JP2004252424A - Splicing structure of optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a dust collection effect from occurring at the tip of an optical fiber brought into contact with each other, and moreover, to make it possible to easily splice the two pieces of optical fibers to each other without the need for a large-scale fusing machine. <P>SOLUTION: In an optical fiber splicing structure for splicing two pieces of optical fibers 11, 12 into the state in which each core tip is in contact with the other without being fused, the tip parts of the optical fibers 11, 12 including the core tips are enclosed in a hermetically sealed space such as the internal space of a connector 24 incorporating, for example, ferrules 13, 14, and this hermetically sealed space is filled with an inert gas or a liquid which is transparent to the light propagating in the optical fibers 11, 12 and is not decomposed by the light. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a structure for connecting two optical fibers.

  2. Description of the Related Art Conventionally, two structures are generally known as a structure for connecting two optical fibers.

One is a structure in which the ends of two optical fibers are fused with the cores aligned on the same axis. Another is a structure in which two optical fibers are connected in a state in which the tips of the respective cores are in contact with each other without being fused. As the more specific structure of the latter, for example, as described in Patent Document 1, two ferrules that respectively fix the tip portions of two optical fibers and the core tips of the optical fibers face each other. A connector comprising a common sleeve tube to be inserted in a state and means for holding the ferrules in a state where the core ends of two optical fibers are in contact with each other is widely known.
Japanese Patent Publication No. 4-69369

  By the way, in an apparatus that handles light having a short wavelength, particularly a wavelength of about 350 to 500 nm emitted from a GaN-based semiconductor laser, the vaporized organic substance and the laser light undergo a photochemical reaction at the light passing end surface of the optical member having a high light density. It has been found that the so-called dust collection effect, in which the substances generated in this way accumulate, occurs. When contaminants adhere to the light passage end face of the optical member in this manner, problems such as an increase in the semiconductor laser driving current necessary for obtaining a predetermined light output and an increase in laser light propagation loss occur. In addition, this dust collection effect is known to be attributed to carbides and to siloxane.

  Even in the above-described optical fiber, when light having a short wavelength as described above is propagated, a dust collection effect can occur at the entrance end face and the exit end face of the core. Therefore, even at the connection portion of the two optical fibers, if the end faces of the core are not completely in contact with each other and part of the end faces are in contact with the outside air, the dust collection effect Will occur.

  As described above, in the connection structure in which two optical fibers are fused, the entire end faces of the core are usually completely joined together, so that the dust collection effect does not occur. However, in order to apply this structure, a dedicated expensive fusion machine is required, and the work is complicated, and such a fusion machine may not be prepared depending on the work site. Further, in the case of this connection structure, in order to reconnect an optical fiber that has been once connected, it is recognized that it is necessary to cut the fusion part and perform the fusion work again.

  On the other hand, even in a structure where the ends of the cores are connected to each other without fusing the two optical fibers, the dust collection effect does not occur if the entire end faces of the cores are completely in contact. In the case of a single mode optical fiber, the dust collection effect is unlikely to occur because the optical fiber is crushed and connected so that the entire core contacts. However, in the case of an optical fiber having a large core diameter such as a multi-mode optical fiber, it is difficult to bring the end faces of the core into contact with each other over the entire surface, so that a part of the core end face is in contact with the outside air. The dust collection effect is easy to occur.

  In view of the above circumstances, the present invention can prevent the dust collection effect from occurring at the tips of optical fibers that are in contact with each other, and can easily connect two optical fibers without requiring a large-scale fusion machine. The purpose is to provide.

  In addition, the present invention has an object to provide an optical fiber connection structure in which two optical fibers can be connected once and then easily connected again.

The connection structure of the first optical fiber according to the present invention is as follows:
In the optical fiber connection structure for connecting the two optical fibers in a state where the tips of the cores are in contact with each other without fusing,
The tip of the optical fiber including the tip of the core is housed in a sealed space,
In this sealed space, an inert gas or a liquid that is transparent to the light propagating through the optical fiber and is not decomposed by the light is sealed.

