JP4642739B2 - Optical component connection method - Google Patents

Description

  The present invention relates to a method for connecting optical components, and particularly to a connection method using a self-forming optical waveguide.

  In recent years, a planar lightwave circuit (PLC) is an optical component that has been actively researched and developed and is being put to practical use. A planar lightwave circuit is an optical integrated circuit characterized in that a large number of functional elements can be integrated on a planar substrate, and various functions can be realized by utilizing the properties of light such as interference. FIG. 1 shows an example of a planar lightwave circuit, here an optical splitter. In addition to the optical splitter, a wavelength multiplexer / demultiplexer, an optical transceiver, and the like can be integrated on a substrate.

  As a technique for connecting optical components such as an optical fiber and a planar lightwave circuit, a connection technique using a self-formed optical waveguide has been studied in various places. This is different from the conventional connection technology using fusion or V-groove, between the light emitting ends of each component to be connected or between the light emitting end and the light incident end (gap). A light curable resin is filled, and light having a wavelength corresponding to the curing start wavelength of the light curable resin is incident on the light curable resin from the light exit end of at least one of the optical components. Another photo-curing resin having a self-forming optical waveguide (core part) formed between the light emitting ends or between the light emitting end and the light incident end, and having a smaller refractive index after curing, if necessary This is a technique for realizing a low-loss connection by forming a clad portion.

  The “light emitting end” in this specification includes an end (portion) that emits the generated light when the optical component has a function of generating light, as well as the optical component itself. It does not have a function of generating light, but also includes an end (portion) from which light incident from the outside and transmitted through the optical component is emitted. In addition, the “light incident end” includes an end (portion) to which light from the outside is incident when the optical component has a function of receiving light from the outside. Does not have a function of receiving light, but also includes an end (portion) on which light transmitted through the optical component and emitted to the outside is incident. Therefore, in an optical component such as an optical fiber or an optical multiplexer / demultiplexer that does not have a light emitting function and a light receiving function, either end (portion) can be a “light emitting end” and a “light incident end”. Please note that.

Here, in the connection technology using the conventional self-forming optical waveguide, the light intensity of the light used for forming the core portion is not specifically defined, or is constant from the start of incidence to the end of formation (patent) Reference 1).
Japanese Patent No. 3444352

  However, when an optical fiber having a small core such as a 1.3 μm band zero-dispersion single mode fiber (SMF) is connected by a self-forming optical waveguide, the difference in refractive index before and after curing of the photo-curing resin to be used It is known that depending on the value, the shape of the self-formed optical waveguide to be formed does not become a straight line having a uniform diameter.

  One reason for this is that when a self-forming optical waveguide is connected, light in the short wavelength region near the UV to 530 nm band is used to form the core, but this wavelength region is less than or equal to the SMF cutoff wavelength. Is incident on the optical fiber, light in a higher-order propagation mode other than the fundamental propagation mode is generated in the optical fiber. Since the higher-order mode light has a larger beam divergence angle than the fundamental mode light, when it is emitted into the photo-curable resin, the self-formed optical waveguide to be formed becomes tapered. In order to form a linear self-forming optical waveguide with a uniform diameter, it is necessary to increase the amount of change in the refractive index before and after curing of the photocurable resin to prevent the diameter of the self-forming optical waveguide from expanding. There is a problem that fine adjustment of the refractive index of the curable resin is difficult.

  On the other hand, when optical components with a large waveguide diameter are connected by a self-forming optical waveguide, the waveguide diameter of the self-forming optical waveguide to be formed fluctuates in the longitudinal direction when the photocuring resin used has a large cure shrinkage rate. There was a possibility. In general, radically curable resins have curing shrinkage due to their characteristics. Therefore, the larger the waveguide diameter, the more the shape of the formed self-formed optical waveguide is distorted, and the straight self-formed optical waveguide is uniform in diameter. There was a problem that could not be formed.

  In this way, when the formed self-formed optical waveguide is deformed and does not become a straight line having a uniform diameter, the connection loss between the optical components increases, and a good connection state cannot be maintained. In addition, coupling loss due to mismatch between the MFD (Mode Field Diameter) of the self-forming optical waveguide and the MFD of the optical fiber, and connection loss due to axial misalignment due to deformation of the self-forming optical waveguide, respectively, occur. Become.

