JP2009003338A - Method of splicing optical fibre - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: a usable raw material is restricted due to compatibility with resins in a hybrid resin produced by mixing a photocurable resin for forming a core part with a photocurable resin for forming a clad part, thereby causing cloudiness with passage of time. <P>SOLUTION: A method of splicing optical fibers includes: arranging the optical fibers 1, 2 to be spliced so as to substantially face a gap; filling a part between one-ends of optical fibers 1, 2 with the curable resin 11 blended with a photoinitiator and a heat polymerization initiator; curing the curable resin 11 by making light of curing start wavelength of the curable resin 11 through the optical fiber 2 from a light source 5 for curing the core part on the curable resin 11 to form the core part 13; adding heat required for heat curing on an entire non-curing part of the curing resin 11 by a heat source 12; and curing the non-curing part with reaction of the heat polymerization initiator in the non-cured curable resin 11 with a main material of the resin to form the clad part 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a connection method between optical fibers or between optical fibers and optical components, which is useful when constructing an optical fiber communication network.

  In recent years, along with the development of optical LAN technology represented by Ethernet (registered trademark) along with the introduction and deployment of optical fiber networks (FTTH: Fiber To The Home) in access communication networks connected to many users, users themselves have built The introduction of optical fiber networks to user-related communication networks is also expanding greatly. In these areas, 1.3 micron band zero-dispersion single mode optical fiber (SMF), multimode optical fiber (MMF), plastic optical fiber (POF), and other optical fibers are used. The demand for is increasing rapidly. In addition, in order to construct an inexpensive optical transmission system, it is also an issue to economically connect technologies between optical fibers and optical components such as light sources and optical wavelength filters.

  Conventionally, various optical connectors and mechanical splicing techniques have been used to connect optical fibers, and connection techniques using alignment by lens systems have been used to connect optical fibers and optical components. . However, reflecting the above background, self-forming optical waveguide technology has been attracting attention as a supplement to an economical optical connection technology that can be simplified and eliminates the need for alignment.

  Self-forming optical waveguide connection is a process for forming a core part having a different refractive index after curing between one end of optical fibers to be connected or between one end of an optical fiber to be connected and an optical component. The core portion and the clad portion are formed by the first curable resin and the second curable resin for forming the clad portion, thereby enabling simple optical connection.

  FIG. 1 shows an example of connecting optical fibers by applying a self-forming optical waveguide connection technique. First, as shown in FIG. 1 (a), optical fibers opposed to each other with a predetermined gap therebetween. A mixed solution (hybrid resin) 3 of the first photocurable resin for forming the core part and the second photocurable resin for forming the clad part, or the first part for forming the core part 1 photo-curing resin (solution) 4 is filled, and the other end of at least one of the optical fibers, here the other end of the optical fiber 2, is cured of the first photo-curing resin from the core portion curing light source 5. A light having a start wavelength is incident. The light propagates through the optical fiber 2 and is emitted from one end thereof into the hybrid resin 3 or resin 4. The first photo-curing resin cures the portion irradiated with the light and increases its refractive index. Therefore, this hardened portion constitutes a waveguide (structure) having a light confinement function. Since this waveguide is continuously formed during light irradiation and grows in the longitudinal direction, a waveguide (core portion) 6 for connecting the cores of the optical fibers 1 and 2 as shown in FIG. It becomes. Next, after confirming the formation of the core portion 6, the hybrid resin 3 is used as it is, and when the resin 4 is used, the resin 4 is removed from between one ends of the optical fibers 1 and 2. After filling the second photo-curing resin (solution) 7 for forming the clad portion, as shown in FIG. 2C, the clad portion curing light source 8 is provided around the formed core portion 6. The clad portion 9 is formed by curing the second photocurable resin by irradiating light having a curing start wavelength of the second photocurable resin.

