a single mode optical fiber and a multimode optical fiber as optical fibers constituting the signal light optical fiber and the pumping light optical fiber, respectively. The optical combiner is inserted into a capillary with a single mode optical fiber and a plurality of multimode optical fibers arranged around the single mode optical fiber so that the multimode optical fiber surrounds the optical combiner. In the part, they are formed in a melted part in which they are fused and reduced in diameter.

  By the way, in the production of this optical combiner, when one single mode optical fiber and a plurality of multimode optical fibers are inserted into the capillary, the plurality of multimode optical fibers surround these single mode optical fibers. It was necessary to use a jig or the like in order to dispose. Moreover, even if it performed using a jig | tool etc., since the fiber diameter is small, this operation | work was very difficult.

  An object of the present invention is to easily manufacture an optical combiner.

The optical combiner of the present invention is
Each of one optical fiber for signal light and a plurality of optical fibers for pumping light constituting the optical combiner,
Single mode core,
A multi-mode core provided to cover the single-mode core and formed of a material having a lower refractive index than the single-mode core;
A clad formed to cover the multimode core and formed of a material having a lower refractive index than the multimode core;
It is comprised with the double core optical fiber provided with.

  The ratio of the outer diameter of the multimode core to the outer diameter of the cladding is preferably 0.76 to 0.95.

The manufacturing method of the optical combiner of the present invention is as follows:
A plurality of double-core optical fibers are integrated by bundling their one end portions, and one double-core optical fiber provided at the center is configured as an optical fiber for signal light, and so as to surround it. Another provided double core optical fiber is configured as an optical fiber for pumping light.

  According to the present invention, each of the single optical fiber for signal light and the multiple optical fibers for pumping light is made of a single mode core and a material provided to cover it and having a lower refractive index than the single mode core. Since it is composed of a dual-core optical fiber including a formed multimode core and a clad formed to cover the multimode core and having a refractive index lower than that of the multimode core, Manufacture can be performed easily.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows an optical combiner 100 according to this embodiment. The optical combiner 100 is used for transmitting high-power light, for example, connected to an optical amplifier of a laser marker or a double clad fiber of a welding fiber laser.

  The optical combiner 100 includes a capillary 110, one signal light double core optical fiber core wire 120, and six pump light double core optical fiber core wires 130. In one signal light double-core optical fiber core wire 120, the coating layer 122 is peeled off from the tip of the core wire by a predetermined length, and the signal light double-core optical fiber 121 is exposed. In each of the six excitation-light double-core optical fibers 130, the coating layer 132 is peeled off from the tip of the core by a predetermined length, and the excitation-light double-core optical fiber 131 is exposed. The optical combiner 100 is inserted into the capillary 110 by bundling these one signal light double core optical fiber 121 and the six excitation light double core optical fibers 131 into a close-packed structure. At the tip portion, they are formed in a melted portion 140 that is melted and integrated to reduce the diameter.

  The capillary 110 is made of, for example, quartz glass. For example, the capillaries 110 are formed to have a total length of 3 to 10 mm (excluding the melting part 140) and an inner diameter of 380 to 400 μm.

  The signal light double core optical fiber core wire 120 has a configuration in which the signal light double core optical fiber 121 is covered with a coating layer 122. The double core optical fiber 121 for signal light is the double core optical fiber 30 described in detail later.

  The signal light double core optical fiber 121 includes a single mode core 121a at the center of the fiber, a multimode core 121b provided so as to cover the single mode core 121a, and a clad 121c provided so as to cover the multimode core 121b. And is composed of. The signal light double-core optical fiber 121 has a light incident on the single-mode core 121a and functions as a single-mode optical fiber.

  The covering layer 122 is made of, for example, an ultraviolet curable resin, a silicon resin, a nylon resin, or the like, and may be composed of a single layer or may be composed of a plurality of layers. The covering layer 122 has a layer thickness of, for example, 55 to 65 μm.

  The excitation-light double-core optical fiber core 130 has a configuration in which the excitation-light double-core optical fiber 131 is covered with a coating layer 132. The pumping light double-core optical fiber 131 is a double-core optical fiber 30 described in detail later.