  As described above, conventionally, in order to reduce these, resin blending is performed to prevent the self-forming optical waveguide from becoming tapered, such as adjusting the refractive index before and after curing of the photocurable resin, and curing shrinkage It has been formed so that the waveguide diameter does not fluctuate or taper. However, these methods require extra labor and cost for resin blending, complicate control of light for curing, and require time for formation.

  It is an object of the present invention to require fine adjustment of refractive index before and after curing of a photocurable resin and complicated control of light for curing when optical components are to be connected by self-forming optical waveguide technology. It is another object of the present invention to provide a connection method that can form a self-forming optical waveguide having a uniform diameter and a straight line.

  In the present invention, in order to solve the above-described problems, when optical components are connected to each other by the self-forming optical waveguide technology, the light intensity of light incident on the photocurable resin is changed in at least two stages. Features. More specifically, the light intensity in the second stage and after is made higher than the light intensity in the first stage. More specifically, the light intensity at the first stage is set such that the light intensity of the higher-order mode light does not exceed the curing threshold value of the photocurable resin.

  That is, the light intensity of the first-stage light incident on the photocurable resin is a value in which only the light intensity of the fundamental mode light exceeds the curing threshold value of the photocurable resin as shown in FIG. Thus, the higher-order mode light does not affect the curing of the photocurable resin, and a self-forming optical waveguide (core portion) having a diameter of 2d is formed only by the fundamental mode light. Further, as shown in FIG. 2 (b), the diameter of the core portion to be formed is thinner than the MFD formed when light of a constant high light intensity is incident from the beginning, so that the light having curing shrinkage can be obtained. With a curable resin, deformation of the diameter due to strain can be reduced.

  After confirming that the core has been reliably formed, light having a light intensity that greatly exceeds the curing threshold of the photocurable resin as shown in FIG. Incident in the resin. Then, as shown in FIG. 3B, a self-forming optical waveguide (core part) having a diameter of 2d ′ (2d ′> 2d) is formed on the outer periphery of the previously formed thin core part.

  Thereby, when performing self-forming optical waveguide connection, it is not necessary to precisely adjust the refractive index before and after the curing of the photocurable resin in advance, and the taper of the core portion can be prevented. Further, as described above, the core portion is formed by gradually increasing the diameter from a small diameter, thereby reducing the influence of curing shrinkage. These effects are effective in general connection between optical components, for example, connection between optical fibers, connection between an optical fiber and a planar lightwave circuit, connection between planar lightwave circuits, and the like.

  According to the present invention, by using a connection method in which the light intensity of light entering the photocurable resin is incident in multiple stages, the refractive index before and after curing of the photocurable resin can be finely adjusted and cured. Therefore, it is possible to form a self-forming optical waveguide having a uniform diameter and a straight line without requiring complicated control of the light, and it is possible to perform connection with lower loss more easily than in the past.

<Embodiment 1>
FIG. 4 shows a first embodiment of a method for connecting optical components according to the present invention, where optical fibers are connected by separately using a photocurable resin for forming a core and a photocurable resin for forming a cladding. In the figure, 1-1 and 1-2 are single mode fibers (SMF), 2 and 3 are photocurable resin solutions, 4 is a light source for forming a core part, and 5 is a cladding part formation. Light source.

  The photo-curable resin solution 2 is a solution containing a first photo-curable resin for core formation with adjusted refractive index after curing, and the photo-curable resin solution 3 is a refractive index after curing. It is a solution containing the second photo-curing resin for forming the clad part with the adjusted rate, and is prepared in advance.

Here, the adjustment of the refractive index after curing may be any value before the curing, but the refractive index n1 after curing of the first photocurable resin and the curing of the second photocurable resin. The subsequent refractive index n2 is
n1> n2
It means to adjust to meet the condition of.

  The light source 4 for forming the core part generates light having a wavelength at which the first photocurable resin in the solution 2 of the photocurable resin starts a curing reaction, and at least one of the SMF 1-1 and 1-2. Here, it is connected to the other end of the SMF 1-1.

