Ferrule, optical connector, substrate and server

Abstract

To provide an optical fiber assembly that does not reduce connection loss even in the case of mounting an optical connector on a substrate and performing reflow solder.SOLUTION: An optical fiber assembly includes: a tabular ferrule 100 formed of a ceramic plate and having an optical fiber insertion hole 103 and a guide pin insertion guide hole 102; and an optical fiber 11 inserted in the optical fiber insertion hole 103 of the ferrule 100. The optical fiber 11 is bonded to the optical fiber insertion hole 103 of the ferrule 100 with an adhesive applied in the optical fiber insertion hole 103.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical fiber assembly used to mechanically connect optical fibers to each other without causing connection loss, and a plate used in the optical fiber assembly. [Background technology]

[0002] In optical communications, optical connectors are used to mechanically connect optical fibers. In particular, the MT connector (Mechanically Transferable connector), developed for optical network equipment, is a reliable multi-fiber optical connector that is widely used, primarily in optical communication networks. This MT connector uses guide pins to detachably connect a pair of optical connectors and is used, for example, to connect optical fiber ribbons and optical fiber cords with 2 to 16 fibers. In addition to this MT connector, an MPO connector is also known, which houses an optical ferrule in a housing and is equipped with guide pins, a latch mechanism, etc.

[0003] For example, Patent Document 1 (Japanese Patent Laid-Open Publication No. 2002-350680) discloses an optical ferrule that allows optical fibers to be physically contacted with each other. The optical ferrule described in Patent Document 1 is an injection-molded product made of a resin composition obtained by blending 100 parts by mass of polyphenylene sulfide resin with 100 to 300 parts by mass of silica having a maximum particle size of 100 μm or less and 50 to 300 parts by mass of barium titanate.

[0004] Patent Document 2 (Japanese Patent Laid-Open Publication No. 2001-174666) discloses an optical ferrule that allows physical contact between optical fibers.

[0005] The optical ferrule described in Patent Document 2 is characterized by being a molded article of a resin composition that contains a base resin, silica, and whiskers as essential components, and has a melt viscosity of 300 to 600 [Pa·sec] at a temperature of 340°C and a shear rate of 900 [1 / sec], as measured using a capillary with a diameter of 0.1 mm and a depth of 30 mm, as specified in JIS-K-7199.Preferably, the base resin is a linear polyphenylene sulfide resin, and the ferrule is an injection-molded article of a resin composition in which 250 to 300 parts by weight of silica and 10 to 70 parts by weight of whiskers are blended with 100 parts by weight of the linear polyphenylene sulfide resin.

[0006] Patent Document 3 (Japanese Patent Laid-Open Publication No. 2004-29415) discloses an optical connector equipped with a ferrule that can maintain dimensional accuracy and dimensional stability and further improve mechanical strength. The optical connector described in Patent Document 3 has an optical fiber hole and a guide hole, and a guide pin is inserted into the guide hole to position the optical fiber connection. The ferrule is molded from a resin composition containing 10 to 20% by weight of polyphenylene sulfide resin and 80 to 90% by weight of silica particles.

[0007] Patent Document 4 (JP 2003-185886 A) discloses an optical connector in which an optical connector ferrule is manufactured by injection molding using a PPS resin composition containing an inorganic filler made of silica particles, and in which the silica hardly falls off even when the optical connector is repeatedly attached and detached, and no scratches that would affect the characteristics of the optical connector are left on the end face of the optical fiber.

[0008] The optical connector described in Patent Document 4 has an optical connector ferrule provided with at least one optical fiber insertion hole and two mating holes for inserting mating pins for connecting optical connectors together, and this optical connector ferrule is molded from a PPS resin composition containing a fibrous filler and silica particles surface-treated with a vinyl silane coupling agent.

[0009] Patent Document 5 (JP 2003-138044 A) discloses a molded article suitable for ferrules of optical connectors and the like, which has excellent injection moldability without impairing the melt fluidity of the resin composition, and in addition, the molded article has excellent mechanical strength and small connection loss even after repeated attachment and detachment. The molded article described in Patent Document 5 is produced by melt-molding a PPS resin composition obtained by blending a molten mixture of (A) a PPS resin having a specific functional group X introduced into the molecular terminal or side chain, and (B) an organic compound having, in the same molecule, a carbon-carbon double bond and an atomic group capable of forming a chemical bond with the functional group X introduced into the PPS resin upon melt mixing, with (C) an inorganic filler that has been surface-treated with a silane coupling agent having a carbon-carbon double bond, or a silane coupling agent having a carbon-carbon double bond and an inorganic filler, and then irradiating the molded article with ionizing radiation.

[0010] Patent Document 6 (JP 2014-240958 A) discloses an optical module that can be surface mounted using a reflow oven and emits laser light without extending an optical fiber outside the mounting substrate.

[0011] The optical module described in Patent Document 6 includes a plurality of optical elements that emit red, green, and blue laser light, a plurality of optical fibers that respectively guide the color laser light from the plurality of optical elements, a mounting substrate on whose top surface the plurality of optical elements are mounted and on which electrodes for supplying electrical signals to the plurality of optical elements are formed as through electrodes that penetrate from the top surface to the bottom surface, and a multiplexing section that is located at a corner of the mounting substrate and that bundles and fixes the emission ends of the plurality of optical fibers to emit multiplexed light obtained by multiplexing the color laser light. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-350680 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-174666 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-29415 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-185886 [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-138044 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-240958 Summary of the Invention [Problem to be solved by the invention]

[0013] The ferrule is a main component of a multi-fiber optical connector, and is formed by molding a synthetic resin material in a mold. The ferrule has an insertion hole for inserting an optical fiber ribbon, and a plurality of optical fiber holes for arranging the optical fibers whose coatings have been removed are provided in communication with the optical fiber tape insertion hole. Guide holes for positioning and connecting optical connectors are also provided parallel to the optical fiber holes and penetrate the ferrule. The coating at the tip of the optical fiber ribbon is removed and the exposed optical fibers are inserted from the rear side of the ferrule, and the exposed optical fibers are inserted into the optical fiber holes of the ferrule and fixed with an adhesive. After the optical fibers are inserted into the ferrule, the connection end faces of the optical fibers are polished together with the connection face of the ferrule.

[0014] A guide pin is inserted and fixed in advance into the guide hole of one of the ferrules that make up the multi-core optical connector, and this guide pin is inserted into the guide hole of the other ferrule, and the connection surfaces of the optical connectors are butted together to connect multiple optical fibers at once. The ferrules of such optical connectors must be aligned with the axial centers of the optical fibers with high precision, and therefore the ferrules are required to have properties such as dimensional stability and mechanical strength.

[0015] Conventionally, polyphenylene sulfide has been known to be used as a molding material for ferrules because it has a small shrinkage rate during molding, excellent dimensional stability over time, high fluidity during molding, and excellent environmental resistance. Polyphenylene sulfide (PPS) has a low melt viscosity and can be compounded with a large amount of filler, making it possible to obtain ferrules with low molding shrinkage and high dimensional accuracy.

[0016] The diameter and pitch of the guide holes and fiber insertion holes in this ferrule require precision on the order of submicrons. For example, it is said that a 1 μm misalignment of the fiber insertion hole will cause a connection loss of approximately 0.2 dB. Therefore, molding is done with the expectation that the ferrule will harden and shrink after molding, but the cure shrinkage rate of the molding material varies greatly, making it extremely difficult to mold ferrules with high dimensional precision. Furthermore, if a temperature change occurs after the ferrule is molded, the ferrule will expand or contract, causing dimensional deformation, which will result in a change in the position of the optical fiber fixed to the ferrule, resulting in an increase in connection loss.

[0017] Therefore, as shown in Patent Documents 1 to 5, ferrules with excellent dimensional accuracy and dimensional stability have been developed. Meanwhile, as shown in Patent Document 6, in recent years, optical modules have been developed in which optical elements are mounted on a substrate and optically coupled to optical fibers. As a result, optically mounted circuits that do not involve electrical wiring, by directly introducing high-speed, high-density optical communications into (or close to) an electronic substrate, are being considered.

[0018] However, in optical modules that connect a photoelectric conversion element mounted on a substrate with a ferrule to which an optical fiber is connected, when an optical connector equipped with a resin ferrule is mounted on a substrate and soldered, the heat generated during the soldering reflow process causes the ferrule's dimensions to fluctuate, resulting in misalignment of the optical fiber and an increase in connection loss.

[0019] In addition, some electronic components on the board become hot during operation, which can subject the optical connector to unprecedented temperature changes, which can also cause misalignment and increase connection loss. In particular, in optical packaging circuits, with the trend toward higher speeds and larger capacities, there is a demand for ferrules that do not cause misalignment of optical fibers and have low connection loss, even when high-density optical connectors are mounted.

[0020] Furthermore, the techniques described in the above patent documents require precise machining of multiple optical fiber insertion holes in the ferrule tip portion to the micron level in accordance with the number of optical fibers in the multi-core configuration. This requires a precision mold for forming the multiple optical fiber insertion holes in the ferrule tip portion, making it impossible to reduce manufacturing costs. This problem becomes particularly pronounced as the number of fibers increases due to the precision of the pins in the mold for forming the fiber insertion holes.

[0021] On the other hand, in recent years, there has been a demand for high-speed, large-capacity information communications, and efforts are being made to increase the density of optical fiber connectors. However, it has been difficult to mold complex shapes at high density with high precision using resin-molded ferrules. Furthermore, existing standard ferrules and optical connectors have been used to connect optical fibers together when connecting optical devices over long distances. Therefore, in order to connect optical fibers and mount them on a circuit board in a small space such as inside a computer, they need to be extremely small components, necessitating a fundamental change in design.

[0022] The present invention has been made to overcome the above drawbacks, and its object is to provide an optical fiber assembly, plate, and optical module that can reliably connect optical fibers and mount them on a substrate even in a small space, and that has low connection loss. Another object of the present invention is to provide an optical fiber assembly, plate, and optical module that do not adversely affect connection loss even when exposed to high temperatures, such as when an optical connector is mounted on a substrate and soldered for reflow.

[0023] Another object of the present invention is to provide an optical fiber assembly, a plate and an optical module that can be formed into precise and complex shapes without the need for molding. Another object of the present invention is to provide an optical fiber assembly, plate and optical module that can be optically connected directly by physical contact even in an environment where a refractive index matching agent or an optical lens cannot be used. [Means for solving the problem]

[0024] (1) An optical fiber assembly according to one aspect comprises a plate-shaped ferrule formed from ceramics and having an optical fiber insertion hole and a guide hole for inserting a guide pin, and an optical fiber inserted into the optical fiber insertion hole of the ferrule, with the optical fiber being fixed to the optical fiber insertion hole of the ferrule by adhesive filled in the optical fiber insertion hole.

