OPTICAL CONNECTOR, OPTICAL CONNECTOR CONNECTING STRUCTURE, AND OPTICAL PACKAGING CIRCUIT

Abstract

[Problem] To provide an optical connector, an optical connector connecting structure, and an optical packaging circuit, with which it is possible to, in high-density packaging of optical fibers, prevent spring force required for the connector from increasing and achieve size reduction.

[Solution] This optical connector is provided with: a first ferrule 110 having a first end surface 112 in which an optical fiber insertion hole 114 into which an optical fiber 30 is inserted and a pair of guide pin insertion holes 116 into which a pair of guide pins 40 are inserted are formed; and a plate-shaped lens holding member 200 bonded to the first end surface 112 of the first ferrule 110 via a refractive index matching adhesive layer. The lens holding member 200 has a member main body 210 and a GRIN lens 250 provided on the member main body 210, and the GRIN lens 250 is optically coupled to the optical fiber 30.

Claims

1. An optical connector comprising: a first ferrule including a first end surface provided with optical fiber insertion holes into which optical fibers are inserted, and with a pair of guide pin insertion holes into which a pair of guide pins are inserted; a plate-shaped lens holding member bonded to the first end surface of the first ferrule via a refractive index matching adhesive layer; and a spacer provided on an opposite side of the first end surface of the lens holding member, wherein the lens holding member includes a member main body and GRIN lenses provided on the member main body, wherein the spacer includes a light guide portion that allows light transmitted through the GRIN lenses to pass, and wherein the GRIN lenses are optically coupled to the optical fibers.

2. The optical connector according to claim 1, wherein the light guide portion of the spacer has a refractive index of 1.2 or more to 1.6 or less.

3. The optical connector according to claim 1, wherein the light guide portion includes an opening filled with fluorinated refrigerant.

4. The optical connector according to claim 1, wherein the spacer includes a frame body, and the frame body includes two or more flow paths.

5. The optical connector according to claim 1, wherein the first end surface of the first ferrule and/or the member main body of the lens holding member is provided with a refractive index matching adhesive resin pool concave portion or convex portion.

6. An optical connector connecting structure comprising: a first ferrule including a first end surface provided with optical fiber insertion holes into which optical fibers are inserted, and with a pair of guide pin insertion holes into which a pair of guide pins are inserted; a plate-shaped lens holding member bonded to the first end surface of the first ferrule via a refractive index matching adhesive layer; a second optical connector disposed to be opposed to the first end surface of the first ferrule; and a spacer including a light guide portion disposed between the lens holding member and the second optical connector, the light guide portion being configured to allow light to pass between the lens holding member and the second optical connector, wherein the lens holding member includes a plate-shaped member main body and GRIN lenses provided on the member main body, and wherein the GRIN lenses are aligned with an end surface of the optical fibers inserted into the optical fiber insertion holes.

7. The optical connector connecting structure according to claim 6, wherein the second optical connector includes a second ferrule including a second end surface, and wherein the second end surface of the second ferrule is provided with optical fiber insertion holes into which optical fibers are inserted, and with a pair of guide pin insertion holes into which a pair of guide pins are inserted.

8. An optical packaging circuit comprising: a refrigerant tank containing refrigerant; and an electronic component, the electronic component being immersed in the refrigerant contained in the refrigerant tank, wherein an optical connector to be connected to the electronic component includes: a first ferrule including a first end surface provided with optical fiber insertion holes into which the optical fibers are inserted, and with a pair of guide pin insertion holes into which a pair of guide pins are inserted; and a plate-shaped lens holding member bonded to the first end surface of the first ferrule via a refractive index matching adhesive layer, wherein the lens holding member includes a member main body and GRIN lenses provided on the member main body, and wherein the GRIN lenses are aligned with end surfaces of the optical fibers inserted into the optical fiber insertion holes.

9. The optical packaging circuit according to claim 8, wherein the lens holding member includes a first surface corresponding to the first end surface of the first ferrule, and a second surface on an opposite side of the first surface, and a spacer is disposed on the second surface of the lens holding member, wherein the spacer includes an opening through which light transmitted through the GRIN lenses are allowed to pass, and wherein the opening is filled with the refrigerant.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0077] FIG. 1 is an exploded perspective view of an optical connector connecting structure according to a first embodiment.

[0078] FIG. 2 is an exploded plan view of the optical connector connecting structure illustrated in FIG. 1.

[0079] FIG. 3 is an exploded front view of the optical connector connecting structure illustrated in FIG. 1.

[0080] FIG. 4 is a plan view of the optical connector connecting structure illustrated in FIG. 1.

[0081] FIG. 5 illustrates a front view, a plan view, a bottom view, a left side view, and a right side view of a ferrule used in the optical connector connecting structure illustrated in FIG. 1.

[0082] FIG. 6 is a schematic explanatory view of a lens holding member according to the first embodiment.

[0083] FIG. 7 is a schematic perspective view illustrating the lens holding member according to the first embodiment.

[0084] FIG. 8 is a reference sectional view (sectional view taken along A-A in FIG. 4) illustrating an operation of an optical connector and a light beam.

[0085] FIG. 9 is a schematic perspective view illustrating a lens holding member according to another embodiment.

[0086] FIG. 10 is a schematic perspective view illustrating a lens holding member according to still another embodiment.

[0087] FIG. 11 is a schematic perspective view illustrating a spacer according to the first embodiment.

[0088] FIG. 12 is a schematic perspective view illustrating a spacer according to another embodiment.

