JP4106038B2 - Photonic crystal optical fiber manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a photonic crystal optical fiber having a photonic crystal structure that is uniform in the longitudinal direction of the fiber in a cladding portion of the optical fiber.

  In a conventional optical fiber, by adding an additive to the core portion, a difference in refractive index is caused between the core and the cladding, thereby causing total reflection between the core and the cladding, so that an optical wave is transmitted in the core. Are guided. And the optical fiber which has various characteristics was obtained by using the optical fiber of a different refractive index profile.

  By the way, in recent years, with an increase in the speed of optical communication networks and optical signal processing, larger-capacity optical fibers are required. Thus, photonic crystal fiber (hereinafter referred to as PCF) has been attracting attention as a technology that opens up new possibilities for optical fibers (see, for example, Non-Patent Document 1).

  PCF has a photonic crystal structure with a uniform two-dimensional period in the longitudinal direction of the optical fiber in the clad part of the optical fiber. There are two main types.

  One is to provide a photonic band gap in a region corresponding to the clad and to confine the light wave in the core by Bragg reflection (see, for example, Non-Patent Document 2).

  The other is to confine the light wave in the core by total reflection using the difference in refractive index between the core and the clad as in the conventional optical fiber. While the conventional optical fiber has a refractive index difference between the core and the clad by doping the core with an additive, the PCF using total reflection is a holey fiber (Holey fiber) shown in FIG. The effective refractive index is lowered by the holes 134 provided in the clad part 133 around the core part 132 as in the case of Fiber.

  PCF130 is realized with ordinary optical fiber such as ultra-wideband single mode transmission area, large effective core area, High-Δ, large structural dispersion, etc., depending on the design (shape and arrangement density) of the holes 134 provided in the cladding part 133 It has characteristics that cannot be done.

As shown in FIG. 14, the PCF manufacturing method is as follows. First, a quartz tube 142 and a quartz rod 141 having a small diameter and a predetermined length are prepared, and hundreds of quartz tubes 142 are bundled around the quartz rod 141. A quartz bundle member 143 is formed, and the quartz bundle member 143 is inserted and disposed in the quartz jacket tube 144 to form the preform 140. Next, an active gas having a dehydrating action is supplied into the quartz jacket tube 144 of the preform 140 to perform a dehydration process in the quartz jacket tube 144. Next, while the N ₂ gas is being supplied from one end side of the preform 140 after the dehydration process, the other end side of the preform 140 is drawn, and the quartz rod 141, the quartz tube 142, and the quartz jacket tube 144 are drawn. Are fused and integrated to obtain PCF 130 having a predetermined diameter (see, for example, Patent Document 1).

Creggan, et al., “Single-Mode Photonic Band Gap Guidance of Light in Air,” Science, (USA), 1999 9 3rd, No.285, p.1537-1539 Knight, JCKnight, "Photonic Band Gap Guidance in Optical Fibers," Science, (USA), November 20, 1998, No.282, p. 1476-1478 JP 2003-206148 A

  By the way, in the conventional method of manufacturing the PCF 130, when the preform 140 is drawn, the quartz rod 141, the quartz tube 142, and the quartz jacket tube 144 are fused and integrated at the same time. However, since this fusion integration is insufficient, a structural defect occurs in the photonic crystal structure of the PCF 130, specifically, the size of the holes 134 of the PCF 130 is uneven, and the transmission loss of the PCF 130 is deteriorated. There was a problem to do.

  In addition, in the dehydration process using the active gas having a dehydrating action, the gap between the quartz rod 141 and the quartz tube 142, the gap between the quartz tubes 142, the quartz tube 142 and the quartz jacket tube 144 in the preform 140. The voids and the OH groups present on the surface portion inside the quartz tube 142 cannot be sufficiently removed, and the remaining OH groups diffuse into the core portion 132 at the time of drawing, leading to deterioration in transmission loss of the PCF 130. There was a problem.

  An object of the present invention created in view of the above circumstances is to provide a method of manufacturing a photonic crystal optical fiber in which a quartz rod, a quartz tube, and a quartz jacket tube are sufficiently fused and integrated.