[0025] This makes it possible to design heat-resistant optical connection components by using ceramics as the plate material. Furthermore, by using ceramic plates as ferrules, there is no need to design runners, which are the passageways for the material required for injection molding, as is the case when manufacturing ferrules with conventional resins. Therefore, it is possible to manufacture ferrules with a thickness of 2.5 mm or less, for which it is difficult to ensure precision with conventional designs. Furthermore, unlike conventional methods, resin molding using dies is not required, and instead, a ceramic plate with high mechanical strength and heat resistance is machined, allowing for the formation of complex and intricate shapes with high precision. This makes it possible to increase the number of optical fibers and achieve high-density optical connections, enabling high-speed, high-capacity communication connections. In this case, a preferred example of ceramics is machinable ceramics, which allow for fine and precise machining.

[0026] Furthermore, when the ferrule is mounted on a substrate and subjected to solder reflow, even if the ferrule is exposed to high temperatures during the solder reflow process, thermal dimensional fluctuations are unlikely to occur. As a result, misalignment of the optical fiber can be suppressed, preventing deterioration of connection loss. In other words, characteristics such as connection loss do not change before and after the solder reflow process, and characteristics do not change even when the ferrule is installed near components that become hot. Furthermore, optical communications using high-power lasers have been considered in recent years, and even if heat is generated at the optical connection point, the ferrule will not be damaged, and characteristics such as connection loss will not change. Moreover, unlike conventional methods, the heat-resistant ferrule is not manufactured using an injection mold made of PPS resin, a super engineering plastic, so it can be manufactured relatively inexpensively.

[0027] Furthermore, because the ceramic ferrule has a thermal expansion coefficient similar to that of the optoelectric conversion element or silicon optical waveguide, its thermal expansion and contraction are similar to those of the optoelectric conversion element or silicon optical waveguide mounted on the substrate, improving reliability. When selecting a material for the machinable ceramic, it is more preferable to select a material whose physical properties, such as the linear expansion coefficient, are similar to those of the optoelectric conversion element or silicon optical waveguide. Furthermore, by making the ferrule plate-shaped, a small and low-profile connection is possible, and optical fibers can be reliably connected even in small spaces, making it possible to optically mount the optical fiber on a circuit board.

[0028] (2) An optical fiber assembly according to a second aspect of the present invention is the optical fiber assembly according to the first aspect of the present invention, wherein the ceramics include machinable ceramics and the optical fiber includes silica glass.

[0029] As a result, the connection end face of the ceramic plate to which the optical fiber is fixed has the core portion of the optical fiber made of quartz glass and the plate body made of machinable ceramics. In this case, the optical fiber is harder than the plate body, so when the connecting end surface of the plate is optically polished to perform optical connection, the connecting end surface of the optical fiber protrudes slightly in a convex shape relative to the connecting end surface of the plate body. Therefore, when this optical fiber assembly is optically connected, the convex shapes of the optical fibers come into contact and deform, creating a physical contact (PC) connection. This suppresses Fresnel reflection and reduces signal attenuation. This eliminates the need for refractive index matching agents or optical lenses at the connection ends of the connector, and allows for low-loss optical signal connection. Whether or not to use a refractive index matching agent, optical lens, etc. on the connection end face is determined appropriately depending on the purpose of the optical connection, and the connection method is not limited to PC connection.

[0030] (3) An optical fiber assembly according to a third aspect of the present invention is the optical fiber assembly according to the first or second aspect of the present invention, wherein the hardness of the ceramic may be lower than the hardness of the optical fiber.

[0031] As a result, the core portion of the optical fiber is harder than the portion of the plate body, so when the connection end surface of the plate is optically polished to perform optical connection, the connection end surface of the optical fiber protrudes in a convex shape relative to the connection end surface of the plate body. Therefore, when this optical fiber assembly is optically connected, the convex shapes of the optical fibers come into contact and deform, creating a physical contact (PC) connection. This suppresses Fresnel reflection, reducing signal attenuation. This eliminates the need for refractive index matching agents or optical lenses at the connection ends of the connector, and allows optical signals to be connected with low loss. In the present invention, the hardness refers to the Vickers hardness (GPa) measured according to JIS Z2244.

[0032] (4) The optical fiber assembly according to the fourth invention is an optical fiber assembly according to any one of the first to third inventions, and the ferrule may be a ferrule for a multi-core optical connector having 12 or more optical fiber insertion holes.

[0033] Instead of using conventional resin molding with a mold, the technology can be machined onto a highly heat-resistant ceramic plate, enabling complex and intricate shapes to be formed with high precision. This allows for a higher number of optical fibers than before, enabling higher-density optical connections and enabling high-speed, high-capacity communication connections.

[0034] The number of connection cores in a multi-core optical connector can be, for example, 16, 24, 32, 36, 48, etc. in addition to 12, and when the number of cores is large, the optical fiber insertion holes may be arranged in two or three rows. In this case, it is preferable to use machinable ceramics, which have low hardness and can be easily and inexpensively processed into fine and precise shapes.

[0035] (5) An optical fiber assembly according to a fifth aspect of the present invention is the optical fiber assembly according to any one of the first to fourth aspects of the present invention, and the amount of dimensional variation of the ferrule when heated at 260° C. may be 0.5 μm or less.

[0036] As a result, when the optical connector is mounted on a circuit board and soldered, even if the ferrule is exposed to high temperatures during the solder reflow process, dimensional fluctuations in the ferrule are unlikely to occur. As a result, misalignment of the optical fiber can be prevented, minimizing adverse effects on connection loss and other issues. Therefore, characteristics such as connection loss do not fluctuate before and after the solder reflow process. Furthermore, characteristics such as connection loss do not fluctuate even when electronic components on the board are subjected to temperature changes due to operation. Therefore, even when optical wiring is mounted on the substrate, an optical fiber assembly with low connection loss can be obtained.

[0037] The dimensional variation amount in the present invention is the average value of the positional variation amount R of each fiber insertion hole compared before and after the heating test, with the midpoint M of the perpendicular bisector connecting the center points G1 and G2 of the guide holes as the reference point (see Figure 27).

[0038] (6) An optical fiber assembly according to a sixth aspect of the present invention is an optical fiber assembly according to any one of the first to fifth aspects of the present invention, wherein the ferrule has a plate body formed in a rectangular shape, and a surface identification structure may be formed at one corner of the plate body.

[0039] It was confirmed that the shape of the optical fiber insertion holes (such as the angle of inclination of the hole relative to the surface of the plate body and the inner diameter of the hole) on one side of the plate body (side A) and the other side (side B) are not strictly identical. As a result, the connection loss values ​​are not the same on both sides of the plate body, but slightly different. In other words, because the plate body is machined using a drill or other tool from one side, the shape of the optical fiber insertion holes is not strictly symmetrical on both sides. Therefore, by forming a side identification structure at one corner of the plate body, it is possible to easily distinguish between side A and side B of the plate body visually using the side identification structure as a reference. The surface identification structure may be a chamfered surface (defined as a C surface) or an identification through hole.

[0040] (7) The optical fiber assembly according to the seventh invention is an optical fiber assembly according to any one of the first to sixth inventions, wherein the plate body (ferrule) has a thin-walled portion where the thickness of the plate body is reduced and formed to include an optical fiber insertion hole, and a thick-walled portion, and a guide groove that is continuous with the optical fiber insertion hole may be formed on the upper end surface of the thick-walled portion.

[0041] This allows the tip of the optical fiber to be guided into the optical fiber insertion hole along the concave guide groove formed on the upper end surface of the thick-walled portion when inserting the optical fiber into the optical fiber insertion hole, making it easy to assemble the optical fiber assembly. Optical fibers are thin wires measuring several tens to several hundred microns, and they must be inserted into insertion holes of almost the same size as the diameter of the optical fiber, making assembling an optical fiber assembly a delicate and difficult task. In particular, when mounting optical fibers on a substrate, high-speed, large-capacity communication is required, so multi-core optical fibers are often used, and it is sometimes necessary to insert several tens of optical fibers into a single plate. The optical fiber assembly according to the seventh invention allows for easy assembly even when multi-core optical fibers are used.

[0042] (8) The optical fiber assembly according to the eighth invention is the optical fiber assembly according to the seventh invention, wherein a plurality of optical fiber insertion holes are arranged in two or more rows, the thin-walled portion has a thickness of two or more, and the guide groove may be provided in a stepped manner for each row of optical fiber insertion holes.

[0043] This allows the optical fiber to be inserted along the stepped concave guide groove, making it easier to insert the optical fiber into the optical fiber insertion holes provided in a small plate, even when there are a large number of optical fiber insertion holes and high-density optical connections are required. Furthermore, compared to the case of a flat plate, the adhesive is sufficiently accumulated in the stepped portion, so that a sufficient amount of adhesive is applied to the inside of the optical fiber insertion hole when the optical fiber is inserted.

[0044] (9) The optical fiber assembly according to the ninth invention is an optical fiber assembly according to any one of the first to eighth inventions, and may have an adhesive reservoir portion including an optical fiber insertion hole recessed on the surface of the plate body (ferrule).

[0045] This allows excess adhesive used to secure the optical fiber to the optical fiber insertion hole to be collected in the adhesive reservoir, preventing the hardened excess adhesive from protruding beyond the surface of the ceramic plate. In particular, since the surface shape of the hardened adhesive is not completely flat, uneven gaps may occur due to the hardened adhesive. According to the optical assembly of the ninth aspect of the present invention, the adhesive is contained in a recessed adhesive reservoir, which keeps the end face of the plate flat and reduces the risk of problems when the ceramic plate is butted against the connecting surface of an optical connector such as a jig or an MT ferrule. This allows for accurate manufacture of the optical fiber assembly as designed, without increasing connection loss.

[0046] (10) The optical fiber assembly according to the tenth invention is an optical fiber assembly according to any one of the first to ninth inventions, and may have a guide hole formed with a hat-shaped cross section, a small hole, and a large hole formed around the small hole.

[0047] This allows the end face of the ceramic plate to be connected to an optical connector such as an MT ferrule by using a guide pin with a flange corresponding to the hat shape. According to the optical fiber assembly of the tenth invention, by inserting a bolt-shaped guide pin from the ceramic plate side, the guide pin can be fixed while suppressing the amount of protrusion of the guide pin. In particular, when fitting and connecting a ceramic plate to an MT ferrule or the like, by using a flanged guide pin, the fiber insertion side of the ceramic plate is not affected by the guide pin, and the entire fiber insertion surface can be used.

[0048] (11) An optical fiber assembly according to an eleventh aspect of the present invention is the optical fiber assembly according to any one of the first to tenth aspects of the present invention, wherein the thickness of the plate body may be 0.3 mm or more and 3.0 mm or less.

