Optical connector and method for connecting optical connector

Abstract

To provide: an optical connector capable of preventing a spring force required for a connector from increasing when mounting optical fibers at high density to reduce a size; an optical connector connection structure; and an optical mounting circuit.SOLUTION: An optical connector includes: a first ferrule 110 including a first end surface 112 having an optical fiber insertion hole 114 for inserting an optical fiber 30 and a pair of guide pin insertion holes 116 for inserting a pair of guide pins 40; and a tabular lens holding member 200 bonded on the first end surface 112 of the first ferrule 110 through a refractive index matching adhesive layer. The lens holding member 200 includes a member body 210 and a GRIN lens 250 provided in the member body 210, and the GRIN lens 250 is optically combined with the optical fiber 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical connector, an optical connector connection structure, and an optical mounting circuit. [Background technology]

[0002] Structures for interconnecting optical fibers typically use two mating ferrule assemblies that contain ferrules to facilitate easy handling and precise positioning of the optical fibers. Patent Document 1 (WO2019 / 244388) proposes an optical connector that uses a GRIN lens to increase optical coupling efficiency and reduce the impact of foreign matter, misalignment, etc. on IL (transmission loss).

[0003] The optical connection part of Patent Document 1 includes a first end and a second end located on the opposite side of the first end. The first end has a first contact surface that contacts a mating connector, a first recess, and a first bottom surface. The second end has a second contact surface that contacts an MT ferrule, a second recess, and a second bottom surface. The first and second bottom surfaces face the optical fiber holding hole of the MT ferrule. This optical connection part further includes a guide hole through which a guide pin can be inserted. The resin constituting the optical connection part has a transmittance of 80% or more and 100% or less for light having a wavelength of 1210 nm or more and 1650 nm or less. An optical connector according to an embodiment includes the optical connection part described above, a plurality of optical fibers, and an MT ferrule. A GRIN lens is fusion-spliced ​​to the tip of each of the plurality of optical fibers (paragraph 0021).

[0004] Patent document 2 (JP 2020-122816 A) discloses a ferrule and optical connector that can easily implement a lensed optical fiber in which a GRIN lens is fusion-spliced ​​to the tip of the optical fiber while suppressing an increase in optical connection loss.

[0005] The ferrule and optical connector described in Patent Document 2 include a main body that holds a plurality of lensed optical fibers having GRIN lenses fusion-spliced ​​to the tips of the optical fibers, and the main body has a lower member including a plurality of grooves extending along the X direction and aligned along the Y direction, and an upper member that faces the plurality of grooves and is separate from the lower member, and the grooves include a first region that supports the optical fiber and a second region that is located between the first region and the front end face and supports the GRIN lens, and the lower member further includes a first recess provided between the first region and the second region, and the first recess houses the fused portion of the optical fiber and the GRIN lens.

[0006] Patent Document 3 (JP 2017-161831 A) discloses a spacer for an optical connector, an optical connector, and an optical connection structure that can increase the durability of the optical connector against attachment and detachment and suppress deterioration in positioning accuracy.

[0007] The spacer for optical connector described in Patent Document 3 has a plate-shaped main body including one end face facing the ferrule end face, the other end face opposite the one end face, and an outer circumferential surface connecting the one end face and the other end face, the main body has an opening facing the optical fiber holding hole and passing light from the one end face to the other end face of the main body, a pair of recesses formed in at least one of the one end face and the other end face, and a pair of guide pin insertion holes formed in the pair of recesses and through which a pair of guide pins penetrate from the one end face to the other end face, the guide pin insertion holes being arranged biased toward the opening side in the recesses. A lens array is provided on the ferrule end face. The lens array has a plurality of collimating lenses that collimate the light emitted from each optical fiber of the ferrule, and the collimating lenses are, for example, GRIN lenses (paragraph 0023).

[0008] Patent Document 4 (JP 2016-95431 A) discloses an optical connector coupling system with improved reliability.

[0009] The optical connector coupling system described in Patent Document 4 includes a first optical fiber, a first optical connector, a second optical fiber, a second optical connector, a spacer portion, and an adapter. The first optical connector includes a first ferrule having a first optical interface portion, and a first housing. The second optical connector includes a second ferrule having a second optical interface portion, and a second housing. The spacer portion is disposed on the first optical ferrule. With the first ferrule and the second ferrule positioned relative to each other, the first optical fiber is optically coupled to the second optical fiber via the first optical interface portion and the second optical interface portion. The first optical interface portion includes a plurality of GRIN (Gradient-Index) lenses arranged in parallel in the X-axis direction (paragraph 0042). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] WO2019 / 244388 publication [Patent Document 2] JP 2020-122816 A [Patent Document 3] JP 2017-161831 A [Patent Document 4] JP 2016-95431 A Summary of the Invention [Problem to be solved by the invention]

[0011] In an optical connector, the optical fibers are secured in a ferrule, and the end face of each optical fiber is positioned so that it is either flush with the terminating face of the ferrule or protrudes slightly beyond the terminating face of the ferrule. The end faces of the optical fibers are typically polished to a specified finish.

[0012] The two ferrule assemblies are positioned and connected to each other via guide pins, and the connected optical connectors are fixed to each other with a clamp spring, etc. In this way, when the two ferrule assemblies are mated, the optical fiber of one ferrule assembly comes into contact with the optical fiber of the other ferrule assembly with a predetermined pressing force.

[0013] The end faces of a pair of optical fibers physically contact each other to allow light transmission between the pair of optical fibers. In such optical connector connection structures, various factors can reduce the efficiency of light transmission between the optical fibers, such as irregularities in the optical fiber end faces, scratches, misalignment between the pair of optical fibers, and foreign objects such as dust and debris between the optical fibers being connected. For example, when optical connectors are repeatedly connected and disconnected, foreign matter such as dust adhering to the surface of the guide pin may get into the guide pin insertion hole, making it impossible to smoothly connect and disconnect the guide pin. In this case, the positioning accuracy of the optical connectors may decrease due to damage to the guide pin insertion hole, and the coupling loss may increase.

[0014] Because the light path that passes between optical fibers is small compared to the size of foreign objects such as dust or debris, such objects tend to interfere with light transmission. In this case, in a beam connector which expands the width of the light beam, the effects of foreign matter, misalignment, etc. are reduced because expanding the beam increases the relative size between the beams with respect to foreign matter such as dust.

[0015] Therefore, in order to reduce the connection loss due to the foreign object, it has been proposed to use a spherical lens to generate an expanded beam, but this requires a complex structure to align the spherical lens with the optical fiber.

[0016] In the optical connection part described in Patent Document 1, a GRIN lens is fusion-spliced ​​to each tip of a plurality of optical fibers. In this case, it is not necessary to use a spherical lens, but the fusion process between the optical fiber and the GRIN lens reduces productivity. In addition, since it is difficult to achieve high accuracy in the fusion process, the connection loss may increase. In addition, the outer diameter of the fusion part between the optical fiber and the GRIN lens is larger than the outer diameters of the optical fiber and the GRIN lens.

[0017] Therefore, if the outer diameter of the fused part is larger than the optical fiber insertion hole of the ferrule, it becomes difficult to insert the fused part into the insertion hole. On the other hand, if the inner diameter of the insertion hole is made larger than the fused part, the clearance between the insertion hole and the GRIN lens becomes large, which makes it easier for the GRIN lens to shift position, increasing the optical connection loss. Therefore, a special structure is required for the ferrule that houses the optical fiber and the GRIN lens.