In order to achieve the above object, a method of manufacturing a photonic crystal optical fiber according to the present invention is a method of manufacturing a photonic crystal optical fiber having a uniform photonic crystal structure in the longitudinal direction of the fiber in a cladding portion of the optical fiber. ,
A quartz bundle member formed by arranging a plurality of quartz tubes sealed at both ends around a quartz rod is inserted into a quartz jacket tube to form a preform, and after performing a dehydration treatment in the preform, Seal one end of the quartz jacket tube and heat-treat the preform to completely seal the gap between the quartz rod and the quartz tube, the gap between the quartz tubes, and the gap between the quartz tube and the quartz jacket tube. Thus, the other end side of the quartz jacket tube is sealed so that the preform is completely sealed, and then the preform that has been fused and integrated is subjected to a drawing process.

  Here, it is preferable that the quartz rod and the quartz tube have a fluorine-doped layer in the outermost layer, and the quartz jacket tube has a fluorine-doped layer in at least an inner surface layer thereof.

Further, during the dehydration process, C ₂ F ₆ as an etching agent is supplied into the preform together with Cl ₂ as a dehydration treatment agent, and the dehydration process and the surface etching process of the quartz rod, the quartz tube, and the quartz jacket tube are performed. Are preferably performed simultaneously.

In addition, a quartz bundle member formed by arranging a plurality of quartz tubes sealed at both ends around a quartz rod is inserted into a quartz jacket tube to form a preform, and the preform is formed at both ends of the quartz jacket tube. After fusing the quartz dummy tube and dehydrating the preform, seal the quartz dummy tube at one end while supplying chlorine and chlorine gas to the preform, and heat-treat the preform. The gap between the quartz rod and the quartz tube, the gap between the quartz tubes, and the gap between the quartz tube and the quartz jacket tube are fused and integrated so that the quartz dummy tube on the other end is sealed. Thus, it is preferable to produce a sealed preform and to perform the drawing process on the sealed preform.

  According to the above, before performing the drawing process on the preform, the quartz rod, the quartz tube, and the quartz jacket tube are fused and integrated, and the fused and unified preform is used for drawing, The photonic crystal structure of the nick crystal optical fiber can be arranged uniformly.

  According to the present invention, an excellent effect that a photonic crystal optical fiber with low transmission loss can be obtained is exhibited.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a perspective view of a PCF obtained by a PCF manufacturing method according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the PCF 10 obtained according to the present embodiment has a core portion 11 at the center thereof, and a cladding portion 12 around the core portion 11, and the core portion in the cladding portion 12. 11 has a photonic crystal structure 13 having a uniform two-dimensional period (honeycomb shape) in the fiber longitudinal direction. The photonic crystal structure 13 is composed of a plurality of holes 14 formed concentrically around the core portion 11 and arranged, and each hole 14 communicates with the longitudinal direction of the fiber (vertical direction in FIG. 1). Yes.

  Next, the manufacturing method of PCF10 which concerns on this Embodiment is demonstrated based on an accompanying drawing.

  Prior to manufacturing the PCF 10 according to the present embodiment, a quartz rod (quartz rod) 21 and a quartz tube 22 are prepared in advance. Here, as shown in FIG. 3, the quartz rod 21 is provided with a fluorine doped layer 32 formed by adding fluorine to pure quartz on the outer periphery of a rod body 31 made of pure quartz. Further, as shown in FIG. 5, the quartz tube 22 is provided with a fluorine doped layer 52 formed by adding fluorine to pure quartz on the outer periphery of a tube body 51 made of pure quartz, and both ends are sealed. It has stopped. It is preferable that the quartz rod 21 and the quartz tube 22 have the same diameter and the same length.

  Next, as shown in FIG. 2, a small-diameter quartz tube 22 constituting the photonic crystal structure 13 of the cladding portion 12 after drawing is drawn around the small-diameter quartz rod 21 that becomes the core portion 11 after drawing. The quartz bundle member 23 is formed by arranging a plurality of, for example, several hundreds in a close-packed manner. Thereafter, the quartz bundle member 23 is inserted and disposed in a quartz jacket tube 24 formed by adding (doping) fluorine to the entire tube shown in FIG.

C ₂ F ₆ as an etching agent is supplied together with Cl ₂ and O ₂ as dehydrating agents into the obtained preform 20, and the surfaces of the dehydrating process, the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 are supplied. Etching is performed simultaneously.

  Thereafter, the preform 20 is subjected to a heat treatment to fuse and integrate the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24, and then the fused and integrated preform 20 is completely sealed. Thereafter, the PCF 10 is obtained by drawing the completely sealed preform 20 so as to have a predetermined fiber diameter.

