JP2009003337A - 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 photo-curable resin 11 for forming a core part; curing the photo-curable resin 11 by making light of curing start wavelength thereof through the optical fiber 2 from a light source 5 for curing the core part on the photo-curable resin 11 to form the core part 12; adding an additive having refractive index lowering action in a non-curing part of the photo-curing resin 11; and curing the non-curing part by being irradiated with the light of the curing start wavelength of the photo-curable resin after adding the additive on the circumference of the formed core part 12 from a light source 8 for curing the clad part to form the clad part 13. <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 light curing for forming a core portion is performed in a gap for connection. After the resin is filled and the core portion is formed by incidence of light having a curing start wavelength of the resin, an additive having a refractive index lowering effect is added to the uncured resin, and the uncured resin is cured to be clad. Forming a portion. Here, the additive having a refractive index lowering action may be a liquid substance or a solid component such as fine particles.

  According to the present invention, the connection between optical fibers or between optical fibers and optical components by the self-forming optical waveguide technology is made economical and efficient, and the problems in the connection by the conventional self-forming optical waveguide technology described above are greatly reduced. Is possible.

  Specifically, regarding the problem of compatibility between resins in the case of using a hybrid resin, the compatibility between the photocurable resin for forming the core part and the additive for reducing the refractive index may be improved. Compared with compatibility, it is much easier and the choice of materials is wider. In addition, with respect to the problem of aging after liquefaction, since mixing is performed at the time of creating the waveguide, there is no problem such as white turbidity accompanying aging.

<First Embodiment>
FIG. 3 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. 8 is a light source for curing the clad part, and 11 is a photocurable resin (solution) for forming the core part.

  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 photocurable resin 11 for forming a core part, in which the refractive index after curing and the curing start wavelength (reaction wavelength) are respectively adjusted, is prepared, and an additive having a refractive index lowering action, more precisely, the resin 11 An appropriate amount of an additive that exhibits a refractive index lowering action when added to an uncured portion is prepared for realizing an arbitrary relative refractive index difference.

  The adjustment of the refractive index after curing described here may be an arbitrary value for the refractive index before curing (in the liquid state), but the refractive index after curing (in the waveguide core portion) is to be connected. It means adjusting so as to be the same as the cores of the optical fibers 1 and 2. Further, the adjustment of the curing start wavelength means that the photocurable resin 11 starts a curing reaction by the light from the core portion curing light source 5 and the photocuring after the addition of the additive by the light from the cladding portion curing light source 8. It refers to selecting the wavelength of the resin, the additive, and each light source so that the functional resin 11 starts a curing reaction.

  Additives that have a refractive index lowering effect include the action of lowering the refractive index of the entire resin in the uncured part by adding other oligomers to the resin main material, and the initiation of polymerization in a photocurable resin. It refers to solids such as liquids or fine particles that affect the agent and have the effect of reducing the crosslinking density during curing by lowering the degree of polymerization. In any case, it is desirable to have good compatibility with the photocurable resin for forming the core part.

  Examples of additives that exert such an action include fluorine compounds and silanol compounds. By adding an appropriate amount of these to make the difference in relative refractive index between the core and clad after curing to a desired value, photocuring is performed to form a clad, for example, for connection of a single mode optical fiber. It is possible to sufficiently obtain a suitable relative refractive index difference of about 0.3 to 0.4%.

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

  First, as shown in FIG. 3A, the optical fibers 1 and 2 are arranged so that one ends to be connected to each other are substantially opposed to each other with a predetermined gap therebetween, and at least one of the optical fibers 1 and 2 is arranged. 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 photocurable resin 11 is filled between end faces of the optical fibers 1 and 2, the light source 5 connected to the other end of the optical fiber 2 is operated, and the photocurable resin 11 is connected from the other end. A light having a wavelength corresponding to the curing start wavelength is incident. Then, the light of the wavelength is emitted from one end of the optical fiber 2 into the photo-curable resin 11, but the photo-curable resin 11 is hardened at the portion irradiated with the light and its refractive index is increased. The 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, as shown in FIG. 3B, a waveguide (core portion) 12 that connects the cores of the optical fibers 1 and 2 is connected. It becomes.

  In addition, as a specific method of filling the photocurable resin 11 between the end faces of the optical fibers 1 and 2, for example, the ends of the optical fibers 1 and 2 of the support base constituting the holding unit described above are opposed to each other. It is only necessary to provide a depressed portion for storing the liquid at a position where the photocurable resin 11 is dropped.

  Next, after confirming that the core portion 12 is reliably formed between the end faces of the optical fibers 1 and 2, an additive having a refractive index lowering effect is added to the uncured portion of the photocurable resin 11. The amount of addition and the time until the completion of the compatibility depend on the amount of the uncured portion of the photocurable resin 11 after the core is formed.