[0018] The ferrule described in Patent Document 2 also has a GRIN lens fused to the end face of the optical fiber, and a recess is formed in the ferrule to accommodate the fused portion, and has the same drawbacks as Patent Document 1.

[0019] In the optical connector described in Patent Document 3, the collimating lens is held in a through hole provided in a lens holding member. Therefore, it is difficult to process the lens holding member, and it is difficult to ensure the accuracy of the work of holding the lens in the very small hole of the lens holding member. In addition, in Patent Document 3, the collimating lens and the ferrule are simply bonded together. However, the end face of the optical fiber is exposed to the ferrule, and when an optical signal is passed from this optical fiber to the collimating lens, there is a problem that optical reflection or loss occurs at the interfaces between the optical fiber and the adhesive, and between the adhesive and the collimating lens.

[0020] In the optical connector coupling system described in Patent Document 4, similarly to Patent Document 3, the GRIN lens provided in the first optical interface section is configured to be provided in a through hole formed in the plate-like first optical interface section. Therefore, the work and precision required for processing the first optical interface section and inserting and arranging the lens in the lens holding member are difficult. Furthermore, in the optical connector coupling system described in Patent Document 4, the lens array is fixed together with the spacer by a latch, which causes problems such as clearance between the guide pins and guide pin holes and misalignment of each component when mating using a spacer with a latch, resulting in variations in optical characteristics. If the holding hole is bent during molding, the attitude of the lensed optical fiber held in the holding hole is likely to become tilted. If the attitude of the lensed optical fiber is tilted near the front end face, an angular deviation of the lensed optical fiber at the front end face occurs, which may increase the optical connection loss between the optical connectors.

[0021] Furthermore, in the optical connectors described in the above patent documents, a large spring force is required when mounting optical fibers at high density (20 N or more is required for 16 channels), which makes it difficult to achieve both high density and compactness. Therefore, an optical connector that can make optical connections with a lower pressing force is desired.

[0022] Recently, optical modules have been developed in which optical elements are mounted on a substrate and optically coupled to optical fibers. This allows high-speed, high-density optical communication to be directly introduced into (or close to) an electronic substrate, and optically mounted circuits without the need for electrical communication wiring are being considered. When processing high-speed, large-volume data, some electronic components on the substrate can become hot due to operation, and this can make it necessary to cool the entire electronic substrate by immersing it in a refrigerant. However, conventional optical communication components were not designed to be immersed in liquid, and optical characteristics of optical circuits are easily changed when they come into contact with liquids such as refrigerants, so there is a problem that immersing an optical connector in a refrigerant will cause it to stop functioning or cause extremely large losses. In addition, the refrigerant may contain foreign matter due to circulation, and immersing an optical connector in this liquid may cause the transmission loss to worsen due to the influence of the foreign matter.

[0023] The present invention has been made to overcome the above-mentioned drawbacks, and its object is to provide an optical connector, an optical connector connection structure thereof, and an optical mounted circuit that can reduce the effects on transmission loss caused by foreign matter such as dust and misalignment on the fiber end face during connection. Another object of the present invention is to provide an optical connector, an optical connector connection structure, and an optical mounted circuit that have high transmission efficiency even when used as parts of an immersion processor.

[0024] Another object of the present invention is to provide an optical connector, an optical connector connection structure, and an optical mounted circuit that can prevent an increase in the spring force required for the connector when optical fibers are mounted at high density, thereby enabling miniaturization. It is still another object of the present invention to provide an optical connector, an optical connector connection structure, and an optical mounted circuit that have a lens holding member that can use a conventional ferrule, has good machining accuracy, and is relatively simple in structure. [Means for solving the problem]

[0025] (1) An optical connector according to one aspect comprises a first ferrule having a first end face in which an optical fiber insertion hole through which an optical fiber is inserted and a pair of guide pin insertion holes through which a pair of guide pins are inserted, a plate-shaped lens holding member adhered to the first end face of the first ferrule via a refractive index matching adhesive layer, and a spacer provided on the side opposite the first end face of the lens holding member, wherein the lens holding member has a member body and a GRIN lens provided on the member body, the spacer has a light guiding portion that passes light that has passed through the GRIN lens, and the GRIN lens is optically coupled to the optical fiber.

[0026] This allows the use of conventional ferrules since no GRIN lens is fused to the end of the optical fiber. By using a GRIN lens to expand the beam diameter and transmit it through space, it is possible to reduce the effects of foreign matter such as dust on the fiber end face during connection, misalignment, etc. on transmission loss. In particular, even if the optical connector is immersed in a coolant, it is possible to reduce the effects of foreign matter contained in the coolant. Also, whereas a large spring force is required when mounting optical fibers at high density (for example, 20N or more for 16 channels), spatial transmission allows for holding with a spring force of about 3N. In other words, unlike the PC (Physical Contact) method, the non-contact optical connection structure allows multiple optical fibers to be optically connected simultaneously without requiring a large force for optical connection.

[0027] In particular, the length of a GRIN lens directly affects the focal length, and heat fusing the surface of a GRIN lens affects the length of the lens, which causes a problem that accurate parallel light rays cannot be obtained and affects the connection loss. In addition, a GRIN lens is formed by giving a concentration distribution to the glass components to create a spatial distribution of the refractive index, so fusing the lens affects the spatial distribution of the concentration, which causes a problem that stable optical characteristics cannot be obtained. The optical connector of the present invention uses a refractive index matching adhesive to bond a plate-shaped lens holding member to the first end face of the first ferrule, so that the optical characteristics can be reliably maintained without fusing at the connection surface between the optical fiber and the GRIN lens.

[0028] The optical connector may be an MT connector or an MPO connector equipped with an MT ferrule. By using an MT ferrule as the first ferrule, a small, high-density connector can be realized using the commonly used MT ferrule.

[0029] (2) An optical connector according to a second aspect of the present invention is the optical connector according to the one aspect of the present invention, wherein the refractive index of the light guiding portion of the spacer may be 1.2 or more and 1.6 or less.

[0030] This can minimize the light reflection that occurs at the interface between the GRIN lens of the lens holding member and the light guide of the spacer. In this case, the light guide of the spacer may be made of a resin or glass having a predetermined refractive index, or may be filled with a liquid having a predetermined refractive index. The spacer body may be made of a transparent resin material, and a refractive index matching agent may be applied between the spacer body and the GRIN lens of the lens holding member.

[0031] (3) An optical connector according to a third aspect of the present invention is the optical connector according to the one aspect or the second aspect of the present invention, wherein the light guiding portion has an opening portion filled with a fluorine-based refrigerant.

[0032] When the optical connector is immersed in a fluorine-based refrigerant, the opening formed in the spacer is filled with the fluorine-based refrigerant. As a result, the light emitted from the GRIN lens of the lens holding member can pass through the light guide of the spacer without being reflected. In addition, since the refrigerant can be used as a filling material for the light guide, the optical connector can be suitably used in a system in which the server is immersed in liquid.

[0033] In an immersion server, the entire electronic board of the optical circuit is submerged in a tank of liquid refrigerant to cool the processor and other components. The liquid refrigerant that fills the inside of an immersion server has a higher specific heat than air, and the flow of the refrigerant reduces the temperature gradient, allowing for efficient heat removal. In addition, if a fluorine-based refrigerant with a low boiling point of 50 degrees Celsius (122 degrees Fahrenheit) is used, it will boil quickly due to the heat generated by the processor and other components. The heat of vaporization that occurs in this case (the heat removed from the surroundings when the liquid becomes a gas) can be used to cool the server. When the optical connector is immersed in a fluorine-based refrigerant, the opening formed in the spacer is filled with the fluorine-based refrigerant. As a result, the light emitted from the GRIN lens of the lens holding member can pass through the light guide of the spacer without being reflected. In addition, since the refrigerant can be used as a filling material for the light guide, the optical connector can be suitably used in a system in which the server is immersed in liquid.