  In more detail, the manufacturing method of PCF10 is demonstrated.

The quartz rod 21 is obtained by drawing a transparent glass preform that has been made transparent by heat treatment of the soot base material. This soot base material is produced by an external CVD (Chemical Vapor Deposition) method. Specifically, as shown in FIG. 4, after the quartz rod 41 (for example, the outer diameter is 25 mm and the length is 1 m) is set in the external CVD apparatus 40, the quartz rod 41 is slowly rotated (for example, 15 rpm). The soot base material 45 (for example, the outer diameter is 35 mm) is obtained by depositing and forming the soot layer 42 on the outer periphery thereof. The deposition of the soot layer 42 is composed of source gas (for example, SiCl _{4 with} a flow rate of 250 cc / min, SiF _{4 with} a flow rate of 100 cc / min, O _{2 with} a flow rate of 15 l / min, and H ₂ with a flow rate of 10 l / min. Gas G) and fuel gas are supplied to the burner 43, and the flame of the burner 43 is used to blow the outer periphery of the quartz rod 41. The soot base material 45 is heated at a predetermined temperature (for example, about 1500 ° C.) in a predetermined atmosphere (for example, a gas composed of He having a flow rate of 10 l / min and Cl ₂ having a flow rate of 200 cc / min). By doing so, a transparent glass preform (for example, an outer diameter of 30 mm) is obtained. By drawing this transparent glass preform by a normal drawing method, the quartz rod 21 (for example, the outer diameter is 500 μm) shown in FIG. 3 is obtained.

  The quartz tube 22 is also produced by the same method as the quartz rod 21. Specifically, as shown in FIG. 6, a quartz tube 61 (for example, an outer diameter of 25 mm, an inner diameter of 18 mm, and a length of 1 m) is set in an external CVD apparatus 40 similar to FIG. The soot base material 65 (for example, the outer diameter is 35 mm and the inner diameter is 18 mm) is obtained by depositing and forming the soot layer 42 on the outer periphery of the tube 61 while slowly rotating the tube 61 (for example, rotating at a rotation speed of 15 rpm). It is done. Thereafter, transparency and drawing are performed in the same manner as the method for manufacturing the quartz rod 21, and the quartz tube 22 (for example, the outer diameter is 500 μm) shown in FIG. 5 is obtained.

  The thicknesses of the fluorine doped layers 32 and 52 in the quartz rod 21 and the quartz tube 22 are set to 1/20 to 1/10 of the outer diameter of the entire quartz rod 21 and the quartz tube 22. For example, when the outer diameter of the entire quartz rod 21 and quartz tube 22 is 500 μm, the thickness of each of the fluorine doped layers 32 and 52 is 25 to 50 μm. At this time, if the thickness of each of the fluorine-doped layers 32 and 52 is less than 25 μm, the effect of lowering the melting point of the surfaces of the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 is not sufficient, as will be described later. This is because bubbles are generated due to poor fusion and integration of the rod 21, the quartz tube 22, and the quartz jacket tube 24. On the other hand, when the layer thickness of each of the fluorine doped layers 32 and 52 exceeds 50 μm, the melting points of the surfaces of the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 are excessively lowered, and the holes of the quartz tube 22 are deformed. This is because the fusion and integration cannot be performed as designed.

  As the quartz jacket tube 24, a fluorine doped layer 72 is provided on the inner surface of the tube main body 71 as shown in FIG. 7B in addition to the whole tube shown in FIG. It may be a thing. Here, the layer thickness of the fluorine doped layer 72 is equal to or less than the outer diameter of the entire quartz rod 21 and the quartz tube 22. For example, when the outer diameter of the entire quartz rod 21 and quartz tube 22 is 500 μm, the layer thickness of the fluorine doped layer 72 is also about 500 μm or less.

  The fluorine content of each of the fluorine doped layers 32 and 52 and the quartz jacket tube 24 is 0.1 mol% or more, preferably 0.1 to 2.1 mol%. Here, the reason why the fluorine content is 0.1 mol% or more is that when the fluorine content is less than 0.1 mol%, the surfaces of the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24, as will be described later. This is because the effect of lowering the melting point of the portion is not sufficient, and poor fusion occurs when the preform 20 is fused and integrated. As a result, in the PCF 10 shown in FIG. 1, the size and arrangement of the holes 14 are not uniform.

