Optical Fiber Connection Configuration

Abstract

To provide a GRIN lens that does not require active alignment upon connecting an optical fiber and the GRIN lens.SOLUTION: The present disclosure is an integrated type GRIN lens that comprises: a plurality of GRIN lenses (12) that are arrayed in a preliminarily determined position; a lens holding part (11) that holds the plurality of GRIN lenses; and a plurality of positioning V-grooves (15) that are arranged on both sides of the plurality of GRIN lenses and abut with guide pins.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an integrated GRIN lens.

Background Art

[0002] An integrated GRIN lens in which GRIN lenses (gradient-index lenses) are arranged in an array has been proposed (see, for example, Patent Document 1). By using an integrated GRIN lens, since the material is glass, the compatibility with a glass optical fiber is good, and the core center position of the optical fiber and the center position of the GRIN lens do not shift due to thermal expansion, and the loss does not increase.

[0003] In the space division multiplexing technique for transmitting a plurality of signal lights through a single optical fiber, the optical power density passing through the core of the optical fiber has become extremely large. When the optical power density is high, the end face may be damaged by the light reflected or scattered by small foreign matters, scratches, etc. on the end face of the optical fiber, and a communication failure may occur. Therefore, it is required to reduce the power density at the connection end face of the optical fiber.

[0004] In addition, when performing connection work between opposing optical fibers in a data center or the like, deterioration of connection characteristics due to adhesion of minute dust to the connection end face has become a problem, and it has become an urgent issue to increase the beam diameter at the time of connection to obtain collimated light. For this reason, a method of attaching a GRIN lens to the tip of an optical fiber to widen the beam diameter to obtain collimated light has attracted attention.

[0005] However, unless the optical axis of the optical fiber and the optical axis of the GRIN lens are accurately aligned and connected, even if the light emitted from the GRIN lens becomes collimated light, it is emitted at an angle from the optical axis of the optical fiber. In this case, even if an attempt is made to couple the collimated lights emitted in opposite directions to each other for connecting opposing optical fibers, it is difficult to couple them with low loss.

[0006] To solve this problem, an active alignment technique is commonly used in which light is incident on an optical fiber and the alignment between the optical fiber and the GRIN lens is adjusted while detecting the angle of the collimated light from the GRIN lens so that the optical axes coincide. However, active alignment takes time for alignment and increases costs, which is a very significant drawback in terms of industrial utility value. This drawback is even more prominent especially when multiple optical fibers are arranged.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present disclosure is to provide a GRIN lens that does not require active alignment when connecting an optical fiber and a GRIN lens.

Means for Solving the Problems

[0009] The present disclosure solves the problems of the present disclosure by an integrated GRIN lens in which GRIN lenses are arranged.

[0010] Specifically, the integrated GRIN lens of the present disclosure includes a plurality of GRIN lenses arranged at predetermined positions, a lens holding portion that holds the plurality of GRIN lenses, a plurality of positioning V-grooves that are arranged on both sides of the plurality of GRIN lenses and abut against positioning guide pins, and comprises.

[0011] Specifically, the method for connecting an optical fiber of the present disclosure is causing the positioning V-grooves provided in two integrated GRIN lenses of the present disclosure to abut against a common guide pin, Fix each GRIN lens provided in the integrated GRIN lens to the tip of a different optical fiber for each integrated GRIN lens. Connect the lens holding parts provided in the two integrated GRIN lenses to each other.

[0012] In the present disclosure, the lens holding part is held by a detachable adapter, and the plurality of positioning V-grooves may be formed in the adapter. In this case, the method for connecting the optical fibers of the present disclosure is to bring the positioning V-groove provided in the adapter of the present disclosure into contact with the guide pin, fix each GRIN lens provided in the integrated GRIN lens to the tip of the optical fiber, and then remove the adapter from the integrated GRIN lens.

Advantages of the Invention

[0013] Since the integrated GRIN lens of the present disclosure is provided with a plurality of positioning V-grooves, the optical axes of the optical fiber and the GRIN lens can be aligned and connected simply by bringing them into contact with the positioning guide pins. Therefore, the present disclosure can provide a GRIN lens that does not require active alignment when connecting the optical fiber and the GRIN lens.

[0014] Furthermore, since the integrated GRIN lens of the present disclosure can easily align and connect the optical fiber and the GRIN lens and emit collimated light parallel to the optical axes of the optical fiber and the GRIN lens, it is possible to reduce the power density at the connection end face of the opposing optical fibers and eliminate the influence of connection loss due to dust adhesion on the connector end face.