  The light source 5 for forming the clad portion generates light having a wavelength at which the second photocurable resin in the solution 3 of the photocurable resin starts a curing reaction, and each of the fibers to be described later (here, SMF1-1). And 1-2) is arranged so as to irradiate between one end.

  In practice, the solutions 2 and 3 are not simultaneously filled between the ends of each fiber, but both solutions are shown in FIG. 4 for convenience. In addition, since the solutions 2 and 3 are not filled between the ends of each fiber at the same time, the wavelengths for starting the curing reaction of the first and second photocurable resins may be the same.

  FIG. 5 shows a connection process in the present embodiment. Hereinafter, the method for connecting optical components of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 4, the SMFs 1-1 and 1-2 are arranged so that one ends to be connected are substantially opposed to each other with a predetermined gap therebetween, and one ends of the SMFs 1-1 and 1-2 are arranged between each other. A solution 2 of a photocurable resin is filled between the end faces.

  The SMF 1-1 and 1-2 are held by a holding means (not shown), for example, a holding base including a support base having a V-groove and a pressing plate for fixing the fiber to the base. Shall be maintained. In addition, the relationship between the central axes of the fibers described above is only required to be maintained in the vicinity of one end to be connected, and it is needless to say that it is not necessary to have such a relationship in the entire length of each fiber. (This point is common to all the embodiments of the present invention).

  Further, as a specific method for filling (interposing) the solution 2 between the end faces of the SMF 1-1 and 1-2, for example, one end of the SMF 1-1 and 1-2 of the support base constituting the holding means described above is used. It is only necessary to provide a depression for storing the liquid at a position where they face each other and drop the solution 2 into the depression.

  Next, as shown in FIG. 5A, when the core portion forming light source 4 connected to the other end of the SMF 1-1 is operated, the light generated by the light source 4 and propagated through the SMF 1-1 is transmitted to the SMF 1. -1 is incident on the solution 2 from one end thereof, whereby the first photocurable resin in the solution 2 reacts and cures, and an optical waveguide (core portion) is formed between the end surfaces of the SMF 1-1 and 1-2. It is formed.

  Here, when the wavelength range of the light source 4 is equal to or less than the cutoff wavelength of the SMF, when light from the light source 4 is incident on the SMF 1-1, a higher-order mode other than the fundamental mode is generated. Since the higher-order mode light has a larger beam divergence angle than the fundamental mode light, the diameter of the formed optical waveguide is increased. Furthermore, the diameter of the optical waveguide to be formed is dependent on light intensity, and generally tends to increase as the light intensity of incident light increases. In addition, when a light having a high light intensity is incident when a radical curable resin is used as the first photocurable resin for forming the core portion, curing shrinkage occurs, and thus the formed optical waveguide is deformed. Excessive connection loss will occur.

  Therefore, in the present invention, the light intensity of light incident on the photocurable resin is changed in at least two stages.

  In the first stage, as shown in FIG. 2A, the peak intensity in the vicinity of the center of the fiber core in the light intensity distribution is slightly higher than the curing threshold value of the first photocurable resin for forming the core part (basic Only the light intensity of the mode light exceeds the curing threshold value of the first photocurable resin, and the light intensity of the higher order mode light does not exceed the curing threshold value of the first photocurable resin) Incident. Then, as shown in FIG. 5A, an optical waveguide 6a having a small diameter is formed and connected to the opposing fiber. In general, the SMF mode power distribution at a short wavelength has the largest power distribution to the fundamental mode. If the core of the optical fiber is a perfect circle, the shape of the fundamental mode is a circle as in the core shape, and the spread angle of the light emitted from the fiber is small. As shown in FIG. An optical waveguide 6a having a small diameter is formed on the extension line.

  After the second stage, after confirming that the optical waveguide 6a has been formed, when the incident light intensity is increased more than in the first stage, the optical waveguide is centered on the optical waveguide due to the optical waveguide effect of the narrow-diameter optical waveguide. Light is distributed. Then, as shown in FIG. 5B, the optical waveguide 6b is formed in the light intensity region exceeding the curing threshold value of the first photocurable resin for forming the core portion. As a result, a linear optical waveguide with little spread of the emitted light is formed. If you want to further expand the final optical waveguide (core part) diameter and MFD, either increase the number of times the curing light is incident after the second stage or increase the light intensity at the second stage. Use it.

