Optical connector and optical connector manufacturing method

An optical connector includes: at least a ferrule and n self-forming optical waveguides, wherein the ferrule includes n optical fiber insertion holes, and optical fibers are each inserted into and included in the optical fiber insertion holes, the number n indicates a natural number not including zero, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of the ferrule is formed with roundness, and end portions of the self-forming optical waveguides are each optically connected to the optical fibers.

BACKGROUND

1. Technical Field

One aspect of the present disclosure relates to an optical connector and an optical connector manufacturing method.

2. Related Art

An optical cable using an optical fiber can perform high-speed communication of a mass of information, and therefore, has been utilized for domestic or industrial information communication. For example, an automobile is equipped with various electric components (e.g., a car navigation system), and an optical cable has been used for optical communication of these electric components. Various optical connectors have been proposed, which include an optical connector (an optical waveguide) configured such that one end of the optical fiber is optically connected (connected so that an optical signal can be transmitted) to multiple optical elements such as photodiodes and an optical connector configured such that end portions of multiple optical fibers are optically connected to each other.

These optical connectors include, for example, one described in JP-A-9-113761. The optical connector described in JP-A-9-113761 includes a pin-equipped ferrule (described as a “ferrule assembly” in JP-A-9-113761) and a hole-equipped ferrule (described as a “ferrule assembly” in JP-A-9-113761). The pin-equipped ferrule is a resin molded component, and has a guide pin as a reference and four optical fiber insertion holes. On the other hand, the hole-equipped ferrule is also a resin molded component, and has a guide pin insertion hole into which a guide pin is to be inserted and four optical fiber insertion holes. The guide pin of the pin-equipped ferrule is inserted into the guide pin insertion hole of the hole-equipped ferrule, and in this manner, these two ferrules are optically connected to each other with surfaces thereof facing each other.

SUMMARY

An optical connector includes at least a ferrule and n self-forming optical waveguides, wherein the ferrule includes n optical fiber insertion holes, and optical fibers are each inserted into and included in the optical fiber insertion holes, the number n indicates a natural number not including zero, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of the ferrule is formed with roundness, and end portions of the self-forming optical waveguides are each optically connected to the optical fibers.

DETAILED DESCRIPTION

However, in the actually-manufactured ferrule, there is a variation in an angle in an axial direction of each optical fiber insertion hole. Further, there is also a variation in a gap between the center points of the optical fiber insertion holes.

Further, when an end surface of the ferrule is polished, the end surface is not formed as a flat surface, but is formed in a rounded shape (polishing sagging). Due to such roundness, a clearance is formed between the optical element and the ferrule and between two ferrules.

Due to each of the above-described variations, an error in the arrangement accuracy of each optical fiber inserted into the ferrule is caused. Due to the roundness of the end surface of the ferrule, a clearance (an air gap) is caused between the fibers connected to each other. For this reason, desired optical connection between the optical element and the optical fiber and between the optical fibers is not achieved, leading to a connection loss.

For reducing the connection loss, a high accuracy is required for arrangement of each optical fiber of the ferrule with respect to the optical elements and arrangement of the optical fibers of two ferrules. However, in the actually-produced ferrule, the above-described various variations and the above-described roundness of the end surface are inevitably caused. For this reason, it is difficult to enhance the arrangement accuracy, assuming that these ferrules are used.

Further, as shown inFIG.18B, the variation in the angle of the optical fiber insertion hole in the rotation direction in the ferrule relatively increases toward an outer peripheral side of the ferrule. Thus, a position shift increases, and an optical loss increases.FIG.18Ashows a ferrule used in a typical optical connector. Moreover,FIG.18Bshows the original positions of optical fiber insertion holes of the ferrule shown inFIG.18Aby solid circles, and shows the shifted position of each optical fiber insertion hole due to the variation in the angle by dashed lines.