Brief Description of the Drawings

[0015]

Figure 1

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Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These examples are merely illustrative, and the present disclosure can be implemented in various modified forms based on the knowledge of those skilled in the art. In the present specification and drawings, components having the same reference numerals indicate the same components as each other.

[0017] (First Embodiment) FIG. 18 shows an example of a connection configuration of an optical fiber according to an embodiment of the present disclosure. The optical fiber connection method of the present disclosure includes a lens fixing procedure for adhesively fixing integrated GRIN lenses 23-1 and 23-2 to the tips of optical fibers 21 and 25, respectively, and a lens connection procedure for connecting the integrated GRIN lenses 23-1 and 23-2.

[0018] In the lens fixing procedure, for example, the integrated GRIN lens 23-1 is brought into contact with the guide pin 14, and each GRIN lens 12 provided in the integrated GRIN lens 23-1 is adhesively fixed to the optical fiber array 22 in which the optical fiber 21 is arranged. Similarly, when adhesively fixing the integrated GRIN lens 23-2 to the tip of the optical fiber 25, the integrated GRIN lens 23-2 is adhesively fixed to the optical fiber array 24.

[0019] In the lens connection procedure, the integrated GRIN lenses 23-1 and 23-2 are connected. At this time, a spacer 26 for adjusting the optical path lengths of the integrated GRIN lenses 23-1 and 23-2 may be disposed between the integrated GRIN lenses 23-1 and 23-2.

[0020] The number of the optical fibers 21 can be any number of 2 or more. The intervals between the optical fibers 21 are arbitrary and may be equal intervals or unequal intervals. Also, the optical fibers 21 may be in one row or two or more rows. Further, the optical fiber arrays 22 and 24 may be those in which the optical fibers 21 and 24 shown in Fig. 18(a) are fixed with V-grooves, or may be those in which the optical fibers 21 and 24 as shown in Fig. 18(b) are fixed in an arbitrary housing. Also, the optical fiber 21 may be a single-mode fiber or a multi-mode fiber, but in the following embodiments, the case where the optical fibers 21 and 24 are multi-mode fibers will be described. Hereinafter, the integrated GRIN lens of the present disclosure will be described in detail.

[0021] Fig. 1 shows an example of the integrated GRIN lens of the present embodiment. In the integrated GRIN lens of the present disclosure, a plurality of GRIN lenses (refractive index distribution type lenses) 12 are arranged. The number of the GRIN lenses 12 can be any number of 2 or more, but in the present embodiment, an example of 8 is shown.

[0022] In the present embodiment, the GRIN lens 12 is embedded in a lens holding portion 11 made of glass and integrally formed. This configuration can be produced, for example, by arranging the matrix of the GRIN lens 12 on a quartz glass rod and stretching them. Thereby, the GRIN lens 12 can be arranged with high precision. Note that the lens holding portion 11 is not limited to quartz glass and may be an inorganic glass containing any component.

[0023] Also, when the lens holding portion 11 is an inorganic glass, the compatibility with many glass optical fibers is good, and the core center position of the optical fiber and the center position of the GRIN lens do not shift due to thermal expansion and the loss does not increase.

[0024] The GRIN lens 12 of this embodiment has an arbitrary lens length that expands and emits the beam diameter of the connected optical fiber. For example, by having a lens length of 1 / 4 pitch for the GRIN lens 12 of this embodiment, the beam diameter of the optical fiber can be expanded to a beam diameter corresponding to the GRIN lens diameter of the GRIN lens 12, and collimated light can be emitted. Here, the lens length of the GRIN lens 12 of the present disclosure is not limited to 1 / 4 pitch, and may be slightly longer than 1 / 4 pitch so as to be slightly focused toward the GRIN lens 12 arranged opposite. In this way, by having the lens length of the GRIN lens 12 be approximately 1 / 4 pitch, collimated light (parallel beam) can be emitted / incident by expanding the beam diameter from the end face of the GRIN lens 12.

[0025] Also, the GRIN lens 12 of the integrated GRIN lens 23-1 expands the beam diameter of the connected optical fiber 21, is focused by the GRIN lens 12 of the integrated GRIN lens 23-2 facing it, and is incident on the connected optical fiber 15. At this time, it is known that the connection loss between the GRIN lenses greatly depends on the beam diameter.