  In addition, about the setting of the light intensity of the light which injects into the photocurable resin from one end of SMF1-1, a well-known optical power meter etc. is connected in advance to one end of SMF1-1 before connection, and driving in the light source 4 is performed. What is necessary is just to measure and record the light intensity at the time of changing an electric current or drive electric power, and to set it according to the record.

  Next, after confirming that the optical waveguides 6a and 6b are securely formed between the end faces of the SMF 1-1 and 1-2, as shown in FIG. The light-curing resin solution 2 for forming the core part is removed from between the end faces of the one ends, and the light-curing resin solution 3 for forming the clad part is filled instead, and the light source is not connected to the fiber. 5 is operated to irradiate light in the vicinity of the core portion 6 composed of the already formed optical waveguides 6a and 6b between the ends of the SMF 1-1 and 1-2. Then, as shown in FIG. 5 (c), the second photocurable resin in the solution 3 reacts and cures, and the cladding portion 7 is formed around the core portion 6.

  FIG. 6 shows the amount of change in connection loss when the core portion is formed by the method of the present invention and the conventional method. In addition, the vertical axis | shaft in a figure is the variation | change_quantity when the time of resin filling is made into the reference value 0. FIG. From FIG. 6, the connection loss at the completion of the connection is larger than that when the resin is filled in the conventional method, whereas the connection loss at the completion of the connection is improved compared to the case when the resin is filled in the method of the present invention. You can see that

  In this way, by changing the light intensity of the light at the time of core formation in two steps, the effect of higher order mode light and curing shrinkage than the conventional self-formed optical waveguide connection that forms with uniform light intensity. Thus, the optical fibers can be connected with low loss.

<Embodiment 2>
FIG. 7 shows an optical component connecting method according to a second embodiment of the present invention, in which optical fibers are connected by mixing a photocurable resin for forming a core and a photocurable resin for forming a cladding. An example of the case is shown. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals. That is, 1-1 and 1-2 are single mode fibers (SMF), 4 is a light source for forming a core part, 5 is a light source for forming a cladding part, and 8 is a mixed solution of a photocurable resin.

  The photo-curable resin mixed solution 8 includes two types of photo-curable resins whose refractive indexes after curing are adjusted, that is, a first photo-curable resin (for example, radical curable resin) for forming a core part, and a clad. It is a mixed solution containing a second photocurable resin (for example, a cationic curable resin) for forming a part, and is prepared in advance.

Here, the adjustment of the refractive index after curing may be any value before the curing, but the refractive index n1 after curing of the first photocurable resin and the curing of the second photocurable resin. The subsequent refractive index n2 is
n1> n2
It means to adjust to meet the condition of.

  The wavelength of the light source 4 for forming the core part is adjusted to a wavelength at which only the first photocurable resin in the mixed solution 8 of the photocurable resin starts the curing reaction, and the light source for forming the clad part. The wavelength of 5 is adjusted to a wavelength at which only the second photocurable resin in the photocurable resin mixed solution 8 starts the curing reaction.

  FIG. 8 shows a connection process in the present embodiment. Hereinafter, the method for connecting optical components of the present invention will be described with reference to FIGS.

  First, as shown in FIG. 7, the SMFs 1-1 and 1-2 are arranged so that the one ends to be connected are substantially opposed to each other with a predetermined gap therebetween, and the one ends of the SMFs 1-1 and 1-2 are arranged with each other. A mixed solution 8 of a photo-curable resin is filled between the end faces.

  Next, as shown in FIG. 8A, when the core portion forming light source 4 connected to the other end of the SMF 1-1 is operated, the light generated by the light source 4 and propagated through the SMF 1-1 is transmitted to the SMF 1. -1 is incident on the mixed solution 8 from one end, whereby only the first photocurable resin in the mixed solution 8 reacts and cures, and an optical waveguide (core) is formed between the end faces of the SMF 1-1 and 1-2. Part) is formed.

