JP2005084202A - Plastic holey fiber and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic holey fiber capable of dealing with various usage conditions of an optical fiber and a manufacturing method thereof.
In a plastic holey fiber 10 having a hole 13 extending in a fiber longitudinal direction in a clad 12 near a core 11, a plurality of holes 13 having different diameters are formed.
[Selection] Figure 1

Description

  The present invention relates to a plastic holey fiber having a large number of holes in a cladding in the vicinity of a core and a method for manufacturing the same.

  Optical fibers that enable high-capacity and high-speed communication are indispensable for the construction of optical communication networks. However, high-speed optical signals and large-capacity optical fibers in future optical communication networks Currently, a photonic crystal fiber (PCF) is attracting attention as a new optical fiber that satisfies this requirement.

  PCF has a photonic crystal structure, which is a periodic structure of refractive index, in the clad covering the core. Specifically, by providing a space of a honeycomb structure such as a honeycomb in the clad, light is forbidden. This is a photonic band gap (PBG) that is a band. For example, Non-Patent Document 1 shows a PCF having a PBG structure as a waveguide principle. Further, Non-Patent Document 2 shows a hollow core PCF having a PBG structure as a wave guiding principle, and this hollow core PCF is a main factor of loss because there is no quartz medium in the core through which light propagates. It has the potential for an ultra-low loss fiber with very low Rayleigh scattering. Further, as shown in Patent Document 1, the PCF of the hollow core can be expected to have a low loss of about 0.01 dB / km.

  On the other hand, recently, although it does not have a complete PBG structure like PCF, a hole is formed in the cladding near the core of an optical fiber having a relative refractive index difference due to a difference in the glass composition of the related art. A holey fiber having characteristics that could not be obtained in the past has been proposed by reducing the effective refractive index and expanding the relative refractive index difference between the core and the clad. For example, as shown in Non-Patent Document 3, four voids are provided in the cladding near the core of a fiber having an ordinary single mode fiber structure to increase the effective relative refractive index difference between the core and the cladding. A holey fiber having zero dispersion and single mode operation in the 0.8 μm band has been reported.

  The conventional holey fiber is made of quartz glass, and is a manufacturing method in which a quartz glass rod is subjected to mechanical drilling and drawn to a predetermined fiber diameter. In contrast, plastic holey fibers have been proposed for the purpose of reducing manufacturing costs and improving flexibility. As an example of a method for producing a plastic holey fiber, there is a method of producing by using an apparatus in which a core and a clad are integrally formed by extrusion and a pin for forming a hole is arranged in an extrusion nozzle for forming the clad. .

Japanese Patent No. 3072842 J. C. Knight et al., “Photonic Band Gap Guidance in Optical Fibers”, Science, (USA), November 20, 1998, No. 282, p. 1476-1478 "Cregan (RFCregan) et al.," Single-Mode Photonic Band Gap Guidance of Light in Air "", Science, (USA), September 3, 1999, No. 285, p. 1535-1539 Hasegawa et al., “Novel hole-assisted lightguide fiber exhibiting large anomalous dispersion and loss below 1 dB / km”, OFC post deadline Paper (OFC Postdeadline Papers), (USA), March 22, 2001, p.PD5-1-PD5-3

  In order to meet the needs of various fiber characteristics, plastic holey fibers having different hole positions and sizes are required. That is, various characteristics such as zero dispersion, polarization plane maintenance, and reduction of bending loss are required.

  However, in the conventional manufacturing method, in order to manufacture a holey fiber having different holes, it is necessary to replace a pin that determines the size of the hole, which requires a lot of cleaning and setup time each time. There is a problem that it leads to cost increase.

  Moreover, the holes of the conventional holey fiber made of plastic are all formed in the same size in the longitudinal direction of the fiber, and such plastic holey fiber cannot cope with various usage conditions.

  Therefore, an object of the present invention is to provide a plastic holey fiber that can solve the above-described problems and can be used in various usage states of optical fibers, and a method for manufacturing the same.

  In order to achieve the above object, a first aspect of the present invention is a plastic holey fiber having a plurality of holes having different diameters in a plastic holey fiber having holes extending in a fiber longitudinal direction in a cladding near a core.

  The invention of claim 2 is a plastic holey fiber having a plurality of holes extending in the fiber longitudinal direction in a clad near the core, wherein holes having different diameters in the fiber longitudinal direction are formed.

  The invention according to claim 3 is the plastic holey fiber according to claim 1, wherein the holes have different diameters in the fiber longitudinal direction.

  The invention of claim 4 is the plastic holey fiber according to any one of claims 1 to 3, wherein the core is made of polymethylmethacrylate and the clad is made of a fluororesin.

