JP5737108B2 - Optical fiber unit and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical fiber unit and a manufacturing method thereof.

With the rapid development of optical fiber networks, the capacity of optical transmission has increased, while optical communication at closer distances, such as between devices and between devices, has begun to be realized.
In such optical communication, there is a method using a lens as one of methods for efficiently optically connecting between a fiber and between a fiber and a device. For example, there are a method of connecting an injection-molded lens array to the tip of an optical fiber array composed of a plurality of optical fibers, a method of processing the tip of an optical fiber core into a lens shape, and the like.

Japanese Patent Laid-Open No. 10-148704 JP-A-6-242353 JP-A-56-036619

However, in the method using a lens array manufactured using injection molding, a high-precision mold is required, or an optical fiber polishing step is required to suppress scattering loss at the end face, etc. This will increase costs. Further, a connection loss (coupling loss) is likely to occur due to a positional shift between the optical fiber and the lens.
Further, in the method of manufacturing the lens by processing the tip of the core of the optical fiber, connection loss is likely to occur when light having a beam diameter larger than the core diameter of the optical fiber is coupled.

  Therefore, it is desirable to realize an optical fiber unit including an optical fiber and a lens with low cost and low connection loss.

The present optical fiber unit includes an optical fiber, a photosensitive film that is bent so as to cover an end portion of the optical fiber, and a part on one side and a part on the other side are bonded with the optical fiber interposed therebetween, and a photosensitive film A first lens defined by the curved surface of the bent portion and a second lens defined by the difference in refractive index of the photosensitive film.
The manufacturing method of the present optical fiber unit includes a step of disposing the end of the optical fiber on the end of the photosensitive film, bending the photosensitive film so as to cover the end of the optical fiber, and forming the optical fiber of the photosensitive film. The first lens is formed by the curved surface of the bent portion of the photosensitive film by bonding the one side portion and the other side portion, and exposing the photosensitive film to change the refractive index. And a step of forming two lenses.

  Therefore, according to the present optical fiber unit and the manufacturing method thereof, there is an advantage that an optical fiber unit including an optical fiber and a lens can be realized at a low cost and with a small connection loss.

(A)-(C) are schematic diagrams which show the structure of the optical fiber unit concerning this embodiment. (A)-(C) are schematic diagrams which show the variation of the position of the 2nd lens in the optical fiber unit concerning this embodiment. (A)-(H) are the schematic diagrams for demonstrating the manufacturing method of the optical fiber unit concerning this embodiment. (A)-(H) are the schematic diagrams for demonstrating the modification of the manufacturing method of the optical fiber unit concerning this embodiment. (A)-(C) are schematic diagrams which show the structure of an optical connector and a blade server provided with the optical fiber unit concerning this embodiment. (A)-(D) are the schematic diagrams which show the structure of the optical fiber unit of 1st Example. It is a schematic diagram which shows the structure of the optical fiber unit of 2nd Example. It is a schematic diagram which shows the structure of the optical fiber unit of 3rd Example.

Hereinafter, an optical fiber unit and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS.
The optical fiber unit according to this embodiment is used for optical connection in an optical communication network, an optical interconnection, an optical device, and the like.
As shown in FIGS. 1A to 1C, the present optical fiber unit includes an optical fiber 1, a photosensitive film 2, a first lens 3, and a second lens 4. The optical fiber unit is also referred to as a lens-attached fiber.

Here, the optical fiber 1 includes a plurality of optical fibers 1. That is, an optical fiber array having a plurality of optical fibers 1 is provided. The lens-attached fiber is also referred to as a lens-attached fiber array or an array-like lens-attached fiber.
The photosensitive film 2 is bent so as to cover the end portion of the optical fiber 1, and a portion on one side and a portion on the other side are bonded with the optical fiber 1 interposed therebetween. Here, the adhesive 5 is filled in the space between the one side part and the other side part of the photosensitive film 2 bent so as to cover the end part of the optical fiber 1. In addition, the one side part and the other side part of the photosensitive film 2 should just adhere | attach at least one part. For example, the cylindrical space formed by the folded portion (folded portion) of the photosensitive film 2 may be filled with the adhesive 5 or filled with a filler that does not function as the adhesive 5. May be. Here, as the filler, for example, matching oil or gel can be used.