  FIG. 2 shows an example in which an optical fiber and an optical component are connected by applying a self-forming optical waveguide connection technique. First, as shown in FIG. A mixed solution (hybrid resin) 3 of the first photocurable resin for forming the core part and the second photocurable resin for forming the clad part between one end of the optical fiber 2 and the optical component 10 opposed to each other. Or the 1st photocurable resin (solution) 4 for core part formation is filled, and the light of the hardening start wavelength of the 1st photocurable resin from the light source 5 for core part hardening to the other end of the optical fiber 2 Is incident. The light propagates through the optical fiber 2 and is emitted from one end thereof into the hybrid resin 3 or resin 4. The first photo-curing resin cures the portion irradiated with the light and increases its refractive index. Therefore, this hardened portion constitutes a waveguide (structure) having a light confinement function. Since this waveguide is continuously formed during light irradiation and grows in the longitudinal direction, the waveguide (core portion) that connects the optical fiber 2 and the core of the optical component 10 as shown in FIG. ) 6. Next, after confirming the formation of the core portion 6, the resin 4 is removed as it is when the hybrid resin 3 is used, and when the resin 4 is used, the resin 4 is removed from between one end of the optical fiber 2 and the optical component 10. At the same time, after filling the second photo-curable resin (solution) 7 for forming the clad part, as shown in FIG. The second photo-curing resin is cured by irradiating light having a curing start wavelength of the second photo-curing resin from, thereby forming the clad portion 9.

The photo-curing resin used for the connection described above is a main material such as an oligomer that becomes a waveguide by cross-linking at the time of curing, photopolymerization that generates radicals and ions to start curing by the incident light. It is comprised from the initiator, the monomer for viscosity adjustment, other additives, etc. In particular, a photocurable resin that is cured by radicals is called a radical curable resin, a resin that is cured by cations is called a cationic curable resin, and a resin that is cured by anions is called an anion curable resin.
Japanese Patent No. 3444352

  Conventionally, a resin used in the self-forming optical waveguide technology has been used by mixing a photocurable resin for forming a core part and a clad part into one liquid (hybridization) (see Patent Document 1). However, in order to make a single solution, it is necessary that the compatibility between the resins is good, and there is a problem that the raw materials that can be used at the time of selection of the resin raw materials are limited. Moreover, even if it was resin with favorable compatibility, there existed a problem that possibility that white turbidity would be caused with the passage of time after one liquid was made.

  In the present invention, in order to solve the above-described problems, when a simple connection between optical fibers or between an optical fiber and an optical component is performed by a self-forming optical waveguide technology, a photopolymerization initiator and a thermal polymerization are formed in a gap for connection. A curable resin blended with an initiator is filled, and light having a curing start wavelength of the resin is incident to form a core portion. Then, heat is applied to the uncured resin to cure the clad portion. At this time, the portion cured by light has a higher cross-linking density than the portion cured by heat, and therefore has a higher refractive index and can serve as a core. Similarly, the portion cured by heat has a function as a low refractive index cladding.

  The reason for the difference in relative refractive index between photocuring and thermal curing is that in photocuring, light energy effectively acts on the photopolymerization initiator, and the generation of radicals and ions is induced efficiently, and the polymerization reaction between resin materials. As shown in FIG. 3 (a), the crosslinking density is increased and the refractive index during curing is increased. On the other hand, in the polymerization reaction by thermal curing, radicals and ions are relatively compared with those of photocuring. This is because the generation efficiency is low, and as shown in FIG. 3B, the crosslink density is low, and the refractive index is low as compared with photocuring.

  According to the present invention, it is possible to efficiently connect the optical fibers or between the optical fiber and the optical component by the self-forming optical waveguide technology, and to greatly alleviate the problems of the resin used in the conventional self-forming optical waveguide technology described above. It becomes.

  Specifically, regarding the compatibility between resins in the case of using a hybrid resin and the problem of white turbidity with the lapse of time after one solution, in the resin used in the present invention, polymerization is a main component and a trace component of the curable resin. The compatibility with the initiator should be good, and compared with the case where the main components of the resin, which is a problem with the hybrid resin, are mixed together, it is much easier to improve the compatibility and mitigate whitening. It is possible to expand the range of options.

<First Embodiment>
FIG. 4 shows a first embodiment of a method for connecting optical fibers according to the present invention, in this case an example in which optical fibers are connected to each other. A light source for use, 11 is a curable resin (solution) in which a photocuring initiator (photopolymerization initiator) and a thermosetting initiator (thermal polymerization initiator) are blended, and 12 is a heat source.