[0049] This allows the plate body to be polished without being damaged, and also allows guide grooves for optical fibers, adhesive reservoirs, etc. to be formed without any problems. If the thickness of the plate body is less than the above range, for example, when forming a guide groove in the plate, the thickness of the thin-walled portion may become too thin, which may cause the plate to break. It may also be impossible to ensure a guide groove of an appropriate length. Furthermore, after bonding and fixing the optical fiber to the plate, the plate end face is polished while attached to a jig, and the pressure applied when polishing the end face may cause the plate to break.

[0050] (12) The optical module of the twelfth invention has an opto-electrical conversion element mounted on a substrate, and an optical fiber assembly of any one of the first to eleventh inventions mounted in close proximity to the opto-electrical conversion element or a silicon optical waveguide and optically connected to it.

[0051] Ceramic plates have excellent heat resistance, so even when an optical fiber assembly and an optoelectronic conversion element are mounted on a substrate and soldered after reflow, there is no dimensional change due to heat, and characteristics such as connection loss do not fluctuate. Furthermore, because the ceramic plate can be made to have a thermal expansion coefficient similar to that of the optoelectronic conversion element or silicon optical waveguide, dimensional fluctuation is minimal, thereby reducing optical loss. Furthermore, high-density optical lines can be mounted even near high-temperature electronic components, enabling high-speed, large-capacity information processing. Examples of optoelectronic conversion elements include vertical-cavity surface-emitting lasers (VCSELs), laser diodes (LDs), and photodetectors (PDs). When selecting a material for machinable ceramics, it is preferable to choose one with physical properties, such as a linear expansion coefficient, similar to those of silicon.

[0052] (13) A plate according to a thirteenth aspect of the present invention is a ceramic plate having a plurality of optical fiber insertion holes and guide holes for inserting guide pins, and having a hardness of 8.0 GPa or less.

[0053] This makes it possible to design heat-resistant optical connection components by using ceramics as the plate material. Furthermore, by using a ceramic plate as a ferrule, it is no longer necessary to design a runner, which is the passageway for the material required for injection molding, as is the case when manufacturing ferrules with conventional resins. Therefore, it is possible to manufacture ferrules with a thickness of 2.5 mm or less, which is difficult to ensure with conventional designs. Furthermore, unlike conventional resin molding using dies, the technology uses a ceramic plate with high mechanical strength and heat resistance, which can be machined to form complex and intricate shapes with high precision. This allows for a higher number of optical fibers than before, enabling higher-density optical connections and enabling high-speed, high-capacity communication connections. In this case, a preferred example of ceramics is machinable ceramics, which have low hardness and can be easily and inexpensively processed finely and precisely.

[0054] Furthermore, when the ferrule is mounted on a substrate and subjected to solder reflow, even if the ferrule is exposed to high temperatures during the solder reflow process, thermal dimensional fluctuations are unlikely to occur. As a result, misalignment of the optical fiber can be suppressed, preventing deterioration of connection loss. In other words, characteristics such as connection loss do not change before and after the solder reflow process, and characteristics do not change even when the ferrule is installed near components that become hot. Furthermore, optical communications using high-power lasers have been considered in recent years, and characteristics such as connection loss do not change even when heat is generated at the optical connection point. Moreover, unlike conventional methods, the heat-resistant ferrule is not manufactured using an injection mold made of PPS resin, a super engineering plastic, so it can be manufactured relatively inexpensively.

[0055] Furthermore, because the ceramic ferrule has a thermal expansion coefficient similar to that of the optoelectric conversion element or silicon optical waveguide, its thermal expansion and contraction are similar to those of the optoelectric conversion element or silicon optical waveguide mounted on the substrate, improving reliability. When selecting a material for the machinable ceramic, it is more preferable to select a material whose physical properties, such as the linear expansion coefficient, are similar to those of the optoelectric conversion element or silicon optical waveguide. Furthermore, by making the ferrule plate-shaped, a small and low-profile connection is possible, and optical fibers can be reliably connected even in small spaces, making it possible to optically mount the optical fiber on a circuit board.

[0056] Furthermore, because the hardness of the plate is 8.0 GPa or less, the quartz fiber typically used in optical communications is harder than the plate. Therefore, when the connecting end surface of the plate is optically polished for optical connection, the connecting end surface of the optical fiber protrudes in a convex shape relative to the connecting end surface of the plate body. Therefore, when this optical fiber assembly is optically connected, the convex shapes of the optical fibers come into contact and deform, creating a physical contact (PC) connection. This suppresses Fresnel reflection, significantly reducing signal attenuation. This eliminates the need for refractive index matching materials or optical lenses at the connection ends of the connector, and allows optical signals to be connected with low loss. In the present invention, hardness refers to Vickers hardness (GPa) measured according to JIS Z 2244. Whether or not to use a refractive index matching agent, optical lens, etc. on the connection end face is determined appropriately depending on the purpose of the optical connection, and the connection method is not limited to PC connection.

[0057] Furthermore, since no injection mold is used as in conventional ferrule manufacturing, the heat-resistant ferrule plate can be manufactured relatively inexpensively. Furthermore, because the thermal expansion coefficient of the ceramic plate is similar to that of silicon, the thermal expansion and contraction of the ceramic plate is similar to that of the silicon optical waveguide, lenses, and other optical elements mounted on the substrate, improving reliability. Furthermore, the plate shape allows for a compact and low-profile connection, enabling reliable connection of optical fibers even in small spaces, enabling optical mounting to a substrate. When selecting a material for machinable ceramics, it is preferable to select a material whose physical properties, such as the linear expansion coefficient, are similar to those of silicon.

[0058] (14) A plate according to a fourteenth aspect of the present invention is the plate according to the thirteenth aspect of the present invention, and may have twelve or more optical fiber insertion holes.

[0059] Instead of using conventional resin molding with a mold, the technology can be machined onto a highly heat-resistant ceramic plate, enabling complex and intricate shapes to be formed with high precision. This allows for a higher number of optical fibers than before, enabling higher-density optical connections and enabling high-speed, high-capacity communication connections. The number of connection cores in a multi-core optical connector can be, for example, 16, 24, 32, 36, 48, etc., in addition to 12, and when the number of cores is large, the optical fiber insertion holes may be arranged in two or three rows, etc. In this case, it is preferable to use machinable ceramics, which have low hardness and can be easily and inexpensively processed into fine and precise shapes.

[0060] (15) A plate according to a fifteenth aspect of the present invention is a plate according to the thirteenth or fourteenth aspect of the present invention, and may have a dimensional variation of 0.5 μm or less when heated at 260°C.

[0061] As a result, when the optical connector is mounted on a circuit board and soldered, even if the ferrule is exposed to high temperatures during the solder reflow process, dimensional fluctuations in the ferrule are unlikely to occur. As a result, misalignment of the optical fiber can be prevented, minimizing adverse effects on connection loss and other issues. Therefore, characteristics such as connection loss do not fluctuate before and after the solder reflow process. Furthermore, characteristics such as connection loss do not fluctuate even when electronic components on the board are subjected to temperature changes due to operation. Therefore, even when optical wiring is mounted on the substrate, an optical fiber assembly with low connection loss can be obtained.

[0062] The dimensional variation in the present invention was measured by measuring the distance L between the midpoint M of the perpendicular bisector connecting the center points G1 and G2 of the guide holes and the center point of each fiber insertion hole, and comparing the results before and after the heating test (see Figure 27).

[0063] (16) The plate according to the 16th invention is a plate according to any one of the 13th to 15th inventions, and has a rectangular plate body with a thickness of 0.3 mm or more and 3.0 mm or less, and may have a machined portion machined into the plate body.

[0064] This allows the plate body to be polished without being damaged, and also allows guide grooves for optical fibers, adhesive reservoirs, etc. to be formed without any problems. If the thickness of the plate body is less than the above range, for example, when forming a guide groove in the plate, the thickness of the thin-walled portion may become too thin, which may cause the plate to break. It may also be impossible to ensure a guide groove of an appropriate length. Furthermore, after bonding and fixing the optical fiber to the plate, the plate end face is polished while attached to a jig, and the pressure applied when polishing the end face may cause the plate to break. The machined parts include a surface identification structure formed on the plate, a guide groove for guiding the optical fiber into the optical fiber insertion hole, an adhesive reservoir, and the cross-sectional shape of the guide hole.Since the material is machinable ceramics, machining is easy, and these machined parts can be precisely machined at low cost.

[0065] In particular, in the case of an optical communication connection method where angled polishing is not required, it is possible to set the thickness of the plate body thin. Examples of cases where angled polishing is not required include when an anti-reflection coating is formed on the connection end face, when the optical fiber used is a multimode optical fiber, when the communication distance is short, and other cases where the loss conditions required for the connection part are not strict. Furthermore, when polishing the connection end face at an angle to prevent Fresnel reflection, if the thickness of the plate body is 0.5 mm or more, the plate body can be polished without being damaged, and guide grooves for the optical fiber, adhesive reservoirs, etc. can be formed without any problems.

[0066] (17) A plate according to a seventeenth aspect of the present invention is the plate according to the sixteenth aspect of the present invention, wherein the machined portion may include a surface identification structure formed at a corner of the plate body.

[0067] It was confirmed that the shape of the optical fiber insertion holes (such as the angle of inclination of the hole relative to the surface of the plate body and the inner diameter of the hole) on one side of the plate body (side A) and the other side (side B) are not strictly identical. As a result, the connection loss values ​​are not the same on both sides of the plate body, but slightly different. In other words, because the plate body is machined using a drill or other tool from one side, the shape of the optical fiber insertion holes is not strictly symmetrical on both sides. Therefore, by forming a side identification structure at one corner of the plate body, it is possible to easily distinguish between side A and side B of the plate body visually using the side identification structure as a reference. The surface identification structure may be a chamfered surface (defined as a C surface) or an identification through hole.

[0068] (18) The plate according to the 18th invention is a plate according to the 16th or 17th invention, wherein the machined portion has a thin portion formed to include an optical fiber insertion hole and in which the thickness of the plate body is reduced, and a thick portion, and a guide groove continuous with the optical fiber insertion hole may be formed on the upper end surface of the thick portion.

[0069] This allows the tip of the optical fiber to be guided into the optical fiber insertion hole along the concave guide groove formed on the upper end surface of the thick-walled portion when inserting the optical fiber into the optical fiber insertion hole, making it easy to assemble the optical fiber assembly. Optical fibers are thin wires measuring several tens to several hundred microns, and because they must be inserted into insertion holes of almost the same size as the diameter of the optical fiber, assembling an optical fiber assembly requires delicate and difficult work. In particular, when mounting optical fibers on a substrate, high-speed, large-capacity communication is required, so multi-core optical fibers are often used, and it is sometimes necessary to insert several tens of optical fibers into a single plate. The plate according to the eighteenth invention allows for easy assembly even when multi-core optical fibers are used.