  The double core optical fiber 131 for excitation light includes a single mode core 131a at the center of the fiber, a multimode core 131b provided so as to cover the single mode core 131a, and a clad 131c provided so as to cover the multimode core 131b. And is composed of. The double-core optical fiber 131 for pumping light functions as a multimode optical fiber when light enters the multimode core 131b.

  The covering layer 132 is made of, for example, an ultraviolet curable resin, a silicon resin, a nylon resin, or the like, and may be composed of a single layer or may be composed of a plurality of layers. The coating layer 132 is formed with a layer thickness of, for example, 55 to 65 μm.

  The double core optical fiber core 120 for signal light and the double core optical fiber core 130 for pumping light have the same configuration, and thus constitute the double core optical fiber core 120 for signal light. The signal light double core optical fiber 121 and the pump light double core optical fiber 131 constituting the pump light double core optical fiber core 130 have the same double core optical fiber structure. This double core optical fiber will be described.

FIG. 3 shows a cross-sectional view of the double-core optical fiber 30 and a corresponding refractive index distribution diagram. The dual core optical fiber 30 includes a single mode core 30a (refractive index n ₁ ) at the center of the fiber, a multimode core 30b (refractive index n ₂ ) provided so as to cover the single mode core 30a, and a multimode core 30b. And a clad 30c (refractive index n ₃ ) provided so as to cover the surface. The dual core optical fiber 30 is, for example, one whose periphery is coated with a coating layer.

  The single mode core 30a is made of, for example, quartz having a high refractive index doped with aluminum, germanium, or the like. The relative refractive index difference Δ1 between the single mode core 30a and the multimode core 30b is 0.04 to 0.4%. The single mode core 30a has a core diameter of 10 to 25 μm, for example.

  Note that rare earth elements such as ytterbium (Yb) are not added to the single mode core 30a. Therefore, the double core optical fiber 30 is different in properties from the double clad fiber.

The multimode core 30b is made of, for example, pure quartz. The multimode core 30b has, for example, a refractive index n ₂ of 1.456 and a core diameter of 95 to 120 μm.

The clad 30c is made of, for example, quartz whose refractive index is lowered by doping with fluorine, boron or the like. The relative refractive index difference Δ ₂ of the clad 30 c with respect to the multimode core 30 b is −0.3 to −1%. The clad 30c has a layer thickness T of 3 to 15 μm, for example.

Since this double core optical fiber 30 is used for transmission of high output light, it is preferable that the core diameter is larger than that of a single mode optical fiber for communication use (for example, the core diameter is 9 μm). On the other hand, since the core diameter is larger than that of a single mode optical fiber for communication use, in order for signal light to propagate in a single mode, a single mode optical fiber for communication use (for example, a relative refractive index difference Δ ₁ is it is smaller the relative refractive index difference delta ₁ compared 0.35%) and.

  In addition, since the dual core optical fiber 30 is used for transmission of high output light, it is a multimode optical fiber for communication use (for example, the core diameter is 50 μm to 62.5 μm, that is, the core diameter is equal to the cladding diameter). The core diameter is preferably larger than the ratio of 0.4 to 0.5), and the ratio of the outer diameter of the multimode core 30b to the outer diameter of the cladding 30c is preferably 0.76 or more. On the other hand, if it exceeds 0.95, the thickness of the clad layer becomes too thin, light leaks in bending with a bending radius of about 60 mm, and bending loss cannot be ignored. That is, the ratio of the outer diameter of the multimode core 30b to the outer diameter of the cladding 30c is preferably 0.76 to 0.95.

  When light enters the single mode core 30a from the fiber end of the double core optical fiber 30, the incident light propagates in the single mode core 30a in a single mode. That is, the double core optical fiber 30 functions as a single mode optical fiber. On the other hand, when light enters the multimode core 30b from the fiber end of the double core optical fiber 30, the incident light propagates in the multimode core 30b in multimode. At this time, the presence of the single mode core 30a does not affect the behavior of light propagating through the multimode core 30b. That is, the double core optical fiber 30 functions as a multimode optical fiber.