[0089] FIG. 13 is a schematic perspective view illustrating a spacer according to still another embodiment.

[0090] FIG. 14 is a schematic perspective view illustrating a spacer according to still one more embodiment.

[0091] FIG. 15 is a schematic perspective view illustrating a spacer according to still one more embodiment.

[0092] FIG. 16 a schematic perspective view illustrating a spacer according to still one more embodiment.

[0093] FIG. 17 is a schematic perspective view illustrating a spacer according to still one more embodiment.

[0094] FIG. 18 is a schematic perspective view illustrating a spacer according to still one more embodiment.

DESCRIPTION OF EMBODIMENTS

[0095] Embodiments of the present invention will be described below with reference to the drawings. A plurality of embodiments are described as embodiments of the present invention. However, each embodiment may be carried out singly or in combination of one or more embodiments.

[0096] In the following description, the same components are denoted by the same reference numerals. The same components have the same names and functions. Accordingly, repeated detailed descriptions thereof are omitted.

First Embodiment

(Optical Connector Connecting Structure 1)

[0097] FIG. 1 is an exploded perspective view illustrating the optical connector connecting structure 1 according to one embodiment. FIG. 2 is an exploded plan view illustrating the optical connector connecting structure 1. FIG. 3 is an exploded front view of the optical connector connecting structure 1.

[0098] As illustrated in FIGS. 1 to 3 and FIG. 6, the optical connector connecting structure 1 according to the present embodiment includes a first ferrule 110, a plate-shaped lens holding member 200 that is bonded to a first end surface 112 of the first ferrule 110 via a refractive index matching adhesive layer (not illustrated), a second optical connector 20 disposed to be opposed to the first end surface 112 of the first ferrule 110, and a spacer 300 including a light guide portion 310 that is disposed between the lens holding member 200 and the second optical connector 20 and is configured to allow light to pass between the lens holding member 200 and the second optical connector 20.

[0099] As illustrated in FIGS. 1 to 5, a first optical connector 10 according to the present embodiment includes the first ferrule 110 including the first end surface 112 provided with optical fiber insertion holes 114 into which optical fibers 30 are inserted, and with a pair of guide pin insertion holes 116 into which a pair of guide pins 40 are inserted, and the plate-shaped lens holding member 200 bonded to the first end surface 112 of the first ferrule 110 via the refractive index matching adhesive layer.

[0100] The second optical connector 20 can include a second ferrule 120, and the plate-shaped lens holding member 200 bonded to a second end surface 122 of the second ferrule 120 via the refractive index matching adhesive layer. In this case, the optical connector connecting structure 1 includes the first ferrule 110 and the second ferrule 120, which are connected to each other, the first lens holding member 200 disposed between the first and second ferrules 110 and 120, a second lens holding member 200, and the spacer 300.

(Refractive Index Matching Adhesive Layer)

[0101] A refractive index matching adhesive used for the refractive index matching adhesive layer preferably has a refractive index after curing of 1.4 or more to 1.5 or less, and more preferably, 1.45 or more to 1.48 or less. With this configuration, a connection loss between the optical fiber 30 and each GRIN lens 250 can be minimized and the generation of reflected light can be minimized.

[0102] Acrylic or epoxy optical adhesive can be used as the refractive index matching adhesive for the refractive index matching adhesive layer. The refractive index matching adhesive may be a thermosetting adhesive or a UV-curable adhesive. If an opaque member is present, it is preferable to use a thermosetting adhesive. If a heat-sensitive member is present, it is preferable to use a UV-curable adhesive. With this configuration, the connection loss between the optical fiber 30 and the GRIN lens 250 can be minimized and the generation of reflected light can be minimized.

(Ferrules)

[0103] The first and second ferrules 110 and 120 each have a substantially rectangular parallelepiped appearance, and is formed by, for example, resin. The first and second ferrules 110 and 120 may be formed of formable resin such as polyphenylene sulfide or liquid crystal polymer (LCP). The resin may contain additives such as silica (S.sub.iO.sub.2) to increase the strength and stability of the resin. The first and second ferrules 110 and 120 may be formed of an inorganic material such as ceramics.

[0104] The first and second ferrules 110 and 120 respectively include the first end surface 112 and the second end surface 112, which are flat surfaces provided on one end in a connecting direction, and back end surfaces 113 and 123, which are provided on the other end. The first and second ferrules 110 and 120 include a pair of side surfaces extending along the connecting direction, a bottom surface, and a top surface.

[0105] The first end surface 112 of the first ferrule 110 and the second end surface 112 of the second ferrule 120 are disposed to be opposed to each other.

[0106] The first end surface 112 and the second end surface 122 are each provided with a pair of guide pin insertion holes (guide holes) 116 arranged in a direction crossing a cross section along an optical axis of each optical fiber 30. The pair of guide pins 40, 40 are inserted into the pair of guide pin insertion holes 116, respectively. In other words, relative positions of the first ferrule 110 and the second ferrule 120 are determined by the pair of guide pins 40, 40.

[0107] The first end surface 112 is provided with the plurality of optical fiber insertion holes 114 into which the optical fibers 30 are inserted. The back end surface 113 of each of the first and second ferrules 110 and 120 is provided with an introduction hole 117 that receives a ribbon fiber formed of the plurality of optical fibers 30 (FIG. 5(d)).

[0108] The plurality of optical fiber insertion holes 114 are formed to penetrate from the first end surface 112 to the introduction holes 117. The optical fibers 30 are inserted and held in the optical fiber insertion holes 114, respectively.