  According to a fifth aspect of the present invention, a cladding material extrusion nozzle into which a cladding material is injected is provided below the core material extrusion nozzle so as to surround the core extruded from the core material extrusion nozzle, and the core material is supplied from the core material extrusion nozzle. And a plastic holey fiber manufacturing method in which a clad material is supplied from a clad material extrusion nozzle and a plurality of holes extending in the longitudinal direction of the fiber are formed in the clad near the core. A plurality of hole forming pin pipes extending to the clad nozzle hole in the clad material extrusion nozzle are arranged so as to surround the outlet part of the core nozzle hole, and a blower hole for supplying gas to the pin pipe is formed in the core material extrusion nozzle Then, the core extruded from the core extrusion nozzle into the clad nozzle hole is pierced with a pin pipe around the core. A plastic holey fiber manufacturing method in which a clad material is surrounded and extruded to produce a plastic holey fiber, and the pressure of the gas supplied to the blow hole is adjusted according to the diameter of the hole to be formed. is there.

  According to the present invention, the hole diameter and size can be easily and freely formed, and an excellent effect that a plastic holey fiber having various characteristics can be produced is exhibited.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a cross-sectional view of a plastic holey fiber 10 of the present embodiment.

  The plastic holey fiber 10 includes a core 11 made of polymethyl methacrylate (PMMA) having excellent transparency, and a clad 12 made of a fluorine resin having a refractive index slightly smaller than that of the core 11 around the core 11. In the clad 12 near the core 11, eight circular holes 13 are formed at equal intervals on the circumference around the core 11. The holes 13 have the same cross section along the fiber axis direction, and the two holes 13a facing the core 11 are formed larger in diameter than the other six holes 13b.

  The diameter of the core 11 is 0.2 mm, the outer diameter of the clad 12 is 1 mm, the outer diameter of the jacket 14 covering the clad 12 is 2 mm, the diameter of the air holes 13 a is 80 μm, and the diameter of the air holes 13 b is 30 μm.

  In the plastic holey fiber 10 according to the present embodiment, polymethyl methacrylate is used for the core and fluorine-based resin is used for the clad. However, the present invention is not limited thereto, and other organic materials may be used for the core or the clad. Further, the arrangement position, quantity, and hole diameter of the holes 13 are not limited thereto. Further, the number of large-diameter holes or small-diameter holes is not limited, and the types of diameters are not limited to two.

  Next, the manufacturing method of the plastic holey fiber 10 of this Embodiment is demonstrated.

  FIG. 3 is a cross-sectional view showing a manufacturing process of the plastic holey fiber 10.

  The plastic holey fiber manufacturing apparatus 30 mainly includes a core material transfer unit 31, a clad material transfer unit 32, and a fiber forming unit 33. The core material transfer section 31 includes a screw 36 that is coupled to a core material extrusion nozzle 35 that constitutes the fiber forming section 33 and feeds the core material, and a motor 37 that is a drive device for the screw 36. A core resin tank 38 is connected to the upstream portion of the transfer unit 31. Similarly, the clad material transfer unit 32 includes a screw 40 that is coupled to the clad material extrusion nozzle 39 constituting the fiber forming unit 33 and feeds the core material, and a motor 41 that is a drive device for the screw 40. A clad resin tank 42 is connected to the upstream portion of the clad material transfer section 32. The core resin tank 38 stores PMMA, which is a core material, and the cladding resin tank 42 stores fluorine-based resin, which is a cladding material. A winder 34 that winds up the plastic holey fiber 10 formed by the fiber forming portion 33 is disposed below the fiber forming portion 33.

  Here, FIG. 4 shows an enlarged cross-sectional view of the fiber forming portion 33.

  The fiber forming unit 33 includes a core material extrusion nozzle 35 and a clad material extrusion nozzle 39, and the core material extrusion nozzle 35 and the clad material extrusion nozzle 39 are joined by a nozzle holder 43.

  The core material extruding nozzle 35 is formed with a core nozzle hole 44 for extruding the core material flowing in from the core material transfer section 31. The core nozzle hole 44 is coupled to the lower end of the extrusion chamber 45, the extrusion chamber 45 coupled to the lower end of the core material transfer section 31, the middle portion 46 having a smaller diameter than the extrusion chamber 45, and the lower end of the intermediate portion 46, The outlet portion 47 is smaller than the diameter of the intermediate portion 46 and has the same size as the core diameter of the fiber to be formed.

  The clad material extrusion nozzle 39 is formed with a clad nozzle hole 48 for extruding the clad material flowing from the clad material transfer section 32. The clad nozzle hole 48 is formed so as to surround the outlet portion 47 of the core nozzle hole 44, and is coupled to the clad material transfer unit 32 via the clad material flow path 49, and coupled to the lower side of the inflow chamber 50. It consists of a reduced diameter portion 51 and an exit portion 52 that is coupled to the lower end of the reduced diameter portion 51 and is smaller than the diameter of the reduced diameter portion 51 and has the same size as the outer diameter of the fiber to be formed.