  Here, when the wavelength range of the light source 4 is equal to or less than the cutoff wavelength of the SMF, when light from the light source 4 is incident on the SMF 1-1, a higher-order mode other than the fundamental mode is generated. Since the higher-order mode light has a larger beam divergence angle than the fundamental mode light, the diameter of the formed optical waveguide is increased. Furthermore, the diameter of the optical waveguide to be formed is dependent on light intensity, and generally tends to increase as the light intensity of incident light increases. In addition, when a light having a high light intensity is incident when a radical curable resin is used as the first photocurable resin for forming the core portion, curing shrinkage occurs, and thus the formed optical waveguide is deformed. Excessive connection loss will occur.

  Therefore, in the present invention, the light intensity of light incident on the photocurable resin is changed in at least two stages.

  In the first stage, as shown in FIG. 2A, the peak intensity in the vicinity of the center of the fiber core in the light intensity distribution is slightly higher than the curing threshold value of the first photocurable resin for forming the core part (basic Only the light intensity of the mode light exceeds the curing threshold value of the first photocurable resin, and the light intensity of the higher order mode light does not exceed the curing threshold value of the first photocurable resin) Incident. Then, as shown in FIG. 8A, an optical waveguide 9a having a small diameter is formed and connected to the opposing fiber. In general, the SMF mode power distribution at a short wavelength has the largest power distribution to the fundamental mode. If the core of the optical fiber is a perfect circle, the shape of the fundamental mode is a circle similar to the core shape, and the spread angle of the light emitted from the fiber is small. As shown in FIG. An optical waveguide 9a having a small diameter is formed on the extension line.

  After the second stage, after confirming that the optical waveguide 9a has been formed, when the incident light intensity is increased more than in the first stage, the optical waveguide is centered on the optical waveguide due to the optical waveguide effect of the narrow-diameter optical waveguide. Light is distributed. And as shown in FIG.8 (b), the optical waveguide 9b is formed in the light intensity area | region exceeding the hardening threshold value of the 1st photocurable resin for core part formation. As a result, a linear optical waveguide with little spread of the emitted light is formed. If you want to further expand the final optical waveguide (core part) diameter and MFD, either increase the number of times the curing light is incident after the second stage or increase the light intensity at the second stage. Use it.

  Next, after confirming that the optical waveguides 9a and 9b are reliably formed between the end faces of the SMF 1-1 and 1-2, as shown in FIG. 8C, the light source 5 not connected to the fiber. Is operated to irradiate light in the vicinity of the core portion 9 including the optical waveguides 9a and 9b already formed between the ends of the SMF 1-1 and 1-2. Then, as shown in FIG. 8C, only the second photocurable resin in the mixed solution 8 reacts and cures, and the clad portion 10 is formed around the core portion 9.

  Thus, even when a mixed solution of the photocurable resin for forming the core part and the photocurable resin for forming the cladding part is used by changing the light intensity of the light at the time of forming the core in two stages, Compared to conventional self-forming optical waveguide connections that form with uniform light intensity, the effects of higher-order mode light and curing shrinkage can be minimized, and optical fibers can be connected with low loss. .

<Embodiment 3>
FIG. 9 shows a third embodiment of an optical component connecting method according to the present invention, in which an optical fiber and a planar lightwave circuit are separately used for a core-forming photocurable resin and a cladding-forming photocurable resin. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals. That is, 1 is a single mode fiber (SMF), 2 and 3 are photocurable resin solutions, 4 is a light source for forming a core part, 5 is a light source for forming a cladding part, and 11 is a planar lightwave circuit (PLC). .

  Here, the light source 4 for forming the core part is connected to the other end of the SMF 1, and the light source 5 for forming the clad part is disposed so as to irradiate between one end of the SMF 1 and the PLC 11 described later.

  In practice, the solutions 2 and 3 are not simultaneously filled between the ends of the SMF 1 and the PLC 11, but both solutions are shown in FIG. 9 for convenience.

  FIG. 10 shows a connection process in the present embodiment. Hereinafter, a method for connecting optical components of the present invention will be described with reference to FIGS. 9 and 10.