[0109] Each optical fiber 30 extends along the connecting direction and are aligned in a row in a horizontal direction crossing the connecting direction. The number of optical fiber insertion holes 114 can be determined depending on the intended use. Only one optical fiber insertion hole 114 (in this case, a single-core ferrule) may be provided, or a plurality of optical fiber insertion holes 114 (in this case, a multi-fiber ferrule) may be provided. The present embodiment illustrates an example of a multi-fiber MT ferrule, such as 12-core, or 16-core MT ferrule, in which the optical fibers 30 are aligned in a row.

[0110] Each optical fiber 30 according to the present embodiment includes a bare optical fiber and a resin coating that covers the bare optical fiber. The resin coating from a middle portion to a tip end in the connecting direction is removed to thereby expose the bare optical fiber.

[0111] The bare optical fibers are held in the optical fiber insertion holes 114, respectively. The tip end of each bare optical fiber is exposed from the first end surface 112. For example, the bare optical fiber flushes with the first end surface 112, or slightly protrudes from the first end surface. In the present invention, the bare optical fiber is also simply referred to as the optical fiber 30.

[0112] In the present embodiment, each optical fiber insertion hole 114 has an inner diameter of 125.5 ?m or more to 127.5 ?m or less, and a multi-mode fiber having an outer diameter of 125 ?m is used as a bare optical fiber. In this case, the core diameter of each optical fiber 30 is 50 ?m.

[0113] The present embodiment illustrates a case where a multi-mode optical fiber having a cladding diameter of 125 ?m is used to transmit an optical signal having a wavelength of 1300 nm. However, each optical fiber 30 may have a cladding diameter of 80 ?m or the like, and may be a multi-mode or single-mode fiber. The wavelength of the optical signal can also be appropriately selected depending on the intended use. For example, a multi-mode fiber (thin cladding fiber) having a core diameter of 50 ?m and a cladding diameter of 80 ?m can be used, or a single-mode fiber having a core diameter of 10 ?m and a cladding diameter of 80 ?m or 125 ?m can be used. In this case, the inner diameter of each optical fiber insertion hole 114, the design of the GRIN lens 250, physical properties of refrigerant, and the like can be appropriately selected depending on the selected optical fiber or optical signal.

(Lens Holding Member 200)

[0114] The first end surface 112 of the first ferrule 110 and the second end surface 122 of the second ferrule 120 are provided with plate-shaped lens holding members 200, 200, respectively.

[0115] The lens holding member 200 includes a plurality of GRIN lenses 250 that diffuse and collimate light output from each optical fiber 30 of the first ferrule 110. The GRIN lenses 250 are respectively held in holding holes 220 that are formed in the lens holding member 200. The lens holding member 200 disposed on the second ferrule 120 includes a plurality of GRIN lenses 250 that collect light beams that have transmitted the light guide portion 310 of the spacer 300. Each GRIN lens 250 is held in the corresponding holding hole 220 formed in the lens holding member 200.

[0116] An array pitch of the GRIN lenses 250 is set to be equal to an array pitch of the optical fibers 30 held in the first and second ferrules 110 and 120. The GRIN lenses 250 are arrayed so as to correspond to the optical fibers 30, respectively, and the GRIN lenses 250 and the optical fibers 30 are optically connected.

[0117] Each GRIN lens 250 has a cylindrical shape and is disposed such that the central axis of the cylindrical shape matches the central axis of the corresponding optical fiber 30. Each optical fiber 30 according to the present embodiment is a multi-mode fiber having an outer diameter of 125 ?m and a core diameter of 50 ?m. In this case, the outer diameter of each GRIN lens 250 is preferably 130 ?m or more to 300 ?m or less, more preferably, 150 ?m or more to 250 ?m or less, and much more preferably, 180 ?m or more to 220 ?m or less.

[0118] With this configuration, the multi-mode beam having a diameter of 50 ?m is enlarged to a diameter of 100 ?m to 120 ?m and is collimated and transmitted. This makes it possible to reduce insertion loss due to foreign matter or the like on the connecting portion. The beam on which a communication signal is superimposed can be collimated by the GRIN lens 250 and a signal can be transmitted in a contactless manner between the first and second ferrules 110 and 120. Consequently, the optical connector can be miniaturized without the need for providing a strong physical contact force to connect high-density optical fibers.

[0119] Unlike in an optical system using a conventional spherical lens, the stable enlarged beam can be achieved in the immersed state without the influence of refrigerant also in the case of using the optical connector for an immersion processor, and the optical connector with high transmission efficiency can be achieved.

[0120] As illustrated in FIG. 6 and FIG. 7, the lens holding member 200 is formed into a plate shape including a first surface 202 opposed to the first end surface 112, a second surface 204 located on the opposite side of the first surface 202, and an outer peripheral surface 206 that connects the first surface 202 and the second surface 204.

[0121] Both ends of the lens holding member 200 are provided with guide holes 224 into which the guide pins 40 that penetrate from the first surface 202 to the second surface 204 are inserted. The interval between the pair of guide holes 224, 224 that are formed in the lens holding member 200 is set to be equal to the interval between the pair of guide pin insertion holes 116, 116 that are formed in the end surface of the first ferrule 110.

[0122] The lens holding member 200 according to the present embodiment will be described in detail below.

[0123] The lens holding member 200 includes a horizontally-long plate-shaped member main body 210 and the GRIN lenses 250 provided on the member main body 210.