  Further, the clad nozzle hole 48 is provided with a plurality of pin pipes 53 for forming holes in the fiber. The pin pipes 53 are concentrically arranged at equal intervals so as to surround the outlet part 47 of the core nozzle hole 44 in the clad nozzle hole 48, and all the pin pipes 53 have the same diameter. A gas blowing hole 54 for supplying gas to the pin pipe 53 is connected to the core material extrusion nozzle 35 for each pin.

  In the present embodiment, since the number of holes formed in the plastic holey fiber 10 is eight, the number of pin pipes 53 is eight. However, the number of pin pipes 53 is not limited to this, and the number of pin pipes 53 is equal to the desired number of holes. The same number may be arranged. Although not shown in the drawing, each gas blower hole 54 is connected to a device that allows gas to flow in and adjusts the pressure in the gas blower hole 54.

  PMMA which is a core material in the core resin tank 38 is sent out to the core nozzle hole 44 by the screw 36 of the core material transfer unit 31. PMMA is extruded into the extrusion chamber 45, the intermediate part 46, and the outlet part 47 in the core nozzle hole 44 to form the core 11. At this time, the diameter of the outlet 47 of the core nozzle hole 44 becomes the diameter of the core 11.

  Further, the fluorine-based resin, which is a clad material in the clad resin tank 42, is sent out to the inflow chamber 50 of the clad nozzle hole 48 through the clad material channel 49 by the screw of the clad material transfer section 32. The clad nozzle hole 48 surrounds the outlet portion 47 of the core nozzle hole 44, and the fluorine-based resin stored in the inflow chamber 50 is extruded from the outlet portion 52 through the reduced diameter portion 51 to form a fiber shape. The outer diameter of the formed fiber becomes the diameter of the outlet portion 52, the cladding 12 is formed around the core 11, and a plastic fiber is formed.

  During extrusion forming of the plastic fiber, air is sent from the gas blowing hole 54 in the fiber forming portion 33 to increase the pressure in the pin pipe 53, thereby forming the hole 13 in the cladding 12 of the fiber 10. At this time, the size of the diameter depends on the pressure in the pin pipe 53, and the pressure of the gas supplied to the gas blowing hole 54 is adjusted in accordance with the diameter of the hole 13 to be formed. The diameter of the air holes 13 can be changed by adjusting the pressure of the air to be introduced. That is, if the pressure in the pin pipe 53 is increased, a hole having a large diameter can be formed. Conversely, if the pressure in the pin pipe 53 is decreased, a hole having a small diameter can be formed.

  When the diameter is changed by only two holes as in the holey fiber 10 shown in FIG. 1, the gas pressure to the two pin pipes 53 facing each other across the outlet 47 of the core nozzle hole 44 is changed to the other 6 holes. It can be manufactured by adjusting it higher than the gas pressure of the pin pipe 53 of the book.

However, the gas flowing into the gas blowing hole 54 is not limited to air, and an inert gas such as He, Ar, N ₂ or the like may be used.

  Thereafter, the periphery of the cladding is covered with a jacket 14 to obtain a plastic holey fiber 10, which is wound up by a winder 34. The jacket 14 can have any refractive index and can be constructed from conventional materials for the jacket 14.

  As described above, the holey fiber 10 consistently performs the composite extrusion molding of the core 11 and the clad 12 in the fiber forming portion 33, and supplies the gas to the pin pipe 53 for hole formation provided in the clad nozzle hole 48. Thus, the holes 13 can be formed in the clad 12, and furthermore, the holes of a desired size can be easily and freely formed by adjusting the pressure of the gas supplied to the pin pipe 53 individually.

  As shown in FIG. 1, the plastic holey fiber 10 manufactured by the above method has two holes 13a larger than the holes 13b.

  The plastic holey fiber 10 is expected to improve the bending characteristics by having the holes 13 in the cladding 12 in the vicinity of the core 11, but the plastic holey fiber 10 manufactured in the present embodiment further has an axis passing through the center of the core. Since the diameter of the two holes 13a arranged above is larger than that of the other holes 13b, the refractive index distribution of the fiber cross section has anisotropy, and the birefringence of its intrinsic polarization axis is bent, external force, etc. Therefore, it can be used as a polarization-maintaining fiber that retains linearly polarized light incident on the holey fiber 10.

  Another embodiment will be described.

  As shown in FIG. 2A, the plastic holey fiber 20 of this form has different diameters of the air holes 23 in the fiber longitudinal direction.