[0026] Here, the ray trajectory of the GRIN lens 12 is represented by the following Equation 1.

Equation

[0027] Substituting the condition for collimated light, gz = 1 / 4π + nπ, and assuming that (r0 = 0) is incident on the center of the GRIN lens 12, Equation 1 becomes

Equation

[0028] Therefore, from Equation 2, it can be understood that by reducing the central refractive index n0 of the GRIN lens 12 and reducing the g value, the beam diameter of the collimated light can be increased and the transmission loss between the lenses can be reduced.

[0029] The GRIN lens 12 of this embodiment is a quartz-based GRIN lens and has a lower central refractive index than a multi-component ion-exchange type GRIN lens. In addition, for a quartz-based GRIN lens, by drawing the GRIN lens base material and changing the GRIN lens diameter, a GRIN lens having a desired g value can be manufactured.

[0030] Assuming that the GRIN lens diameter thinned by drawing is r and the refractive index of the outer diameter is n(r), the g value is expressed by the following equation.

Equation

[0031] Here, the n0 value of a general GRIN lens base material made by doping Ge into quartz (n = 1.457) is about 1.475. The GRIN lens diameter r is set to be larger than the core diameter (62.5 μm) of the optical fiber 21 or 25 and smaller than the pitch interval (250 μm) of the optical fiber array 22 or 24 in order to be larger than the emission diameter of the optical fiber.

[0032] From the above, when substituting into Equation 3, the g value ranges from 1.25 to 4.98. By setting an appropriate g value, it is easy to expand the beam diameter, which is the object of the present disclosure, and reduce the transmission loss. Although a GRIN lens doped with Ge in quartz is shown in this embodiment, an appropriate g value can be set in the same manner with other compositions by the above method.

[0033] Here, a spacer 26 is disposed between the integrated GRIN lenses 23-1 and 23-2. The spacer 26 is filled with a transparent body so that no space is created between each GRIN lens 12 provided in the integrated GRIN lens 23-1 and each GRIN lens 12 provided in the integrated GRIN lens 23-2. For example, transparent glass can be exemplified. As a result, in this embodiment, since the optical path from the GRIN lens 12 provided in the integrated GRIN lens 23-1 to the GRIN lens 12 provided in the integrated GRIN lens 23-2 is confined in the glass, it has a lens action even though both end faces thereof are flat, and the beam diameter is expanded from the end faces without any loss of its lens function in any liquid or gas with a refractive index in air, and collimated light (parallel beam) can be emitted / incident.

[0034] Note that the spacer 26 is, for example, a transparent body 261 as shown in FIG. 2(a). As shown in FIG. 2(b), the spacer 26 only needs to be a transparent body 262 between each GRIN lens 12 provided in the integrated GRIN lens 23-1 and each GRIN lens 12 provided in the integrated GRIN lens 23-2, and the other regions 261 may block light between the transparent bodies 262. Also, as shown in FIG. 2(c), the spacer 26 may be merely a space 263 between each GRIN lens 12, and may have a structure formed of a frame having the same shape as the outer periphery of the integrated GRIN lens 23 so as to have only a function of keeping the distance between the two integrated GRIN lenses constant.

[0035] The lens holding portion 11 is provided with two positioning V-grooves 15 that come into contact with the guide pins 14. The two positioning V-grooves 15 are arranged at predetermined positions with respect to the GRIN lens 12. For example, the positioning V-groove 15 of the lens holding portion 11 provided in the integrated GRIN lens 23-1 is arranged at a position where each GRIN lens 12 is connected to the optical fiber 21 when it comes into contact with the guide pin 14. The same applies to the positioning V-groove 15 of the integrated GRIN lens 23-2. Thereby, by pressing the integrated GRIN lens 23 against the guide pin 14 from below or above, the optical fibers 21 and 25 can be connected with high precision.

[0036] As shown in FIG. 3, the lens holding portion 11 may be held by a detachable adapter 13. FIG. 3(a) shows a cross-sectional structure perpendicular to the guide pin 14, and FIG. 3(b) shows an A-A cross-sectional structure. 11S is the surface on the spacer 26 side, and 11A is the surface on the optical fiber array 22 or 24 side. The adapter 13 can be composed of any member, and can be composed of a resin such as Teflon (registered trademark).