  The photosensitive film 2 has an optical fiber 1 sandwiched between a portion on one side and a portion on the other side, and is bonded and fixed to an end portion of the optical fiber 1. For this reason, the adhesive 5 is filled between the one side portion of the photosensitive film 2 and the optical fiber 1 and between the other side portion of the photosensitive film 2 and the optical fiber 1. Here, the photosensitive film 2 and the optical fiber 1 are bonded together, but the present invention is not limited to this, and the photosensitive film 2 may be simply fitted into the end of the optical fiber 1.

  The photosensitive film 2 is a film whose refractive index changes upon exposure, that is, a film whose refractive index changes in the light irradiation portion. Here, as the photosensitive film 2, for example, a polysilane film having a property that the refractive index is lowered by exposure is used. For example, the refractive index can be lowered to about 1.57 by exposing a polysilane film having a refractive index of about 1.74 to ultraviolet rays for exposure. In addition, examples of the photosensitive film 2 having a property that the refractive index is lowered by exposure include a film using a norbornene-type polymer.

  The first lens 3 is a cylindrical lens defined by the curved surface of the bent portion of the photosensitive film 2. That is, in the first lens 3, the radius of curvature of the lens is defined by the bending radius of the bent portion of the photosensitive film 2. Here, one first lens 3 is provided for a plurality of optical fibers 1. That is, the curved surface of the bent portion of the photosensitive film 2 that defines the first lens 3 is provided so as to extend along the direction in which the plurality of optical fibers 1 constituting the optical fiber array are arranged.

  The second lens 4 is a cylindrical lens that is provided between the optical fiber 1 and the first lens 3 and is defined by the refractive index difference of the photosensitive film 2. Here, the second lens 4 has a lens shape having a convex curved surface on the first lens 3 side, and is defined by a region having a refractive index higher than the refractive index of the photosensitive film 2 in other regions. That is, in the second lens 4, the radius of curvature of the lens is defined by the radius of curvature of the region having a higher refractive index than the refractive index of other regions. One second lens 4 is provided for each of the plurality of optical fibers 1.

  Here, the direction (lens axis direction) in which the curved surface (convex surface; lens surface) of the bent portion of the photosensitive film 2 defining the first lens 3 extends and the high refraction of the photosensitive film 2 defining the second lens 4 are described. The second lens 4 is provided with respect to the first lens 3 so that the direction (lens axis direction) in which the curved surface (convex surface; lens surface) of the rate region extends is orthogonal. That is, the first lens 3 and the first lens 3 are arranged so that the direction in which the first lens 3 enlarges or reduces the light and the direction in which the second lens 4 enlarges or reduces the light are orthogonal to the light propagation direction of the optical fiber 1. A second lens 4 is provided. As described above, the first lens 3 and the second lens 4 expand or contract light in a direction orthogonal to the light propagation direction of the optical fiber 1. Therefore, the first lens 3 and the second lens 4 are cylindrical lenses in which the light refraction directions are orthogonal to each other.

  In the present embodiment, the photosensitive film 2 includes grooves 6 for holding the optical fibers 1 on the surfaces of both ends. Here, since an optical fiber array is used, a plurality of (here, three) grooves 6 for holding the respective optical fibers 1 are provided on the respective surfaces of both ends of the photosensitive film 2. Yes. Here, the groove 6 is formed in a size substantially equal to the outer shape of the optical fiber 1. For example, when the coating of the optical fiber 1 is removed and the optical fiber 1 is disposed in the groove 6 of the photosensitive film 2, the groove 6 is formed to have a size approximately equal to the cladding diameter of the optical fiber 1.

  Moreover, in this embodiment, the curable resin in which the refractive index after hardening is equal to the refractive index of the photosensitive film 2 after the exposure on one side and the other side across the optical fiber 1 of the photosensitive film 2. Is glued by. In this case, the curable resin functions as the adhesive 5. For this reason, in the space between the one side part and the other side part of the photosensitive film 2 bent so as to cover the end part of the optical fiber 1, the refractive index after curing has a photosensitive film after exposure. A curable resin 5 having a refractive index of 2 is filled. In the present embodiment, as will be described later, a light-shielding film 10 is provided so as to cover the second lens formation region, the entire film is exposed, and the refractive index of the region other than the second lens formation region is changed to be photosensitive. A second lens 4 defined by the refractive index difference of the film 2 is formed. For this reason, the refractive index of the photosensitive film 2 after exposure is the refractive index of the photosensitive film 2 after performing exposure for forming the second lens 4. In this case, since the bent portion of the photosensitive film 2 that defines the first lens 3 is also exposed, the refractive index of the photosensitive film 2 after the exposure is the refractive index of the first lens 3. Here, the curable resin is a thermosetting resin.