[0124] The member main body 210 has a configuration in which a lower-side plate member 212 elongated in a lateral direction (horizontal direction) and an upper-side plate member 214 elongated in the lateral direction (horizontal direction) are vertically joined together. To join the lower-side plate member 212 and the upper-side plate member 214, the lower-side plate member 212 and the upper-side plate member 214 may be bonded with adhesive.

[0125] The holding holes 220 for holding the GRIN lenses 250 are formed between an upper surface (joint surface) of the lower-side plate member 212 and a lower surface (joint surface) of the upper-side plate member 214. Specifically, concave portions 216 are formed in the joint surface of the lower-side plate member 212, and the joint surface of the upper-side plate member 214 is joined with the lower-side plate member 212, thereby forming the holding holes 220 between the concave portion 216 and the joint surface of the upper-side plate member 214.

[0126] A sectional shape of each concave portion 216 may be a U-shape, a V-shape, a semicircular shape, or the like. In the present embodiment, as illustrated in FIG. 6, each concave portion 216 is formed with an inverted triangular cross section. The joint surface (lower surface) of the upper-side plate member 214 is formed as a flat surface. Accordingly, if the joint surface (upper surface) of the lower-side plate member 212 is joined with the joint surface (lower surface) of the upper-side plate member 214, the holding holes 220 each having an inverted triangular cross section are formed between the joint surfaces. In the embodiment illustrated in FIGS. 6 and 7, the plurality of holding holes 220 each having an inverted triangular shape are formed continuously (in a saw-tooth shape) along a longitudinal direction of the member main body 210.

[0127] The lens holding member 200 can be formed of an inorganic material such as quartz, glass, or ceramics, resin, or the like that can be processed by precision work. Each concave portion 216 having an inverted triangular cross section and each holding hole 220 having an inverted triangular cross section can be accurately formed, for example, by cutting the member main body 210. The lens holding member 200 may be formed of transparent resin. With excellent processing accuracy, each GRIN lens 250 can be disposed in the corresponding holding hole 220 as designed, and can be aligned (optically coupled) with the end surface of the corresponding optical fiber 30.

[0128] To hold each GRIN lens 250 in the corresponding holding hole 220 of the lens holding member 200, the GRIN lens 250 is disposed in the corresponding concave portion 216 of the lower-side plate member 212. After that, the joint surface of the upper-side plate member 214 may be joined with the joint surface of the lower-side plate member 212. The GRIN lens 250 can be bonded and fixed to the corresponding holding hole 220 with adhesive. For example, the GRIN lens 250 may be disposed in the corresponding concave portion 216 and then the concave portion 216 may be filled with adhesive to thereby fix the GRIN lens 250 to the corresponding concave portion 216, or the GRIN lens 250 may be held in the corresponding holding hole 220 and then the holding hole 220 may be filled with adhesive for bonding.

[0129] Lower-side concave portions 218 formed at both ends of the lower-side plate member 212 may have a semicircular, U-shape, or V-shape section. Upper-side concave portions 222 formed at both ends of the upper-side plate member 214 may have a semicircular shape, U-shape, V-shape section.

[0130] In the present embodiment, each lower-side concave portion 218 formed in the lower-side plate member 212 has an inverted triangular cross section, and each upper-side concave portion 222 has a triangular cross section. Accordingly, if the joint surface of the upper-side plate member 214 is joined with the joint surface (upper surface) of the lower-side plate member 212, the guide holes (guide pin insertion holes) 224 each having a rhombic cross section are formed between the joint surfaces.

[0131] The concave portions each having an inverted triangular cross section and the holding holes 220 each having an inverted triangular cross section can be accurately formed by cutting the lens holding member 200.

[0132] In the case of bonding the joint surface of the lower-side plate member 212 with the joint surface of the upper-side plate member 214 with adhesive, adhesive such as a thermosetting epoxy resin-based adhesive or a cyanoacrylate-based adhesive is used. Specifically, acrylic adhesive, epoxy adhesive, vinyl adhesive, silicone adhesive, rubber adhesive, urethane adhesive, methacrylic adhesive, nylon adhesive, bisphenol adhesive, diol adhesive, polyimide adhesive, fluorinated epoxy adhesive, or fluorinated acrylic adhesive can be used. In particular, silicone adhesive and acrylic adhesive are preferably used.

[0133] The lens holding member 200 may be provided with an adhesive pool portion to prevent the guide pins 40 from being bonded to the guide pin insertion holes 116 with the adhesive used to join the lower-side plate member 212 and the upper-side plate member 214 and the adhesive used to fix the GRIN lenses 250 to the lens holding member 200. For example, the adhesive pool portion may be provided between the guide pin insertion holes 116 and the holding holes 220.

[0134] In the lens holding member 200 having a configuration as described above, each GRIN lens 250 held in the lens holding member 200 is aligned with the end surface of the corresponding optical fiber 30 inserted into the optical fiber insertion hole 114 and is optically coupled.

[0135] Accordingly, light output from the optical fiber 30 passes through the GRIN lens 250. The number of GRIN lenses 250 is not limited to one, and a plurality of GRIN lenses 250 may be provided. A plurality of GRIN lenses 250 may be provided at regular intervals along the longitudinal direction (lateral direction) of the lens holding member 200.

[0136] In the optical connector according to one embodiment, the member main body may be formed by joining the lower-side plate member with the upper-side plate member, and the joined surface between the lower-side plate member and the upper-side plate member may be provided with holding holes for holding the GRIN lenses, respectively.