[0070] (19) The plate according to the 19th invention is a plate according to any one of the 16th to 18th inventions, and the machined portion may include an adhesive reservoir portion formed on the surface of the plate body including the optical fiber insertion hole.

[0071] As a result, excess adhesive used to secure the optical fiber to the optical fiber insertion hole is collected in the adhesive reservoir, preventing excess cured adhesive from remaining around the optical fiber insertion hole. In particular, the surface shape of the cured adhesive is not completely flat, which can cause uneven gaps due to the cured adhesive. According to the optical assembly of the eleventh invention, the adhesive is contained in the recessed portion, so the end face of the plate can be kept flat, and problems are less likely to occur when the ceramic plate is butted against the connecting surface of an optical connector such as an MT ferrule and fixed. Therefore, optical fiber assemblies can be manufactured precisely as designed, without increasing connection loss.

[0072] (20) The plate according to the 20th invention is a plate according to any one of the 16th to 19th inventions, and may have a guide hole formed with a hat-shaped cross section, a small hole, and a large hole formed around the small hole.

[0073] This allows the end face of the ceramic plate to be connected to an optical connector such as an MT ferrule by using a guide pin with a flange corresponding to the hat shape. According to the plate of the twentieth invention, by inserting a bolt-shaped guide pin from the ceramic plate side, the guide pin can be fixed while suppressing the amount of protrusion of the guide pin.

[0074] (twenty one) An optical fiber assembly according to a twenty-first aspect of the present invention comprises a plate according to any one of the thirteenth to twentieth aspects of the present invention connected to one end of an optical fiber with an adhesive.

[0075] This allows for an optical fiber assembly in which one end can be mounted on a board by providing it on the board side, and the other end can be connected to an optical fiber for long-distance communication between computers, etc., by providing it on the housing of a computer, etc. In other words, by using the optical fiber assembly of the 21st invention, optical wiring inside a housing of a computer and optical wiring for long-distance communication can be connected to each other.

[0076] (twenty two) The optical fiber assembly according to the 22nd invention may be the optical fiber assembly according to the 21st invention, in which an optical connector is connected to the other end of the optical fiber, and the optical connector may be an MT connector equipped with an MT ferrule.

[0077] Optical fibers equipped with MT ferrules can be incorporated into MPO connectors, etc. In this way, the optical connector on the other end is an optical connector of a standard generally used for long-distance communications, which provides excellent compatibility with existing optical lines and makes it easy to introduce computers that use optically integrated circuits. Furthermore, when one end of the optical fiber is incorporated into an optical package circuit, the other end is provided with a standardized MT ferrule, providing excellent connection compatibility when connecting multiple optical package circuits together.

[0078] (twenty three) The optical module of the 23rd invention may have an opto-electrical conversion element mounted on a substrate, and the optical fiber assembly of the 21st or 22nd invention may be mounted in close proximity to the opto-electrical conversion element or the silicon optical waveguide and optically connected to it.

[0079] Ceramic plates have excellent heat resistance, so even when an optical fiber assembly and an optoelectronic conversion element are mounted on a substrate and soldered after reflow, there is no dimensional change due to heat, and characteristics such as connection loss do not fluctuate. Furthermore, because the ceramic plate can be made to have a thermal expansion coefficient similar to that of the optoelectronic conversion element or silicon optical waveguide, dimensional fluctuation is minimal, thereby reducing optical loss. Furthermore, high-density optical lines can be mounted even near high-temperature electronic components, enabling high-speed, large-capacity information processing. Examples of optoelectronic conversion elements include vertical-cavity surface-emitting lasers (VCSELs), laser diodes (LDs), and photodetectors (PDs). When selecting a material for machinable ceramics, it is preferable to choose one with physical properties, such as a linear expansion coefficient, similar to those of silicon. [Brief explanation of the drawings]

[0080] [Figure 1] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a plate-shaped ferrule of Embodiment 1. [Figure 2] 1(b) and a reference perspective view of the plate-shaped ferrule of the first embodiment. [Figure 3] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a plate-shaped ferrule of a second embodiment. [Figure 4] 3(b) and a reference perspective view of the plate-shaped ferrule of the second embodiment. [Figure 5] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a plate-shaped ferrule showing a modified example of the second embodiment. [Figure 6] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a plate-shaped ferrule of a third embodiment. [Figure 7] 6(b) and a reference perspective view of the plate-shaped ferrule of the third embodiment. [Figure 8] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a plate-shaped ferrule of a fourth embodiment. [Figure 9] 8(b) and a reference perspective view of the plate-shaped ferrule of the fourth embodiment. [Figure 10] FIG. 1 is a schematic diagram of an optical module mounted on a substrate. [Figure 11] FIG. 1 is a schematic diagram of an optical module mounted in proximity to electronic components on a substrate. [Figure 12] 3 is a schematic diagram illustrating a step of fixing an optical fiber to the plate-like ferrule of the first embodiment. FIG. [Figure 13] 3A to 3C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of a modified example of the plate-shaped ferrule of the first embodiment. [Figure 14]13(b) and a reference perspective view of a modified example of the plate-shaped ferrule of the first embodiment. [Figure 15] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing an example of a 16-core plate-shaped ferrule. [Figure 16] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing an example of a 24-core plate-shaped ferrule. [Figure 17] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing another example of a 24-core plate-shaped ferrule. [Figure 18] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing an example of a 32-core plate-shaped ferrule. [Figure 19] 10A to 10C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing another example of a 32-core plate-shaped ferrule. [Figure 20] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing an example of a 36-core plate-shaped ferrule. [Figure 21] FIG. 1 is a front view showing an example of an 84-core plate-shaped ferrule. [Figure 22] 3 is a schematic explanatory view for explaining the state of the connection end face of the plate-shaped ferrule of the first embodiment. FIG. [Figure 23] FIG. 10 is a schematic explanatory view showing an example of a jig for fixing a plate-shaped ferrule. [Figure 24] 1A to 1C are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view showing an example of a jig for fixing a plate-shaped ferrule. [Figure 25] 1A and 1B are schematic explanatory diagrams showing an example of incorporating a plate-shaped ferrule into an MPO connector. [Figure 26] FIG. 1 is a schematic enlarged view showing an example of incorporating a plate-shaped ferrule into an MPO connector. [Figure 27] FIG. 10 is a schematic explanatory diagram for explaining a method for measuring the amount of variation in end face dimensions. DETAILED DESCRIPTION OF THE INVENTION

[0081] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Embodiments 1 to 4 of the present invention will be described. Each embodiment may be implemented alone or in combination with one or more of the 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 descriptions thereof will not be repeated.

[0082] [Embodiment 1] 1(a), (b), (c), (d), (e), and (f) are respectively a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of the plate-shaped ferrule of Embodiment 1. Figures 2(a) and 2(b) are respectively a cross-sectional view taken along line A-A' in Figure 1(b) and a reference perspective view of the plate-shaped ferrule of Embodiment 1.

[0083] The optical fiber assembly of this embodiment is formed from a ceramic plate and includes a plate-shaped ferrule 100 having an optical fiber insertion hole 103 and a guide hole 102 for inserting a guide pin, and an optical fiber 11 inserted into the optical fiber insertion hole 103 of the ferrule 100.

[0084] (Plate body) The plate of this embodiment is formed in a rectangular shape, and can be formed in a rectangular shape, for example. The dimensions of the ceramic plate 100 can be a width of 5 mm to 8 mm, a height of 2 mm to 4 mm, and a thickness of 0.3 mm to 3.0 mm. However, depending on the optical connection specifications and the number of connection fibers, the width and height may be wider than those shown here. The thickness of the ceramic plate 100 is preferably 0.5 mm or more, and preferably 2.5 mm or less. Furthermore, the thickness of the ceramic plate 100 can be 2.5 mm or less when the diameter of the optical fiber 11 is 0.25 mm, and can be 1.25 mm or less when the diameter of the optical fiber 11 is 0.125 mm. This allows the inner diameter of the optical fiber insertion hole 103 to be processed with high precision. In particular, when using a single-core optical fiber and polishing the connection end face at an angle, if the thickness of the plate body is 0.5 mm or more, the plate body can be polished without being damaged, and guide grooves for the optical fiber 11, adhesive reservoirs, etc. can be formed without any problems.

[0085] On the other hand, if angled polishing is not required for the optical communication connection method, the thickness of the plate body can be made thinner. Examples of cases where angled polishing is not required include when an anti-reflection coating is formed on the connection end face, when the optical fiber 11 used is a multimode optical fiber, or when the loss requirements for the connection part are not strict, such as when the communication distance is short. In these cases, the thickness of the ceramic plate 100 can be approximately 0.3 mm, and the preferred thickness of the ceramic plate 100 is 0.3 mm or more and 2.5 mm or less.

[0086] A more preferable thickness of the ceramic plate 100 may vary depending on whether or not the thin-walled portion 123 is provided (see the second embodiment and a modified example of the second embodiment described later). That is, when the optical polishing is performed at right angles and the optical fiber insertion holes 103 are formed in two or more rows and the thin-walled portions 123 are provided in multiple stages, the thickness of the ceramic plate 100 is more preferably 0.5 mm or more. Furthermore, when the connection end face is optically polished at an angle of 8° and the optical fiber insertion holes 103 are formed in a single row, the thickness of the ceramic plate 100 is more preferably 0.5 mm or more. Furthermore, when the connection end face is optically polished at an angle of 8° and the optical fiber insertion holes 103 are formed in two or more rows and the thin-walled portions 123 are provided in multiple stages, the thickness of the ceramic plate 100 can be 0.5 mm, but from the viewpoint of ensuring sufficient strength, the thickness of the ceramic plate 100 is more preferably 0.6 mm or more. Other examples of more preferable thicknesses of the ceramic plate 100 include 1.0 mm or more and 1.2 mm or more, with the upper limit being 2.5 mm or less.

[0087] The ceramic plate 100 shown in FIG. 1 has a horizontal width L1 of 6.4 mm, a vertical dimension L2 of 2.5 mm, and a thickness of 0.5 mm.

[0088] Furthermore, in the plate of this embodiment, for example, the distance between a pair of guide holes 102 can be 4.6 mm or more and 5.3 mm or less, the pitch of the optical fiber insertion holes 103 can be 0.125 mm or more and 0.25 mm or less, and the dimension between the optical fiber insertion holes 103 arranged at both ends can be 2.75 mm or more and 3.75 mm or less. The inner diameter of the guide holes 102 can be 0.55 mm or more and 0.7 mm or less. The size of the ceramic plate 100 can be designed to be compatible with MT ferrules.