  Examples of the optical fibers 1 and 2 include POF, MMF, and SMF. However, the optical fibers 1 and 2 are not limited thereto, and are 1.55 μm band dispersion shifted fiber (DSF), dispersion compensating optical fiber (DCF), and photonic crystal optical fiber ( (PCF), hole-assisted optical fiber (HAF), and the like can also be applied.

  First, a curable resin 11 containing a photopolymerization initiator and a thermal polymerization initiator, in which the relative refractive index difference after curing and the curing start wavelength (reaction wavelength) are adjusted, is prepared.

  The adjustment of the relative refractive index difference after curing described here refers to adjusting the relative refractive index difference between the core portion and the cladding portion after the photocuring and thermal curing are completed. As a specific adjustment method, for example, adding germanium or the like can increase the refractive index of the entire resin, and adding fluorine can decrease the refractive index of the entire resin. Further, the relative refractive index difference can be changed depending on the type and blending amount of the polymerization initiator. The adjustment of the curing start wavelength means that the wavelength of the resin (main material), each polymerization initiator, and the light source is set so that the curable resin 11 starts a curing reaction by light from the light source 5 for curing the core part. Refers to making a choice.

  The reason for the difference in relative refractive index between photocuring and thermal curing is that in photocuring, light energy effectively acts on the photopolymerization initiator, and the generation of radicals and ions is induced efficiently, and the polymerization reaction between resin materials. As shown in FIG. 3 (a), the crosslinking density is increased and the refractive index during curing is increased. On the other hand, in the polymerization reaction by thermal curing, radicals and ions are relatively compared with those of photocuring. This is because the generation efficiency is low, and as shown in FIG. 3B, the crosslink density is low, and the refractive index is low as compared with photocuring.

  Hereinafter, the connection process between the optical fibers in the present embodiment will be described.

  First, as shown in FIG. 4A, the optical fibers 1 and 2 are arranged so that one ends to be connected are substantially opposed to each other with a predetermined gap therebetween, and at least one of the optical fibers 1 and 2 is disposed. Here, the core portion curing light source 5 is connected to the other end of the optical fiber 2.

  As the detailed arrangement of each optical fiber at this time, two arrangements can be considered depending on whether the light source 5 is connected to only one of the optical fibers or both.

  That is, when the light source 5 is connected to only one of the optical fibers, it is necessary to dispose the central axes so as to coincide with each other with a gap (first arrangement). In addition, when the light source 5 is connected to both optical fibers, the central axes are not necessarily aligned, and even when there is a certain degree of axial displacement due to the “photo soldering effect” in the self-forming waveguide technology. The effect of enabling connection with loss is used (second arrangement). However, in order to connect with lower loss, it is desirable to connect with the central axes aligned even when a light source is connected to both optical fibers.

  Each optical fiber 1 and 2 is held by a holding means (not shown), for example, a holding base comprising a support base having a V-groove and a pressing plate for fixing the fiber to this base, and the above-described arrangement relationship is maintained until the end of the connection work. Shall be maintained. Moreover, the relationship of the central axis between each optical fiber mentioned above should just be maintained in the vicinity of one end which should be connected, and it does not need to be in such a relationship in the whole length of each optical fiber. Needless to say, this point is common to all embodiments of the present invention.

  Next, the curable resin 11 containing the photopolymerization initiator and the thermal polymerization initiator is filled between the end faces of the optical fibers 1 and 2 and the light source 5 connected to the other end of the optical fiber 2 is operated. Then, light having a wavelength corresponding to the curing start wavelength of the curable resin 11 is incident from the other end. Then, the light having the wavelength is emitted from one end of the optical fiber 2 into the curable resin 11, and the curable resin 11 is cured at a portion irradiated with the light and its refractive index is increased. Constitutes a waveguide (structure) having a light confinement function. Since this waveguide is continuously formed during light irradiation and grows in the longitudinal direction, as shown in FIG. 4B, a waveguide (core portion) 13 that connects the cores of the optical fibers 1 and 2 is connected. It becomes.

  In addition, as a specific method of filling the curable resin 11 between the end faces of the optical fibers 1 and 2, for example, one ends of the optical fibers 1 and 2 of the support base constituting the holding unit described above face each other. A depression for storing the liquid is provided at the position, and the curable resin 11 may be dropped into the depression.