[0034] The refractive index of the coolant in the immersion processor is preferably 1.2 or more and 1.6 or less. By immersing the optical connector in a coolant tank that contains the coolant, the coolant fills the openings of the spacer, cooling the optical mounted circuit and simultaneously optically connecting each component without any problems. When Fluorinert (registered trademark) is used as the coolant, the refractive index is 1.25 or more and 1.30 or less. In addition, conventional spherical lenses such as plastic lenses designed for use in air cannot form an expanded beam when used in an immersion processor because the lens does not function or the focal length changes significantly. On the other hand, by using a GRIN lens as in the present invention, an expanded beam can be realized in an immersion state without being affected by the refrigerant.

[0035] In an optical connector according to another aspect of the present invention, the optical connector may be immersed in a coolant for cooling an electronic component.

[0036] In recent years, there has been active development of optical modules in which optical elements are mounted on a substrate and optically coupled to optical fibers. Optically mounted circuits that introduce high-speed, high-density optical communications directly onto electronic substrates (or close to the substrate) without the use of electrical wiring are being considered. On the other hand, since some electronic components on the board become hot during operation, the entire electronic board is sometimes cooled by submerging it in a liquid refrigerant. However, the optical characteristics of optical circuits are easily changed when they come into contact with liquids such as refrigerants, so there is a problem that submerging optical connectors in a refrigerant often results in them not functioning or in extremely large losses. Unlike conventional optical systems that use spherical lenses, the optical connector of another invention can achieve a stable expanded beam even in an immersion state without being affected by the refrigerant, even when the optical connector is used in an immersion processor, making it possible to produce an optical connector with high transmission efficiency.

[0037] (4) An optical connector according to a fourth aspect of the present invention is the optical connector according to any one of the first to third aspects of the present invention, wherein the spacer has a frame body, and the frame body may have two or more flow paths.

[0038] The spacer may have a flow path in the frame for guiding the coolant to the light guiding section. This flow path allows the coolant to be smoothly guided to the light guiding section, and the light guiding section can be efficiently filled with the coolant, thereby stabilizing the optical characteristics in a short time. The spacer may have one flow passage, but preferably has two or more. By having two or more flow passages, air present in the opening of the frame body can be efficiently released to the outside when immersed in the coolant, so that the light guide can be filled with the coolant more efficiently.

[0039] (5) The optical connector of the fifth invention is an optical connector of any one of the first to fourth inventions, wherein a recess or protrusion for a resin pool of refractive index matching adhesive may be formed on the first end face of the first ferrule and / or on the member body of the lens holding member.

[0040] This makes it possible to make the thickness of the adhesive layer uniform, thereby stabilizing the optical characteristics, and also prevents excess adhesive from entering the guide pin insertion holes, etc., thereby suppressing the occurrence of problems such as the guide pins not being able to be inserted correctly.

[0041] (6) An optical connector connection structure according to a sixth aspect of the present invention comprises a first ferrule having a first end face in which an optical fiber insertion hole through which an optical fiber is inserted and a pair of guide pin insertion holes through which a pair of guide pins are inserted, a plate-shaped lens holding member adhered to the first end face of the first ferrule via a refractive index matching adhesive layer, a second optical connector arranged opposite the first end face of the first ferrule, and a spacer arranged between the lens holding member and the second optical connector and having a light guiding portion that can pass light between the lens holding member and the second optical connector, wherein the lens holding member has a plate-shaped member body and a GRIN lens provided on the member body, the GRIN lens is aligned with the end face of the optical fiber inserted in the optical fiber insertion hole, and the member body is formed by joining a lower plate member and an upper plate member, and a holding hole for holding the GRIN lens is formed in the joining surface between the lower plate member and the upper plate member.

[0042] This allows the use of conventional ferrules since no GRIN lens is fused to the end of the optical fiber. The main body of the member is formed by joining a lower plate member and an upper plate member, and a retaining hole for holding a GRIN lens is formed on the joining surface between the lower plate member and the upper plate member, so that a lens holding member having a retaining hole can be manufactured easily and precisely. In addition, the GRIN lens can be placed in the holding hole before the lower plate member and the upper plate member are joined together, and then the lower plate member and the upper plate member can be joined together, so that the GRIN lens can be held in the holding hole with high precision.

[0043] By using a GRIN lens to expand the beam diameter and transmit it through space, it is possible to reduce the impact of foreign matter such as dust on the fiber end face during connection, misalignment, etc. on IL (transmission loss). In particular, even if the optical connector is immersed in a refrigerant, it is possible to reduce the impact of foreign matter contained in the refrigerant. Furthermore, when mounting 16 or more channels at high density, the spring force required for MPO is 20 N or more, whereas for spatial transmission, a spring force of about 3 N is sufficient for holding. In other words, unlike the PC (Physical Contact) method, the non-contact optical connector connection structure 1 can simultaneously connect multiple optical fibers without requiring a large force for optical connection. Furthermore, since the plate-shaped lens holding member is bonded to the first end face of the first ferrule using a refractive index matching adhesive, the optical characteristics can be reliably maintained at the connection surface between the optical fiber and the GRIN lens.

[0044] The optical connector may be an MT connector or an MPO connector equipped with an MT ferrule, or may be a dedicated connector. By using an MT ferrule as the first ferrule, a small, high-density connector can be realized using the commonly used MT ferrule.

[0045] (7) An optical connector connection structure according to a seventh aspect of the present invention is the optical connector connection structure according to the sixth aspect of the present invention, wherein the second optical connector includes a second ferrule having a second end face, and the second end face of the second ferrule may be formed with an optical fiber insertion hole through which an optical fiber is inserted and a pair of guide pin insertion holes through which a pair of guide pins are inserted.

[0046] This makes it possible to reduce the impact on transmission loss caused by misalignment and other foreign objects such as dirt on the fiber end face during connection, and also makes it possible to provide an optical connector connection structure that prevents an increase in the spring force required for the connector when optical fibers are mounted at high density, making it possible to reduce the size.

[0047] (8) An optical mounting circuit according to an eighth aspect of the present invention has a refrigerant tank containing a refrigerant and an electronic component, the electronic component being immersed in the refrigerant in the refrigerant tank, and an optical connector connected to the electronic component includes a first ferrule having a first end face in which an optical fiber insertion hole through which an optical fiber is inserted and a pair of guide pin insertion holes through which a pair of guide pins are inserted, and a plate-shaped lens holding member bonded to the first end face of the first ferrule via a refractive index matching adhesive layer, the lens holding member having a member body and a GRIN lens provided on the member body, and the GRIN lens is aligned with the end face of the optical fiber inserted into the optical fiber insertion hole.

[0048] This makes it possible to reduce the impact on transmission loss caused by misalignment and other foreign objects such as dirt on the fiber end face during connection, and also makes it possible to provide an optical connector connection structure that prevents an increase in the spring force required for the connector when optical fibers are mounted at high density, making it possible to reduce the size.

[0049] (9) An optical mounting circuit according to a ninth aspect of the present invention is the optical mounting circuit according to the eighth aspect of the present invention, wherein the lens holding member has a first surface on the first end face side of the first ferrule and a second surface opposite the first surface, a spacer is disposed on the second surface side of the lens holding member, and the spacer has an opening that allows light that has passed through the GRIN lens to pass through, and the opening is filled with a medium.