[0089] 1 shows an example of a 12-fiber ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.7 mm, the distance between a pair of guide holes 102 is 4.6 mm, the inner diameter φ of the optical fiber insertion holes 103 is 125 μm, and the pitch of the optical fiber insertion holes 103 is 250 μm.

[0090] The optical fiber insertion holes 103 penetrate the plate body in the thickness direction, and a plurality of optical fiber insertion holes 103 are provided in a row along the longitudinal direction of the rectangular plate body. The ferrule 100 used in the optical fiber assembly of this embodiment is a so-called multi-core ferrule. The optical fiber 11 is fixed to the optical fiber insertion hole 103 of the ceramic plate 100 by the adhesive filled in the optical fiber insertion hole 103 . The member to be connected to the connecting end surface of the ceramic plate 100 is not particularly limited, and may be connected to, for example, an existing MT ferrule or an optical element. The connection method is also not particularly limited, and may be fixed and connected using an adhesive, or may be physically contacted or pressed and fixed by various means such as the jig 400 described below, a flanged guide pin, or a clip.

[0091] (machinable ceramics) The ceramics used in the present invention are preferably machinable ceramics. Machinable ceramics have low hardness, allowing for fine and precise machining at low cost. Furthermore, the ceramic ferrule 100 may be metallized using the Mo-Mn method or active metal method to make it compatible with solder reflow. Machinable ceramics are materials that can be machined to a desired shape. Preferably, composite ceramics can be used, which are obtained by adding a machinable ceramic to a structural oxide ceramic, such as an alumina ceramic, and sintering the resulting mixture through a solid-state reaction. Composite ceramics manufactured using this method (e.g., alumina-machinable ceramic composites: machinable alumina) have a structure in which cracks develop at the interface between the structural oxide ceramic particles (alumina) and the machinable ceramic particles. The feature of this machinable ceramic is that it can be made machinable without significantly deteriorating the physical properties of the basic structural oxide ceramics, compared to when machinability is imparted by making them porous. Furthermore, structural oxide ceramics with well-known properties, such as alumina and zirconia, can be made machinable.

[0092] By using the ceramic plate 100 made of machinable ceramics, it is possible to design heat-resistant optical connecting parts such as heat-resistant ferrules. By using the same interface for the ceramic plate 100 as for optical connectors such as MT ferrules, it is possible to achieve connection compatibility with optical connectors such as MT ferrules. In this case, the positions and sizes of the optical fiber insertion holes 103 and guide holes 102 are the same for the ceramic plate 100 and the MT ferrule. That is, the ceramic plate 100 and the MT ferrule can be positioned using guide pins. Furthermore, the optical fiber 11 attached to the ceramic plate 100 can be connected to the optical fiber 11 attached to the MT ferrule.

[0093] Therefore, the ceramic plate 100 can also be used as a substitute for an MT ferrule. A mechanical holding member may be provided between the ceramic plate 100 and the optical fiber 11 to hold them together. When connecting the ceramic plate 100 to an MT ferrule, the optical fiber 11 may be held by a holding member connecting the two. When mounting the ceramic plate 100 on a substrate 14, the optical fiber 11 may be held by a holding member fixed to the substrate 14.

[0094] The machinable ceramic used in the ceramic plate 100 of this embodiment is preferably a nitride-based machinable ceramic, and among nitride-based machinable ceramics, a machinable ceramic that is a composite of boron nitride and fine ceramics is more preferred. This provides excellent mechanical strength and processability, allowing for precision processing.

[0095] The density of this machinable ceramic is 2.5g / cm 3 More than 4.0g / cm 3 may be less than or equal to 3.4 g / cm 3 More than 3.6g / cm 3The flexural strength of the machinable ceramic may be 100 MPa or more and 550 MPa or less, and preferably 300 MPa or more and 350 MPa or less. The Vickers hardness of the machinable ceramic may be 1.0 GPa or more and 8.0 GPa or less, and preferably 2.0 GPa or more and 5.0 GPa or less, and preferably 2.2 GPa or more and 2.5 GPa or less. The average coefficient of linear thermal expansion of the machinable ceramic is 0.5 (10 -6 K) or more 10(10 -6 K) or less, and -6 K) or above 5.0(10 -6 K) or less is preferred. This provides excellent processability and heat resistance, and also has thermal properties similar to those of other optical elements such as silicon, making it possible to minimize connection loss.

[0096] The aspect ratio of the processing precision of the ceramic plate 100 can be set to 10:1. In this case, if the thickness of the plate body is 0.8 mm, high-precision processing is possible with the same design even for 80 μm fiber holes. In the case of MT ferrules made of resin such as PPS, when the optical fiber 11 is bonded to the MT ferrule, adhesive is dripped and filled into the bonding window. Therefore, when the MT ferrule is exposed to high temperatures, the difference in thermal expansion coefficient between the resin such as PPS and the adhesive causes the fiber to be pulled in. This makes it impossible to make a PC connection and makes it difficult to maintain a stable connection.

[0097] As shown in FIGS. 1 and 2, in the first embodiment, a ferrule 100 has a plate body formed in a rectangular shape, and a chamfered portion 110 may be formed at one corner of the plate body.

[0098] As described above, it has been confirmed that the surface on one side (surface A) of the plate body and the surface on the other side (surface B) are not completely identical in terms of the shape of the optical fiber insertion hole 103 (such as the angle of inclination of the hole relative to the surface of the plate body and the inner diameter φ of the hole). As a result, the connection loss is not completely identical on both sides of the plate body. In other words, since the plate body is machined from one side using a drill or the like, the shape of the optical fiber insertion hole 103 is not strictly symmetrical on both sides. Therefore, by forming a chamfer (surface C) at one corner of the plate body, it is possible to easily distinguish between surfaces A and B of the plate body visually.

[0099] 1, surface C 110 is provided at the upper right corner of surface A, but surface C 110 may be provided at other corners, or surface C 110 may be provided at multiple corners to make it possible to distinguish between surface A and surface B. Also, instead of chamfering (surface C), curved surfaces (radii) may be formed at the corners of the plate body.

[0100] 13 and 14 show a modified example in which an identification through-hole 111 is provided instead of the C-face 110 in Fig. 1. This allows the through-hole to be formed using a drill or the like, making it easy to process ceramics. This also makes it possible to identify the surface direction, and to provide a boss on the substrate 14 to assist in fitting so that the installation direction of the plate is determined uniformly. This makes it possible to prevent the ferrule 100 from being attached in the wrong direction relative to the light source.

[0101] The plate-shaped ferrule 100 of the present invention has an optical fiber insertion hole 103 and a guide hole 102 for inserting a guide pin. Since the plate-shaped ferrule 100 is made of ceramic, the ferrule 100 is less likely to undergo dimensional fluctuations even when exposed to high temperatures during the solder reflow process (usually around 260°C) when the optical connector 12 is mounted on the substrate 14 by solder reflow.

[0102] The dimensional variation of the ferrule 100 of this embodiment is preferably 0.5 μm or less, more preferably 0.1 μm or less, and even more preferably 0.05 μm or less. The dimensional variation is measured using the end face dimensional variation measurement method described below, and is the average value of the positional variation R of each fiber insertion hole compared before and after the heating test.

[0103] The linear expansion coefficient of the ferrule 100 is similar to that of the optoelectronic conversion element or silicon optical waveguide, so there is little dimensional fluctuation even when heated in the solder reflow process (maximum temperature in the temperature profile is 260°C for several minutes), and dimensional accuracy can be improved.

[0104] 12 is a schematic diagram illustrating a process for fixing an optical fiber 11 to the ceramic plate 100 of embodiment 1. When a ribbon-shaped optical fiber 11 is used, the tip of the optical fiber 11 is exposed as shown in Fig. 12(a). Furthermore, an adhesive is applied to the optical fiber insertion hole 103 on the insertion surface side of the ceramic plate 100, and the optical fiber is inserted into the optical fiber insertion hole 103 of the ceramic plate 100 as shown in Fig. 12(b).

[0105] (glue) In the ceramic plate 100 of the present invention, the optical fiber 11 is fixed to the optical fiber insertion hole 103 of the ferrule 100 by an adhesive filled in the optical fiber insertion hole 103. That is, before inserting the optical fiber 11 into the optical fiber insertion hole 103 of the ceramic plate 100 of the present invention, adhesive is applied to the optical fiber insertion hole 103 on the insertion surface side of the ceramic plate 100. The applied adhesive is then pushed out and passed through to pass the optical fiber 11 through the optical fiber insertion hole 103. In this manner, the small space between the optical fiber 11 and the optical fiber insertion hole 103 is filled with adhesive, and when the adhesive hardens, the optical fiber 11 is reliably fixed to the ceramic plate 100. It is preferable to use an adhesive with a relatively low viscosity. When the optical fiber 11 is inserted, the adhesive enters the optical fiber insertion hole 103 together with the optical fiber 11.

[0106] It is preferable to have the tip of the optical fiber 11 point upward when the optical fiber 11 is inserted into the optical fiber insertion hole 103. By doing so, the adhesive adhering to the surface of the optical fiber 11 that has passed through the optical fiber insertion hole 103 returns to the optical fiber insertion hole 103 by its own weight and / or capillary action, and the adhesive accumulates in the hole portion of the ceramic plate 100 through which the optical fiber 11 passes. By hardening the adhesive in this state, more adhesive is present on the side where the optical fiber 11 protrudes from the ceramic plate 100, reinforcing the optical fiber 11, making it less likely to crack or break internally when polishing the splice end face, thus preventing an increase in splice loss and splice failure.

[0107] Usable adhesives include ultraviolet curing adhesives, heat curing adhesives, and two-component reactive adhesives, all of which have excellent heat resistance. When an ultraviolet-curing adhesive is used, the adhesive is filled between the optical fiber insertion hole 103 and the optical fiber 11, and then cured by irradiating it with ultraviolet light. An example of a thermosetting adhesive is an epoxy adhesive. The epoxy adhesive has excellent adhesive properties with the quartz glass of the optical fiber 11 and the machinable ceramic of the ceramic plate 100. Therefore, even if the thickness of the ceramic plate 100 is reduced, the optical fiber 11 can be reliably fixed. Furthermore, even if the ceramic plate 100 to which the optical fiber 11 is adhered is optically polished, the optical fiber 11 will not fall off. After the adhesive has completely solidified, the connecting surface, which is the tip surface of the ceramic plate 100 (ferrule), is polished to remove any adhesive that has leaked and solidified from the optical fiber insertion hole, and the end surface of the optical fiber 11 is optically polished to a mirror finish.