In the present embodiment, the second lens 4 may be provided in the vicinity of the first lens 3 as shown in FIG. 2A, for example, or as shown in FIG. 3 may be provided on the portion of the first lens 3 between the optical fiber 1 and the flat portion between the first lens 3 and the optical fiber 1 as shown in FIG. Also good.
Among these, as shown in FIG. 2A, when the second lens 4 is provided in the vicinity of the first lens 3, the second lens is utilized by utilizing the film thickness at the bent portion of the photosensitive film 2. 4 will be formed. Therefore, the adhesive 5 does not intervene in the second lens 4 and the adhesive 5 does not affect the loss. Therefore, the adhesive 5 does not intervene in the second lens 4 as in other cases. There is no need to take measures.

  In addition, as shown in FIG. 2B, when the second lens 4 is provided in a portion on the first lens 3 between the first lens 3 and the optical fiber 1, one side of the photosensitive film 2 is provided. The second lens 4 is formed in a portion where the portion and the other portion are overlapped and bonded. For this reason, when the one side part and the other side part of the photosensitive film 2 are bonded with the adhesive 5, a load is applied to the second lens forming area and the adhesive is applied to an area other than the second lens forming area. It is preferable that the adhesive 5 is not interposed in the second lens 4 so that 5 is pushed out. This is because the refractive index of the second lens 4 is larger than the refractive index of the adhesive 5, and therefore when the adhesive 5 is present in the second lens 4, the light propagates through the second lens 4. This is because light is diffused and a loss may occur.

Next, the manufacturing method of the optical fiber unit concerning this embodiment is demonstrated, referring FIG.
First, the end of the optical fiber 1 is disposed on the end of the photosensitive film 2 [see FIG. 3B]. Here, since an optical fiber array having a plurality of optical fibers 1 is used as the optical fiber 1, the end of the optical fiber array is disposed on the end of the photosensitive film 2.

Next, the photosensitive film 2 is bent so as to cover the end portion of the optical fiber 1, and the one side portion and the other side portion are bonded to each other with the optical fiber 1 of the photosensitive film 2 interposed therebetween, and the photosensitive film 2 is folded. The first lens 3 is formed by the curved surface of the curved portion [see FIGS. 3D and 3E]. This is called a first lens forming step.
Next, the photosensitive film 2 is exposed to change the refractive index to form the second lens 4 [see FIG. 3 (F)]. This is called a second lens forming step.

  In the present embodiment, in the first lens forming step, a curable resin 5 having a refractive index after curing equal to the refractive index of the photosensitive film 2 after exposure is provided on the photosensitive film 2. Then, the photosensitive film 2 is bent so as to cover the end portion of the optical fiber 1, the curable resin 5 is cured, and the one side portion and the other side portion are bonded with the optical fiber 1 of the photosensitive film 2 interposed therebetween. Then, the first lens 3 is formed by the curved surface of the bent portion of the photosensitive film 2 [see FIGS. 3D and 3E].

  In the present embodiment, the second lens forming step is performed after the first lens forming step. Therefore, in the second lens forming step, the photosensitive film 2 is exposed to change the refractive index, and the second lens 4 is formed between the optical fiber 1 and the first lens 3. Thereby, the second lens 4 defined by the refractive index difference of the photosensitive film 2 is formed between the optical fiber 1 and the first lens 3.

This will be specifically described below.
First, as shown in FIG. 3A, the back surface of the photosensitive film 2 (here, a polysilane film having a refractive index of 1.74), that is, the surface opposite to the surface on which the groove 6 for holding the optical fiber 1 is formed. A light shielding film 10 for forming the second lens 4 is provided on the side surface so as to cover the second lens formation region. In addition, since the light shielding film 10 is patterned according to the lens pattern of the 2nd lens 4, it is also called a light shielding pattern. Further, the back surface of the photosensitive film 2 is a surface that becomes the outer side when the first film 3 is formed by bending the photosensitive film 2 so as to cover the end portion of the optical fiber 1.

  Here, the number of the light shielding films 10 is set in accordance with the number of the optical fibers 1. For example, when two optical fibers 1 are provided, two second lenses 4 are provided, and the number of light shielding films 10 is also two. However, the light shielding film 10 is provided at a position symmetrical with respect to the center line in the length direction of the photosensitive film 2 so as to overlap when the photosensitive film 2 is folded in half. For this reason, a total of four light-shielding films 10 are provided on each of the two sides. The size of the light shielding film 10 corresponds to the size of the cross section of the second lens 4 and has a desired radius of curvature, width, and depth. Such a light shielding film 10 may be formed by evaporating copper, for example.