[0050] This makes it possible to reduce the impact on transmission loss caused by misalignment and other foreign objects such as dirt on the fiber end face during connection, and also makes it possible to provide an optical connector connection structure that prevents an increase in the spring force required for the connector when optical fibers are mounted at high density, making it possible to reduce the size.

[0051] The refractive index of the coolant in the immersion processor is preferably 1.2 to 1.6. Therefore, by immersing the optical connector in a water tank containing the coolant, the coolant fills the opening of the spacer, cooling the optical connector connection structure and simultaneously enabling each component to be optically connected without any problems. When Fluorinert (registered trademark) is used as the coolant, the preferred refractive index is 1.25 to 1.30. In addition, conventional spherical lenses such as plastic lenses designed for use in air cannot form an expanded beam when used in an immersion processor because the lens does not function or the focal length changes significantly. On the other hand, by using a GRIN lens as in the present invention, an expanded beam can be realized in an immersion state without being affected by the refrigerant. [Brief description of the drawings]

[0052] [Figure 1] FIG. 2 is an exploded perspective view of the optical connector connection structure of the first embodiment. [Diagram 2] 2 is an exploded plan view of the optical connector connection structure of FIG. 1. [Diagram 3] 2 is an exploded front view of the optical connector connection structure of FIG. 1. [Figure 4] 2 is a plan view of the optical connector connection structure of FIG. 1. [Diagram 5] 2A to 2C are 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 connection structure of FIG. [Figure 6] FIG. 2 is a schematic explanatory diagram of a lens holding member according to the first embodiment. [Figure 7] FIG. 2 is a schematic perspective view for explaining a lens holding member according to the first embodiment. [Figure 8] 5 is a reference cross-sectional view (cross-sectional view taken along line AA' in FIG. 4) for explaining the function of the optical connector and the light beam. [Figure 9] FIG. 11 is a schematic perspective view for explaining a lens holding member according to another embodiment. [Figure 10] FIG. 11 is a schematic perspective view illustrating a lens holding member according to still another embodiment. [Figure 11]FIG. 2 is a schematic perspective view for explaining a spacer according to the first embodiment. [Figure 12] FIG. 13 is a schematic perspective view for explaining a spacer of another embodiment. [Figure 13] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. [Figure 14] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. [Figure 15] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. [Figure 16] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. [Figure 17] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. [Figure 18] FIG. 13 is a schematic perspective view for explaining a spacer of still another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Although multiple embodiments of the present invention will be described, each of the embodiments may be implemented alone or in combination with one or more of the multiple embodiments. In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same, so detailed description thereof will not be repeated.

[0054] [Embodiment 1] (Optical connector connection structure 1) Fig. 1 is an exploded perspective view showing an optical connector connection structure 1 according to one embodiment, Fig. 2 is an exploded plan view showing the optical connector connection structure 1, and Fig. 3 is an exploded front view of the optical connector connection structure 1. As shown in Figures 1 to 3 and 6, the optical connector connection structure 1 of this embodiment comprises a first ferrule 110, a plate-shaped lens holding member 200 adhered to a first end face 112 of the first ferrule 110 via a refractive index matching adhesive layer (not shown), a second optical connector 20 arranged opposite the first end face 112 of the first ferrule 110, and a spacer 300 arranged between the lens holding member 200 and the second optical connector 20 and having a light-guiding section 310 that can pass light between the lens holding member 200 and the second optical connector 20.

[0055] Furthermore, as shown in Figures 1 to 5, the first optical connector 10 of this embodiment comprises a first ferrule 110 having a first end face 112 on which are formed an optical fiber insertion hole 114 through which the optical fiber 30 is inserted and a pair of guide pin insertion holes 116 through which a pair of guide pins 40 are inserted, and a plate-shaped lens holding member 200 adhered to the first end face 112 of the first ferrule 110 via a refractive index matching adhesive layer.

[0056] The second optical connector 20 can have a second ferrule 120 and a plate-shaped lens holding member 200 bonded to the second end face 122 of the second ferrule 120 via a refractive index matching adhesive layer. In such a case, the optical connector connection structure 1 includes a first ferrule 110 and a second ferrule 120 that are connected to each other, a first lens holding member 200 disposed between the first and second ferrules 110, 120, a second lens holding member 200′, and a spacer 300.

[0057] (Refractive index matching adhesive layer) The refractive index matching adhesive used in the refractive index matching adhesive layer preferably has a refractive index after curing of 1.4 to 1.5, more preferably 1.45 to 1.48, which can minimize the connection loss between the optical fiber 30 and the GRIN lens 250 and can also minimize the generation of reflected light. The refractive index matching adhesive of the refractive index matching adhesive layer can be an acrylic or epoxy optical adhesive. The refractive index matching adhesive can be a thermosetting adhesive or a UV curing adhesive. If there is an opaque member, a thermosetting adhesive is preferable, and if there is a member that is weak against heat, a UV curing adhesive is preferable. This can minimize the connection loss between the optical fiber 30 and the GRIN lens 250 and the occurrence of reflected light.

[0058] (Ferrule) The first and second ferrules 110, 120 each have a substantially rectangular parallelepiped appearance and are molded, for example, from a resin. The first and second ferrules 110, 120 may be made of a moldable resin such as polyphenylene sulfide or liquid crystal polymer (LCP), and may contain an additive such as silica (SiO2) to enhance the strength and stability of the resin. They may also be made of an inorganic material such as ceramics. The first and second ferrules 110, 120 have flat first end face 112 and second end face 122 provided on one end side in the connection direction, and rear end faces 113, 123 provided on the other end side. The first and second ferrules 110, 120 also have a pair of side faces extending along the connection direction, a bottom face, and a top face. A first end face 112 of the first ferrule 110 and a second end face 122 of the second ferrule 120 are disposed opposite to each other.

[0059] A pair of guide pin insertion holes (guide holes) 116 are formed in the first end face 112 and the second end face 122 and aligned in a direction intersecting a cross section along the optical axis of the optical fiber 30. A pair of guide pins 40, 40 are inserted into the pair of guide pin insertion holes 116. That is, the relative positions of the first ferrule 110 and the second ferrule 120 are determined by the pair of guide pins 40, 40.

[0060] The first end face 112 is formed with a plurality of optical fiber insertion holes 114 into which the optical fibers 30 are inserted. The rear end faces 113 of the first and second ferrules 110, 120 are formed with introduction holes 117 for receiving a ribbon fiber consisting of a plurality of optical fibers 30 (FIG. 5(d)). The optical fiber insertion holes 114 are formed so as to penetrate from the first end face 112 to the introduction hole 117 side. The optical fibers 30 are inserted into and held in the optical fiber insertion holes 114, respectively.

[0061] The optical fibers 30 each extend along the connection direction and are arranged in a row in the horizontal direction intersecting the connection direction. The number of optical fiber insertion holes 114 can be determined according to the purpose. There may be one (in which case it is a single-core ferrule) or multiple (in which case it is a multi-core ferrule). In this embodiment, an example of a multi-core MT ferrule with 12 cores, 16 cores, etc., in which the optical fibers 30 are arranged in a row is described. The optical fiber 30 of this embodiment has a bare optical fiber and a resin coating covering the bare optical fiber, and the resin coating is removed from the middle to the tip in the connection direction to expose the bare optical fiber. A bare optical fiber is held in the optical fiber insertion hole 114. The tip of each bare optical fiber is exposed at the first end face 112 and is, for example, flush with the first end face 112 or protrudes slightly. In the present invention, the bare optical fiber is also simply referred to as the optical fiber 30.