[0108] (Connection end face) Fig. 22 is a schematic explanatory diagram for explaining the state of the connection end face of the ceramic plate 100 of embodiment 1. Fig. 22 is a part (enlarged view of the connection end face) of a cross section of the ceramic plate 100 cut at the optical fiber insertion hole 103, and only the connection direction is enlarged by about 200 times. Optical fibers are generally made of silica glass, and their Vickers hardness (JIS Z2244; hereinafter simply referred to as hardness) is usually 8.6 GPa or more and 9.8 GPa or less. The hardness of the machinable ceramic of the ceramic plate 100 of this embodiment is 8 GPa or less, which is lower than that of silica glass.

[0109] As a result, the connecting end face of the optical fiber assembly has a higher hardness at the portion of the optical fiber 11 than at the main body portion of the ceramic plate 100. Therefore, when the connecting end face of the optical fiber assembly is optically polished to perform optical connection, the main body portion of the ceramic plate 100, which has a lower hardness, is polished in order. As a result, as shown in Fig. 22, at the connecting end face of the optical fiber assembly after optical polishing, the connecting end face of the optical fiber 11 protrudes in a convex shape relative to the end face of the main body of the ceramic plate 100. Therefore, when this optical fiber assembly is optically connected, the convex shapes of the optical fibers 11 come into contact and deform, resulting in a physical contact (PC) connection. This suppresses Fresnel reflection, significantly reducing signal attenuation. This eliminates the need to use a refractive index matching agent or optical lens at the connection end of the connector, and allows optical signals to be connected with low loss.

[0110] Whether or not to use a refractive index matching agent, an optical lens, etc. on the connection end face is determined appropriately depending on the application or purpose of the optical connection. When a refractive index matching agent is used, it can be made to be approximately the same as the refractive index of the glass of the optical fiber 11. This makes it possible to suppress Fresnel reflection. Furthermore, when an optical lens is used, the type of lens is appropriately selected, and is not limited to a spherical lens. For example, a GRIN lens having a refractive index distribution inside the glass may be used.

[0111] <Connection end face comparison test> Ceramic plates 100 made of different materials were prepared, optical fibers 11 were mounted, the optical connection end faces were polished, and the states of the connection end faces were compared.

[0112] (1) Example As the machinable ceramic, nitride-based machinable ceramic (Photoveel II-S manufactured by Ferrotec Material Technologies Corporation) was prepared and machined into the shape 12 shown in Figure 1 of embodiment 1. This machinable ceramic is a composite of boron nitride and fine ceramics, and has a Vickers hardness of 2.3 GPa. Then, adhesive (thermosetting epoxy resin) was applied to the vicinity of the optical fiber insertion hole 103 on the opposite side from the connection end face, and 12 optical fibers 11 with a diameter of 125 μm were inserted into the optical fiber insertion hole 103, and the adhesive was hardened by heating. The optical fibers were all quartz optical fibers and had a Vickers hardness of 9 GPa. The ceramic plate 100 thus obtained was fixed to a jig 400 (see Figures 23 and 24) with adhesive to form an MT ferrule, and the connection end surface of the ceramic plate 100 was optically polished using a general-purpose optical connector polishing machine.

[0113] Twelve optical fiber assemblies of the example were fabricated by the above method, and the connection end faces of the ceramic plates 100 were measured using an end face shape measuring instrument for MT ferrules (daisi-MT). As a result, it was confirmed that the optical fiber assembly of the example had a shape in which the optical fiber 11 protruded from the connection end face of the ceramic plate 100, as shown in Figure 22, and the protrusion amount had an average value of 2.471 μm and a standard deviation of 181. This result is thought to be due to the fact that the optical fiber 11 is harder than the ceramic plate 100 of the embodiment, and therefore when the ceramic plate 100 fitted with the optical fiber 11 is optically polished, the ceramic plate 100 is polished more, causing the end face of the optical fiber 11 to protrude in a convex shape relative to the end face of the ceramic plate 100.

[0114] (2) Comparative Example Twelve optical fiber assemblies were fabricated in the same manner as in Example 1, except that silicon nitride ceramics (HPSN606) were used as the ceramics, which have a Vickers hardness of 13 GPa. The connection end face of the comparative example thus obtained was measured using an end face shape measuring instrument for MT ferrules (daisi-MT).

[0115] As a result, it was confirmed that the optical fiber assembly of the comparative example had a shape in which the optical fiber 11 was recessed from the connection end face of the ceramic plate 100, and the average amount of the recess was 1.433 μm with a standard deviation of 352. This result is thought to be due to the fact that the ceramic plate 100 of the comparative example is harder than the optical fiber 11, and therefore when the ceramic plate 100 with the optical fiber 11 attached is optically polished, more of the optical fiber 11 is polished, causing the end face of the optical fiber 11 to become recessed relative to the end face of the ceramic plate 100.

[0116] <Solder reflow heating test> (1) Connection loss measurement A solder reflow heating test was performed by mounting an optical fiber 11 on the ferrule 100 of this embodiment. The optical fiber 11 used was a Corning 12-core Ribbon fiber (MFD: 9.2 μm±0.4 μm; 1,310 nm), and the solder reflow heating test was performed under the conditions of 260° C. × 3 hours. Thereafter, the ferrule 100 with the optical fiber 11 mounted thereon was returned to room temperature (20°C), and the optical fiber 11 was attached to a jig 400 described below, and connected to an MT ferrule 200 (12MT-PA-SLS manufactured by Hakusan) using a 12-fiber clip. The connection end face was PC polished at an 8-degree angle on the MT ferrule 200 side, and was polished to a right-angle flat on the ceramic plate 100 side, and the connection was made via a refractive index matching material (S918X-31 manufactured by FITEL).

[0117] As a result, the connection loss when connecting on the A side of the ceramic plate 100 was 0.39 dB on average and 0.89 dB on maximum, and the connection loss when connecting on the B side was 0.43 dB on average and 1.53 dB on maximum. This confirmed that the ceramic plate 100 of this embodiment exhibits excellent low-loss performance.

[0118] (2) Measurement of end face dimensional variation As in the above-described measurement of the connection loss, an optical fiber 11 was mounted in the ferrule 100 of this embodiment, and the eccentricity of the optical fiber insertion hole 103 was measured before and after a solder reflow heating test (260°C x 3 hours). Note that the eccentricity in this case is the average value of the positional fluctuation amount R of each fiber insertion hole 103 compared before and after the heating test, with the midpoint M of the perpendicular bisector connecting the center points G1 and G2 of the guide hole 102 as the reference point, as shown in Fig. 27 .

[0119] As a result of the measurement, the average positional fluctuation amount in the X-axis direction (optical fiber alignment direction) was 0.03 μm, and the average positional fluctuation amount in the Y-axis direction was 0.03 μm. Therefore, the dimensional fluctuation amount in this measurement was 0.042 μm. This confirmed that machinable ceramics, which have excellent heat resistance, maintain excellent positional accuracy even when exposed to high temperatures.

[0120] [Embodiment 2] 3(a), (b), (c), (d), (e), and (f) are respectively a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of the plate-shaped ferrule of Embodiment 2. Also, FIGS. 4(a) and 4(b) are respectively a cross-sectional view taken along line A-A' in FIG. 3(b) and a reference perspective view of the plate-shaped ferrule of Embodiment 2. As shown in Figure 3, in embodiment 2, the plate body has a thin-walled portion 123, which is formed to include the optical fiber insertion hole 103 and has a reduced thickness, and a thick-walled portion 122, and a guide groove 121 (recessed groove) that is continuous with the optical fiber insertion hole 103 is formed on the upper end surface of the thick-walled portion 122.

[0121] The thin-walled portion 123 is formed by cutting approximately the upper half of the plate body. A thick-walled portion 122 (the portion of the plate body before cutting) is formed in approximately the lower half of the plate body. Part of the boundary between the thin-walled portion 123 and the thick-walled portion 122 is a horizontal line passing through approximately the centers of the multiple optical fiber insertion holes 103, and as shown in Figure 4, a guide groove 121 that continues into the optical fiber insertion hole 103 is formed on the upper end surface of the thick-walled portion 122. The tip of the optical fiber 11 can be easily inserted into the optical fiber insertion hole 103 along this guide groove 121.

[0122] The thickness (plate thickness) of thin portion 123 is preferably 0.3 mm or more, and is preferably formed to have a depth of 0.1 mm or more relative to the thickness of thick portion 122 (that is, the thickness of thin portion 123 is preferably 0.1 mm or more thinner than the thickness of thick portion 122). For example, when the thickness of the plate body is 1.0 mm, the plate thickness of thin portion 123 is preferably 0.3 mm or more and 0.9 mm or less. By making the thickness of the thin-walled portion 123 0.3 mm or more, the plate thickness can be ensured even when the connection end face is polished at an angle of 8. Also, by making the thickness of the thin-walled portion 123 0.1 mm or more deeper than the thick-walled portion 122, the tip of the optical fiber 11 can be easily inserted into the optical fiber insertion hole 103.

[0123] If the thickness of the thin portion 123 is thinner than the above range, the thin portion 123 may be damaged. If the thickness is thicker than the above range, the length of the guide groove 121 formed on the upper end surface of the thick portion 122 may be too short, and the optical fiber 11 may not be guided along the guide groove 121. The cross-sectional shape of the guide groove 121 is semicircular. The cross-sectional shape of the guide groove 121 may be semicircular or rectangular. The size (radius) of the guide groove 121 may be the same as that of the fiber, or may be larger than the fiber. Furthermore, although Figures 3 and 4 illustrate the case where the optical fiber insertion holes 103 are arranged in a single row, if the optical fiber insertion holes 103 are arranged in multiple rows, multiple thin-walled sections 123 may be provided in a stepped manner to form multiple guide grooves 121 that are continuous with each of the optical fiber insertion holes 103 arranged in multiple stages above and below.

[0124] [Modification of the second embodiment] 5(a), (b), (c), (d), (e), and (f) are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view, respectively, of a plate-shaped ferrule showing a modified example of embodiment 2. In the modified example of the second embodiment, the optical fiber insertion holes 103 are arranged in two or more rows. The plate body is formed with a thin portion 123 and a thick portion 122, and the thin portion 123 has two thickness steps, and the upper end surface of the thick portion 122 and each step of the thin portion 123 are formed in a staircase shape. Guide grooves 121a, b... (recessed grooves) that continue to the optical fiber insertion holes 103 are formed on the upper end surface of the thick portion 122 and on the stepped portion of the thin portion 123. Therefore, steps are provided in a staircase-like manner at the insertion opening portions of the two rows of optical fiber insertion holes 103 through which the optical fibers 11 are inserted, and guide grooves 121a, b are provided at each step.

[0125] This allows the optical fiber 11 to be placed in the recessed groove provided in the stepped portion, and then inserted into the optical fiber insertion hole 103. Therefore, even when there are a large number of optical fiber insertion holes 103 and high-density optical connections are to be made, the optical fiber 11 can be easily inserted into the optical fiber insertion holes 103 provided in the small-sized ceramic plate 100. Furthermore, compared to the case of a flat ceramic plate 100, the adhesive is sufficiently accumulated in the stepped portion, so that a sufficient amount of adhesive is filled and applied inside the optical fiber insertion hole 103 when the optical fiber 11 is inserted.