  The quartz rod 21 and the quartz tube 22 obtained by the above-described method are each cut to a predetermined length. The quartz tube 22 is sealed at both ends during this cutting. Thereafter, in order to remove dirt and dust adhering to the surface of each cutting member, large dust such as debris is washed away using running water, and then ultrasonic cleaning is performed using ethyl alcohol and trichlorethylene. Thereafter, dirt and dust released from the surface of each cutting member are washed away with pure water, and then acid-washed with 1 to 2% hydrofluoric acid to finish the surface. When the quartz rod 21 and the quartz tube 22 are cut, the quartz rod 21 is cut 20-30 mm longer than the quartz tube 22 (for example, the quartz rod 21 is cut to a length of 250 mm and the quartz tube 22 is cut to a length of 230 mm). .

  Next, when the preform 20 is formed using the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24, that is, the quartz bundle member 23 composed of the quartz rod 21 and the quartz tube 22 is replaced with a quartz jacket. When the preform 20 is formed by being inserted into the tube 24, the quartz tubes 22 need not be crossed with each other (the quartz tube 22 is not twisted), and both ends must be arranged at the same position. For this reason, it is preferable to form the quartz bundle member 23 and insert the quartz bundle member 23 into the quartz jacket tube 24 at the same time while giving fine vibrations by ultrasonic waves in pure water. Specifically, as shown in FIG. 8, a quartz jacket tube 24 having a predetermined dimension is disposed in an oblique manner in an ultrasonic cleaner 81 containing pure water 82, and quartz quartz tube 24 is disposed in the quartz jacket tube 24. The preform 21 is manufactured by sequentially arranging the rod 21 and the quartz tube 22 to form the quartz bundle member 23. Since the dimensional accuracy in the longitudinal direction of the quartz jacket tube 24 greatly affects the quality of this arrangement, the inner diameter variation is adjusted to ± 0.1 mm or less.

  Next, the obtained preform 20 is put in a drying container, and the attached water is evaporated and dried, and then subjected to a dehydration treatment. This drying process is performed by using a vacuum vessel and evacuating the inside of the vacuum vessel with an oil rotary vacuum pump.

Next, as shown in FIG. 9, after the quartz dummy tubes 91 and 92 are fused to both ends of the quartz jacket tube 24 in the preform 20, Cl ₂ and O ₂ are mixed at a predetermined ratio (for example, from the quartz dummy tube 91 side). , Cl ₂ is introduced at a rate of 20 cc / min, O ₂ at a rate of 50 cc / min), and exhaust is performed from the quartz dummy tube 92 side at a predetermined rate (for example, a rate of approximately 80 Pa (0.6 Torr) / min). The inside of the quartz jacket tube 24 is replaced with Cl ₂ and O ₂ for a predetermined time. Thereafter, C ₂ F ₆ is further introduced from the quartz dummy tube 91 side at a predetermined rate (for example, a rate of 20 cc / min), and the pressure in the preform 20 is kept constant (for example, about 73 Pa (0.55 Torr)). In this state, the preform 20 is heated using the oxyhydrogen burner 93. Thereby, the surface etching process of the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 is performed while the dehydration process in the quartz jacket tube 24 is performed.

Next, after the surface etching treatment / dehydration treatment, as shown in FIG. 10, the quartz dummy tube 92 is sealed while introducing Cl ₂ and O ₂ from the quartz dummy tube 91 side. Thereafter, the preform 20 is heated again to the melting temperature of fluorine using the oxyhydrogen burner 93 again. Thereby, the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 are fused and integrated. Thereafter, as shown in FIG. 11, the quartz dummy tube 91 is sealed to completely seal the preform 20, thereby producing the sealed preform 110.

  The sealed preform 110 is drawn to a predetermined outer diameter (for example, outer diameter φ125 μm) to form a fiber, thereby obtaining the PCF 10 (for example, length 2.6 km) shown in FIG. When the wavelength spectral characteristic of the PCF 10 was examined, as shown in FIG. 12, the transmission loss at a wavelength of 1550 nm was 4.2 dB / km, which was a very low loss.

  Next, the operation of the present embodiment will be described.