[0062] In this embodiment, the inner diameter of the optical fiber insertion hole 114 is set to 125.5 μm or more and 127.5 μm or less, and a multimode fiber with an outer diameter of the bare optical fiber of 125 μm is used. In this case, the core diameter of the optical fiber 30 is 50 μm. In this embodiment, a case where a 1300 nm optical signal is transmitted through a multimode optical fiber with a cladding diameter of 125 μm will be described, but the optical fiber 30 may have a cladding diameter of 80 μm or the like, may be multimode or single mode, and the wavelength of the optical signal may be appropriately selected according to the purpose. For example, a multimode fiber (thin cladding fiber) with a core diameter of 50 μm and a cladding diameter of 80 μm may be used, or a single mode fiber with a core diameter of 10 μm and a cladding diameter of 80 μm or 125 μm may be used. In this case, the inner diameter of the optical fiber insertion hole 114, the lens design of the GRIN lens 250, the physical properties of the refrigerant, etc. may be appropriately selected according to the optical fiber or optical signal selected.

[0063] (Lens holding member 200) Plate-shaped lens holding members 200, 200' are provided on a first end face 112 of the first ferrule 110 and a second end face 122 of the second ferrule 120, respectively. The lens holding member 200 has a plurality of GRIN lenses 250 that diffuse and collimate the light emitted from the optical fiber 30 of the first ferrule 110. The GRIN lenses 250 are held in holding holes 220 formed in the lens holding member 200. In addition, the lens holding member 200' disposed on the second ferrule 120 side has a plurality of GRIN lenses 250 that focus the light transmitted through the light guiding section 310 of the spacer 300. The GRIN lenses 250 are held in holding holes 220 formed in the lens holding member 200'. The arrangement pitch of each GRIN lens 250 is set to be equal to the arrangement pitch of the optical fibers 30 held in the first and second ferrules 110, 120. Each GRIN lens 250 is arranged corresponding to the optical fibers 30, and the GRIN lenses 250 and the optical fibers 30 are optically connected to each other.

[0064] Each GRIN lens 250 has a cylindrical shape and is arranged so that the central axis of the cylinder coincides with the central axis of the optical fiber 30. In this embodiment, the optical fiber 30 is a multimode fiber having an outer diameter of 125 μm and a core diameter of 50 μm, and in this case, the outer diameter of each GRIN lens 250 is preferably 130 μm or more and 300 μm or less, more preferably 150 μm or more and 250 μm or less, and further preferably 180 μm or more and 220 μm or less. As a result, the multimode beam diameter of 50 μm is expanded to a linear diameter of 100 μm to 120 μm and collimated before transmission, reducing transmission loss due to foreign matter at the connection. Also, the beam carrying the communication signal is collimated by the GRIN lens 250, and the signal can be transmitted contactlessly between the first and second ferrules 110, 120, so that even when connecting high-density optical fibers, there is no need to apply strong force at the physical contact, and the optical connector can be made compact. Furthermore, unlike conventional optical systems that use spherical lenses, even when the optical connector is used in an immersion processor, it is possible to achieve a stable expanded beam even in an immersion state without being affected by the refrigerant, making it an optical connector with high transmission efficiency.

[0065] As shown in Figures 6 and 7, the lens holding member 200 is formed in a plate shape including a first surface 202 facing the first end face 112, a second surface 204 on the opposite side of the first surface 202, and an outer peripheral surface 206 connecting the first surface 202 and the second surface 204.

[0066] Furthermore, guide holes 224, through which guide pins 40 penetrating from the first surface 202 to the second surface 204 are inserted, are formed at both ends of the lens holding member 200. The distance between the pair of guide holes 224, 224 formed in the lens holding member 200 is set to be equal to the distance between the pair of guide pin insertion holes 116, 116 formed in the end face of the first ferrule 110.

[0067] Details of the lens holding member 200 of this embodiment are as follows. The lens holding member 200 has a member body 210 in the shape of a horizontally long plate, and a GRIN lens 250 provided on the member body 210 . The member body 210 is configured by joining a lower plate member 212 that is long in the lateral direction (horizontal direction) and an upper plate member 214 that is long in the lateral direction (horizontal direction) together. The lower plate member 212 and the upper plate member 214 may be joined together by using an adhesive. A retaining hole 220 for retaining the GRIN lens 250 is formed between the upper surface (bonding surface) of the lower plate member 212 and the lower surface (bonding surface) of the upper plate member 214. That is, a recess 216 is formed in the bonding surface of the lower plate member 212, and the bonding surface of the upper plate member 214 is bonded to the bonding surface of the lower plate member 212, thereby forming the retaining hole 220 between the recess 216 and the bonding surface of the upper plate member 214.

[0068] The cross-sectional shape of the recess 216 may be U-shaped, V-shaped, semicircular, or the like. In this embodiment, as shown in Fig. 6, the recess 216 is formed with an inverted triangular cross section. Since the joint surface (lower surface) of the upper plate member 214 is formed as a flat surface, when the joint surface (lower surface) of the upper plate member 214 is joined to the joint surface (upper surface) of the lower plate member 212, a holding hole 220 with an inverted triangular cross section is formed between them. In the embodiment shown in Figs. 6 and 7, a plurality of inverted triangular holding holes 220 are formed continuously (in a sawtooth shape) along the longitudinal direction of the member main body 210.

[0069] The lens holding member 200 can be formed from inorganic materials such as quartz, glass, and ceramics that can be precisely machined, resin, and the like. By machining the member body 210 by cutting or the like, it is possible to accurately form the recess 216 having an inverted triangular cross section and the holding hole 220 having an inverted triangular cross section. The lens holding member 200 may also be formed from a transparent resin. Because of the high machining precision, the GRIN lens 250 can be positioned in the holding hole 220 as designed, and can be aligned (optically coupled) with the end face of the optical fiber 30.

[0070] To hold the GRIN lens 250 in the holding hole 220 of the lens holding member 200, the GRIN lens 250 is placed in the recess 216 of the lower plate member 212, and then the bonding surface of the upper plate member 214 is bonded to the bonding surface of the lower plate member 212. The GRIN lens 250 can be bonded and fixed in the holding hole 220 using an adhesive. For example, the GRIN lens 250 may be placed in and held in the recess 216, and then the recess 216 may be filled with an adhesive to fix the GRIN lens 250 to the recess 216, or the GRIN lens 250 may be held in the holding hole 220, and then the holding hole 220 may be filled with an adhesive to bond the GRIN lens 250.

[0071] The cross-sectional shape of the lower recesses 218 formed at both ends of the lower plate member 212 may be semicircular, U-shaped, or V-shaped. The cross-sectional shape of the upper recesses 222 formed at both ends of the upper plate member 214 may be semicircular, U-shaped, or V-shaped. In this embodiment, the cross-sectional shape of the lower recess 218 formed in the lower plate member 212 is an inverted triangular shape, and the upper recess 222 is a triangular shape. Therefore, when the joint surface of the upper plate member 214 is joined to the joint surface (upper surface) of the lower plate member 212, a guide hole (guide pin insertion hole) 224 having a diamond-shaped cross section is formed between them.

[0072] By cutting the lens holding member 200, it is possible to accurately form the recesses having an inverted triangular cross section and the holding holes 220 having an inverted triangular cross section.