  Next, the manufacturing method of this optical combiner 100 is demonstrated.

  First, a capillary 110 and seven double core optical fibers are prepared. The capillary 110 has a length of, for example, 30 to 80 mm. Each of the double core optical fiber cores has a core length of, for example, 0.5 to 5 m.

  For each of the seven double core optical fibers, the coating layer is peeled off from the tip of one of the core wires by a predetermined length to expose the double core optical fiber 30. At this time, the peeling length of the coating layer is set to 20 to 40 mm, for example.

  These double core optical fibers 30 are bundled so as to have a close-packed structure and inserted from one end side of the capillary 110. Of the seven double-core optical fibers 30 inserted into the capillary 110 and arranged so as to have a close-packed structure, one double-core optical fiber 30 arranged at the center is a double-core light for signal light. The fiber 121 becomes the other, and the other six become the excitation-use double core optical fiber 131.

  Then, the central portion of the capillary 110 is heated and melted from the side by arc discharge, flame, or the like, and the gaps are integrated while collapsing. At this time, heating temperature shall be 1500-2000 degreeC, for example. Further, the length of the part to be fused and integrated is set to 1 to 3 mm, for example.

  And after cooling, the optical combiner 100 is manufactured by making a notch in the side surface of the melt-integrated part and cutting at that part.

  According to this method of manufacturing an optical combiner, which of the seven double core optical fibers 30 becomes the signal light double core optical fiber 121 is determined by the seven double core optical fibers 30 in the capillary 110. Determined after being inserted and placed. Therefore, when an optical fiber is inserted into the capillary 110, it is not necessary to use a jig or the like to place the specific optical fiber at the center. Further, since the seven optical fibers are bundled and inserted into the capillary 110, the operation is easier than the operation of handling the small-diameter optical fibers one by one. Furthermore, it is not necessary to prepare two types of optical fibers for signal light and optical fibers for excitation light as optical fibers to be inserted into the capillary 110, so that manufacturing efficiency is expected.

  Each of the double core optical fibers 30 can be inserted into the capillary 110 using a jig or the like. Even in this case, it is not necessary to prepare two types of optical fibers for signal light and optical fibers for pumping light as optical fibers to be inserted into the capillary 110, and the production efficiency is expected.

  In the optical combiner 100 configured as described above, one end of the single mode optical fiber 200 is connected to the end face of the signal light double core optical fiber core wire 120, and the end face of the pump light double core optical fiber core wire 130 is connected. One end of the multimode optical fiber 300 is connected and used. These are connected by fusion connection such as arc discharge or connector connection.

  The single mode optical fiber 200 includes a core provided at the center of the fiber, a lower refractive index clad provided around the core, and a coating layer covering the clad. The single mode optical fiber 200 has, for example, a core diameter of 10 to 25 μm, a cladding diameter of 123 to 127 μm, a fiber diameter of 230 to 260 μm, and a fiber length of 0.5 to 5 m. The core of the single mode optical fiber 200 has a diameter that is the same as or slightly smaller than the core diameter of the single mode core 121a of the signal light double core optical fiber 121, and they are connected so as to correspond to each other. The

  The multimode optical fiber 300 includes a core provided in the center of the fiber, a lower refractive index clad provided around the core, and a coating layer covering the clad. The multimode optical fiber 300 has, for example, a core diameter of 95 to 100 μm, a cladding diameter of 123 to 127 μm, a fiber diameter of 230 to 260 μm, and a fiber length of 0.5 to 5 m. The core of the multimode optical fiber 300 has a diameter that is the same as or slightly smaller than the core diameter of the multimode core 131b of the pumping light dual-core optical fiber 131, and they are connected so as to correspond to each other. The

  Then, a signal light source is connected to the other end side of the single mode optical fiber 200, and six excitation light sources are connected to each of the other end sides of the six multimode optical fibers 300.