  In the method of manufacturing the PCF 10 according to the present embodiment, the preform 20 is subjected to heat treatment before the preform 20 is drawn, and the quartz rod 21, the quartz tube 22, and the quartz jacket tube 24 are partially melted. And fusion integration. By performing heat treatment on the preform 20, the quartz rod 21, the quartz tube 22, and the jacket tube 24 are fused and integrated. At this time, the outermost layer of the quartz rod 21 and the quartz tube 22 and the inner surface layer of the jacket tube 24 are combined. Partially melts. This partial melt is diffused by a capillary phenomenon, and the gap between the quartz bundle members 23 (the gap between the quartz rod 21 and the quartz tube 22, the gap between the quartz tubes 22, and the gap between the quartz tube 22 and the quartz jacket tube 24). ) And the arrangement of the quartz rod 21 and the quartz tube 22 in the quartz bundle member 23 is prevented from being disturbed. The partial melt completely seals the gap between the quartz rod 21 and the quartz tube 22, the gap between the quartz tubes 22, and the gap between the quartz tube 22 and the quartz jacket tube 24. Therefore, the fused integration of the quartz rod 21, the quartz tube 22, and the jacket tube 24 can be performed simultaneously and uniformly over the radial direction of the preform 20.

  As a result, according to the manufacturing method according to the present embodiment, when the preform 20 is drawn, the interface between the quartz rod 21 and the quartz tube 22, the interface between the quartz tubes 22, and the quartz tube 22 and the quartz jacket tube 24. Bubbles are no longer generated at the interface with the material, and it contains less impurities such as bubbles that adversely affect transmission loss compared to conventional manufacturing methods that fuse and integrate when drawing. A PCF 10 having a structure can be obtained.

  In addition, since drawing (fibrous) can be performed uniformly over the radial direction of the preform 20, the size and arrangement of the quartz tubes 22 during drawing are not uneven. As a result, in the PCF 10 shown in FIG. 1, the size and arrangement of the holes 14 are uniform.

  In the method of manufacturing the PCF 10 according to the present embodiment, the quartz rod 21 and the quartz tube 22 having the fluorine doped layers 32 and 52 as the outermost layer and the quartz jacket tube 24 doped with fluorine at least in the inner surface layer are used. Therefore, the melting point is lower than that of a quartz rod, a quartz tube, and a jacket tube made of pure quartz. For this reason, when the preform 20 is subjected to heat treatment to fuse and integrate the quartz rod 21, quartz tube 22, and jacket tube 24, the outermost layer of the quartz rod 21 and quartz tube 22 and the inner surface layer of the jacket tube 24. Can be partially melted easily.

  Further, in the method of manufacturing the PCF 10 according to the present embodiment, the dehydration process is performed in the previous process of the fusion integration of the preform 20, but in this dehydration process, the quartz rod 21, the quartz tube 22, The surface of the quartz jacket tube 24 is etched. The dehydration process is performed while etching the gap between the quartz rod 21 and the quartz tube 22, the gap between the quartz tubes 22, and the gap surface between the quartz tube 22 and the quartz jacket tube 24. For this reason, the OH groups contained in the surfaces of the quartz rod 21 and the quartz tube 22 and the inner surface layer of the jacket tube 24 can be effectively and efficiently removed. As a result, unlike the conventional case, there is no possibility that the remaining OH group diffuses into the core portion at the time of drawing and causes deterioration of PCF transmission loss. That is, a low transmission loss PCF 10, that is, a high-quality PCF 10 can be obtained.

  In the method for manufacturing the PCF 10 according to the present embodiment, the fusion-integrated preform 20 is completely sealed to produce a sealed preform 110, and the sealed preform 110 is drawn. ing. Accordingly, it is possible to prevent moisture containing air, that is, OH groups from being mixed into the preform 20 at the time of drawing, and the influence of the OH groups on the PCF transmission loss can be further reduced.

  Further, the clad portion 12 of the PCF 10 obtained by the manufacturing method according to the present embodiment is made of fluorine-doped quartz because the above-described partial melt is uniformly diffused. For this reason, the refractive index is lower than that of the clad portion made of pure quartz. Therefore, the refractive index difference between the core portion 11 and the cladding portion 12 of the PCF 10 is larger than the refractive index difference between the core portion and the cladding portion of the conventional PCF, and the effect of confining the light wave in the core portion 11 is higher. Become.

  As mentioned above, it cannot be overemphasized that embodiment of this invention is not limited to embodiment mentioned above, and various things are assumed in addition.