  Further, as described above, when the second lens 4 is provided in the vicinity of the first lens 3, when the second lens 4 is provided at a portion of the first lens 3 between the first lens 3 and the optical fiber 1, the first lens 3 is provided. May be provided in a flat portion between the optical fiber 1 and the optical fiber 1, but the arrangement of the light shielding film 10 may be determined according to each case. FIG. 3 shows an example in which the second lens 4 is provided in a flat portion between the first lens 3 and the optical fiber 1.

  Next, as shown in FIG. 3B, a groove 6 for holding the optical fiber 1 is formed on the surface of the photosensitive film 2. Here, the groove | channel 6 is provided in the surface on the opposite side to the surface in which the light shielding pattern of the photosensitive film 2 is provided. Here, the number of grooves 6 is a number corresponding to the number of optical fibers 1. For example, in the case of having two optical fibers 1, two grooves 6 are provided. However, the photosensitive film 2 is bent and the optical fiber 1 is sandwiched between the end portion on one side and the end portion on the other side, and the photosensitive film 2 is bonded and fixed to the end portion of the optical fiber 1. For this reason, a total of four grooves 6 are provided on the surface of both end portions of the photosensitive film 2, two each. The size of the groove 6 corresponds to the size of the optical fiber 1 and has a desired width, depth, and length. For example, when the optical fiber 1 having a clad diameter of about 125 μm is used, the width of the groove 6 is about 125 μm and the depth is about 63 μm. Such grooves 6 may be formed on the surface of the photosensitive film 2 by, for example, laser processing. The groove 6 is also referred to as a fiber holder groove.

Next, the end of the optical fiber 1 is placed in the groove 6 formed on the surface of one end of the photosensitive film 2. Here, the coating of the end of the optical fiber 1 is removed, and the end of the optical fiber 1 from which the coating has been removed is placed in the groove 6 formed on the surface of the photosensitive film 2.
After arranging the optical fiber 1 on the photosensitive film 2 in this manner, the photosensitive film 2 is bent so as to cover the end of the optical fiber 1 as shown in FIGS. The first lens 3 is formed by the curved surface of the bent portion of the photosensitive film 2 by bonding the one side portion and the other side portion with the optical fiber 1 of the photosensitive film 2 interposed therebetween. In this case, the light shielding pattern 10 formed on the back surface of the photosensitive film 2 as described above is located on the outer surface.

In the present embodiment, first, the adhesive 5 is dropped on the surface of the photosensitive film 2 as shown in FIG. Here, as the adhesive 5, a thermosetting resin (here, a refractive index of about 1.57) having a refractive index after curing equal to the refractive index of the photosensitive film 2 after exposure is dropped.
Next, as shown in FIG. 3 (D), the photosensitive film 2 is bent so as to cover the end of the optical fiber 1, and heat is applied to cure the thermosetting resin 5, thereby forming the optical fiber of the photosensitive film 2. The first lens 3 is formed by the curved surface of the bent portion of the photosensitive film 2 by adhering the portion on one side and the portion on the other side of 1.

  In particular, in the present embodiment, the photosensitive film 2 is bent so as to cover the end portion of the optical fiber 1, and the one side portion and the other side portion of the photosensitive film 2 are overlapped with the optical fiber 1 interposed therebetween. Thus, as shown in FIG. 3E, a load is applied to the second lens formation region, that is, the light shielding pattern formation region. As a result, the thermosetting resin 5 interposed between the one side portion and the other side portion of the photosensitive film 2 in the second lens forming region is pushed out to a region other than the second lens forming region, and the second lens is formed. The thermosetting resin 5 is not interposed in the formation region. Thereafter, heat is applied to cure the thermosetting resin 5 so that one side of the photosensitive film 2 is bonded to the other side, and the photosensitive film 2 is bonded to the end of the optical fiber 1. And fix. Then, at the same time, the first lens 3 defined by the curved surface of the bent portion of the photosensitive film 2 and having a desired bending radius is formed.