One object of the present disclosure is to provide the following optical connector and the method for manufacturing such an optical connector. With this optical connector, the connection loss can be easily reduced while use of the ferrule having the variation in the angle of each optical fiber insertion hole in the axial direction, the variation in the gap between the center points of the optical fiber insertion holes, or the roundness of the end surface is acceptable.

An optical connector (the present optical connector) according to one aspect of the present disclosure includes: at least a ferrule and n self-forming optical waveguides, wherein the ferrule includes n optical fiber insertion holes, and optical fibers are each inserted into and included in the optical fiber insertion holes, the number n indicates a natural number not including zero, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of the ferrule is formed with roundness, and end portions of the self-forming optical waveguides are each optically connected to the optical fibers.

An optical connector manufacturing method (the present manufacturing method) according to one aspect of the present disclosure includes: preparing two ferrules and photo-curing resin, each ferrule including at least n optical fiber insertion holes and including optical fibers in the optical fiber insertion holes, the optical fibers being inserted therein; arranging the two ferrules to face each other and arranging the photo-curing resin between the ferrules; confirming that there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of one of the ferrules is formed with roundness, and an end surface of the other ferrule is formed with no roundness; curing end portions of the photo-curing resin with the core gap by incident light entering the end portions of the photo-curing resin from the optical fibers, thereby transferring the core gap onto the photo-curing resin and forming the n self-forming optical waveguides at the photo-curing resin such that a variation in the core gap on one end side of the self-forming optical waveguides is smaller than a variation in the core gap on the other end side; forming a clad by curing of the photo-curing resin; and detaching the other ferrule from the self-forming optical waveguides, thereby forming a ferrule body including the one of the ferrules and the self-forming optical waveguides, wherein the number n indicates a natural number not including zero.

According to the present optical connector and the present manufacturing method, the pre-detached ferrule forms the self-forming optical waveguides in a state in which the variation in the core gap on one end side of the self-forming optical waveguides is smaller than the variation in the core gap on the other end side. Thus, a loss in connection among the self-forming optical waveguides and the optical fibers in the ferrule on one end side can be reduced. Further, use of the ferrule having the variation in the angle of each optical fiber insertion hole in the axial direction, the variation in the gap between the center points of adjacent ones of the optical fiber insertion holes, or the roundness of the end surface is acceptable, and on the other hand, the optical connector can include the self-forming optical waveguides and the optical fibers and the end portions of the self-forming optical waveguides can be favorably connected to each other. Further, the connection loss can be easily reduced, and improvement in the yield of the optical connector and reduction in a manufacturing cost accompanied by such improvement can be achieved.

Further, the detached ferrule can be, as a master ferrule, repeatedly used for the step of manufacturing another optical connector. The highly-accurate ferrule with smaller various variations and roundness is detached and repeatedly used, and therefore, the self-forming optical waveguides can be manufactured with the highly-accurate constant core gap in the ferrule detached from the end portions of the self-forming optical waveguides. Thus, the end portions of the self-forming optical waveguides duplicated with the same core gap by the master ferrule are optically connected to each other. Thus, on this point, the connection loss of the optical connector can be also easily reduced.

An optical connector according to the first aspect of the present embodiment includes: at least a ferrule and n self-forming optical waveguides, wherein the ferrule includes n optical fiber insertion holes, and optical fibers are each inserted into and included in the optical fiber insertion holes, the number n indicates a natural number not including zero, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of the ferrule is formed with roundness, and end portions of the self-forming optical waveguides are each optically connected to the optical fibers.

According to the optical connector according to the second aspect of the present embodiment, in the optical connector according to the first aspect, the ferrule includes two ferrules, the two ferrules are arranged facing each other, and the self-forming optical waveguides are provided between the two ferrules, each of the two ferrules includes n optical fiber insertion holes, and the optical fibers are each inserted into and included in the optical fiber insertion holes, there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, end surfaces of the two ferrules are formed with roundness, the n self-forming optical waveguides are divided in half along a direction perpendicular to a light propagation direction, and a core gap between adjacent ones of the self-forming optical waveguides at end surfaces thereof is identical among the divided self-forming optical waveguides.