[0037] In FIG. 3, an example is shown in which the adapter 13 has a through hole for arranging the lens holding portion 11, and the lens holding portion 11 is held in the through hole. When this configuration is adopted, the lens holding portion 11 is pressed against the guide pin 14 from below (FIG. 3(a)), and after the lens holding portion 11 and each GRIN lens 12 are adhered to the tip of the optical fiber array 22 or 24, the adapter 13 is pulled out toward the spacer 26 side (FIG. 3(b)), and the adapter 13 can be removed. Thereby, in this embodiment, it is possible to prevent the adhesive from hitting the guide pin 14, and the integrated GRIN lens 23 can be made smaller. Note that the lens holding portion 11 may be held by the adapter 13 in advance, or the lens holding portion 11 may be attached to the adapter 13 when fixing to the optical fiber array 22 or 24. Note that the adapter 13 may be left without being removed after being adhered to the tip of the optical fiber array 22 or 24.

[0038] In FIG. 3(b), an example is shown in which the thickness T13 of the adapter 13 is the same as the thickness T11 of the lens holding portion 11, but the thickness T13 of the adapter 13 may be larger than T11. For example, as shown in FIG. 4, the thickness T13 may be equal to or greater than the thicknesses of the lens holding portion 11 and the spacer 26. In the case of this configuration, the spacer 26 is made to have the same shape as the lens holding portion 11, and these are adhered in advance, and the spacer 26 and the lens holding portion 11 are held by the adapter 13. Thereby, the spacer 26 and the lens holding portion 11 can be miniaturized and lightened. Note that FIG. 4 shows an example in which the spacer 26 is a transparent body, but as described above, a space may be adopted.

[0039] FIG. 5 shows another example of the A-A cross-sectional configuration of the lens holding portion 11 shown in FIG. 3. In FIG. 5, it is closed from the surface of the adapter 13 on the side of the optical fiber array 22 or 24 toward the surface of the spacer 26. In this way, the portion of the lens holding portion 11 that contacts the adapter 13 has a taper in the thickness direction of the lens holding portion 11. Thereby, in the present embodiment, the adapter 13 can be easily removed.

[0040] FIG. 6 shows an example of the attachment / detachment configuration of the lens holding portion 11. The adapter 13 is provided with a notch 34 for arranging the lens holding portion 11, and the lens holding portion 11 is detachably held in the notch 34. From the viewpoint of attachment / detachment, the shapes of the notch 34 and the lens holding portion 11 can adopt a shape that widens as it approaches the outer edge of the adapter 13 such as a trapezoid.

[0041] When this configuration is adopted, the lens holding portion 11 is arranged in the notch 34 (FIG. 6(a)), the adapter 13 is pressed against the guide pin 14 from below (FIG. 6(b)), and after the lens holding portion 11 and each GRIN lens 12 are adhered to the tip of the optical fiber array 22 or 24, the adapter 13 can be removed by pulling it downward (FIG. 6(c)).

[0042] FIG. 7 shows an example of the attachment / detachment configuration of the lens holding portion 11. The adapter 13 is provided with a through hole 31 for arranging the lens holding portion 11, and the lens holding portion 11 is provided with an engaging portion that engages at a predetermined position of the through hole 31. The engaging portion arranges the GRIN lenses 12 at predetermined positions with respect to the guide pin 14. For example, the lens holding portion 11 is provided with a convex portion 32 that protrudes in a direction parallel to the straight line connecting two positioning V-grooves 15, and the through hole 31 is provided with a notch 33 that engages with the convex portion 32.

[0043] When this configuration is adopted, when the lens holding portion 11 is disposed in the through hole 31 such that the convex portion 32 and the notch 33 are engaged (FIG. 7(a)), a plurality of GRIN lenses 12 are arranged at predetermined positions with respect to the positioning V-groove 15. In this state, the adapter 13 is pressed against the guide pin 14 from below (FIG. 7(b)). After the lens holding portion 11 and each GRIN lens 12 are adhered to the tip of the optical fiber array 22 or 24, the adapter 13 can be removed by pulling it downward (FIG. 7(c)). Thereby, even when the through hole 31 is enlarged so that the lens holding portion 11 can be easily attached and detached, the GRIN lens 12 can be arranged at a fixed position with respect to the adapter 13.

[0044] As shown in FIG. 8, the notch 34 and the lens holding portion 11 shown in FIG. 6 may include a convex portion 32 and a notch 33 that engage with each other at a predetermined position.