[0073] When the bonding surface of the lower plate member 212 and the bonding surface of the upper plate member 214 are bonded with an adhesive, examples of the adhesive that can be used include thermosetting epoxy resin-based and cyanoacrylic-based adhesives. Specifically, adhesives that can be used include acrylic-based, epoxy-based, vinyl-based, silicone-based, rubber-based, urethane-based, methacrylic-based, nylon-based, bisphenol-based, diol-based, polyimide-based, fluorinated epoxy-based, and fluorinated acrylic-based adhesives. In particular, silicone-based and acrylic-based adhesives are preferably used.

[0074] In order to prevent the guide pin 40 from adhering to the guide pin insertion hole 116 due to the adhesive used to join the lower plate member 212 and the upper plate member 214 and the adhesive used to fix the GRIN lens 250 to the lens holding member 200, an adhesive reservoir may be provided in the lens holding member 200. For example, an adhesive reservoir may be provided between the guide pin insertion hole 116 and the holding hole 220.

[0075] In the lens holding member 200 configured in this manner, the GRIN lens 250 held in the lens holding member 200 is aligned with and optically coupled to the end face of the optical fiber 30 inserted into the optical fiber insertion hole 114. Therefore, the light emitted from the optical fiber 30 is transmitted through the GRIN lens 250. The number of GRIN lenses 250 is not limited to one, and multiple GRIN lenses may be provided. Multiple GRIN lenses may be provided at regular intervals along the longitudinal direction (lateral direction) of the lens holding member 200.

[0076] In one embodiment of the optical connector, the member body is formed by joining a lower plate member and an upper plate member, and a retaining hole for holding a GRIN lens may be formed on the joining surface between the lower plate member and the upper plate member.

[0077] The main body of the member is formed by joining a lower plate member and an upper plate member, and a retaining hole for holding a GRIN lens is formed on the joining surface between the lower plate member and the upper plate member, so that a lens holding member having a retaining hole can be manufactured easily and precisely. In addition, the GRIN lens can be placed in the holding hole before the lower plate member and the upper plate member are joined together, and then the lower plate member and the upper plate member can be joined together, so that the GRIN lens can be held in the holding hole with high precision.

[0078] In one embodiment of the optical connector, a recess is formed on the joint surface of the lower plate member, and a retaining hole may be formed between the recess and the joint surface of the upper plate member by joining the joint surface of the upper plate member to the joint surface of the lower plate member.

[0079] To hold a GRIN lens in the holding hole of the lens holding member, the GRIN lens is placed in a recess formed in the joining surface of the lower plate member, and then the joining surface of the upper plate member is joined to the joining surface of the lower plate member. This makes it relatively easy to manufacture the lens holding member, improves the machining accuracy of the holding hole, and allows the GRIN lens to be held in the lens holding member with high accuracy.

[0080] In one embodiment of the optical connector, a lower recess for a guide hole is formed at both ends of the joint surface of the lower plate member, and an upper recess for a guide hole is formed at both end portions of the joint surface of the upper plate member, and by joining the joint surfaces of the lower plate member and the upper plate member, guide holes may be formed between the lower recess and the upper recess at both ends of the lens holding member.

[0081] This makes it possible to manufacture the lens holding member having the guide holes (guide pin insertion holes) with high accuracy and relatively easily. In addition, the lens holding member can be formed from inorganic materials such as quartz, glass, and ceramics that can be precisely machined, or from resin. By machining the member body, it is possible to accurately form the recess with an inverted triangular cross section and the holding hole with an inverted triangular cross section.

[0082] In an optical connector according to one embodiment, the lens holding member may have a lower recess having an inverted triangular cross section, an upper recess having a triangular cross section, and a guide hole having a diamond cross section.

[0083] The lens holding member can be formed from inorganic materials such as quartz, glass, and ceramics that can be precisely machined, or from resin. By machining the member body, it is possible to accurately form a recess having an inverted triangular cross section and a guide hole having an inverted triangular cross section for inserting a guide pin.

[0084] In an optical connector according to an embodiment, the joint surface of the lower plate member and the joint surface of the upper plate member may be bonded together with an adhesive. The joint surface of the lower plate member and the joint surface of the upper plate member are bonded with an adhesive, so that the lens holding member can be easily manufactured.

[0085] (Lens holding member 200a of another embodiment) In a lens holding member 200a of another embodiment, a holding hole 220 for holding a GRIN lens 250 is circular (cylindrical) and is formed integrally with a lower plate member 212 and an upper plate member 214, not separately. Fig. 9 shows a schematic perspective view for explaining a lens holding member 200a of another embodiment. The inner diameter of the holding hole 220 of the lens holding member 200a of the other embodiment is preferably 1 µm to 3 µm larger than the diameter of the GRIN lens 250. When fixing a GRIN lens 250 to lens holding member 200a of another embodiment, an adhesive is applied to GRIN lens 250 and then inserted into holding hole 220. When GRIN lens 250 is inserted into holding hole 220, misalignment may occur between the cross-sectional center position of GRIN lens 250 and the cross-sectional center position of holding hole 220, but the curing contraction stress of the adhesive acts to hold GRIN lens 250 at the cross-sectional center of holding hole 220 when cured, resulting in lens holding member 200a with high assembly precision.

[0086] (GRIN lens 250) The GRIN lens 250 is configured so that its refractive index gradually changes (has a refractive index distribution) from the center to the periphery. The GRIN lens 250 held by the lens holding member 200 is configured to expand the light beam emitted from the optical fiber 30. The GRIN lens 250 is configured to collimate the divergent light emitted from the optical fiber 30 and emit parallel light in a direction. The GRIN lens 250 has flat optical surfaces on both sides, which makes it easy to attach the GRIN lens 250 to the holding hole 220 of the lens holding member 200. GRIN lenses can be used that have a refractive index distribution created by an "ion exchange" process in which a base material rod is immersed in a high-temperature molten salt. After ion exchange, the rod is cut to the desired length and both ends are polished. The length of the GRIN lens 250 is preferably 0.5 mm or more and 1.5 mm or less, and more preferably 0.8 mm or more and 1.2 mm or less, in which case the sizes of the lens holding member 200 and the holding hole 220 can be reduced. The GRIN lens 250 of the lens holding member 200 arranged on the second ferrule 120 side is configured to collect the parallel light beam that passes through the light guiding portion of the spacer and enters the GRIN lens 250, and focus the light beam on the optical fiber 30.

[0087] (Spacer 300) As shown in FIG. 1 to FIG. 3 and FIG. 11, the spacer 300 is sandwiched between the pair of lens holding members 200, 200′ between the first end face 112 of the first ferrule 110 and the second end face 122 of the second ferrule 120. That is, the spacer 300 can control the distance between the first end face 112 of the first ferrule 110 and the second end face 122 of the second ferrule 120 to be constant. The distance between the pair of lens holding members 200 is controlled by the spacer 300, so that the distance between the pair of ferrule end faces is controlled. The spacer 300 may be bonded to at least one of the lens holding members 200 or may be joined by welding (laser welding, etc.). When the spacer 300 is bonded to the lens holding member 200, the connector used for bonding is preferably an MPO connector.