  Thereafter, as shown in FIG. 3C, light having a wavelength corresponding to the curing start wavelength of the photocurable resin after addition of the additive from the cladding portion curing light source 8 is formed around the formed core portion 12. By irradiating, the photocurable resin (solution) 11 ′ after addition of the additive having a refractive index lowering action is cured, and the clad portion 13 is formed.

<Second Embodiment>
FIG. 4 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, 8 is a light source for curing the clad part, 10 is an optical component, and 11 is a photocurable resin (solution) for forming the core part.

  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 photocurable resin 11 for forming a core part, in which the refractive index after curing and the curing start wavelength (reaction wavelength) are respectively adjusted, is prepared, and an additive having a refractive index lowering action, more precisely, the resin 11 An appropriate amount of an additive that exhibits a refractive index lowering action when added to an uncured portion is prepared for realizing an arbitrary relative refractive index difference.

  The adjustment of the refractive index after curing described here may be an arbitrary value for the refractive index before curing (in the liquid state), but the refractive index after curing (in the waveguide core portion) is to be connected. It means that the optical fiber 2 and the optical component 10 are adjusted to have the same level as the core. Further, the adjustment of the curing start wavelength means that the photocurable resin 11 starts a curing reaction by the light from the core portion curing light source 5 and the photocuring after the addition of the additive by the light from the cladding portion curing light source 8. It refers to selecting the wavelength of the resin, the additive, and each light source so that the functional resin 11 starts a curing reaction.

  Additives that have a refractive index lowering effect include the action of lowering the refractive index of the entire resin in the uncured part by adding other oligomers to the resin main material, and the initiation of polymerization in a photocurable resin. It refers to solids such as liquids or fine particles that affect the agent and have the effect of reducing the crosslinking density during curing by lowering the degree of polymerization. In any case, it is desirable to have good compatibility with the photocurable resin for forming the core part.

  Examples of additives that exert such an action include fluorine compounds and silanol compounds. By adding an appropriate amount of these to make the difference in relative refractive index between the core and clad after curing to a desired value, photocuring is performed to form a clad, for example, for connection of a single mode optical fiber. It is possible to sufficiently obtain a suitable relative refractive index difference of about 0.3 to 0.4%.

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

  First, as shown in FIG. 4A, 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 photocurable resin 11 is filled between the end faces of the optical fiber 2 and the optical component 10, the light source 5 connected to the other end of the optical fiber 2 is operated, and the photocurable resin 11 is connected from the other end. A light having a wavelength corresponding to the curing start wavelength is incident. Then, the light of the wavelength is emitted from one end of the optical fiber 2 into the photo-curable resin 11, but the photo-curable resin 11 is hardened at the portion irradiated with the light and its refractive index is increased. The 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, as shown in FIG. 4B, the waveguide (core portion) connecting the cores of the optical fiber 2 and the optical component 10 to each other. ) 12.

  In addition, as a specific method of filling the photocurable 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 that constitutes the holding means described above and one end of the optical component 10 are used. What is necessary is just to provide the depression part for a liquid reservoir in the position which mutually opposes, and the photocurable resin 11 should just be dripped at this depression part.

  Next, after confirming that the core portion 12 is securely connected between the end faces of the optical fiber 2 and the optical component 10, an additive having a refractive index lowering effect is added to the uncured portion of the photocurable resin 11. Added. The amount of addition and the time until the completion of the compatibility depend on the amount of the uncured portion of the photocurable resin 11 after the core is formed.

  Thereafter, as shown in FIG. 4C, light having a wavelength corresponding to the curing start wavelength of the photocurable resin after addition of the additive from the cladding portion curing light source 8 is formed around the formed core portion 12. By irradiating, the photocurable resin (solution) 11 ′ after addition of the additive having a refractive index lowering action is cured, and the clad portion 13 is formed.

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 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 , 12: Waveguide (core portion), 7: Second photocurable resin (solution), 8: Light source for curing the clad portion, 9, 13: Cladding portion, 10: Optical component, 11: For forming the core portion Photocurable resin (solution), 11 ′: Photocurable resin (solution) after addition of an additive having a refractive index lowering effect.

Claims (2)

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,
Between one end of each optical fiber or between one end of an optical fiber and an optical component, a photocurable resin is filled,
Light having a wavelength corresponding to the curing start wavelength of the photocurable resin is incident on the photocurable resin from at least one optical fiber to cure the photocurable resin, or between one end of each optical fiber or A core is formed between one end of the optical fiber and the optical component,
Add an additive having a refractive index lowering action to the uncured portion of the photocurable resin,
The clad part is formed by irradiating the periphery of the formed core part with light having a wavelength corresponding to the curing start wavelength of the photocurable resin after addition of the additive to cure the photocurable resin. Optical fiber connection method. The optical fiber connection method according to claim 1,
By adjusting the amount of the additive having a refractive index lowering effect added to the uncured portion of the photocurable resin, the relative refractive index difference between the core portion and the clad portion after curing is set to a desired value. A characteristic optical fiber connection method.

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