In this embodiment, since the light shielding pattern 10 formed on the photosensitive film 2 is formed on the surface opposite to the groove 6 for holding the optical fiber 1, the photosensitive film 2 is bent. When attached to the end of the optical fiber 1, the light shielding pattern 10 is positioned on the outer surface of the photosensitive film 2.
After forming the first lens 3 in this way, as shown in FIGS. 3F to 3H, the entire photosensitive film 2 is exposed to form a second lens covered with the light shielding pattern 10. The second lens 4 is formed between the optical fiber 1 and the first lens 3 by changing the refractive index of the region other than the region. Thereby, the second lens 4 defined by the refractive index difference of the photosensitive film 2 is formed between the optical fiber 1 and the first lens 3. In the exposure of the photosensitive film 2, light is irradiated from a direction perpendicular to the surface of the photosensitive film 2 on which the light shielding pattern 10 is formed.

  In the present embodiment, the transparent container 11 filled with the solution 12 having a refractive index close to the refractive index of the photosensitive film 2 after exposure (here, a solution having a refractive index of about 1.57) is filled as described above. A polysilane film 2 having a refractive index of about 1.74 on which the first lens 3 is formed is inserted into the optical fiber 1. Then, the polysilane film 2 is exposed by irradiating the entire film with ultraviolet rays until the refractive index of the polysilane film 2 reaches about 1.57. Thus, the 2nd lens 4 by a refractive index difference is formed by making the refractive index of area | regions other than the 2nd lens formation area covered with the light-shielding pattern 10 of the polysilane film 2 into about 1.57. Thereby, the second lens 4 defined by a region having a refractive index (here, about 1.74) higher than the refractive index (here, about 1.57) of the polysilane film 2 in the other region is formed. That is, the second lens 4 is formed by making the refractive index of a part of the photosensitive film 2 different from the refractive index of the other part.

  Here, in order to ensure that the second lens 4 extending in the direction perpendicular to the film surface can be formed by irradiating light perpendicularly to the light shielding pattern 10, the photosensitive film 2 is provided with an equivalent refractive index. The exposure is performed in a state of being placed in the solution 12 having the above, but is not limited thereto. For example, if the second lens 4 extending in a direction perpendicular to the film surface can be formed, the light is not put into a solution as in a manufacturing method (see FIG. 4) of a modified example of the present embodiment described later. Exposure may be performed by irradiating the pattern 10 with light perpendicularly. For example, when the second lens 4 is provided in a flat portion between the first lens 3 and the optical fiber 1 [see FIG. 2C], when the second lens 4 is provided in the vicinity of the first lens 3 [FIG. )] Or in the case where the first lens 3 and the optical fiber 1 are provided at a portion on the first lens 3 [see FIG. 2 (B)]. Two lenses 4 are easy to form. For this reason, exposure may be performed by irradiating light to the light shielding pattern 10 vertically without entering the solution as in a manufacturing method (see FIG. 4) of a modified example of the present embodiment described later.

After forming the second lens 4 in this way, as shown in FIG. 3G, the light shielding pattern (mask) 10 is removed by, for example, wet etching.
In this way, an optical fiber unit including the photosensitive film 2 having the first lens 3 and the second lens 4 as shown in FIG. 3H is completed at the end of the optical fiber 1.
Therefore, according to the optical fiber unit and the manufacturing method thereof according to the present embodiment, there is an advantage that an optical fiber unit including the optical fiber 1 and the lenses 3 and 4 can be realized at low cost and with little connection loss. is there.

  In particular, the optical fiber unit manufactured as described above does not require the use of a mold, and the polishing process of the optical fiber 1 is not required, so that the manufacturing cost can be reduced. Further, when the photosensitive film 2 is bonded to the end face of the optical fiber 1, when a curable resin 5 having a refractive index after curing equal to the refractive index of the photosensitive film 2 after exposure is used, Since the end face is covered with the curable resin 5, the scattering loss due to the roughness of the end face of the optical fiber 1 can be reduced. Further, it is possible to reduce a loss due to a positional deviation between the optical fiber 1 and the lenses 3 and 4 provided at the end portions. That is, since the first lens 3 is formed by folding and attaching the photosensitive film 2 to the end portion of the optical fiber 1, the position of the first lens 3 with respect to the end portion of the optical fiber 1 depends on how the photosensitive film 2 is bent. Can be adjusted. For this reason, the 1st lens 3 can be located symmetrically in the thickness direction of the optical fiber 1, the position shift of the optical fiber 1 and the 1st lens 3 can be suppressed, and loss can be reduced. Further, by accurately aligning the position of the light shielding pattern 10 for forming the second lens 4 and the position of the fiber holding groove 6, the positional deviation between the optical fiber 1 and the second lens 4 is suppressed. It is possible to reduce the loss.