Moreover, the connection structure of the second optical fiber according to the present invention is:
As in the above, in the optical fiber connection structure in which the two optical fibers are connected in a state where the tips of the cores are in contact with each other without being fused,
The tip of the optical fiber including the tip of the core is housed in a container having a fluid supply port and a fluid discharge port connected to the fluid circulation device,
This container is filled with a circulating inert gas or a liquid that is transparent to light propagating through an optical fiber and is not decomposed by the light.

  In the connection structure of the first and second optical fibers of the present invention, connecting two optical fibers means not only connecting individual optical fibers but also connecting fiber arrays or fiber bundles. This includes the case where the fibers in the fiber array or fiber bundle are connected in a one-to-one correspondence.

  In addition, the inert gas here refers to a gas that is inert to the material constituting the optical fiber, the connector, and the like, and specifically includes a dry gas such as dry nitrogen and argon. It is done.

  When the inert gas is enclosed in the sealed space in the connection structure of the first optical fiber, and when the inert gas is filled in the container in the connection structure of the second optical fiber, More desirably, the inert gas contains oxygen, a halogen group gas, and / or a halogen compound gas having a concentration of 1 ppm or more. That is, these internal atmospheres include (1) a mixed gas of an inert gas and oxygen having a concentration of 1 ppm or more, (2) an inert gas, and at least one of a halogen group gas and a halogen compound gas. The mixed gas (3) is more preferably any one of a mixed gas of an inert gas, oxygen having a concentration of 1 ppm or more, and at least one of a halogen group gas and a halogen compound gas.

  Further, it is desirable that these halogen group gas and halogen compound gas contain fluorine atoms. The halogen compound gas is desirably at least one selected from the group consisting of fluorides of carbon, nitrogen, sulfur and xenon and chlorides of carbon, nitrogen, sulfur and xenon.

The halogen group gas is a halogen gas such as chlorine gas (Cl ₂ ) or fluorine gas (F ₂ ), and the halogen compound gas is a chlorine atom (Cl), bromine atom (Br), iodine atom (I), A gaseous compound containing a halogen atom such as a fluorine atom (F).

Examples of the halogen compound gas include CF ₃ Cl, CF ₂ Cl ₂ , CFCl ₃ , CF ₃ Br, CCl ₄ , CCl ₄ -O ₂ , C ₂ F ₄ Cl ₂ , Cl-H ₂ , CF ₃ Br, PCl ₃ , CF ₄ , SF ₆ , NF ₃ , XeF ₂ , C ₃ F ₈ , CHF _{3 and the} like can be mentioned, but fluorine or chlorine and carbon (C), nitrogen (N), sulfur (S), xenon (Xe) Compounds are preferred, and those containing fluorine atoms are particularly preferred.

  Further, it is desirable that the outermost surface layer of the coating applied to the exit end face and the entrance end face of the optical fiber is made of a material that is inert to the halogen group gas and the halogen compound gas. The inert material is preferably at least one selected from the group consisting of oxides of indium, gallium, aluminum, titanium and tantalum and nitrides of gallium, aluminum, titanium and tantalum.

  Moreover, it is desirable that the inert gas or liquid used in the connection structure of the first and second optical fibers does not contain a silicone-based organic material.

Furthermore, the connection structure of the third optical fiber according to the present invention is:
As in the above, in the optical fiber connection structure in which the two optical fibers are connected in a state where the tips of the cores are in contact with each other without being fused,
The tip of the optical fiber including the tip of the core is isolated from the outside by a solid that is solidified after being supplied to the tip in a molten state and is transparent to the light propagating through the optical fiber and not decomposed by the light. It is characterized by being.

  Here, as the solid as described above, low melting point glass or the like can be suitably used.

  As a specific structure for connecting the two optical fibers without fusing as described above, for example, the tip ends of the two optical fibers are fixed to different ferrules, and the ferrules are respectively connected to each other. It is possible to apply a structure in which the core ends of the optical fibers are inserted into a common sleeve tube with the core ends facing each other, and the ferrules are held so that the core ends of the two optical fibers are in contact with each other.

  The optical fiber connection structure according to the present invention is suitable when the wavelength of light propagating through the two optical fibers is in the range of 350 to 500 nm.