[0137] The member main body is formed by joining the lower-side plate member with the upper-side plate member, and the joint surface between the lower-side plate member and the upper-side plate member is provided with the holding holes for holding the GRIN lenses, respectively. This configuration makes it possible to manufacture the lens holding member including the holding holes easily and accurately.

[0138] Each GRIN lens can be disposed in the corresponding holding hole before the lower-side plate member and the upper-side plate member are joined together, and then the lower-side plate member and the upper-side plate member can be joined together. Consequently, the GRIN lens can be held in the corresponding holding hole accurately.

[0139] In the optical connector according to one embodiment, the joint surface of the lower-side plate member may be provided with concave portions, and the joint surface of the upper-side plate member may be joined with the joint surface of the lower-side plate member to thereby form holding holes between the concave portions and the joint surface of the upper-side plate member.

[0140] To hold each GRIN lens in the corresponding holding hole of the lens holding member, the GRIN lens may be disposed in the corresponding concave portion formed in the joint surface of the lower-side plate member. After that, the joint surface of the upper-side plate member may be joined with the joint surface of the lower-side plate member. Accordingly, the lens holding member can be manufactured relatively easily. In addition, the holding hole processing accuracy can be increased and the GRIN lens can be held in the lens holding member accurately.

[0141] In the optical connector according to one embodiment, lower-side concave portions for guide holes may be formed at both ends of the joint surface of the lower-side plate member, upper-side concave portions for guide holes may be formed at both ends of the joint surface of the upper-side plate member, and guide holes may be formed between the lower-side concave portions and the upper-side concave portions at both ends of the lens holding member by joining the joint surface of the lower-side plate member with the joint surface of the upper-side plate member.

[0142] With this configuration, the lens holding member including the guide holes (guide pin insertion holes) can be created accurately and relatively easily.

[0143] The lens holding member can be formed of an inorganic material such as quartz, glass, or ceramics, resin, or the like that can be processed by precision work. Each concave portion having an inverted triangular cross section and each holding hole having an inverted triangular cross section can be accurately formed by processing the member main body.

[0144] In the optical connector according to one embodiment, the lens holding member may include the lower-side concave portions each having an inverted triangular cross section, the upper-side concave portions each having a triangular sectional shape, and the guide holes each having a rhombic cross section.

[0145] The lens holding member can be formed of an inorganic material, such as quartz, glass, or ceramics, resin, or the like that can be processed by precision work. Each concave portion having an inverted triangular cross section and each guide hole for guide pin insertion hole having an inverted triangular cross section can be accurately formed by processing the member main body.

[0146] In the optical connector according to one embodiment, the joint surface of the lower-side plate member and the joint surface of the upper-side plate member may be bonded with adhesive.

[0147] The joint surface of the lower-side plate member and the joint surface of the upper-side plate member are bonded with adhesive, thereby making it possible to easily manufacture the lens holding member.

(Lens Holding Member 200a of Another Embodiment)

[0148] In a lens holding member 200a according to another embodiment, the holding holes 220 for holding the GRIN lenses 250, respectively, have a circular shape (cylindrical shape), and are integrally formed with the lower-side plate member 212 and the upper-side plate member 214 without being separated therefrom. FIG. 9 is a schematic perspective view illustrating the lens holding member 200a according to another embodiment. The inner diameter of each holding hole 220 of the lens holding member 200a according to another embodiment is preferably 1 ?m to 3 ?m larger than the diameter of each GRIN lens 250.

[0149] In the case of fixing each GRIN lens 250 to the lens holding member 200a according to another embodiment, the GRIN lens 250 is coated with adhesive and is then inserted into the corresponding holding hole 220. When the GRIN lens 250 is inserted into the holding hole 220, a misalignment may occur between the central position of the cross section of the GRIN lens 250 and the central position of the cross section of the holding hole 220. However, a curing shrinkage stress of adhesive acts and the GRIN lens 250 is held at the center of the cross section of the holding hole 220 during curing.

[0150] Accordingly, the lens holding member 200a with high assembly accuracy can be obtained.

(GRIN Lens 250)

[0151] Each GRIN lens 250 is configured to have a refractive index that gradually changes toward the outer periphery from the central portion thereof (including a refractive index distribution). Each GRIN lens 250 held in the lens holding member 200 is configured to enlarge a light beam output from the corresponding optical fiber 30. The GRIN lens 250 is configured to collimate diverging rays output from the optical fiber 30 and to output parallel rays in an intended direction. The GRIN lens 250 includes flat optical surfaces on both surfaces, respectively, which facilitates mounting of the lens holding member 200 of the GRIN lens 250 into the holding hole 220.

[0152] As the GRIN lens, the GRIN lens in which a refractive index distribution is formed by an ion exchange process of immersing a base material rod in high-temperature molten salt can be used. The rod obtained after the ion exchange process is cut to a length depending on the intended use and the both ends of the rod are polished.

[0153] The length of the GRIN lens 250 is preferably 0.5 mm or more to 1.5 mm or less, and more preferably, 0.8 mm or more to 1.2 mm or less. In this case, the sizes of the lens holding member 200 and the holding hole 220 can be reduced.

[0154] Each GRIN lens 250 of the lens holding member 200 disposed on the second ferrule 120 is configured to collect light beams corresponding to parallel rays that have passed through the light guide portion of the spacer and are incident on the GRIN lens 250, and to focus the light beams on the optical fiber 30.