An optical connector according to a third aspect of the present embodiment is that the optical connector of the first aspect further includes an optical element and the self-forming optical waveguides being provided between the optical element and the ferrule.

According to the above configurations, the pre-detached ferrule forms the self-forming optical waveguides in a state in which the variation in the core gap on one end side of the self-forming optical waveguides is smaller than the variation in the core gap on the other end side. Thus, a loss in connection among the self-forming optical waveguides and the optical fibers in the ferrule on one end side can be reduced. Further, use of the ferrule having the variation in the angle of each optical fiber insertion hole in the axial direction, the variation in the gap between the center points of the optical fiber insertion holes, or the roundness of the end surface is acceptable, and on the other hand, the optical connector can include the self-forming optical waveguides and the optical fibers and the end portions of the self-forming optical waveguides can be favorably connected to each other. Further, the connection loss can be easily reduced, and improvement in the yield of the optical connector and reduction in a manufacturing cost accompanied by such improvement can be achieved.

An optical connector manufacturing method according to the fourth aspect of the present embodiment includes: preparing two ferrules and photo-curing resin, each ferrule including at least n optical fiber insertion holes and including optical fibers in the optical fiber insertion holes, the optical fibers being inserted therein; arranging the two ferrules to face each other and arranging the photo-curing resin between the ferrules; confirming that there are variations in an angle of each optical fiber in a core axial direction and a core gap between adjacent ones of the optical fibers, an end surface of one of the ferrules is formed with roundness, and an end surface of the other ferrule is formed with no roundness; curing end portions of the photo-curing resin with the core gap by incident light entering the end portions of the photo-curing resin from the optical fibers, thereby transferring the core gap onto the photo-curing resin and forming the n self-forming optical waveguides at the photo-curing resin such that a variation in the core gap on one end side of the self-forming optical waveguides is smaller than a variation in the core gap on the other end side; forming a clad by curing of the photo-curing resin; and detaching the other ferrule from the self-forming optical waveguides, thereby forming a ferrule body including the one of the ferrules and the self-forming optical waveguides, wherein the number n indicates a natural number not including zero.

The optical connector manufacturing method according to the fifth aspect of the present embodiment, further includes, in the optical connector manufacturing method according to the fourth aspect: preparing another ferrule and another photo-curing resin, the another ferrule including n optical fiber insertion holes and including optical fibers in the optical fiber insertion holes, the optical fibers inserted therein; further forming other self-forming optical waveguides by the optical connector manufacturing method according to the fourth aspect by means of the detached other ferrule; forming another ferrule body including the another ferrule and the other self-forming optical waveguides; and optically connecting the self-forming optical waveguides and the other self-forming optical waveguides to each other.

An optical connector manufacturing method according to a sixth aspect of the present embodiment is that the optical connector manufacturing method of the fourth aspect further includes preparing an optical element and optically connecting the self-forming optical waveguides and the optical element to each other.

In addition to the above effect, according to the configurations and the manufacturing methods, the detached ferrule can be, as a master ferrule, repeatedly used for the step of manufacturing another optical connector. The highly-accurate ferrule with smaller various variations and roundness is detached and repeatedly used, and therefore, the self-forming optical waveguides can be manufactured with the highly-accurate constant core gap in the ferrule detached from the end portions of the self-forming optical waveguides. Thus, the end portions of the self-forming optical waveguides duplicated with the same core gap by the master ferrule are optically connected to each other. Thus, on this point, the connection loss of the optical connector can be also easily reduced.

An optical connector manufacturing method according to a seventh aspect of the present embodiment is that the optical connector manufacturing method of any one of the fourth to sixth aspects further includes applying a mold release agent to the other ferrule in advance.

According to this manufacturing method, the mold release agent is applied so that loss of the end portions of the self-forming optical waveguides upon detachment of the ferrule can be reduced. Thus, the ferrule can be smoothly detached from the self-forming optical waveguides.