In addition, this invention is not limited to the structure described in embodiment mentioned above, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, an optical fiber unit including an optical fiber array as the optical fiber 1 is described as an example. However, the present invention is not limited to this, and an optical fiber including a single optical fiber as an optical fiber. It may be a fiber unit.

In the above-described embodiment, the second lens forming process is performed after the first lens forming process. However, the present invention is not limited to this. For example, the second lens forming process is performed before the first lens forming process. You may make it perform a process.
That is, similarly to the manufacturing method of the above-described embodiment (see FIG. 3), as shown in FIG. 4 (A), after the light-shielding pattern 10 is provided on the photosensitive film 2, FIGS. As shown in FIG. 4, before the optical fiber 1 is arranged and the first lens 3 is formed, the entire photosensitive film 2 is exposed and covered with the light shielding pattern 10 as shown in FIG. The second lens 4 may be formed by changing the refractive index of the region other than the second lens forming region. Specifically, the polysilane film 2 is exposed by irradiating the entire film with ultraviolet rays until the refractive index of the polysilane film 2 reaches about 1.57. Thus, the 2nd lens 4 by a refractive index difference is formed by making the refractive index of area | regions other than the 2nd lens formation area covered with the light-shielding pattern 10 of the polysilane film 2 into about 1.57. Thereby, the second lens 4 defined by a region having a refractive index (here, about 1.74) higher than the refractive index (here, about 1.57) of the polysilane film 2 in the other region is formed.

  As shown in FIG. 4G, the light shielding pattern 10 (mask) is removed by, for example, wet etching. The light shielding pattern 10 is removed by the manufacturing method of the above-described embodiment (see FIG. 3). Similarly to the above, it may be performed after the first lens 3 is formed, or may be performed after the second lens 4 is formed and before the first lens 3 is formed. Here, exposure is performed by simply irradiating light perpendicularly to the light shielding pattern 10, but as in the manufacturing method of the above-described embodiment (see FIG. 3), the light shielding pattern 10 is reliably perpendicular. In order to be able to form a second lens 4 extending in a direction perpendicular to the film surface by irradiating light on the photosensitive film 2, the photosensitive film 2 is exposed in a solution 12 having an equivalent refractive index. May be performed.

  Moreover, in the above-mentioned embodiment and modification, although thermosetting resin is used as the adhesive agent 5, it is not restricted to this, For example, photocurable resin can also be used. In this case, light is irradiated when curing for adhesion. For the photocurable resin as the adhesive 5, a photocurable resin (in this case, a refractive index of about 1.57) whose refractive index after curing is equal to the refractive index of the photosensitive film 2 after exposure is used. preferable. In addition, when using a thermosetting resin, what is necessary is just to irradiate an ultraviolet-ray until the refractive index of the photosensitive film 2 will be about 1.57 in a 2nd lens formation process. On the other hand, when using a photocurable resin, light (for example, ultraviolet rays) is also irradiated when it is cured for adhesion. For this reason, the refractive index of the photosensitive film 2 may fall by the light (for example, ultraviolet-ray) irradiated when hardening photocurable resin. In this case, the ultraviolet irradiation time in the second lens forming step is adjusted in consideration of the decrease in the refractive index of the photosensitive film 2 during the light irradiation time during bonding (ultraviolet irradiation time; bonding time). That is, the refractive index of the photosensitive film 2 is reduced due to ultraviolet irradiation when the second lens 4 is formed, and the refractive index of the photosensitive film 2 is reduced due to light irradiation (ultraviolet irradiation) when curing the photocurable resin. And finally, the refractive index of the photosensitive film 2 may be set to a desired refractive index (here, about 1.57).

  Moreover, the optical connector 21 can be comprised by providing the ferrule 20 further in the optical fiber unit of the above-mentioned embodiment as shown, for example in FIG. 5 (A), (B). FIG. 5B shows a state where the ferrule 20 on one side is removed. For example, as shown in FIG. 5C, such an optical connector 21 is used to connect a transmission signal between the midplane 23 and each blade 24 in the blade server 22 when the transmission signal is an optical signal. Can be used.

Hereinafter, it demonstrates still in detail according to an Example. However, the present invention is not limited to the following examples.
In the present embodiment, a fiber with a lens including the first lens 3 and the second lens 4 is actually manufactured by using the one optical fiber 1 and the polysilane film 2 (photosensitive film) by the above-described manufacturing method. The lens function was confirmed and the performance was evaluated.
[First embodiment]
In the first embodiment, as the fiber with lens, first and second fibers 30 and 31 of different types, that is, the first lens fiber 30 in which the second lens 4 is formed in the thickness portion of the film 2, and the film A second lens-attached fiber 31 in which the second lens 4 is formed in the portion where the two are superposed is produced.