(Spacer 300)

[0155] As illustrated in FIGS. 1 to 3 and FIG. 11, the spacer 300 is held by a pair of lens holding members 200 and 200 between the first end surface 112 of the first ferrule 110 and the second end surface 122 of the second ferrule 120. Accordingly, the spacer 300 can control the distance between the first end surface 112 of the first ferrule 110 and the second end surface 122 of the second ferrule 120 to be constant. The spacer 300 controls the distance between the pair of lens holding members 200 and 200, thereby controlling the distance between a pair of ferrule end surfaces. The spacer 300 may be bonded to at least one of the lens holding members 200, or may be joined by welding (laser welding or the like). In the case of bonding the spacer 300 to the lens holding member 200, an MPO connector is preferably used as the connector during bonding.

[0156] As illustrated in FIG. 11, the spacer 300 includes a spacer main body 305 including one end surface 301, another end surface 302 on the opposite side of the one end surface 301, and an outer peripheral surface 303 that connects the one end surface 301 and the other end surface 302. The one end surface 301 of the spacer 300 is opposed to the first end surface 112 of the first ferrule 110, and the other end surface 302 of the spacer 300 is opposed to the second end surface 122 of the second ferrule 120.

[0157] The spacer main body 305 may include an opening 311 functioning as the light guide portion 310 that allows light to pass between the one end surface 301 and the other end surface 302. In the present embodiment, as illustrated in FIG. 11, the spacer 300 is provided with a pair of guide holes 320, 320 for inserting the guide pins, and with the opening 311 through which light is allowed to pass. An optical path formed between the pair of lens holding members 200 and 200 passes through the opening 311 (light guide portion 310). The inside of the opening 311 may be filled with gas or liquid having a predetermined refractive index. In a case where the optical connector is immersed, the opening may be filled with a predetermined refrigerant. The inside of the opening 311 may be provided with transparent resin or glass having a predetermined refractive index.

[0158] If the spacer main body 305 includes the opening 311, the spacer main body 305 is formed in a frame shape. If the spacer 300 includes no opening, the spacer main body 305 may be formed of a transparent plate-like member (e.g., a sheet) that is transparent with respect to the wavelength of light to pass therethrough.

[0159] The both ends of the spacer 300 are provided with the pair of guide holes 320, 320 into which the guide pins 40 that penetrate from the one end surface 301 to the other end surface 302 are inserted.

[0160] The interval between the pair of guide holes 320, 320 is set to be equal to the interval between the pair of guide pin insertion holes 116, 116 and the pair of guide holes 224, 224.

[0161] In the present embodiment, the one end surface 301 of the spacer 300 is bonded to the lens holding member 200 disposed on the first end surface 112 of the first ferrule 110. The other end surface 302 of the spacer 300 contacts the lens holding member 200 disposed on the second end surface 122 of the second ferrule 120 during connection with the second ferrule 120.

[0162] In this case, the first ferrule 110, the lens holding member 200 bonded to the first ferrule 110, and the spacer 300 constitute the optical connector (first optical connector) 10.

[0163] The pair of guide pins 40 are inserted into the pair of guide pin insertion holes 116, the pair of guide hole 224 in the first ferrule 110, and the pair of guide holes 320 of the spacer 300, thereby fixing the positions of the first optical connector 10, the lens holding member 200, and the spacer 300.

[0164] In the present embodiment, the ferrule and the optical connector for optically coupling the multi-mode optical fibers 30 are described. The present invention can also be applied to a ferrule and an optical connector for optically coupling single-mode optical fibers 30.

(Operation of Optical Connector)

[0165] Next, optical coupling between the optical fiber 30 fixed to the first ferrule 110 of the first optical connector 10 and the optical fiber 30 fixed to the second optical connector 20 will be described below.

[0166] The light beam that has propagated in the optical fiber 30 fixed to the first ferrule 110 and is incident on each GRIN lens 250 of the lens holding member 200 is enlarged by the GRIN lens 250, and is then output toward the light guide portion 310 (opening 311) of the spacer 300. As illustrated in FIG. 8, the GRIN lens 250 collimates diverging rays from the optical fiber 30 and converts the diverging rays into substantially parallel light beams.

[0167] When the light beam enlarged by the GRIN lens 250 propagates in the light guide portion 310 and enters the GRIN lens 250 of the second optical connector 20, the light beam is collected on the end surface of the optical fiber 30 fixed to the second ferrule 120 by the GRIN lens 250 and propagates in the optical fiber 30.

[0168] Thus, the optical fiber 30 fixed to the first ferrule 110 and the optical fiber 30 fixed to the second ferrule 120 are optically coupled via the lens holding member 200 and the spacer 300.

[0169] In the optical connector connecting structure 1 according to the present embodiment, the light beam is enlarged between the first optical connector 10 and the second optical connector 20. Accordingly, in the optical connector connecting structure 1 according to the present embodiment, light is transferred in the formed of an enlarged light beam, thereby preventing a connection loss caused due to an axial misalignment between the first optical connector 10 and the second optical connector 20 in a plane (XY-plane) orthogonal to a light coupling direction (Z-axis direction) or due to the presence of foreign matter. Accordingly, the connection loss of optical characteristics due to an axial misalignment, foreign matter on an optical fiber end surface during connection, and the like can be reduced.

[0170] The second optical connector 20 may include the second ferrule 120 including the second end surface 122, and the second end surface 122 of the second ferrule 120 may be provided with optical fiber insertion holes into which the optical fibers 30 are inserted and a pair of guide pin insertion holes into which the pair of guide pins 40 are inserted.