An optical connector according to an eighth aspect of the present embodiment is that in the optical connector of any one of the first to third aspects, the starting location of an axis deviation correction part of each self-forming optical waveguide on a ferrule side is different between adjacent ones of the self-forming optical waveguides.

The optical connector manufacturing method according to the ninth aspect of the present embodiment, further including in any one of the optical connector manufacturing methods of the fourth to sixth aspects: differentiating a starting location of an axis deviation correction part of each self-forming optical waveguide on a side close to the one of the ferrules between adjacent ones of the self-forming optical waveguides, and providing a time difference in a time of end of formation of the axis deviation correction part between adjacent ones of the self-forming optical waveguides.

According to these configuration and manufacturing method, optical connection among the adjacent self-forming optical waveguides can be reduced while use of the ferrule having the variation in the angle of each optical fiber insertion hole in the axial direction or the variation in the gap between the center points of the optical fiber insertion holes is acceptable. Thus, the connection loss of the optical connector can be easily reduced.

An optical connector according to a tenth aspect of the present embodiment is that in the optical connector of any one of the first to third aspects or the eighth aspect, the ferrule is held in a single split sleeve.

An optical connector manufacturing method according to an eleventh aspect of the present embodiment is that the optical connector manufacturing method of any one of the fourth to sixth aspects and the ninth aspect further includes holding the ferrules in a single split sleeve.

According to these configuration and manufacturing method, the optical connector can be formed taking an inner diameter portion of the split sleeve as a reference surface. Thus, positioning of the ferrule is facilitated.

An optical connector manufacturing method according to a twelfth aspect of the present embodiment is that the optical connector manufacturing method of any one of the fourth to sixth aspects, the ninth aspect, and the eleventh aspect further includes causing light to simultaneously enter the photo-curing resin from the n optical fibers.

According to this manufacturing method, there is no need to provide an exit time difference when the light exits from the n optical fibers into the photo-curing resin. Thus, reduction in the cost for manufacturing the optical connector and improvement in the yield of the optical connector can be achieved.

Hereinafter, a first embodiment according to the present disclosure will be described with reference toFIGS.1to11, and a second embodiment will be described with reference toFIGS.12,13A, and13B. First, a structure in common between an optical connector1of the first embodiment and an optical connector11of the second embodiment will be described below.

In both embodiments, each of the optical connector1and the optical connector11includes at least a ferrule2and n self-forming optical waveguides5ato5d(hereinafter referred to as optical waveguides5ato5d). The number n is a natural number not including zero, and n=4 is satisfied in the embodiment shown in each figure. Moreover, in the first embodiment, the optical connector1further includes a ferrule3. Note that a Z-axis direction in each figure is a longitudinal direction of the ferrule2or3and is a common direction among the figures. A clad7is formed around each of the n optical waveguides5ato5d.

The ferrule2includes n optical fiber insertion holes2a, and optical fibers4ato4dare each inserted into and included in the optical fiber insertion holes2a. Note that the ferrule3also includes n optical fiber insertion holes3aand optical fibers4ato4dare each inserted into and included in the optical fiber insertion holes3a.

The ferrule2or3is made of zirconia (ZrO2), and the outer shape thereof can be a circular shape as shown inFIGS.3A and3BorFIGS.5A and5Bor a not-shown rectangular shape. The outer diameter of the circular shape is about 1.25 mm to 2.5 mm. In the case of the rectangular shape, a long side has a dimension of about 1.25 mm to 2.5 mm, and a short side has a dimension of equal to or smaller than that of the long side.

The number of optical fiber insertion holes2a,3a(hereinafter referred to as holes2a,3a) is four or six. The hole diameter of the optical fiber insertion hole2a,3ais slightly larger than 0.125 mm (125 μm) and equal to or smaller than about 0.2 mm, considering the above-described type of optical fiber4ato4dto be inserted. Arrangement of the holes2a,3ais one line×four holes as shown inFIGS.3A and3BorFIGS.5A and5Bor two lines×two holes as shown inFIG.17Ain a case where the number of holes2a,3ais four. In a case where the number of holes2a,3ais six, the holes2a,3aare each arranged at the vertices of a regular hexagon as shown inFIG.17B. A gap between the center points of adjacent ones of the holes2a,3ais about 0.25 mm to 0.45 mm.