[0088] 11, the spacer 300 includes a spacer body 305 including one end face 301, another end face 302 opposite to the one end face 301, and an outer circumferential surface 303 connecting the one end face 301 and the other end face 302. The one end face 301 of the spacer 300 faces the first end face 112 of the first ferrule 110, and the other end face 302 of the spacer 300 faces the second end face 122 of the second ferrule 120. The spacer body 305 may have an opening 311 as a light guide section 310 for passing light between one end face 301 and the other end face 302. In this embodiment, as shown in FIG. 11, the spacer 300 is provided with a pair of guide holes 320, 320 for inserting guide pins and an opening 311 for passing light. The optical path formed between the pair of lens holding members 200, 200' passes through this opening 311 (light guide section 310). The inside of this opening 311 may be filled with gas or liquid having a predetermined refractive index. When the optical connector is immersed in liquid, a predetermined refrigerant may be filled. Also, the inside of the opening 311 may be provided with a transparent resin or glass having a predetermined refractive index. When the spacer body 305 has the opening 311, the spacer body 305 is formed in a frame shape. When the spacer 300 does not have an opening, the spacer body 305 may be formed of a plate-like member (e.g., a sheet) that is transparent to the wavelength of light to be transmitted.

[0089] Further, at both ends of the spacer 300, a pair of guide holes 320, 320 are formed, through which a guide pin 40 penetrating from one end face 301 to the other end face 302 is inserted. The interval between the pair of guide holes 320, 320 is set equal to the interval between the pair of guide pin insertion holes 116, 116 and the pair of guide holes 224, 224.

[0090] In this embodiment, one end face 301 of the spacer 300 is bonded to the lens holding member 200 arranged on the first end face 112 of the first ferrule 110. The other end face 302 of the spacer 300 abuts against the lens holding member 200 arranged on the second end face 122 of the second ferrule 120 when connecting with the second ferrule 120. Here, the first ferrule 110, the lens holding member 200 bonded to the first ferrule 110, and the spacer 300 form an optical connector (first optical connector) 10. As shown in FIG.

[0091] A pair of guide pins 40 are inserted through a pair of guide pin insertion holes 116, a pair of guide holes 224 in the first ferrule 110, and a pair of guide holes 320 in the spacer 300, thereby fixing the positions of the first optical connector 10, the lens holding member 200, and the spacer 300.

[0092] In this embodiment, a ferrule and an optical connector for optically coupling multimode optical fibers 30 to each other have been described, but the present invention can also be applied to a ferrule and an optical connector for optically coupling single mode optical fibers 30 to each other.

[0093] (Function of optical connector) 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. The light beam propagates through the optical fiber 30 fixed to the first ferrule 110 and enters the GRIN lens 250 of the lens holding member 200, is expanded by the GRIN lens 250, and is emitted toward the light guiding section 310 (opening 311) of the spacer 300. As shown in Fig. 8, the GRIN lens 250 collimates the divergent light from the optical fiber 30 and converts it into a substantially parallel light beam.

[0094] The light beam expanded by the GRIN lens 250 propagates through the light-guiding section 310 and, when it enters the GRIN lens 250 of the second optical connector 20, is focused by the GRIN lens 250 on the end face of the optical fiber 30 fixed to the second ferrule 120, and propagates through the optical fiber 30. In this manner, 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 .

[0095] According to the optical connector connection structure 1 of this embodiment, the light beam is expanded between the first optical connector 10 and the second optical connector 20. Therefore, according to the optical connector connection structure 1 of this embodiment, light is exchanged in the form of an expanded light beam, so that it is possible to suppress connection loss caused by axial misalignment or the presence of foreign matter between the first optical connector 10 and the second optical connector 20 in a plane (XY plane) perpendicular to the optical coupling direction (Z-axis direction). Therefore, it is possible to reduce connection loss in optical characteristics caused by axial misalignment, foreign matter on the end face of the optical fiber during connection, etc.

[0096] The second optical connector 20 includes a second ferrule 120 having a second end face 122, and the second end face 122 of the second ferrule 120 may be formed with an optical fiber insertion hole through which the optical fiber 30 is inserted and a pair of guide pin insertion holes through which a pair of guide pins 40 are inserted. As a result, the pair of guide pins 40 accurately align the pair of guide pin insertion holes 116 in the first ferrule 110, the pair of guide holes 224 in the lens holding member 200, the pair of guide holes 320 in the spacer 300, the pair of guide holes 224 in the lens holding member 200', and the optical fiber insertion hole 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 each other, thereby forming the optical connector connection structure 1.

[0097] The optical mounting circuit according to this embodiment has a refrigerant tank containing a refrigerant and electronic components, and the electronic components are immersed in the refrigerant of the refrigerant tank. In this case, the refractive index of the refrigerant is preferably 1.2 to 1.6. By having the refractive index within the above range, the influence of light reflection occurring at the interface between the GRIN lens 250 and the refrigerant can be minimized, and the connection loss can also be minimized. When Fluorinert (registered trademark) is used as the refrigerant, the refractive index is preferably 1.25 to 1.30, more preferably 1.26 to 1.28. This makes it a chemically stable insulator and allows it to be used in a variety of cooling applications. In addition, since a variety of boiling points are available, it can be used in single-phase applications where it is kept liquid, or in two-phase applications where it is boiled and cooled by the latent heat of vaporization. The optically integrated circuit refers to electronic devices that are required to operate with extremely high performance and stability, such as supercomputers and data centers, and that generate a large amount of heat themselves, but is not limited to these. The electronic components include a processor, a memory, a server, etc., and these electronic components have optical connectors.

[0098] The optical connector used in the optical mounted circuit can be the same as the optical connector used in the above embodiment. That is, the optical connector comprises a first ferrule 110 having a first end face 112 on which an optical fiber insertion hole 114 through which an optical fiber is inserted and a pair of guide pin insertion holes 116 through which a pair of guide pins 40 are inserted, and a lens holding member 200 bonded to the first end face 112 of the first ferrule 110 via a refractive index matching adhesive layer, the lens holding member 200 having a member body 210 and a GRIN lens 250 provided on the member body 210, and the GRIN lens 250 is aligned to correspond to the end face of the optical fiber inserted into the optical fiber insertion hole 114. Furthermore, the lens holding member 200 has a first surface 202 on the side of the first end face 112 of the first ferrule 110, and a second surface 204 opposite the first surface 202, and a spacer 300 is arranged on the second surface 204 side of the lens holding member 200, and the spacer 300 has an opening 311 (light guiding section 310) that allows light that has passed through the GRIN lens 250 to pass through, and the opening 311 (light guiding section 310) is filled with a refrigerant. The optical mounted circuit of this embodiment is an immersion cooling system that uses a fluorocarbon based cooling liquid.

[0099] (Assembly Instructions) Next, the process of placing the lens holding member 200 on the first end face 112 of the first ferrule 110 will be described. With each of the pair of jig guide pins inserted into the corresponding guide pin insertion hole 116 of the first ferrule 110 and the guide hole 224 of the lens holding member 200, the lens holding member 200 is temporarily placed slightly away from the first end face 112. Thereafter, a refractive index matching adhesive is supplied between the rear face of the lens holding member 200 and the first end face 112, and then the lens holding member 200 and the first end face 112 are brought into close contact with each other, thereby fixing the lens holding member 200 to the first ferrule 110 via the refractive index matching adhesive. Finally, each of the pair of jig guide pins is removed from the corresponding guide pin insertion hole 116 and guide hole 224.

[0100] In this manner, each GRIN lens 250 is positioned relative to the end face of the corresponding optical fiber 30, so that each GRIN lens 250 is optically coupled to the corresponding optical fiber 30. Furthermore, each guide pin insertion hole 116 is positioned relative to the corresponding guide hole 224, so that each guide pin insertion hole 116 communicates with the corresponding guide hole 224.