  First, as shown in FIG. 9, the SMF 1 and the PLC 11 are arranged so that one ends to be connected are substantially opposed to each other with a predetermined gap therebetween, and a photocurable resin is provided between the end faces of the one ends of the SMF 1 and the PLC 11. Of solution 2. Note that the one end to which the PLC 11 should be connected refers to an end face provided with a light emitting part or an incident part.

  Note that the SMF 1 and the PLC 11 have a holding means (not shown), for example, a support base having a V-groove on one side and a plane on which the PLC can be mounted on the other side so that the center of the light emitting or incident part coincides with the V-groove. It is held by a holding means comprising a pressing plate for fixing the fiber and the PLC to this stand, and the above-described arrangement relationship is maintained until the end of the connection work. In addition, the relationship of the central axis between the light emitting portion or the incident portion of the fiber and the PLC described above may be maintained in the vicinity of one end to be connected, and is in such a relationship in the entire length of the fiber. Needless to say, this is not necessary (this point is common to all embodiments of the present invention).

  In addition, as a specific method for filling (interposing) the solution 2 between the end faces of the SMF 1 and the PLC 11, for example, the liquid reservoir is stored at a position where the ends of the SMF 1 and the PLC 11 of the support base constituting the holding means face each other. For example, a depressed portion may be provided, and the solution 2 may be dropped into the depressed portion.

  Next, as shown in FIG. 10A, when the core portion forming light source 4 connected to the other end of the SMF 1 is operated, the light generated by the light source 4 and propagated through the SMF 1 is supplied from one end of the SMF 1 to the solution. 2, whereby the first photocurable resin in the solution 2 reacts and cures, and an optical waveguide (core portion) is formed between the end faces of the SMF 1 and the PLC 11.

  Here, when the wavelength range of the light source 4 is equal to or less than the cutoff wavelength of the SMF, when light from the light source 4 is incident on the SMF 1, higher-order modes other than the fundamental mode are generated. Since the higher-order mode light has a larger beam divergence angle than the fundamental mode light, the diameter of the formed optical waveguide is increased. Furthermore, the diameter of the optical waveguide to be formed is dependent on light intensity, and generally tends to increase as the light intensity of incident light increases. In addition, when a light having a high light intensity is incident when a radical curable resin is used as the first photocurable resin for forming the core portion, curing shrinkage occurs, and thus the formed optical waveguide is deformed. Excessive connection loss will occur.

  Therefore, in the present invention, the light intensity of light incident on the photocurable resin is changed in at least two stages.

  In the first stage, as shown in FIG. 2A, the peak intensity in the vicinity of the center of the fiber core in the light intensity distribution is slightly higher than the curing threshold value of the first photocurable resin for forming the core part (basic Only the light intensity of the mode light exceeds the curing threshold value of the first photocurable resin, and the light intensity of the higher order mode light does not exceed the curing threshold value of the first photocurable resin) Incident. Then, as shown in FIG. 10A, an optical waveguide 12a having a small diameter is formed and connected to the opposing PLC. In general, the SMF mode power distribution at a short wavelength has the largest power distribution to the fundamental mode. If the core of the optical fiber is a perfect circle, the shape of the fundamental mode is a circle similar to the core shape, and the spread angle of the light emitted from the fiber is small. As shown in FIG. An optical waveguide 12a having a small diameter is formed on the extension line.

  After the second stage, after confirming that the optical waveguide 12a is formed, when the incident light intensity is increased more than in the first stage, the optical waveguide is centered on the optical waveguide due to the optical waveguide effect of the narrow-diameter optical waveguide. Light is distributed. Then, as shown in FIG. 10B, the optical waveguide 12b is formed in a light intensity region exceeding the curing threshold value of the first photocurable resin for forming the core portion. As a result, a linear optical waveguide with little spread of the emitted light is formed. If you want to further expand the final optical waveguide (core part) diameter and MFD, either increase the number of times the curing light is incident after the second stage or increase the light intensity at the second stage. Use it.