  In the connection structure of the first optical fiber according to the present invention, it is transparent to the inert gas or the light propagating through the optical fiber in the sealed space containing the tip of the optical fiber, and is not decomposed by the light. Since the liquid is sealed, if the tip of the core is not in contact with the entire surface, the non-contact portion is in contact with the inert gas or liquid. Therefore, the organic matter causing the dust collection effect and the laser beam propagating through the optical fiber do not cause a photochemical reaction, and the dust collection effect can be suppressed from occurring at the tip of the optical fiber.

  In the second optical fiber connection structure according to the present invention, the container containing the tip of the optical fiber is transparent to the inert gas circulating or the light propagating through the optical fiber, and is decomposed by the light. Even in this structure, if the tip of the core is not in contact with the entire surface, the part that is not in contact is in contact with the inert gas or liquid. Therefore, the organic matter causing the dust collection effect and the laser beam propagating through the optical fiber do not cause a photochemical reaction, and the dust collection effect can be suppressed from occurring at the tip of the optical fiber.

  In addition, when an inert gas or liquid used in the first and second optical fiber connection structures that does not include a silicone-based organic material is applied, a photochemical reaction occurs between these and the laser beam. It is possible to prevent the generation of pollutants.

  In the third optical fiber connection structure according to the present invention, the optical fiber tip including the tip of the core is solidified after being supplied to the tip in the molten state, and the light propagating through the optical fiber is solidified. Since it is isolated from the outside by a solid that is transparent and not decomposed by the light, if the tip of the core is not in contact with the entire surface, the non-contacted portion is in contact with the solid. Therefore, also in this structure, the organic matter causing the dust collection effect and the laser light propagating through the optical fiber do not cause a photochemical reaction, and the dust collection effect can be suppressed from occurring at the tip of the optical fiber.

  Since the first to third optical fiber connection structures according to the present invention described above do not fuse two optical fibers, the two optical fibers can be easily connected without requiring a large-scale fusion machine. It can be connected.

  For connecting the tip portions of the two optical fibers, it is possible to adopt an appropriate detachable structure such as a conventionally known connector, so that the connection portion is covered with a solid solidified after melting. Other than the third connection structure, the two optical fibers can be connected once and then easily connected again.

  Further, in the optical fiber connection structure according to the present invention, in particular, the tip portions of the two optical fibers are fixed to different ferrules, and the ferrules are in a state where the core tips of the respective optical fibers face each other to form a common sleeve tube. When a structure in which the ferrules are inserted and the core ends of the two optical fibers are held in contact with each other is applied, the ferrule can be inserted into the ferrule simply by inserting the ferrule into the sleeve tube serving as a guide. Since the fixed optical fibers are automatically aligned on the same axis, it is easy to align the optical fibers.

  In the optical fiber connection structure according to the present invention, oxygen, a halogen group gas and / or a halogen compound gas having a concentration of 1 ppm or more are contained in the above-described inert gas sealed in a sealed space or circulated in the container. In particular, the hydrocarbon deposits are reduced by oxidative decomposition, and the silicon compound deposits are decomposed and removed by the halogen-based gas. Can be obtained.

  In addition, when the outermost surface layer of the coating applied to the exit end face and the entrance end face of the optical fiber is made of a material inert to the halogen group gas and the halogen compound gas, the light is emitted by these highly reactive gases. It is possible to prevent the end face of the fiber from deteriorating.

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

  FIG. 1 shows a sectional side view of an optical fiber connection structure according to a first embodiment of the present invention. This optical fiber connection structure is made up of two cylindrical ferrules 13 and 14 in which the tip portions of two multi-mode optical fibers (hereinafter simply referred to as optical fibers) 11 and 12 are inserted and fixed. And circular flanges 15 and 16 fixed in the vicinity of the rear ends of these ferrules 13 and 14, a connector 24 through which the ferrules 13 and 14 are inserted, and attached to the outer periphery of the ferrule 13 inside the flange 15. And an O-ring 28 attached to the inside of the flange 16 and to the outer periphery of the ferrule 14.

  The ferrules 13 and 14 are made of a material made of ceramic, glass, metal, or a combination thereof. When formed from ceramic or glass, the side surface is preferably metallized by metal plating or sputtering. And after attaching each front-end | tip part of the optical fibers 11 and 12, the front-end | tip of the ferrules 13 and 14 is grind | polished flat or spherically.