It is a perspective view of PCF obtained by the manufacturing method of the photonic crystal optical fiber which concerns on preferable one Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the photonic crystal optical fiber which concerns on preferable one Embodiment of this invention, and is a perspective view of the preform used for manufacture of a photonic crystal optical fiber. It is a cross-sectional view of the quartz rod in the preform of FIG. It is the schematic at the time of manufacturing the quartz rod of FIG. It is a cross-sectional view of the quartz tube in the preform of FIG. It is the schematic at the time of manufacturing the quartz tube of FIG. It is a cross-sectional view of the quartz jacket tube of FIG. It is the schematic at the time of manufacturing the preform of FIG. It is the schematic at the time of performing a dehydration process to the preform of FIG. It is the schematic at the time of fusing and integrating the preform after a dehydration process. It is a longitudinal cross-sectional view after completely sealing the preform after fusion integration. It is a figure which shows an example of the wavelength spectral characteristic of the photonic crystal optical fiber which concerns on one suitable embodiment of this invention. Here, the horizontal axis in the figure is the wavelength [nm], and the vertical axis is the loss [dB / km]. It is a perspective view of the conventional photonic crystal optical fiber. It is a figure for demonstrating the manufacturing method of the conventional photonic crystal optical fiber, and is a perspective view of the preform used for manufacture of a photonic crystal optical fiber.

Explanation of symbols

20 Preform 21 Quartz rod 22 Quartz tube 23 Quartz bundle member 24 Quartz jacket tube

Claims (7)

In a method of manufacturing a photonic crystal optical fiber having a uniform photonic crystal structure in the longitudinal direction of the fiber in the cladding portion of the optical fiber,
A quartz bundle member formed by arranging a plurality of quartz tubes sealed at both ends around a quartz rod is inserted into a quartz jacket tube to form a preform, and after performing a dehydration treatment in the preform, Seal one end of the quartz jacket tube and heat-treat the preform to completely seal the gap between the quartz rod and the quartz tube, the gap between the quartz tubes, and the gap between the quartz tube and the quartz jacket tube. The photonic is characterized by sealing and sealing the other end of the quartz jacket tube to completely seal the preform, and then drawing the fused and integrated preform. Crystal optical fiber manufacturing method.   2. The photonic crystal optical fiber according to claim 1, wherein the quartz rod and the quartz tube have a fluorine-doped layer as an outermost layer, and the quartz jacket tube has a fluorine-doped layer as at least an inner surface layer thereof. Method. During the dehydration process, C ₂ F ₆ as an etching agent is supplied into the preform together with Cl ₂ as a dehydration process agent, and the surface of the dehydration process, the quartz rod, the quartz tube, and the quartz jacket tube is supplied. The method of manufacturing a photonic crystal optical fiber according to claim 1 or 2, wherein the etching process is performed simultaneously. A quartz bundle member formed by arranging a plurality of quartz tubes sealed at both ends around a quartz rod is inserted into a quartz jacket tube to form a preform, and a quartz dummy is formed at both ends of the quartz jacket tube of the preform. the tube was fused, after the dehydration treatment in the preform, sealed at one end of the quartz dummy tube while supplying chlorine, chlorine gas into the preform, the quartz is subjected to heat treatment to the preform The gap between the rod and the quartz tube, the gap between the quartz tubes, and the gap between the quartz tube and the quartz jacket tube are fused and integrated so that the quartz dummy tube on the other end is sealed. The method for producing a photonic crystal optical fiber according to any one of claims 1 to 3, wherein a sealed preform is produced and the drawing process is performed on the sealed preform.   5. The photonic according to claim 1, wherein the thickness of each fluorine doped layer of the quartz rod and the quartz tube is 25 to 50 μm, and the fluorine content of each fluorine doped layer is 0.1 mol% or more. Crystal optical fiber manufacturing method.   6. The photonic crystal optical fiber according to claim 1, wherein the entire quartz jacket tube is doped with fluorine, and the fluorine content of the entire quartz jacket tube is 0.1 mol% or more. Manufacturing method.   6. The quartz jacket tube according to claim 1, wherein the inner surface layer has a fluorine-doped layer having a thickness of 500 μm or less, and the fluorine content of the fluorine-doped layer is 0.1 mol% or more. The manufacturing method of the photonic crystal optical fiber of description.

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