Each optical fiber4ato4dis of a type that a clad surrounds a not-shown core, is a single mode or a multimode, and is any of a step index fiber or a graded index fiber. Further, each optical fiber4ato4dis made of glass or plastic. The outer diameter of the clad is 0.125 mm (125 μm) in the case of the single-mode optical fiber. Note that the mode field diameter of a single-mode fiber with a band of 1550 nm is 10.5 μm.

In the present embodiment, a variation θ1, θ2in the angle of each hole2ain an axial direction (the Z-axis direction) as shown inFIGS.4A and4Bis acceptable. Further, a variation in a gap2c1to2c3between the center points of adjacent ones of the holes2aas shown inFIGS.5A and5Band the roundness of an end surface2bof the ferrule2as shown inFIG.6are acceptable. The entirety of the end surface2bof the ferrule2is rounded by polishing. The same also applies to an end surface3bof the ferrule3.

In the first embodiment, a variation θ1, θ2in the angle of each hole3ain the axial direction (the Z-axis direction) and a variation in a gap3c1to3c3between the center points of adjacent ones of the holes3aare also acceptable. Thus, there are variations in the angle of each optical fiber4ato4dinserted into the holes2a,3ain a core axial direction and a gap between the cores of adjacent ones of the optical fibers4ato4d.

One end portion of each optical waveguide5ato5dis optically connected to a corresponding one of the optical fibers4ato4dof the ferrule2. In the first embodiment, the other end portion of each optical waveguide5ato5dis further optically connected to a corresponding one of the optical fibers4ato4dof the ferrule3.

Further, manufacturing methods in the first and second embodiments both have the following common steps as shown inFIGS.10A to10D,11,13A, and13B.

In the manufacturing method in each embodiment, at least two ferrules2,13and photo-curing resin10are first prepared. The ferrule13also includes n optical fiber insertion holes13a(hereinafter referred to as holes13a), and optical fibers4ato4dare each inserted into and included in the optical fiber insertion holes13a.

A variation θ1, θ2in the angle of each hole13ain the axial direction (the Z-axis direction) is also acceptable, and as shown inFIG.11, a variation in a gap13c1to13c3between the center points of adjacent ones of the holes13ais also acceptable. Thus, there are variations in the angle of each optical fiber4ato4dinserted into the hole13ain a core axial direction and a gap between the cores of adjacent ones of the optical fibers4ato4d. Note that (Variation in Gap13c1to13c3)<(Variation in Gap2c1to2c3) is satisfied. Further, it is confirmed that the variation θ1, θ2in the angle of each hole13aand the variation in the gap13c1to13c3between adjacent ones of the holes13afall within the standards for the optical connector1or11.

Note that the end surface13bof the ferrule13is formed in a planar shape with no roundness as shown inFIGS.10A to10D. Using a not-shown dedicated tool, surface polishing is performed for an outer surface of the end surface13bof the ferrule13satisfying (Variation in Gap13c1to13c3)<(Variation in Gap2c1to2c3). In this manner, the ferrule13is manufactured without the end surface13bbeing rounded. On the other hand, it can be recognized that the end surface2bis, with the roundness, greatly deformed from a planar state.

The photo-curing resin10is of a clad selective polymerization type. The material of the photo-curing resin10is a solution obtained in such a manner that a photopolymerization initiator is added to a liquid mixture of two or more types of monomer. Such a solution is polymerized and cured into polymer by incident light with such a wavelength band that the photopolymerization initiator has a sensitivity. As described above, in the present embodiment, the variation θ1, θ2in the angle of each hole2a,13a, the variation in the gap2c1to2c3,13c1to13c3, and the roundness of the end surface2bare acceptable. Thus, it is confirmed that there are the variations in the angle of each optical fiber4ato4dof the ferrule2in the core axial direction and the core gap between adjacent ones of the optical fibers4ato4dand the end surface2bis formed with the roundness. Moreover, it is confirmed that the end surface13bof the other ferrule13is formed with no roundness as described above.