  The connector 24 has flange portions 21 and 22 formed at both ends of the sleeve tube 20 having an inner diameter slightly larger than the outer diameter of the ferrules 13 and 14, respectively. The gas introduction part 23 which has the through-hole 23a which connects these is formed. A screw thread is formed on the outer periphery of the gas introducing portion 23, and a valve 25 for closing the through hole 23a is attached to that portion by screwing.

  Note that the flanges 15 and 16 are fixed to the ferrules 13 and 14 by, for example, solder over the entire circumference at the positions indicated by black circles a in the drawing. As this solder, it is preferable to use so-called flux-free solder which does not generate organic gas.

  In addition, after inserting the ferrules 13 and 14 into the connector 24 from the front end side, the flanges 15 and 16 are respectively connected to the flange portions 21 and 22 of the connector 24 via O-rings 27 and 28, respectively. Fixed at 29. Therefore, the inside of the connector 24 is sealed by the O-rings 27 and 28 and the flanges 15 and 16 with respect to the outside. As a result, the core ends of the two optical fibers 11 and 12 fixed to the ferrules 13 and 14 are in pressure contact with each other in a coaxial state, and the optical fibers 11 and 12 are optically connected to each other. The O-rings 27 and 28 are preferably made of a fluororesin.

  When connecting the optical fibers 11 and 12 as described above, the portion of the connector 24 is arranged in the inert gas atmosphere as described above, and the valve 25 is connected to a vacuum pump (not shown) to connect the inside of the connector 24. This inert gas is introduced into the connector 24 by reducing the pressure. Thereafter, the valve 25 is closed, so that the inert gas is sealed in the connector 24 in which the ferrules 13 and 14 are accommodated to form a sealed space.

  As a result, if the tips of the cores of the optical fibers 11 and 12 are not in contact with the entire surface, the non-contact portions are in contact with the inert gas. Therefore, the organic substance that causes the dust collection effect and the light propagating through the optical fibers 11 and 12 do not cause a photochemical reaction, and the dust collection effect can be prevented from occurring at the tips of the optical fibers 11 and 12.

  In the case of this example, a laser beam having a wavelength in the range of 350 to 500 nm is propagated in the optical fibers 11 and 12, and the laser beam in this wavelength range easily exhibits the dust collection effect. It can be said that the application of is particularly effective.

  Note that, if the inside of the connector 24 is subjected to a deaeration process before the inert gas is sealed in the connector 24, the dust collection effect can be more reliably suppressed.

  In addition, since the optical fiber connection structure according to the present embodiment does not fuse the two optical fibers 11 and 12, the two optical fibers 11 and 12 can be simply connected without requiring a large-scale fusion machine. It can be connected. Since the ferrules 13 and 14 can be easily removed from the connectors 24 by loosening and removing the bolts 29, the two optical fibers 11 and 12 can be connected once and then easily reconnected.

  Furthermore, in the optical fiber connection structure according to the present embodiment, the optical fibers 11 and 12 fixed to the ferrules 13 and 14 are automatically connected to each other only by inserting the ferrules 13 and 14 through the sleeve tube 20 serving as a guide. Since they are aligned on the same axis, it is easy to align the optical fiber.

  In addition, as a preferable thing of the said inert gas, nitrogen, a noble gas, etc. are mentioned. Further, it is desirable that this inert gas contains at least one of oxygen, halogen group gas, and halogen compound gas having a concentration of 1 ppm or more and 30% or less. Suitable examples of the halogen group gas and the halogen compound gas are as described above.

  When the inert gas contains oxygen having a concentration of 1 ppm or more, the deterioration of the optical fibers 11 and 12 can be more effectively suppressed. The reason why such an effect is improved is that oxygen in the inert gas oxidizes and decomposes solid matter generated by photodecomposition of hydrocarbon components. In order to include oxygen in the sealing atmosphere as described above, clean air (atmospheric components) may be sealed inside the connector 24.

  Further, even when at least one of the halogen group gas and the halogen compound gas as described above is included in the inert gas, the deterioration of the optical fibers 11 and 12 can be similarly suppressed. These halogen-based gases exert a deterioration suppressing effect from a very small amount, but in order to obtain a remarkable deterioration suppressing effect, the content concentration of the halogen-based gas is preferably 1 ppm or more. Such a deterioration suppressing effect is obtained because the halogen-based gas contained in the sealing atmosphere decomposes the deposit generated by the photodecomposition of the organosilicon compound gas.