[0045] Note that the shapes of the convex portion 32 and the notch 33 in FIGS. 7 and 8 are arbitrary and are not limited to triangles but may be polygons. Further, the through hole 31 may include a convex portion, and the lens holding portion 11 may include a notch that engages with the convex portion. Furthermore, in the present disclosure, as shown in FIG. 9, the GRIN lenses 12 may be two-dimensionally arranged.

[0046] (Second Embodiment) FIG. 10 shows an example of the integrated GRIN lens of the present embodiment. In the first embodiment, the integrated configuration in which the GRIN lens 12 is embedded in the lens holding portion 11 is provided. In the present embodiment, the assembled configuration in which the GRIN lens 12 is fixed with the adhesive 42 in the alignment V-groove 41 provided in the lens holding portion 11 is provided.

[0047] When this configuration is adopted, the GRIN lens 12 is disposed in the alignment V-groove 41 of the lens holding portion 11, and while the GRIN lens 12 is pressed by the lid 43, the GRIN lens 12 is fixed with the adhesive 42. Then, the lens holding portion 11 is pressed against the guide pin 14 from below, and the lens holding portion 11 and the GRIN lens 12 are adhesively fixed to the end face of the optical fiber array 22 or 24.

[0048] Note that the fixing of the GRIN lens 12 to the lens holding portion 11 may be performed at the time of mounting on the end face of the optical fiber array 22 or 24, or may be performed in advance before this mounting. In this case, the lens holding portion 11 may not include the alignment V-groove 41 for arranging the GRIN lens 12. For example, an alignment V-groove arranged at the same position as the alignment V-groove 41 may be prepared separately from the lens holding portion 11, and the GRIN lens 12 may be aligned using this, and in that state, the GRIN lens 12 may be fixed to the lens holding portion 11 with an adhesive.

[0049] FIG. 10 shows an example in which the lid 43 is arranged between the guide pins 14, but the present disclosure is not limited to this. For example, as shown in FIG. 11, the lid 43 is lengthened across the guide pins 14. Thereby, the adhesion area of the lid 43 can be widened. The width W43 of the lid 43 is arbitrary, but for example, it may be the same as the width W11 of the lens holding portion 11.

[0050] FIGS. 10 and 11 show an example in which the surface of the lid 43 in contact with the GRIN lens 12 is flat, but the present disclosure is not limited to this. For example, as shown in FIG. 12, the surface of the lid 43 may also be provided with an alignment V-groove 44 that supports the GRIN lens 12 on two surfaces. Thereby, the interval between the GRIN lenses 12 can be made more accurate.

[0051] Here, in the case of this configuration, a configuration for preventing the adhesive used for fixing the lid 43 and the lens holding portion 11 from reaching the guide pins 14 may be provided in at least one of the lid 43 or the lens holding portion 11. For example, a liquid reservoir 45 is provided in at least one of the lid 43 or the lens holding portion 11.

[0052] As shown in FIG. 12, the shape for arranging the guide pin 14 in the lid 43 may be a positioning V-groove. In this case, the positioning V-groove for arranging the guide pin 14 in the lid 43 is configured not to contact the guide pin 14. Further, as shown in FIG. 13, the shape for arranging the guide pin 14 in the lens holding portion 11 and the lid 43 may be a tapered shape with one side widened so as to facilitate passing the guide pin 14 therethrough.

[0053] Note that, in FIGS. 10 to 13, an example in which one GRIN lens 12 is fixed to each alignment V-groove 41 is shown, but the present disclosure is not limited thereto. For example, as shown in FIG. 14, two or more GRIN lenses 12 may be fixed to the alignment V-groove 41.

[0054] (Third Embodiment) FIG. 15 shows an example of the integrated GRIN lens 23-1 and the spacer 26 of the present embodiment. In the present embodiment, a wavelength filter 51 is provided between the integrated GRIN lens 23-1 and the spacer 26. The wavelength filter 51 has a function of transmitting light of a specific wavelength corresponding to the GRIN lens 12, and they may all be different or some of them may have a common wavelength.

[0055] The wavelength filter 51 is fixed in advance on the surface of the spacer 26, and the integrated GRIN lens 23-1, the spacer 26, and the integrated GRIN lens 23-2 are connected. Thereby, a WDM filter can be configured only by connecting the optical fiber arrays 22 and 24.