[0126] In addition, when the optical fiber insertion holes 103 are provided in two or more rows and the guide grooves 121 are provided in multiple stages as in this modified example, it is preferable that the thickness of the ceramic plate 100 is 0.5 mm or more. Furthermore, when the optical fiber insertion holes 103 are provided in two or more rows and the connection end faces are polished at an angle, the thickness of the ceramic plate 100 can be 0.5 mm, but from the viewpoint of ensuring sufficient strength, it is more preferable that the thickness of the ceramic plate 100 is 0.6 mm or more. 6 shows an example in which the thickness of the ceramic plate 100 is 1.0 mm and the distance between each guide groove (depth of each step) is 0.1 mm. If the thickness of the ceramic plate 100 is 0.6 mm, the distance between each guide groove (depth of each step) may be set to 0.05 mm or more.

[0127] [Embodiment 3] 6(a), (b), (c), (d), (e), and (f) are respectively a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view of the plate-shaped ferrule of embodiment 3. Also, FIGS. 7(a) and 7(b) are respectively a cross-sectional view taken along line A-A' in FIG. 6(b) and a reference perspective view of the plate-shaped ferrule of embodiment 3. In this embodiment, an adhesive reservoir 130 including an optical fiber insertion hole 103 is recessed on the surface of the plate body. The adhesive reservoir 130 may be a groove formed in the plate body so as to include all of the optical fiber insertion holes 103 formed in the plate body. In other words, since the multi-fiber optical fiber insertion holes 103 are arranged in a row along the longitudinal direction of the plate body, the adhesive reservoir 130 is formed as a recess that is long in the longitudinal direction of the plate body so as to include all of the optical fiber insertion holes 103. The length dimension (width dimension) of the adhesive reservoir 130 may be large enough to accommodate all the fiber holes, and the vertical width dimensions may be large enough to accommodate the fiber holes.

[0128] The thickness of adhesive reservoir 130 is preferably 0.3 mm or more, and it is preferable that it has a depth of 0.1 mm or more relative to the thickness of the plate body (that is, it is preferable that the thickness of thin portion 123 is thinner than the thickness of thick portion 122 by 0.1 mm or more). For example, if the thickness of the plate body is 1.0 mm, the thickness of adhesive reservoir 130 is preferably 0.3 mm or more and 0.9 mm or less. By making the thickness of adhesive reservoir 130 0.3 mm or more, the plate thickness can be ensured even when the connection end face is ground at an angle of 8. Also, by forming adhesive reservoir 130 so that its depth is 0.1 mm or more relative to the plate body, the adhesive can be suitably filled.

[0129] The optical fiber 11 can be fixed in the optical fiber insertion hole 103 in the same manner as described above. That is, after applying adhesive to the adhesive reservoir 130, the optical fiber 11 is inserted into the optical fiber insertion hole 103. At this time, the optical fiber 11 is inserted into the optical fiber insertion hole 103 with adhesive attached to the tip of the optical fiber 11, and the adhesive then hardens.

[0130] As described above, by forming the adhesive reservoir 130 so as to include the fiber holes, the adhesive is contained within the adhesive reservoir 130, and excess hardened adhesive does not protrude beyond the surface of the ceramic plate 100. Therefore, the end face of the ceramic plate 100 can be kept flat, and defects such as gaps are less likely to occur when the ceramic plate 100 is butted against the connecting surface of the optical connector 12, such as an MT ferrule, and fixed. Also, compared to when the adhesive reservoir 130 is not present, the optical fiber 11 can be reliably fixed to the ceramic plate 100 with a sufficient amount of adhesive.

[0131] [Embodiment 4] In this embodiment, a different diameter structure 140 is formed in the guide hole 102 as a structure for fixing the plate body. 8(a), (b), (c), (d), (e), and (f) are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view, respectively, of the plate-shaped ferrule of embodiment 4, and FIGS. 9(a) and 9(b) are a cross-sectional view taken along line A-A' in FIG. 8(b) and a reference oblique view of the plate-shaped ferrule of embodiment 4, respectively. In the fourth embodiment, the guide hole 102 is formed to have a hat-shaped cross section, and has a small hole 141 and a large hole 142 formed around the small hole 141. The small hole 141 is formed on the connecting end face side, and the large hole 142 is formed on the opposite side.

[0132] By using a hat-shaped flanged guide pin, the end face of the ceramic plate 100 can be fixed to the end face of the optical connector 12 such as an MT ferrule. This allows the end face of the ceramic plate 100 to be fixed without using adhesive, so characteristics such as connection loss do not fluctuate. In this case, the thickness of the plate body may be 0.5 mm or more and 2.5 mm or less, and preferably 0.5 mm or more and 1.3 mm or less. By setting the thickness within the above range, the inner diameter φ of the optical fiber insertion hole 103 corresponding to the optical fiber 11 having a diameter of 0.125 mm can be processed with high precision. On the other hand, from the viewpoint of making the ferrule 100 compatible with optical fibers 11 having a wide range of diameters, it is preferable that the thickness of the plate body be 0.5 mm or more and 2.5 mm or less.

[0133] With the configuration of this embodiment, by using a guide pin with a flange corresponding to the hat shape, the end face of the ceramic plate 100 can be connected to an optical connector such as an MT ferrule, and the amount of protrusion of the guide pin can be reduced. Furthermore, when fitting and connecting the ceramic plate 100 to an MT ferrule or the like, by using a flanged guide pin, the flange portion of the guide pin can be stored in the large hat-shaped hole, so that the entire fiber insertion surface can be used while maintaining the position of the guide pin. This embodiment is particularly excellent when used as a module mounted on a substrate 14 as shown in Fig. 11. That is, when a structure for fixing with guide pins is provided on the substrate side, the holes for inserting the guide pins become through holes, and therefore a mechanism for holding the guide pins cannot be provided on the substrate, and therefore the mechanism of this embodiment for holding the guide pins is required on the ceramic plate side.

[0134] 8 and 9 show an example in which the cross section of the guide hole 102 is formed in a rectangular hat shape, but the shape is not limited to a rectangular shape and may be any shape (such as a wedge shape) that corresponds to the guide pin.

[0135] [Other embodiments] In the above embodiment, an example of the ceramic plate 100 having 12 optical fiber insertion holes 103 provided at 12 locations is shown, but the ceramic plate 100 of the present invention is not limited to 12 fibers. Machinable ceramics have excellent mechanical strength and heat resistance, so they can be formed into complex and intricate shapes with high precision using cutting, grinding, electrical discharge machining, laser processing, etc. This enables high-density optical connections and enables high-speed, high-capacity communication connections.

[0136] 15 shows an example of a 16-core ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.55 mm, and the distance between a pair of guide holes 102 is 5.3 mm. The inner diameter φ of the optical fiber insertion holes 103 is 125 μm, and the pitch of the optical fiber insertion holes 103 is 250 μm. The outer dimensions of the ceramic plate 100 illustrated in FIG. 15 are the same as those illustrated in FIG. 1 in the first embodiment.

[0137] 16 shows an example of a 24-fiber ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.7 mm, and the distance between a pair of guide holes 102 is 4.6 mm. The optical fiber insertion holes 103 are arranged in two stages spaced apart by 0.25 mm from the center line connecting the centers of the guide holes 102, and the inner diameter φ of the optical fiber insertion holes 103 in each stage is 125 μm, and the pitch of the optical fiber insertion holes 103 is 250 μm. The outer dimensions of the ceramic plate 100 illustrated in FIG. 16 are the same as those illustrated in FIG. 1 in the first embodiment.

[0138] 17 shows another example of a 24-core ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.7 mm, and the distance between a pair of guide holes 102 is 4.6 mm. The inner diameter φ of the optical fiber insertion holes 103 is 80 μm, and the optical fiber insertion holes 103 are provided with 12 cores on each side at a pitch of 125 μm, and the optical fiber insertion holes 103 are provided 125 μm apart on each side from the midpoint connecting the centers of the guide holes 102 (i.e., the pitch at the center is doubled to 250 μm).

[0139] 18 shows an example of a 32-fiber ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.55 mm, and the distance between a pair of guide holes 102 is 5.3 mm. The optical fiber insertion holes 103 are configured in two stages spaced apart by 0.25 mm from the center line connecting the centers of the guide holes 102, and the inner diameter φ of the optical fiber insertion holes 103 in each stage is 125 μm, and the pitch of the optical fiber insertion holes 103 is 250 μm. The outer dimensions of the ceramic plate 100 illustrated in FIG. 18 are the same as those illustrated in FIG. 1 in the first embodiment.

[0140] 19 shows another example of a 32-core ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.55 mm, and the distance between a pair of guide holes 102 is 5.3 mm. The inner diameter φ of the optical fiber insertion holes 103 is 80 μm, and the optical fiber insertion holes 103 are provided with 16 cores on each side at a pitch of 125 μm, and the optical fiber insertion holes 103 are provided 125 μm apart on each side from the midpoint connecting the centers of the guide holes 102 (i.e., the pitch at the center is doubled to 250 μm).

[0141] 20 shows an example of a 36-fiber ceramic plate 100. In this example, the inner diameter of the guide holes 102 is 0.7 mm, and the distance between a pair of guide holes 102 is 4.6 mm. The optical fiber insertion holes 103 are arranged in three rows, one on the center line connecting the centers of the guide holes 102 and the other 0.25 mm apart from the center line, with the inner diameter φ of the optical fiber insertion holes 103 in each row being 125 μm, and the pitch of the optical fiber insertion holes 103 being 250 μm. The outer dimensions of the ceramic plate 100 illustrated in FIG. 20 are the same as those illustrated in FIG. 1 in the first embodiment.

[0142] Other examples include a 48-core ceramic plate 100 with three rows of 16 cores, and an 84-core ceramic plate 100 with seven rows of 12 cores, as shown in FIG.

[0143] [Optical module] The optical module of the present invention is configured by mounting an optical connector 12 equipped with a ferrule 100 on a substrate 14 by solder reflow. A schematic diagram of the optical module mounted on the substrate 14 is shown in FIG. The ceramic plate 100 of this embodiment can be fixed directly on or near a substrate 14 and connected to an opto-electric conversion element 13 via an optical fiber 11. Examples of the opto-electric conversion element 13 include a vertical cavity surface emitting laser (VCSEL), a laser diode (LD), and a photodetector (PD).