  Next, after confirming that the core portion 13 is reliably formed between the end faces of the optical fibers 1 and 2, the heat source 12 applies an amount of heat necessary for thermosetting to the entire uncured portion of the curable resin 11. Add. Then, the thermal polymerization initiator in the uncured curable resin 11 reacts with the main material of the resin in the resin 11 and cures to form the clad portion 14 as shown in FIG.

  From the above, it is possible to form a waveguide in which the photocured portion becomes the core portion and the thermocured portion becomes the clad portion.

<Second Embodiment>
FIG. 5 shows a second embodiment of an optical fiber connection method according to the present invention, in this case, an example in which an optical fiber and an optical component are connected. In the figure, 2 is an optical fiber, and 5 is a core portion. A light source for curing, 10 is an optical component, 11 is a curable resin (solution) in which a photocuring initiator (photopolymerization initiator) and a thermosetting initiator (thermal polymerization initiator) are blended, and 12 is a heat source.

  Examples of the optical component 10 include a light emitting element such as a semiconductor laser and various light receiving elements. However, the optical component 10 is not limited to this, and can also be applied to an optical circuit element such as a quartz-based planar lightwave circuit (PLC).

  First, a curable resin 11 containing a photopolymerization initiator and a thermal polymerization initiator, in which the relative refractive index difference after curing and the curing start wavelength (reaction wavelength) are adjusted, is prepared.

  The adjustment of the relative refractive index difference after curing described here refers to adjusting the relative refractive index difference between the core portion and the cladding portion after the photocuring and thermal curing are completed. As a specific adjustment method, for example, adding germanium or the like can increase the refractive index of the entire resin, and adding fluorine can decrease the refractive index of the entire resin. Further, the relative refractive index difference can be changed depending on the type and blending amount of the polymerization initiator. The adjustment of the curing start wavelength refers to the wavelength of the resin (the main material), each polymerization initiator, and the light source so that the curable resin 11 starts the curing reaction by the light from the light source 5 for curing the core part. Refers to selecting.

  The reason for the difference in relative refractive index between photocuring and thermal curing is that in photocuring, light energy effectively acts on the photopolymerization initiator, and the generation of radicals and ions is induced efficiently, and the polymerization reaction between resin materials. As shown in FIG. 3 (a), the crosslinking density is increased and the refractive index during curing is increased. On the other hand, in the polymerization reaction by thermal curing, radicals and ions are relatively compared with those of photocuring. This is because the generation efficiency is low, and as shown in FIG. 3B, the crosslink density is low, and the refractive index is low as compared with photocuring.

  Hereinafter, a connection process between the optical fiber and the optical component in the present embodiment will be described.

  First, as shown in FIG. 5A, the optical fiber 2 and the optical component 10 are arranged so that one end of the optical fiber 2 and one end to be connected to the optical component 10 are substantially opposed to each other with a gap therebetween. The light source 5 is connected to at least one of the optical fiber 2 and the optical component 10, here the other end of the optical fiber 2. The light source 5 can be connected to the other end of the optical component 10 because the optical component 10 is an optical circuit element such as a PLC, and light from the light source 5 can be transmitted between one end and the other end. Limited to cases only.

  As the detailed arrangement of the optical fiber and the optical component at this time, there are two possible arrangements depending on whether the light source 5 is connected only to the optical fiber or to both the optical fiber and the optical component.

  That is, when the light source 5 is connected only to the optical fiber, it is necessary to arrange it so that the central axes thereof coincide with each other with a gap (first arrangement). In addition, when the light source 5 is connected to both the optical fiber and the optical component, the center axis is not necessarily aligned, and there is a certain degree of misalignment due to the “photo soldering effect” in the self-forming waveguide technology. In the second embodiment, an effect that connection can be made with low loss is used (second arrangement). However, in order to connect with lower loss, it is desirable to make the connection with the center axis coincident even when the light source is connected to both the optical fiber and the optical component.

  The optical fiber 2 and the optical component 10 are held by a holding means (not shown), for example, a holding base including a support base having a V-groove and a groove suitable for the optical part, and a pressing plate for fixing the fiber and the optical part to the base. It is assumed that the above-described arrangement relationship is maintained until the end of the connection work. In addition, the relationship of the central axis between the optical fiber and the optical component described above only needs to be maintained in the vicinity of one end to be connected, and does not require such a relationship in the entire length of the optical fiber. Needless to say, this point is common to all embodiments of the present invention.