  Here, as shown in FIGS. 6A to 6D, a polysilane film having a thickness of about 170 μm and a refractive index of about 1.74 is used to fabricate the first lens-attached fiber 30 and the second lens-attached fiber 31. 2 was used. An optical fiber 1 having a cladding diameter of about 125 μm was used. For this reason, a groove having a width of about 125 μm, a depth of about 63 μm, and a length of about 5 mm was formed as a fiber holder groove 6 in the polysilane film 2. As the adhesive 5, a thermosetting resin having a refractive index of about 1.57 was used.

The first lens 3 provided in the first lens-attached fiber 30 has a bending radius of about 700 μm, the second lens 4 has a curvature radius of about 188 μm, a width of about 370 μm, and a depth of about 170 μm.
The first lens 3 provided in the second lens-attached fiber 31 has a bending radius of about 700 μm, the second lens 4 has a curvature radius of about 125 μm, a width of about 250 μm, and a depth of about 400 μm.

Then, for the first and second fibers with a lens 30 and 31 manufactured in this way, the lens performance was confirmed and the performance was evaluated.
Here, the first lens-attached fiber 30 and the second lens-attached fiber are set so that the distance between the first lens 3 of the first lens-attached fiber 30 and the second lens-attached fiber 31 is about 600 μm. The fiber 31 was opposed to each other with a spacer (not shown) having a thickness of about 600 μm interposed therebetween. Then, light having a wavelength of about 850 nm from a VCSEL (Vertical Cavity Surface Emitting Laser) is incident on the optical fiber 1 side of the second lens-attached fiber 31, and the first lens-attached fiber 30 and the second lens-attached fiber. The intensity of the light propagating through 31 and emitted from the optical fiber 1 side of the first lens-attached fiber 30 was measured.

As a result, the connection loss between the first lens-attached fiber 30 and the second lens-attached fiber 31 was about 1.2 dB.
[Second Embodiment]
In the second embodiment, as shown in FIG. 7, the third and fourth fibers 32 and 33 of the same type as the lens-attached fiber, that is, the third and second lenses formed with the second lens in the thickness portion of the film are used. Fibers 32 and 33 with four lenses were produced.

Here, the third and fourth lens-attached fibers 32 and 33 are manufactured by using the same heat treatment as the polysilane film 2, the optical fiber 1, and the adhesive 5 similar to the above-described first and second lens-attached fibers 30 and 31. A curable resin was used.
The first lens 3 provided in the third lens-equipped fiber 32 has a bending radius of about 550 μm, the second lens 4 has a curvature radius of about 175 μm, a width of about 340 μm, a depth of about 170 μm, The distance between the two lenses 4 and the optical fiber 1 was about 1.25 mm.

The first lens 3 provided in the fourth lens-equipped fiber 33 has a bending radius of about 550 μm, the second lens 4 has a curvature radius of about 195 μm, a width of about 360 μm, a depth of about 170 μm, The distance between the two lenses 4 and the optical fiber 1 was about 1.74 mm.
The third lens-attached fiber 32 and the fourth lens-attached fiber are set so that the distance between the first lens 3 of the third lens-attached fiber 32 and the fourth lens-attached fiber 33 is about 620 μm. The connection loss was calculated by facing the 33 and found to be about 1.29 dB.
[Third embodiment]
In the third embodiment, as shown in FIG. 8, the second lens is formed in the same type of the fifth and sixth lens-attached fibers 34 and 35, that is, the portion where the films are overlapped. Fibers 34 and 35 with the fifth and sixth lenses were produced.

Here, in order to produce the fifth and sixth lens-attached fibers 34 and 35, the heat as the polysilane film 2, the optical fiber 1, and the adhesive 5 similar to the first and second lens-attached fibers 30 and 31 described above. A curable resin was used.
The first lens 3 included in the fifth lens-attached fiber 34 has a bending radius of about 1130 μm, the second lens 4 has a curvature radius of about 160 μm, a width of about 320 μm, a depth of about 170 μm, The distance between the two lenses 4 and the optical fiber 1 was about 1.25 mm.