[0171] With this configuration, the pair of guide pins 40 can accurately position the pair of guide pin insertion holes 116 in the first ferrule 110, the pair of guide hole 224 of the lens holding member 200, the pair of guide holes 320 of the spacer 300, the pair of guide holes 224 of the lens holding member 200, and the optical fiber insertion holes of the second ferrule 120. As a result, the optical fiber 30 of the first optical connector 10 and the optical fiber 30 of the second optical connector 20 are optically connected to thereby form the optical connector connecting structure 1.

[0172] An optical packaging circuit according to the present embodiment includes a refrigerant tank containing refrigerant, and an electronic component, and the electronic component is immersed in the refrigerant tank. In this case, the refractive index of refrigerant is preferably 1.2 or more to 1.6 or less. By setting the refractive index in the above-described range, the effect of light reflection at the interface between the GRIN lens 250 and the refrigerant can be minimized, thereby minimizing the connection loss.

[0173] If Fluorinert? is used as refrigerant, the refractive index is preferably 1.25 or more to 1.30 or less, and more preferably, 1.26 or more to 1.28 or less. Thus, a chemically stable insulator can be obtained and can be used for various cooling purposes. In addition, insulators having various boiling points can be selected, and thus can be used for a single-phase use in liquid and for a two-phase use to be boiled and cooled by latent heat of evaporation.

[0174] The optical packaging circuits refer to, but are not limited to, electronic devices, such as super computers and data centers, that require ultra-high-performance operation and stable operation, and that generate a large amount of heat from themselves.

[0175] Examples of electronic components include a processor, a memory, and a server, and these electronic components include an optical connector.

[0176] As the optical connector used for the optical packaging circuit, the optical connector used in the above-described embodiments can be used.

[0177] Specifically, the optical connector includes the first ferrule 110 including the first end surface 112 provided with the optical fiber insertion holes 114 into which the optical fibers are inserted, and the pair of guide pin insertion holes 116 into which the pair of guide pins 40 are inserted, and the lens holding member 200 bonded to the first end surface 112 of the first ferrule 110 via a refractive index matching adhesive layer. The lens holding member 200 includes the member main body 210 and the GRIN lenses 250 provided on the member main body 210. Each GRIN lens 250 is aligned with the end surface of each optical fiber inserted into the corresponding optical fiber insertion hole 114.

[0178] The lens holding member 200 includes the first surface 202 corresponding to the first end surface 112 of the first ferrule 110, and the second surface 204 on the opposite side of the first surface 202. The spacer 300 is disposed on the second surface 204 of the lens holding member 200. The spacer 300 includes the opening 311 (light guide portion 310) through which light that has passed through the GRIN lens 250 is allowed to pass, and the opening 311 (light guide portion 310) is filled with refrigerant.

[0179] The optical packaging circuit according to the present embodiment is an immersion cooling system using a fluorocarbon-based coolant.

(Assembly Method)

[0180] Next, a process of locating the lens holding member 200 on the first end surface 112 of the first ferrule 110 will be described.

[0181] The lens holding member 200 is temporarily placed at a position slightly apart from the first end surface 112 in a state where each of a pair of jig guide pins is inserted into the corresponding guide pin insertion hole 116 of the first ferrule 110 and the corresponding guide hole 224 of the lens holding member 200. After that, a refractive index matching adhesive is supplied to a space between the back surface of the lens holding member 200 and the first end surface 112, and then the lens holding member 200 and the first end surface 112 are brought into close contact with each other to thereby fix the lens holding member 200 to the first ferrule 110 via the refractive index matching adhesive. Lastly, each of the pair of jig guide pins is drawn out from the corresponding guide pin insertion hole 116 and the corresponding guide hole 224.

[0182] Thus, each GRIN lens 250 is positioned with respect to the end surface of the corresponding optical fiber 30, thereby allowing each GRIN lens 250 to be optically coupled to the corresponding optical fiber 30. Each guide pin insertion hole 116 is positioned with respect to the corresponding guide hole 224, thereby allowing each guide pin insertion hole 116 to communicate with the corresponding guide hole 224.

(Lens Holding Member 200b of Another Embodiment)

[0183] FIG. 10 illustrates a lens holding member 200b provided with a pair of resin pool concave portions 280 formed on the first end surface 112 side of the first ferrule 110 of the lens holding member 200b. Each resin pool concave portion 280 is formed of a recessed groove running in the vertical direction between the holding holes 220 and the guide holes 224. The refractive index matching adhesive is filled in a space between the pair of resin pool concave portion 280, thereby easily forming the adhesive layer with a uniform thickness and stabilizing the optical characteristics. This configuration prevents an excess adhesive from entering the guide hole 224 and the like, thereby preventing the occurrence of a malfunction such as a failure to accurately insert the guide pins 40.

[0184] As the resin pool structure, not only the concave portions (resin pool concave portions 280), but also convex portions may be provided. The use of concave portions as the resin pool structure makes it possible to reduce the dipping amount of adhesive, and to secure the strength in the vicinity of the guide pin insertion holes 116.

[0185] The resin pool concave portions 280 or the convex portions of the lens holding member 200b according to the present embodiment may be provided on the lens holding member 200b including the circular (cylindrical) holding holes 220 illustrated in FIG. 9.

[0186] The resin pool convex portion or the concave portion may be provided on the side of the lens holding member 200, or may be provided on the side of the spacer 300.