  Next, the curable resin 11 containing the photopolymerization initiator and the thermal polymerization initiator is filled between the end faces of the optical fiber 2 and the optical component 10, and the light source 5 connected to the other end of the optical fiber 2 is operated. Then, light having a wavelength corresponding to the curing start wavelength of the curable resin 11 is incident from the other end. Then, the light having the wavelength is emitted from one end of the optical fiber 2 into the curable resin 11, and the curable resin 11 is cured at a portion irradiated with the light and its refractive index is increased. Constitutes a waveguide (structure) having a light confinement function. Since this waveguide is continuously formed during light irradiation and grows in the longitudinal direction, as shown in FIG. 5B, the waveguide (core portion) connecting the cores of the optical fiber 2 and the optical component 10 to each other. ) 13.

  In addition, as a specific method of filling the curable resin 11 between the end faces of the optical fiber 2 and the optical component 10, for example, the optical fiber 2 of the support base and the one end of the optical component 10 constituting the holding means described above are connected to each other. It is only necessary to provide a depression for storing the liquid at a position opposite to the liquid and drop the curable resin 11 into the depression.

  Next, after confirming that the core portion 13 is securely connected between the end faces of the optical fiber 2 and the optical component 10, an amount necessary for thermosetting the entire uncured portion of the curable resin 11 by the heat source 12. Add heat. Then, the thermal polymerization initiator in the uncured curable resin 11 reacts with the main material of the resin in the resin 11 and cures to form the clad portion 14 as shown in FIG.

  From the above, it is possible to form a waveguide in which the photocured portion becomes the core portion and the thermocured portion becomes the clad portion.

Process diagram showing an example of connecting optical fibers using self-forming optical waveguide technology Process diagram showing an example of connection between optical fiber and optical component by self-forming optical waveguide technology Schematic diagram showing the difference in crosslink density between a resin cured with a photocuring initiator and a resin cured with a thermosetting initiator Process drawing which shows 1st Embodiment of the optical fiber connection method of this invention Process drawing which shows 2nd Embodiment of the connection method of the optical fiber of this invention

Explanation of symbols

  1, 2: optical fiber, 3: mixed solution of first and second photocurable resins (hybrid resin), 4: first photocurable resin (solution), 5: light source for curing core part, 6 , 13: Waveguide (core part), 7: Second photocurable resin (solution thereof), 8: Light source for curing the clad part, 9, 14: Cladding part, 10: Optical component, 11: Photocuring initiator (Photopolymerization initiator) and thermosetting initiator (thermal polymerization initiator) in a curable resin (solution), 12: heat source.

Claims (4)

Fill the optical fiber or the optical fiber and the optical component between one end of each optical fiber or between one end of the optical fiber and the optical component, and cure the curable resin to a desired ratio. In a method of connecting by forming a self-forming optical waveguide consisting of a core part and a clad part having a refractive index difference,
A method of connecting optical fibers, characterized in that a desired relative refractive index difference is achieved by a difference in the crosslink density using a curable resin containing two different crosslink density materials. The optical fiber connection method according to claim 1,
The material for realizing two different crosslink densities is two different curing initiators. An optical fiber connecting method, wherein: In the optical fiber connection method according to claim 2,
The two different types of curing initiators are a photocuring initiator and a thermosetting initiator. An optical fiber connection method, wherein: A method of connecting optical fibers or optical fibers and optical components,
Arrange one end of each optical fiber or one end of the optical fiber and the optical component so as to face each other with a gap,
Filled with a curable resin containing a photocuring initiator and a thermosetting initiator between one end of each optical fiber or between one end of the optical fiber and an optical component,
Light of a wavelength corresponding to the curing start wavelength of the curable resin is incident on the curable resin from at least one optical fiber to cure the curable resin, and between one end of each optical fiber or between the optical fibers. A core is formed between one end and the optical component,
A method of connecting optical fibers, wherein a heat is applied to an uncured portion of the curable resin to cure the curable resin to form a clad portion.

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