[0101] (Lens holding member 200b of another embodiment) 10 shows a lens holding member 200b in which a pair of resin pool recesses 280 are formed on the first end surface 112 side of the first ferrule 110 of the lens holding member 200b. The resin pool recesses 280 are formed as grooves running vertically between the holding hole 220 and the guide hole 224. By filling the gap between the pair of resin pool recesses 280 with a refractive index matching adhesive, the thickness of the adhesive layer can be easily made uniform, and the optical characteristics can be stabilized. This also makes it possible to prevent excess adhesive from entering the guide hole 224, etc., and thus suppresses the occurrence of problems such as the guide pin 40 being unable to be inserted correctly. The resin pool may have a structure having a convex portion in addition to a concave portion (resin pool concave portion 280). By forming the resin pool as a concave portion, the amount of adhesive dripping can be reduced and the strength of the area around the guide pin insertion hole 116 can be ensured. The resin pool recess 280 or protrusion of the lens holding member 200b of this embodiment may be provided on the lens holding member 200b in which the holding hole 220 shown in FIG. 9 is circular (cylindrical). Moreover, the resin pool convex or concave portion may be provided on the lens holding member 200 side or on the spacer 300 side.

[0102] (Spacer 300a of another embodiment) 12 is a diagram showing an example of a spacer 300a in which a flow path 350 is formed. The spacer 300a of this embodiment has a frame having an opening 311, and the frame is formed with a flow path 350 that communicates the opening 311 with the outside of the frame. This allows external gas or liquid (such as a refrigerant) to be introduced into the opening 311 through the flow path 350. Note that the flow path 350 may penetrate from one end surface 301 to the other end surface 302 of the spacer main body 305 as shown in FIG. 12, or a concave flow path 350 that does not penetrate may be formed in the end surface of the spacer main body 305 as shown in FIG. 13.

[0103] (Spacer 300b of another embodiment) 13 is a schematic perspective view showing an example of a spacer 300b provided with two or more flow paths 350. In this embodiment, two flow paths 351, 352 are provided on one end face 301 and the other end face 302 of the spacer main body 305 so as to face each other (on the front and back of the frame portion), and these flow paths 351, 352 can be formed on the top and bottom of the frame. By providing a plurality of flow paths 351, 352, when an optical connector including the spacer 300a is immersed in a refrigerant, air present in the opening 311 of the frame can be released to the outside through the flow path 351, and can be easily replaced with the refrigerant.

[0104] (Spacer 300c of another embodiment) 14 is a schematic perspective view showing an example of a spacer 300c in which a through-hole 331 serving as a light guiding section is provided in a spacer body 305. The through-hole 331 is a through-hole in which an opening 311 for guiding an optical signal and a guide hole 320 for inserting a guide pin 40 are integrated together. A flow path 350 may be further provided in this spacer 300c.

[0105] (Spacer 300d of another embodiment) 15 is a schematic perspective view showing an example of a spacer 300d in which a through-hole 332 serving as a light guide is provided in a spacer body 305. The through-hole 332 of this embodiment is formed to penetrate the plate-like spacer body 305 in the shape of a slit. Therefore, the through-hole 332 of this embodiment is an integrated unit of an opening 311 for guiding an optical signal, a guide hole 320 for inserting a guide pin 40, and a flow path 350 for introducing a liquid or the like. The innermost part of the through-hole 332 is provided at a position corresponding to the guide hole.

[0106] (Spacer 300e of another embodiment) 16 is a schematic perspective view showing an example of a spacer 300e in which a spacer body 305 is provided with a plurality of openings 312. The plurality of openings 312 are provided so that the central axis of each of them coincides with that of the GRIN lens 250. The size of the openings 312 is set to have a diameter equal to or larger than that of the optical surface of the GRIN lens 250. As a result, since a plurality of openings 312 are provided for each GRIN lens 250, it is possible to reliably prevent intrusion of stray light from adjacent GRIN lenses 250.

[0107] (Spacer 300f of another embodiment) 17 shows an example of a spacer 300f according to still another embodiment, in which the entire spacer 300f is made of a transparent resin or glass having a predetermined refractive index. In this case, since the spacer body 305 of the spacer 300f functions as the light guide section 310, the spacer 300f is provided with a guide hole 320, but does not need to have a through hole (such as an opening 311). In this case, the spacer 300f is in close contact or bonded to the lens holding member 200, and is configured so that liquid does not enter the optical path even when immersed in a refrigerant or the like. This makes it possible to reduce connection loss without being affected by liquid. In the example of Fig. 17, the spacer 300f is a resin or glass body having a predetermined thickness, but is not limited to this, and the spacer 300f may be a resin film or the like.

[0108] (Spacer 300g in another embodiment) Fig. 18 shows an example in which guide hole 320 of spacer 300f (Fig. 17) is guide hole 321 formed in a slit shape penetrating outer circumferential surface 303 of spacer body 305. In this case, spacer 300g can be easily processed.

[0109] In the present invention, the optical connector connection structure 1 corresponds to the "optical connector connection structure", the optical fiber 30 corresponds to the "optical fiber", the first ferrule 110 corresponds to the "first ferrule", the second ferrule 120 corresponds to the "second ferrule", the optical fiber insertion hole 114 corresponds to the "optical fiber insertion hole", the guide pin insertion hole 116 corresponds to the "guide pin insertion hole", the first end face 112 corresponds to the "first end face", the lens holding member 200 corresponds to the "lens holding member", the member body 210 corresponds to the "member body", the GRIN lens 250 corresponds to the "GRIN lens", the second optical connector 20 corresponds to the "second optical connector", and the spacer 300 corresponds to the "spacer".

[0110] Although a preferred embodiment of the present invention is as described above, the present invention is not limited thereto. It is understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the actions and effects of the configuration of the present invention are described in this embodiment, these actions and effects are merely examples and do not limit the present invention. [Explanation of symbols]

[0111] 1 Optical connector connection structure 10 First optical connector (optical connector) 20 Second Optical Connector 30 Optical Fiber 40 Guide pin 110 First ferrule 114 Optical fiber insertion hole 116 Guide pin insertion hole 120 Second Ferrule 200 Lens holding member 210 Main body of material 212 Lower plate member 214 Upper plate member 216 Recess 220 Retaining hole 224 Guide hole (guide pin insertion hole) 250GRIN lens 300 Spacer 310 Light guide section 311 Opening 320 Guide hole (guide pin insertion hole) 350 Channel

Claims

1. An optical connector to be connected to an electronic component immersed in a refrigerant in a refrigerant tank, a first ferrule having an optical fiber insertion hole through which an optical fiber is inserted; a spacer provided on the connection end surface side of the first ferrule, the spacer has an opening through which light from the optical fiber passes and into which the coolant is filled; The optical connector, wherein the beam diameter of light passing through the opening is expanded.

2. The optical connector according to claim 1 , wherein the spacer further has a flow path for passing the coolant and / or the air in the opening.

3. a collimating lens between the optical fiber of the first ferrule and the opening of the spacer, the collimating lens collimating light of the optical fiber; 2. The optical connector according to claim 1, wherein the coolant in the opening through which the collimated light passes has a refractive index of 1.2 or more and 1.6 or less.

4. A method for connecting an optical connector to an electronic component immersed in a refrigerant in a refrigerant tank, comprising the steps of: a first ferrule having an optical fiber insertion hole through which an optical fiber is inserted; a spacer provided on the connection end surface side of the first ferrule and having an opening through which light of the optical fiber passes; and a step of connecting a second ferrule provided on the electronic component in this order; and filling the opening of the spacer with the coolant.

Images