  In the holey fiber 20, holes 23 are formed at equal intervals on the circumference around the core 21 in the clad 22 near the core 21, and all the holes 23 have the same diameter in the fiber cross section. The diameter varies in the longitudinal direction of the fiber. That is, from the end of the fiber to a predetermined length, a relatively small-diameter hole 23a is formed as shown in FIG. 2 (b), which is a cross-sectional view taken along line AA of FIG. 2 (a). As shown in FIG. 2C, which is a cross section taken along the line BB, a hole 21b having a diameter larger than that of the hole 21a is formed continuously with the portion. Here, the diameter of the hole 21a is 30 μm, and the diameter of the hole 23b is 80 μm. The communicating portion 23c of the holes 23a and 23b has a tapered shape in which the hole diameter gradually changes.

  However, although the hole 23 is comprised by two types of hole 23a, 23b from which a diameter differs, the number of holes, an arrangement position, a diameter, and each hole length are not limited to this.

  The manufacturing method does not change the pressure in each pin pipe 53 for each pin in the method for manufacturing the holey fiber 10 of the present embodiment, but changes the pressure of all the pin pipes 53 during the fiber manufacturing.

  In the holey fiber 20 shown in FIG. 2, during the fiber formation, a hole 23a is first formed by keeping the internal pressure of the pin pipe 53 constant, and the pressure in the pin pipe 53 is gradually increased in the middle to thereby form a tapered hollow fiber 20a. It is obtained by forming the hole 23c and forming the hole 23b having a large diameter by making the high pressure constant.

  In this way, by changing the pressure of the gas supplied to the pin pipe 53 via the gas blowing hole 54 at an arbitrary time, the holes 23 having different diameters can be continuously formed in the fiber longitudinal direction.

  The plastic holey fiber 20 can form holes by changing the diameter so as to change the refractive index distribution in the fiber cross section according to the bending diameter when the fiber is laid or processed. For example, at locations where the radius of curvature is small, by using a fiber with a large hole diameter, the average refractive index of the cladding can be reduced and the relative refractive index difference between the core and the cladding can be increased. Increase in radiation loss due to bending can be suppressed. Conversely, at locations where the radius of curvature is large and the bending loss is not so large, the hole diameter can be reduced to increase the fiber strength.

  Accordingly, a plastic holey fiber having a plurality of holes having different diameters or holes having different diameters in the longitudinal direction of the fiber can be easily produced, and characteristics suitable for the use of the plastic fiber can be provided.

  Further, when manufacturing various types of plastic holey fibers, various types of plastic holey fibers can be manufactured without changing the number and size of the pin pipes 53, and the work time can be reduced.

  Finally, it goes without saying that a plastic holey fiber having a plurality of holes having different diameters and having holes whose diameters change in the longitudinal direction of the fiber also relates to the present invention.

1 is a cross-sectional view of a plastic holey fiber which is a preferred embodiment according to the present invention. (A) is a structural view of a plastic holey fiber according to another embodiment, (b) is a cross-sectional view taken along the line AA, and (c) is a cross section taken along the line BB. FIG. It is a figure explaining the manufacturing method of the plastic holey fiber shown in FIG. It is an expanded sectional view of the fiber formation part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plastic holey fiber 11 Core 12 Clad 13 Hole 33 Fiber formation part 35 Core material extrusion nozzle 39 Clad material extrusion nozzle 44 Core nozzle hole 47 Outlet part 48 Clad nozzle hole 53 Pin pipe 54 Gas blower hole

Claims (5)

  A plastic holey fiber having a hole extending in a longitudinal direction of a fiber in a clad near a core, wherein a plurality of holes having different diameters are formed.   A plastic holey fiber having a plurality of holes extending in a fiber longitudinal direction in a cladding near a core, wherein holes having different diameters in the fiber longitudinal direction are formed.   The plastic holey fiber according to claim 1, wherein the holes have different diameters in the fiber longitudinal direction.   The plastic holey fiber according to any one of claims 1 to 3, wherein the core is made of polymethyl methacrylate and the clad is made of a fluorine resin. A clad material extrusion nozzle is provided below the core material extrusion nozzle so that the clad material is injected so as to surround the core extruded from the core material extrusion nozzle, and the core material is supplied from the core material extrusion nozzle. And a plastic holey fiber manufacturing method in which a plurality of holes extending in the longitudinal direction of the fiber are formed in the cladding near the core, and the cladding in the cladding material extrusion nozzle is formed below the core material extrusion nozzle. A plurality of hole-forming pin pipes extending to the nozzle holes are disposed so as to surround the outlet part of the core nozzle hole, and a gas blowing hole for supplying gas to the pin pipe is formed in the core material extrusion nozzle, and the core extrusion nozzle is formed. While forming a hole with a pin pipe around the core in the core pushed out from the clad nozzle hole, A plastic holey fiber is manufactured by surrounding and extruding a lad material, and the pressure of the gas supplied to the gas blowing hole is adjusted according to the diameter of the hole to be formed. Method.

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