  Next, after confirming that the optical waveguides 12a and 12b are surely formed between the end faces of the SMF 1 and the PLC 11, as shown in FIG. 10C, the core portion extends from between the end faces of the one ends of the SMF 1 and the PLC 11. The photocurable resin solution 2 for forming is removed, and instead, the photocurable resin solution 3 for forming the clad portion is filled, and the light source 5 not connected to the fiber is operated to operate the SMF 1 and the PLC 11. The light is irradiated to the vicinity of the core portion 12 composed of the already formed optical waveguides 12a and 12b between the ends of the optical waveguides. Then, as shown in FIG. 10C, the second photocurable resin in the solution 3 reacts and cures, and a clad portion 13 is formed around the core portion 12.

  In this way, by changing the light intensity of the light at the time of core formation in two steps, the effect of higher order mode light and curing shrinkage than the conventional self-formed optical waveguide connection that forms with uniform light intensity. The optical fiber and the PLC can be connected with low loss.

<Embodiment 4>
FIG. 11 shows an optical component connecting method according to a fourth embodiment of the present invention, in which an optical fiber and a planar lightwave circuit are mixed with a photocurable resin for forming a core and a photocurable resin for forming a clad. In the figure, the same components as those in Embodiments 2 and 3 are denoted by the same reference numerals. That is, 1 is a single mode fiber (SMF), 4 is a light source for forming a core part, 5 is a light source for forming a cladding part, 8 is a mixed solution of a photocurable resin, and 11 is a planar lightwave circuit (PLC).

  FIG. 12 shows the connection process in the present embodiment. Hereinafter, the optical component connecting method of the present invention will be described with reference to FIGS. 11 and 12.

  First, as shown in FIG. 11, the SMF 1 and the PLC 11 are arranged so that one ends to be connected to each other are substantially opposed to each other with a predetermined gap therebetween, and a photocurable resin is provided between the end faces of the one ends of the SMF 1 and the PLC 11. The mixed solution 8 is filled.

  Next, as shown in FIG. 12A, when the core forming light source 4 connected to the other end of the SMF 1 is operated, the light generated by the light source 4 and propagated through the SMF 1 is mixed from one end of the SMF 1. Incident into the solution 8, whereby only the first photocurable resin in the mixed solution 8 reacts and cures, and an optical waveguide (core portion) is formed between the end faces of the SMF 1 and the PLC 11.

  Here, when the wavelength range of the light source 4 is equal to or less than the cutoff wavelength of the SMF, when light from the light source 4 is incident on the SMF 1, higher-order modes other than the fundamental mode are generated. Since the higher-order mode light has a larger beam divergence angle than the fundamental mode light, the diameter of the formed optical waveguide is increased. Furthermore, the diameter of the optical waveguide to be formed is dependent on light intensity, and generally tends to increase as the light intensity of incident light increases. In addition, when a light having a high light intensity is incident when a radical curable resin is used as the first photocurable resin for forming the core portion, curing shrinkage occurs, and thus the formed optical waveguide is deformed. Excessive connection loss will occur.

  Therefore, in the present invention, the light intensity of light incident on the photocurable resin is changed in at least two stages.

  In the first stage, as shown in FIG. 2A, the peak intensity in the vicinity of the center of the fiber core in the light intensity distribution is slightly higher than the curing threshold value of the first photocurable resin for forming the core part (basic Only the light intensity of the mode light exceeds the curing threshold value of the first photocurable resin, and the light intensity of the higher order mode light does not exceed the curing threshold value of the first photocurable resin) Incident. Then, as shown in FIG. 12A, an optical waveguide 14a having a small diameter is formed and connected to the opposing PLC. In general, the SMF mode power distribution at a short wavelength has the largest power distribution to the fundamental mode. If the core of the optical fiber is a perfect circle, the shape of the fundamental mode is a circle similar to the core shape, and the spread angle of the light emitted from the fiber is small. As shown in FIG. An optical waveguide 14a having a small diameter is formed on the extension line.