  Since the tips of the optical fibers 11 and 12 are closely fixed to each other, it is not necessary to form a coat film. When the coating film is not formed, a refractive index step does not occur, and thus the propagation efficiency of propagation light is usually the highest.

  However, an appropriate coat film may be formed at the tip of those as required. In that case, as the material of the outermost surface layer of the coating film to be coated, an oxide or nitride of silicon (Si), molybdenum (Mo), chromium (Cr), tin (Sn), or zirconium (Zr), etc., halogen-based In the case of using a material reactive to gas, these outermost surface layers are etched, and the reliability of the apparatus using the optical fibers 11 and 12 is lowered.

  Therefore, as the material of the outermost surface layer of the coating film covering the tips of the optical fibers 11 and 12, for example, indium (In), gallium (Ga), aluminum (Al), titanium (Ti) or tantalum (Ta) It is preferable to use a material inert to the halogen-based gas, such as an oxide or a nitride.

  In order to enclose the inert gas inside the connector 24, in addition to the above, a pressurized inert gas may be introduced into the connector 24 through the valve 25.

  Further, instead of sealing the inside of the connector 24 using the O-rings 27 and 28, the ferrules 13 and 14 can be sealed by being pressed into the sleeve tube 20.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless necessary (the same applies hereinafter).

  In the optical fiber connection structure according to the second embodiment, ferrules 13 and 14 fixing the tip portions of the optical fibers 11 and 12 are inserted into one cylindrical sleeve tube 30, respectively. The ferrules 13 and 14 are fixed to the sleeve tube 30 so that the twelve core tips are in pressure contact with each other. For example, this fixing is performed by, for example, solder-sealing over the entire circumference at a location indicated by a black circle “a” in the drawing. By carrying out the fixing with the solder in an inert gas atmosphere, an inert gas is sealed in the sleeve tube 30.

  Thereby, also in this embodiment, the same effect as in the first embodiment can be obtained. However, in this structure, it is impossible to reconnect the optical fibers 11 and 12 once connected by reusing each element as it is.

  In the first and second embodiments described above, the same applies even when a liquid that is transparent to the light propagating through the optical fibers 11 and 12 and is not decomposed by the light is used instead of the inert gas. An effect can be obtained. As such a liquid, for example, pure water can be suitably used.

  Next, an optical fiber connection structure according to a third embodiment of the present invention will be described. 3 and 4 show the overall perspective shape and side sectional shape of the optical fiber connection structure according to the third embodiment, respectively. This optical fiber connection structure is such that a general connector 40 is housed in a container 60 and means for circulating an inert gas in the container 60 is provided.

  The connector 40 has a sleeve tube 41 through which the tip ends of two cylindrical ferrules 13 and 14 are inserted, and holes through which the optical fibers 11 and 12 held by the ferrules 13 and 14 pass, The outer pipes 43 and 44 for receiving the rear ends of the ferrules 13 and 14 and compression springs 45 and 46 disposed between the bottom surfaces of the outer pipes 43 and 44 and the ferrules 13 and 14, respectively. ing.

  Male threads are formed on the outer circumferences of both ends of the sleeve tube 41, while female threads are formed on the inner circumferences of the distal ends of the outer tubes 43 and 44 so that they can be screwed together. Therefore, after inserting the front ends of the ferrules 13 and 14 into the sleeve tube 41 and the rear ends into the outer tubes 43 and 44, respectively, the outer tubes 43 and 44 are turned and screwed into the sleeve tube 41. The tips of the ferrules 13 and 14 are in contact with each other. When the outer tubes 43 and 44 are further turned and tightened from there, the tips of the ferrules 13 and 14, that is, the tips of the optical fibers 11 and 12, are brought into pressure contact with each other by the action of the compression springs 45 and 46. The fibers 11 and 12 are optically connected to each other.