  On the other hand, the end face of the melting part 140 of the optical combiner 100 is fusion-bonded by arc discharge or the like to a double-clad fiber having a core doped with a rare earth element and first and second clads. At this time, the single mode core 121a of the signal light dual-core optical fiber 121 at the end face of the melted portion is the core of the double-clad fiber, and each of the six pump-light dual-core optical fibers 131 131b is connected so as to correspond to the first clad of the double clad fiber.

  The signal light output from the signal light source has a wavelength of 1000 to 1700 nm, for example, and is, for example, 1080 nm which is the wavelength of the laser output of a fiber laser using ytterbium. This signal light is propagated through the core of the single mode optical fiber 200 to the single mode core 121a of the signal light double core optical fiber 121, and is incident on the core of the double clad fiber through the melting part 140 of the optical combiner 100. The On the other hand, the pumping light output from the pumping light source has a wavelength of, for example, 800 to 1700 nm, for example, 970 nm which is the pumping wavelength of ytterbium (Yb) doped in the first cladding of the double-clad fiber. This pumping light is propagated through the core of the multimode optical fiber 300 to the multimode core 131b of the double core optical fiber 131 for pumping light, passes through the melting part 140 of the optical combiner 100, and becomes the first clad of the double clad fiber. Incident.

  The excitation light incident on the first clad of the double clad fiber propagates through the region surrounded by the second clad while being repeatedly reflected at the interface between the first clad and the second clad, and passes through the core when passing through the core. The rare earth element doped in is made into an inversion distribution state excited by outermost electrons, and the signal light propagating through the core is amplified by the stimulated emission.

  In this embodiment, the optical combiner 100 includes one signal light double core optical fiber 121 and six pump light double core optical fibers 131. The number of pumping light double-core optical fibers is not limited to six as long as the optical combiner includes a heavy core optical fiber and a plurality of pumping light double-core optical fibers. For example, it may be an optical combiner configured such that one double-core optical fiber for signal light is double-wrapped by 18 double-core optical fibers for pump light, and may be used for one signal light It may be an optical combiner configured such that 36 double-core optical fibers for pumping light are surrounded by a triple, and 60 single-core optical fibers for signal light may be used. It is also possible to use an optical combiner configured such that the double core optical fibers for excitation light are enclosed in a quadruple manner.

  As described above, the present invention is useful for an optical combiner and a manufacturing method thereof.

It is a perspective view which shows the optical combiner of this embodiment, and the single mode fiber and multimode fiber connected to it. It is sectional drawing of II-II in FIG. It is the schematic diagram which showed typically the cross-sectional view of a double core optical fiber, and the refractive index distribution map corresponding to it.

Explanation of symbols

30 Duplex core optical fibers 30a, 121a, 131a Single mode cores 30b, 121b, 131b Multimode cores 30c, 121c, 131c Clad 100 Optical combiner 121 Double core optical fiber for signal light (optical fiber for signal light)
131 Double core optical fiber for pumping light (optical fiber for pumping light)

Claims (3)

It is composed of one optical fiber for signal light and a plurality of optical fibers for excitation light, and the plurality of excitation light beams are surrounded at the tip of the optical fiber for signal light so as to surround it. An optical combiner in which fibers are arranged and integrated,
Each of the one optical fiber for signal light and the plurality of optical fibers for pump light is
Single mode core,
A multi-mode core provided to cover the single-mode core and formed of a material having a lower refractive index than the single-mode core;
A clad formed to cover the multimode core and formed of a material having a lower refractive index than the multimode core;
An optical combiner comprising a double core optical fiber having An optical combiner according to claim 1, wherein
In the double core optical fiber constituting the one signal light optical fiber and the plurality of pump light optical fibers, the ratio of the outer diameter of the multimode core to the outer diameter of the cladding is 0.76 to 0. .95, an optical combiner.   A single mode core, a multimode core provided to cover the single mode core and made of a material having a lower refractive index than the single mode core, and a multimode core provided to cover the multimode core A single double core provided at the center of a plurality of double core optical fibers including a clad formed of a material having a refractive index lower than that of the core A method of manufacturing an optical combiner, wherein the optical fiber is configured as an optical fiber for signal light, and another double-core optical fiber provided so as to surround the optical fiber is configured as an optical fiber for pumping light.

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