(Spacer 300a of Another Embodiment)

[0187] FIG. 12 illustrates an example of a spacer 300a provided with a flow path 350. The spacer 300a according to the present embodiment includes a frame body including the opening 311. The frame body is provided with the flow path 350 through which the opening 311 communicates with the outside of the frame body. With this configuration, outside gas or liquid (refrigerant etc.) can be introduced into the opening 311 via the flow path 350. The flow path 350 may penetrate from the one end surface 301 of the spacer main body 305 to the other end surface 302 as illustrated in FIG. 12, or the flow path 350 having a concave shape that does not penetrate the end surface of the spacer main body 305 may be formed as illustrated in FIG. 13.

(Spacer 300b of Another Embodiment)

[0188] FIG. 13 is a schematic perspective view illustrating an example of a spacer 300b provided with two or more flow paths 350. In the present embodiment, two flow paths 351 and 352 are provided to be opposed to the one end surface 301 and the other end surface 302 of the spacer main body 305 (on the front and back surfaces of the frame body portion), and the flow paths 351 and 352 can be formed at the top and bottom of the frame body. The provision of the plurality of flow paths 351 and 352 enables air in the opening 311 of the frame body to escape to the outside through the flow path 351 and to be easily replaced with refrigerant when the optical connector including the spacer 300a is immersed in the refrigerant.

(Spacer 300c of Another Embodiment)

[0189] FIG. 14 is a schematic perspective view illustrating an example of a spacer 300c provided with a penetrating portion 331 formed as the light guide portion on the spacer main body 305. The penetrating portion 331 is a through-hole formed by integrating the opening 311 for guiding an optical signal with the guide holes 320 for inserting the guide pin 40. This spacer 300c may be further provided with the flow path 350.

(Spacer 300d of Another Embodiment)

[0190] FIG. 15 is a schematic perspective view illustrating an example of a spacer 300d provided with a penetrating portion 332 formed as the light guide portion on the spacer main body 305. The penetrating portion 332 according to the present embodiment is formed to penetrate the plate-shaped spacer main body 305 in a slit shape. Accordingly, the penetrating portion 332 according to the present embodiment has a configuration in which the opening 311 for guiding an optical signal, the guide holes 320 for inserting the guide pins 40, and the flow path 350 for introducing liquid or the like are integrated together. A back portion of the penetrating portion 332 is provided at a position corresponding to the guide holes.

(Spacer 300e of Another Embodiment)

[0191] FIG. 16 is a schematic perspective view illustrating an example of a spacer 300e provided with a plurality of openings 312 on the spacer main body 305. The plurality of openings 312 are provided such that the central axis of each opening matches the GRIN lens 250.

[0192] The diameter of each opening 312 is set to be equal to or larger than the diameter of an optical surface of the GRIN lens 250. With this configuration, the plurality of openings 312 are provided for each GRIN lens 250, and thus penetration of stray light from the adjacent GRIN lenses 250 can be reliably prevented.

(Spacer 300f of Another Embodiment)

[0193] FIG. 17 illustrates an example of a spacer 300f according to still another embodiment. The entire spacer 300f is formed of a transparent resin or glass having a predetermined refractive index. In this case, the spacer main body 305 of the spacer 300f functions as the light guide portion 310. Accordingly, the spacer 300f is provided with the guide holes 320, but need not be provided with a through-hole (opening 311, etc.).

[0194] In this case, the spacer 300f is brought into close contact or bonded with the lens holding member 200, and thus is configured to prevent liquid from entering the optical path even when the spacer is immersed in refrigerant or the like. With this configuration, the connection loss can be reduced without the influence of liquid. While FIG. 17 illustrates an example where the spacer 300f is formed of resin or glass having a predetermined thickness, the spacer is not limited to this example. The spacer 300f may be formed of a resin film or the like.

(Spacer 300g of Another Embodiment)

[0195] FIG. 18 illustrates an example where the guide holes 320 of the spacer 300f (FIG. 17) are formed as guide holes 321 in a slit shape that penetrates the outer peripheral surface 303 of the spacer main body 305. In this case, the spacer 300g can be easily processed.

[0196] In the present invention, the optical connector connecting structure 1 corresponds to an optical connector connecting structure, the optical fiber 30 corresponds to an optical fiber, the first ferrule 110 corresponds to a first ferrule, the second ferrule 120 corresponds to a second ferrule, the optical fiber insertion hole 114 corresponds to an optical fiber insertion hole, the guide pin insertion hole 116 corresponds to a guide pin insertion hole, the first end surface 112 corresponds to a first end surface, the lens holding member 200 corresponds to a lens holding member, the member main body 210 corresponds to a member main body, the GRIN lens 250 corresponds to a GRIN lens, the second optical connector 20 corresponds to a second optical connector, and the spacer 300 correspond to a spacer.

[0197] While preferred embodiments of the present invention have been described above, the present invention is not limited only to these embodiments. It can be understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Although operations and effects obtained by the configurations according to the present invention are described in the embodiments of the present invention, these operations and effects are merely examples and are not intended to limit the present invention.

REFERENCE SIGNS LIST

[0198] 1 optical connector connecting structure [0199] 10 first optical connector (optical connector) [0200] 20 second optical connector [0201] 30 optical fiber [0202] 40 guide pin [0203] 110 first ferrule [0204] 114 optical fiber insertion hole [0205] 116 guide pin insertion hole [0206] 120 second ferrule [0207] 200 lens holding member [0208] 210 member main body [0209] 212 lower-side plate member [0210] 214 upper-side plate member [0211] 216 concave portion [0212] 220 holding hole [0213] 224 guide hole (guide pin insertion hole) [0214] 250 GRIN lens [0215] 300 spacer [0216] 310 light guide portion [0217] 311 opening [0218] 320 guide hole (guide pin insertion hole) [0219] 350 flow path