  In the second and subsequent stages, after confirming that the optical waveguide 14a has been formed, if the incident light intensity is increased more than in the first stage, the optical waveguide is centered on the optical waveguide due to the optical waveguide effect of the narrow-diameter optical waveguide. Light is distributed. And as shown in FIG.12 (b), the optical waveguide 14b is formed in the light intensity area | region exceeding the hardening threshold value of the 1st photocurable resin for core part formation. As a result, a linear optical waveguide with little spread of the emitted light is formed. If you want to further expand the final optical waveguide (core part) diameter and MFD, either increase the number of times the curing light is incident after the second stage or increase the light intensity at the second stage. Use it.

  Next, after confirming that the optical waveguides 14a and 14b are reliably formed between the end faces of the SMF 1 and the PLC 11, the light source 5 not connected to the fiber is operated as shown in FIG. Light is irradiated to the vicinity of the core portion 14 composed of the already formed optical waveguides 14a and 14b between one ends of the SMF 1 and the PLC 11. Then, as shown in FIG. 12 (c), only the second photocurable resin in the mixed solution 8 reacts and cures, and a clad portion 15 is formed around the core portion 14.

  Thus, even when a mixed solution of the photocurable resin for forming the core part and the photocurable resin for forming the cladding part is used by changing the light intensity of the light at the time of forming the core in two stages, Compared to the conventional self-forming optical waveguide connection that forms with uniform light intensity, the effects of higher-order mode light and curing shrinkage can be minimized, and the optical fiber and PLC are connected with low loss. Can do.

<Other embodiments>
In the optical component connecting method of the present invention, planar lightwave circuits can be connected in the same manner as described above. However, in that case, at least one of the planar lightwave circuits has a function of generating light having a wavelength at which the photocurable resin for forming the core portion initiates a curing reaction, and the light emitting portion at one end to be connected The light from the light source that can emit the light of the wavelength from the light source that generates the light of the wavelength at which the photocurable resin for forming the core part initiates the curing reaction should be connected from the light incident part. It is necessary to have a function of transmitting to the light emitting part at one end.

A perspective view showing an example of a planar lightwave circuit Explanatory diagram showing the relationship between the light intensity of the curing light and the diameter of the formed optical waveguide Explanatory diagram showing the relationship between the light intensity of the curing light and the diameter of the formed optical waveguide The block diagram which shows Embodiment 1 of the connection method of the optical component of this invention Process drawing which shows Embodiment 1 of the connection method of the optical component of this invention Graph showing the amount of change in splice loss according to the present invention and the prior art The block diagram which shows Embodiment 2 of the connection method of the optical component of this invention Process drawing which shows Embodiment 2 of the connection method of the optical component of this invention The block diagram which shows Embodiment 3 of the connection method of the optical component of this invention Process drawing which shows Embodiment 3 of the connection method of the optical component of this invention The block diagram which shows Embodiment 4 of the connection method of the optical component of this invention Process drawing which shows Embodiment 4 of the connection method of the optical component of this invention

Explanation of symbols

  1, 1-1, 1-2: single mode fiber (SMF), 2, 3: photocurable resin solution, 4, 5: light source, 6, 6a, 6b, 9, 9a, 9b, 12, 12a, 12b, 14, 14a, 14b: Core part (optical waveguide), 7, 10, 13, 15: Clad part, 8: Mixed solution of photocurable resin, 11: Planar light wave circuit (PLC).

Claims (3)

A wavelength corresponding to the curing start wavelength of the photo-curable resin, in which the optical components are filled with light-curing resin between the light emitting ends of each component or between the light emitting end and the light incident end. Light enters the photocurable resin from the light exit end of at least one of the optical components, and self between the light exit ends of each component or between the light exit end and the light entrance end. In a method of connecting by forming a formed optical waveguide,
The light intensity at the time of forming the core incident on the photocurable resin is changed in at least two stages . At this time, only the light intensity of the fundamental mode is the light intensity in the first stage. A method for connecting optical components, characterized in that the value exceeds a curing threshold value of the photosensitive resin, and the light intensity in the second stage is higher than the light intensity in the first stage . In the connection method of the optical component of Claim 1 ,
An optical component connection method, wherein at least one of the optical components is an optical fiber. In the connection method of the optical component of Claim 1 ,
An optical component connection method, wherein at least one of the optical components is a planar lightwave circuit.

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