[0144] In addition, the ceramic plate 100 of this embodiment may be optically connected by mounting an opto-electrical conversion element 13 or a silicon optical waveguide on the substrate 14 and mounting an optical fiber assembly in close proximity to the opto-electrical conversion element 13 or the silicon optical waveguide. The optical module can include an opto-electrical conversion element 13, a ferrule 100 having an optical fiber insertion hole 103 at a position corresponding to the opto-electrical conversion element 13, and an optical fiber 11 that is inserted into the optical fiber insertion hole 103 of the ferrule 100 and optically connected to the opto-electrical conversion element 13. An optical waveguide can be provided between the opto-electrical conversion element 13 and the optical fiber 11.

[0145] The ceramic plate 100 of the embodiment shown in Fig. 10(a) can be connected to any suitable device, such as an existing MT ferrule 200, with the optical fiber 11' extending from the MT ferrule 200 routed to the housing 10. The ceramic plate 100 of this embodiment can also be connected to a general MPO housing as an optical connector 12 by using a jig 400, which will be described later. A compression spring may be built into the housing to mechanically connect the optical fiber 11. The end face of the optical connector 12 may be polished at an 8-degree angle to reduce return loss. On the other hand, if a high level of connection loss is not required due to a short communication distance and many optical connection points, the end face of the optical connector 12 may be polished at a right angle. If necessary, an anti-reflection film may be applied to the connection end face to perform right-angle polishing.

[0146] Furthermore, when optically mounting an electronic circuit on a substrate 14, an optical transceiver having an opto-electrical conversion element 13 may be provided on the end of the substrate 14 to be connected to the optical connector 12 (FIG. 10(a)). An example of an optical transceiver is one in which a light-receiving element and a light-emitting element as the opto-electrical conversion element 13 are housed in a device holder together with a lens. In this device-holder type optical transceiver, the leads of the opto-electrical conversion element 13 (or its FPC) are soldered to the substrate 14 and connected to a ferrule 100 attached to a receptacle fixed to the substrate 14.

[0147] 10(b) is a schematic diagram of an optical module mounted in proximity to an electronic component 15 on a substrate 14. When mounting on an electronic substrate, it is preferable to position the optical terminal as close as possible to the electronic component 15. In this case, as shown in FIG. 10(b), an optical connector 12 that can be wired perpendicular to the substrate 14 can be used. The optical-electrical conversion element 13' may be directly connected to the lens portion of the element, or may be indirectly connected via a silicon optical waveguide, for example.

[0148] 11(a) is a schematic diagram of an optical module mounted in proximity to an electronic component 15 on a substrate 14. In this case, the ferrule 100 connects an optical fiber 11 to an opto-electric conversion element 13′ mounted on the substrate 14, and the optical fiber 11 is wired parallel to the substrate 14 while maintaining a predetermined radius of curvature by the R-forming portion 300. This allows the optical connector 12 to be mounted in proximity to an electronic component 15 such as a CPU without applying a load to the optical fiber 11. In addition, in Figure 11(a), an example is shown in which one end of the optical fiber 11 is the ferrule 100 of this embodiment and the other end is a general-purpose MT ferrule 200, but this is not limited to this, and the other end may also be the ferrule 100 of this embodiment.

[0149] When one end of the optical fiber 11 is fixed to the substrate 14 and the other end is connected to another electronic device, a structure such as that shown in Fig. 11(a) can be employed. In this case, a standardized MT ferrule can be provided at the other end of the optical fiber 11, as shown in Fig. 11(b), to improve connection compatibility. In this way, an optical fiber provided with an MT ferrule at the other end can be incorporated into various general-purpose connectors such as an MPO connector, and can therefore be easily connected to optical fiber cables for various applications. For example, when one end of the optical fiber 11 is incorporated in an optically mounted circuit, the other end can be fixed to the housing 10 of a network switch (optical switch), a CPU server, a GPU server, or the like, so that it can be connected from the outside. This enables on-board optical communication between multiple servers, etc.

[0150] Furthermore, as shown in FIG. 11(b), by providing a standardized MT ferrule at the other end of the optical fiber 11, a plurality of mounted optical circuits can be connected to each other even within a device such as a server. For example, when one end of the optical fiber 11 is incorporated into an optical package circuit, the other end is a standardized MT ferrule, so that optical package circuits of various specifications can be easily connected via the MT ferrule.

[0151] (Jig 400) 23 and 24 show an example of a jig 400 for fixing a plate-shaped ferrule 100. Fig. 23 is a schematic explanatory view showing an example of the jig 400 for fixing the ferrule 100. Figs. 24(a), (b), (c), (d), (e), and (f) are a front view, a plan view, a right side view, a left side view, a bottom view, and a rear view, respectively. A jig 400 for polishing the end face of a ceramic plate 100 connected to an optical fiber 11 has a jig body 410 provided with a recess 402 for passing the optical fiber 11 (including the tape). A fixing hole is provided in the end face of the jig body 410, and this fixing hole is provided at a position that aligns with a guide hole 102 provided in the ceramic plate 100. Guide pins can be fitted into the fixing hole and guide hole 102 to position and fix the plate to the jig body 410.

[0152] With the ceramic plate 100 of the present invention fixed to the jig 400, the connecting end surface of the ceramic plate 100 can be polished using a polishing tool such as a grinding machine. The connection end faces of the ceramic plate 100 and the MT ferrule 200 are each polished to an 8-degree oblique protrusion, a right-angle flat surface, or a right-angle protrusion. Since the end face polishing of the ceramic plate 100 is stable to the same level as that of the MT ferrule, variations due to connection and disconnection can be eliminated.

[0153] The ceramic plate 100 can be connected to the jig 400 using guide pins. If necessary, the ceramic plate 100 may be fixed to the jig 400 using an adhesive or the like. 23 and 24, by making its external dimensions the same as those of an internationally standardized MT ferrule when combined with ceramic plate 100, it can be inserted directly into an existing polishing machine for optical polishing. For example, in the case of ceramic plate 100 shown in Fig. 1, its thickness is 0.5 mm, so the external shape of jig 400 can be made approximately 0.5 mm shorter on the connection end face side of a standard MT ferrule.

[0154] The jig 400 of the present invention may be used as a temporary holder for optical polishing, and after optical polishing is completed, the ceramic plate 100 may be removed from the jig 400 and used for optical connection. Furthermore, as will be described later, the jig 400 of the present invention may be used for optical connection of the ceramic plate 100 in a state in which the jig 400 and the ceramic plate 100 are bonded together after optical polishing is completed.

[0155] (Use with existing optical connectors) 25 is a schematic explanatory diagram showing an example of incorporating the ceramic plate 100 into an MPO connector 500. The MPO connector is a connector for connecting multiple optical fibers 11 together, and is an internationally standardized connector that is widely used. As shown in FIG. 25, the guide pin of the pin keeper 540 is inserted into the ceramic plate 100 fixed by the jig 400, and further, the spring 530, the spring bush 520, and the MPO boot 510 are passed through the optical fiber 11. 24 is designed to have the same dimensions as a standardized MT ferrule when combined with the ceramic plate 100, and can therefore be directly incorporated into the MPO housing 550. Therefore, even when connecting to an existing MT ferrule, optical connection can be easily made by using the MPO connector 500, ensuring connection compatibility.

[0156] 26(a) is a schematic enlarged view showing an example of incorporating the ceramic plate 100 into the MPO connector 500. A guide pin is fixed to the connection end face side of the pin keeper 540, and the guide pin is inserted into the jig 400 and further into the ceramic plate 100. 26(b) shows an example in which an existing MT ferrule 450 is used instead of the jig 400. The MT ferrule 450 is internationally standardized, and its connection end face can be optically polished using a polishing device. It can also be incorporated into an MPO connector 500.

[0157] In the above embodiment, the ceramic plate 100 is provided on the end face of the optical fiber 11 and used as a cable connecting member (for example, surface A is the connector connecting surface and surface B is the fiber insertion side). However, the ceramic plate 100 of the present invention can be used not only as a cable connecting member, but also as a block, for example, with both surfaces A and B serving as connecting surfaces. In this case, it can also be used for connecting optical elements, for example.

[0158] In the present invention, the ferrule 100 or the ceramic plate 100 corresponds to the "ferrule" or "plate", the optical fiber 11 corresponds to the "optical fiber", the optical fiber insertion hole 103 corresponds to the "optical fiber insertion hole", the guide hole 102 corresponds to the "guide hole", the chamfered portion (C surface) 110 or the identification through hole 111 corresponds to the "surface identification structure", the thin-walled portion 123 corresponds to the "thin-walled portion", the thick-walled portion 122 corresponds to the "thick-walled portion", the guide groove (recessed groove) 121 corresponds to the "guide groove", the adhesive reservoir 130 corresponds to the "adhesive reservoir", the small hole 141 corresponds to the "small hole", and the large hole 142 corresponds to the "large hole".

[0159] Although a preferred embodiment of the present invention has been described above, the present invention is not limited thereto. It will be 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]

[0160] 10. Cabinet 11 Optical Fiber 12 Optical Connector 13 Photoelectric conversion element 14 PCB 15 Electronic Components 100 Ferrule (ceramic plate) 102 Guide hole 103 Optical fiber insertion hole 110 Chamfered part, C surface 121 Guide groove (concave groove) 122 Thick wall part 123 Thin-walled section 130 Adhesive reservoir 140 Different diameter structure 141 Small hole 142 Large hole 200 MT ferrule 300 R forming part 400 Jig

Claims

1. A plate-shaped ferrule made of ceramic, a plurality of optical fiber insertion holes into which a plurality of optical fibers are respectively fixed; a pair of guide holes into which the pair of guide pins are respectively inserted; The hardness of the plate body is lower than the hardness of the optical fiber, and the optical fiber can be physically contacted with the plate body.

2. 2. The ferrule according to claim 1, wherein the connection end surface having the optical fiber mounting hole is a polished surface of the optical fiber and the plate body, and the optical fiber can be connected by physical contact.

3. The plate body has a groove on its surface, the groove is formed to include all of the optical fiber insertion holes formed in the plate body, 2. The ferrule according to claim 1, wherein the thickness of the plate body in the groove is 0.3 mm or more and 0.9 mm or less.

4. An optical connector capable of physical contact connection, The ferrule according to claim 1; an optical fiber fixed to the optical fiber insertion hole, The optical fiber is a tape-shaped optical fiber aligned in a row, and the row of optical fibers is arranged parallel to the pair of guide holes.

5. A substrate that can be soldered reflowed, an optical connector having the ferrule according to claim 1; an optical fiber fixed to the optical fiber insertion hole; a photoelectric conversion element connected to the optical fiber.

6. A server capable of communicating via optical fiber, an optical connector having the ferrule according to claim 1; an optical fiber fixed to the optical fiber insertion hole; an optical mounting circuit connected to the optical fiber, A server in which the optically mounted circuits within the server are optically connected to each other.

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