The first lens 3 provided in the sixth lens-attached fiber 35 has a bending radius of about 1130 μm, the second lens 4 has a curvature radius of about 213 μm, a width of about 400 μm, a depth of about 170 μm, The distance between the two lenses 4 and the optical fiber 1 was about 1.73 mm.
The fifth lens-attached fiber 34 and the sixth lens-attached fiber are set so that the distance between the first lens 3 of the fifth lens-attached fiber 34 and the first lens 3 of the sixth lens-attached fiber 35 is about 720 μm. The connection loss was determined by facing 35 and found to be about 1.32 dB.
[First comparative example]
As a first comparative example, the distance between the two optical fibers 1 was set to about 4.5 mm, spatial propagation was performed without a lens, and the connection loss was determined to be about 30 dB or more.
[Second Comparative Example]
As a second comparative example, two spherical lenses having a refractive index of about 1.57 formed by injection molding at the end of the optical fiber 1 are prepared, and these are made to face each other so that the distance between the lenses is about 600 μm. The connection loss was found to be about 0.7 dB.
[Function check and performance evaluation]
When the lens-attached fibers 30 to 35 of each example are used, the loss is slightly higher than that of the injection molded lens of the second comparative example. However, as compared with the case of the first comparative example without the lens, the first lens 3 and the second lens 4 included in the lens-attached fibers 30 to 35 of the respective examples exhibit the enlargement / condensing function and the connection loss. It became clear that it can be reduced.

In addition, since a positional deviation accuracy in a plane perpendicular to the propagation axis direction can be expected by providing a lens on the distal end side of the optical fiber 1, in each of the above-described embodiments, the positional deviation tolerance between the lens-attached fibers. Measurement was performed by automatic alignment.
As a result, the loss fluctuation amount of the lens-attached fibers 30 to 35 of each example was about 0.6 to about 0.8 dB with respect to the in-plane positional deviation of ± 10 μm. This was almost the same value as the loss variation of about 0.6 dB with respect to the in-plane positional deviation of ± 10 μm in the injection molded lens of the second comparative example.

  Thus, the 1st lens 3 and the 2nd lens 4 with which the fiber 30-35 with a lens of each Example manufactured as the above-mentioned embodiment is equipped with a function as a lens, and connection loss decreases. In addition, it was confirmed that it was also effective for positional deviation.

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Photosensitive film 3 1st lens 4 2nd lens 5 Adhesive (curable resin)
6 groove 10 light shielding film (light shielding pattern)
DESCRIPTION OF SYMBOLS 11 Transparent container 12 Solution 20 Ferrule 21 Optical connector 22 Blade server 23 Mid plane 24 Blade 30 Fiber with 1st lens 31 Fiber with 2nd lens 32 Fiber with 3rd lens 33 Fiber with 4th lens 34 Fiber with 5th lens 35 1st Fiber with 6 lenses

Claims (6)

Optical fiber,
A photosensitive film that is bent so as to cover an end of the optical fiber, and a part on one side and a part on the other side are bonded with the optical fiber interposed therebetween;
A first lens defined by the curved surface of the bent portion of the photosensitive film;
An optical fiber unit comprising: a second lens defined by a difference in refractive index of the photosensitive film.   That one part and the other part of the photosensitive film across the optical fiber are bonded by a curable resin whose refractive index after curing is equal to the refractive index of the photosensitive film after exposure. The optical fiber unit according to claim 1, wherein the optical fiber unit is characterized. Placing the end of the optical fiber on the end of the photosensitive film;
The photosensitive film is bent so as to cover the end of the optical fiber, and the one part and the other part of the photosensitive film are bonded to each other with the optical fiber interposed therebetween, and the bent part of the photosensitive film is bonded. Forming a first lens by the curved surface of
And a step of forming a second lens by changing the refractive index by exposing the photosensitive film.   In the first lens forming step, a curable resin having a refractive index after curing equal to the refractive index of the photosensitive film after exposure is provided on the photosensitive film, and the photosensitive film is covered so as to cover an end portion of the optical fiber. The photosensitive film is bent, the curable resin is cured, and the one side portion and the other side portion of the photosensitive film are bonded to each other with the optical fiber interposed therebetween, and the photosensitive film is bent by the curved surface of the bent portion. The method for manufacturing an optical fiber unit according to claim 3, wherein one lens is formed.   The method of manufacturing an optical fiber unit according to claim 3 or 4, wherein the second lens forming step is performed after the first lens forming step.   5. The method of manufacturing an optical fiber unit according to claim 3, wherein the second lens forming step is performed before the first lens forming step.