[0056] FIG. 16 shows a further application example to the WDM filter. In this example, a wavelength filter 51 is arranged between the spacer 26 and the integrated GRIN lens 23-2, and a mirror 52 is arranged on the surface of the spacer 26 facing the wavelength filter 51. The wavelength filter 51 and the mirror 52 are fixed to the spacer 26 in advance.

[0057] An example of a ray trajectory for the WDM filter shown in FIG. 16 is shown in FIG. 17. The optical fiber 25-1 is connected to a position deviated from the center of the GRIN lens 12A. The light incident on the GRIN lens 12B from the optical fiber 25-1 is obliquely incident on the spacer 26 and reflected by the mirror 52 toward the wavelength filter 51B. The light transmitted through the wavelength filter 51B passes through the GRIN lens 12A and is incident on the optical fiber 25-2. A part of the light incident on the GRIN lens 12B is reflected by the wavelength filter 51B. The light reflected by the wavelength filter 51B is reflected by the mirror 52 toward the wavelength filter 51C. By repeating these, the light transmitted through the wavelength filters 51B to 51E is incident on the optical fibers 25-2 to 25-5, respectively. By adopting this, wavelength division multiplexing can be performed.

[0058] In the above-described embodiment, an example of aligning the GRIN lens 12 by bringing the positioning V-groove 15 into contact with the guide pin 14 has been shown. However, instead of the positioning V-groove 15, the GRIN lens 12 may be aligned using a guide pin hole with high positioning accuracy.

Industrial Applicability

[0059] The present disclosure can be applied to any optical connection of a plurality of optical fibers and is extremely valuable industrially.

Explanation of Signs

[0060] 11: Lens holding part 12: GRIN lens (graded index lens) 13: Adapter 14: Guide pin 15: Positioning V-groove 21, 25: Optical fiber 22, 24, 122, 124: Optical fiber array 23, 23-1, 23-2: Integrated GRIN lens 26: Spacer 31: Through hole 32: Protrusion 33, 34: Notch 41, 44: V-grooves for alignment 42: Adhesive 43: Lid 45: Liquid pool 51: Wavelength filter 52: Mirror 261: Region other than the transparent body in the spacer 262: Transparent body 263: Space

Claims

1. A first and a second optical fiber array, guide pins for aligning a first plurality of optical fibers arranged in the first optical fiber array and a second plurality of optical fibers arranged in the second optical fiber array with each other, a first plurality of quartz-based GRIN lenses made of quartz glass, arranged at positions connectable to the first plurality of optical fibers, a first lens holding part made of quartz glass for holding the first plurality of quartz-based GRIN lenses, a second plurality of quartz-based GRIN lenses made of quartz glass, arranged at positions connectable to the second plurality of optical fibers, a second lens holding part made of quartz glass for holding the second plurality of quartz-based GRIN lenses, a spacer made of glass for adjusting the optical path lengths of the first plurality of quartz-based GRIN lenses and the second plurality of quartz-based GRIN lenses, comprising: an optical fiber connection configuration usable in liquids and gases with any refractive index, the first plurality of quartz-based GRIN lenses and the first lens holding part are integrally formed of quartz glass, and the second plurality of quartz-based GRIN lenses and the second lens holding part are integrally formed of quartz glass, the first lens holding part, the spacer, and the second lens holding part are provided with positioning V-grooves for arranging the first plurality of quartz-based GRIN lenses at positions where the first plurality of quartz-based GRIN lenses are connected to the first plurality of optical fibers, at positions where the positioning V-grooves provided in the first lens holding part or the second lens holding part abut against the guide pins and the positioning V-grooves provided in the spacer, the first lens holding part or the second lens holding part and the spacer are fixed in advance, by abutting the positioning V-grooves against the guide pins, alignment of the first plurality of quartz-based GRIN lenses and the second plurality of quartz-based GRIN lenses with the first plurality of optical fibers and the second plurality of optical fibers is possible, the optical paths of the first plurality of quartz-based GRIN lenses, the spacer, and the second plurality of quartz-based GRIN lenses are confined in the glass of the first plurality of quartz-based GRIN lenses, the glass of the spacer, and the glass of the second plurality of quartz-based GRIN lenses, an optical fiber connection configuration.

2. The plurality of first quartz-based GRIN lenses have their g-values set by changing the GRIN lens diameter, and have a length such that they are focused toward the plurality of second quartz-based GRIN lenses. The optical fiber connection configuration according to claim 1.

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