  The container 60 has an upper and lower split structure composed of an upper box 61 and a lower box 62. The upper box 61 and the lower box 62 are held by a hinge 63 so as to be swingable. The latch fittings 64 are fixed to each other. The upper box 61 and the lower box 62 are provided with a gas supply port 65 and a gas discharge port 66, respectively. In addition, semicircular openings are formed in the left and right side walls of the upper box 61 and the lower box 62, and cylindrical fiber receivers 67 and 68 are arranged in these openings. These fiber receivers 67 and 68 are formed of an elastic member such as fluorine-based rubber, for example, and between the optical fibers 11 and 12 passed through the hollow portion and in a closed state of the boxes 61 and 62 It is designed to keep the space between them.

  The gas supply port 65 and the gas discharge port 66 are connected by a gas circulation pipe 70. In the middle of the gas circulation pipe 70, the tank 71 and the gas pressure pump 72 for storing the inert gas as described above are interposed. ing. In this example, the above-described gas circulation pipe 70, tank 71, and gas pressure pump 72 constitute a fluid circulation device.

  The optical fibers 11 and 12 are respectively passed through fiber receivers 67 and 68, and then optically connected to each other using the connector 40 as described above. This portion of the connector 40 is held on the bottom surface of the lower box 62, the upper box 61 is closed from above, and the latch fitting 64 is tightened so that both boxes 61, 62 are kept airtight and integrated. Turn into. Thus, the portion of the connector 40 to which the tip ends of the optical fibers 11 and 12 are connected is housed in the container 60. In addition, by applying a coating made of an elastic member such as a fluorine-based rubber to the end surface portions where both the boxes 61 and 62 are in contact with each other, an airtight state between the boxes 61 and 62 is more reliably ensured. It is desirable to make it.

  When a portion of the connector 40 is accommodated in the container 60, the gas pressure pump 72 is driven, whereby the inert gas stored in the tank 71 is circulated through the container 60. As this inert gas, what was used in 1st Embodiment can be used suitably.

  Therefore, if the tips of the cores of the optical fibers 11 and 12 are not in contact with the entire surface, the non-contacted portion is in contact with the inert gas. Therefore, the organic substance that causes the dust collection effect and the light propagating through the optical fibers 11 and 12 do not cause a photochemical reaction, and the dust collection effect can be prevented from occurring at the tips of the optical fibers 11 and 12.

  Also in this example, laser light having a wavelength in the range of 350 to 500 nm is propagated in the optical fibers 11 and 12, and the laser light in this wavelength range easily exhibits the dust collection effect. Is particularly effective.

  In addition, if the inside of the container 60 that accommodates the connector 40 is subjected to a deaeration process before the inert gas is circulated, the dust collection effect can be more reliably suppressed.

  Also, since the optical fiber connection structure according to the present embodiment does not fuse the two optical fibers 11 and 12, the two optical fibers 11 and 12 can be easily connected without requiring a large-scale fusion machine. It can be connected. Since the ferrules 13 and 14 can be easily detached from the connector 40 by loosening and removing the outer tubes 43 and 44 of the connector 40, the two optical fibers 11 and 12 are connected once and then reconnected easily. You can also.

  Furthermore, in the optical fiber connection structure according to the present embodiment, the optical fibers 11 and 12 fixed to the ferrules 13 and 14 are automatically connected to each other only by inserting the ferrules 13 and 14 through the sleeve tube 41 serving as a guide. Since they are aligned on the same axis, it is easy to align the optical fiber.

  In this case as well, if at least one of oxygen, halogen group gas, and halogen compound gas having a concentration of 1 ppm or more is included in the inert gas, the same effects as described in the first embodiment can be obtained. Can be obtained. Moreover, it is the same as that of 1st Embodiment that liquids, such as a pure water, can be used instead of the said inert gas.

  Furthermore, if the container 60 is a closed container by closing the gas supply port 65 and the gas discharge port 66 formed in the upper box 61 and the lower box 62, respectively, or omitting them from the beginning, it is inactive. It is also possible to enclose and use a liquid such as gas or pure water.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. In the optical fiber connection structure according to the fourth embodiment, ferrules 13 and 14 that fix the tip portions of the optical fibers 11 and 12 are inserted into one cylindrical sleeve tube 80, respectively. The ferrules 13 and 14 are fixed to the sleeve tube 80 so that the twelve core tips are in pressure contact with each other. For example, this fixing is performed by, for example, solder-sealing over the entire circumference at a location indicated by a black circle “a” in the drawing.

  A notch 80a is formed in a part near the center of the sleeve tube 80. After the ferrules 13 and 14 are fixed to the sleeve tube 80 as described above, the molten low melting point glass 81 is poured into the notches 80a. The molten low-melting-point glass that flows flows to this portion while extruding the air at the connection portion of the optical fibers 11 and 12, and gradually cools and solidifies.

  Also in this example, laser light having a wavelength in the range of 350 to 500 nm is propagated through the optical fibers 11 and 12, but the low melting point glass 81 is transparent to laser light in this wavelength range. Also, it is not decomposed by this light.

  As described above, in the present embodiment, the tips of the optical fibers 11 and 12 including the tips of the cores are separated from the outside by the low melting point glass 81 solidified after being supplied to the tips in the molten state. It has become. Therefore, if the tips of the cores of the optical fibers 11 and 12 are not in contact with the entire surface, the non-contacted portion comes into contact with the low melting point glass 81. Accordingly, even in this structure, the organic matter causing the dust collection effect and the laser light propagating through the optical fibers 11 and 12 do not cause a photochemical reaction, and the dust collection effect occurs at the tips of the optical fibers 11 and 12. This can be reliably suppressed.

1 is a side sectional view showing an optical fiber connection structure according to a first embodiment of the present invention; Sectional drawing which shows the connection structure of the optical fiber by the 2nd Embodiment of this invention FIG. 5 is an overall perspective view showing an optical fiber connection structure according to a third embodiment of the present invention. Side sectional view showing an optical fiber connection structure according to the third embodiment. Sectional drawing which shows the connection structure of the optical fiber by the 4th Embodiment of this invention

Explanation of symbols

11, 12 Multimode optical fiber
13, 14 Ferrule
15, 16 Flange
21, 22 Connector flange
24 connectors
25 Valve
27, 28 O-ring
30 sleeve tube
40 connectors
41 Connector sleeve tube
43, 44 Connector outer tube
60 containers
65 Gas supply port
66 Gas outlet
67, 68 Fiber receiver
70 Gas circulation piping
71 tanks
72 Gas pressure pump
80 sleeve tube
81 Low melting point glass

Claims (8)

In the optical fiber connection structure for connecting the two optical fibers in a state where the tips of the cores are in contact with each other without fusing,
The tip of the optical fiber including the tip of the core is housed in a sealed space,
An optical fiber connection structure characterized in that an inert gas or a liquid that is transparent to light propagating through the optical fiber and is not decomposed by the light is sealed in the sealed space.   2. The inert gas is sealed in the sealed space, and oxygen, a halogen group gas, and / or a halogen compound gas having a concentration of 1 ppm or more are mixed in the inert gas. The optical fiber connection structure described. In the optical fiber connection structure for connecting the two optical fibers in a state where the tips of the cores are in contact with each other without fusing,
The tip of the optical fiber including the tip of the core is housed in a container having a fluid supply port and a fluid discharge port connected to the fluid circulation device,
An optical fiber connection structure characterized in that the container is filled with a circulating inert gas or a liquid that is transparent to light propagating through the optical fiber and is not decomposed by the light.   The container is filled with the circulating inert gas, and oxygen, halogen group gas, and / or halogen compound gas having a concentration of 1 ppm or more are mixed in the inert gas. The optical fiber connection structure according to claim 3.   The optical fiber connection structure according to any one of claims 1 to 4, wherein the inert gas or liquid does not contain a silicone-based organic substance. In the optical fiber connection structure for connecting the two optical fibers in a state where the tips of the cores are in contact with each other without fusing,
The tip of the optical fiber including the tip of the core is isolated from the outside by a solid that is solidified after being supplied to the tip in a molten state and is transparent to the light propagating through the optical fiber and not decomposed by the light. An optical fiber connection structure characterized by that.   The tip portions of the two optical fibers are fixed to different ferrules, the ferrules are inserted into a common sleeve tube with the core tips of the optical fibers facing each other, and the ferrules are connected to the two ferrules. The optical fiber connection structure according to claim 1, wherein the optical fiber core ends are held in contact with each other.   The optical fiber connection structure according to claim 1, wherein a wavelength of light propagating through the two optical fibers is in a range of 350 to 500 nm.

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