Next, the photo-curing resin10is arranged between two ferrules2,13, and accordingly, is arranged on the end surface2band the end surface13b. Next, light enters end portions of the photo-curing resin10from each optical fiber4ato4d, and accordingly, the end portions of the photo-curing resin10are polymerized and cured with the core gap (i.e., each of the above-described gaps2c1to2c3,13c1to13c3) between adjacent ones of the optical fibers4ato4d. By such polymerization curing, the core gaps (2c1to2c3,13c1to13c3) are transferred onto the end portions of the photo-curing resin10. The wavelength λw of the light for polymerizing and curing the photo-curing resin10can be set as necessary according to the photopolymerization initiator. This wavelength kw is, as one example, 365 nm to 1675 nm.

After transfer, the light continuously enters the photo-curing resin10from the optical fibers4ato4d, and accordingly, the n optical waveguides5ato5dare formed at the photo-curing resin10. The core diameter of each optical waveguide5ato5dis preferably the same as the core diameter of each optical fiber4ato4d, and is preferably uniform along an optical axis direction of each optical waveguide5ato5d. The mode field diameter of each optical waveguide5ato5dis the same (10.5 μm) as that of the single-mode fiber.

As described above, (Variation in Gap13c1to13c3)<(Variation in Gap2c1to2c3) is satisfied. Thus, the variation in the core gap13c1to13c3on one end side (an end portion connected to the ferrule13) of the optical waveguides5ato5dis smaller than the variation in the core gap2c1to2c3on the other end side (an end portion connected to the ferrule2) of the optical waveguides5ato5d.

Next, the dads7are formed. The clad7is of a clad selective polymerization type. In each optical waveguide5ato5d, at least one type of monomer is in polymerization reaction with the wavelength kw. As a result, in the cured core region, a non-polymerization-reacted monomer component is, at the same level of concentration as that in the liquid mixture, dispersed as unreacted monomer. At the same time, only one type of monomer is consumed and polymerized in the core region. Thus, at a boundary surface between the core and the clad, a monomer concentration gradient is caused, and interdiffusion progresses. Accordingly, the function of the clad can be obtained. Finally, the entirety of the photo-curing resin10is irradiated with ultraviolet light (UV irradiation), and accordingly, the cores and the entirety of the dads7are cured and formed and the optical waveguides5ato5dare obtained.

Next, as shown inFIG.10D, the ferrule13is detached from the optical waveguides5ato5d, and in this manner, a ferrule body14including the ferrule2and the optical waveguides5ato5dis formed.

The detached ferrule13is, as a master ferrule, repeatedly used for the step of manufacturing another ferrule body. The highly-accurate ferrule13with smaller various variations, the planar end surface13b, and less deformation is detached and repeatedly used, and therefore, the ferrule body14of which core gap between the end portions of adjacent ones of the optical waveguides5ato5dis a highly-accurate constant core gap (13c1to13c3) in the ferrule13can be duplicated.

The optical connector having the above-described common structure and manufactured by the common manufacturing steps will be described in more detail separately in the first and second embodiments. Note that the same contents as the description above will be omitted or simply described. First, the optical connector1according to the first embodiment will be described.

In the optical connector1, the ferrules2,3are arranged facing each other in a split sleeve8shown inFIG.8. The optical waveguides5ato5dare provided between the ferrule2and the ferrule3. The n optical waveguides5ato5dare divided in half along a direction perpendicular to a light propagation direction (the Z-axis direction inFIG.9). A division line is shown inFIG.9. The core gap between adjacent ones of the optical waveguides5ato5dat the end surfaces thereof is the same among the divided optical waveguides5ato5d. Further, the flat end surfaces are connected to each other without any clearance in the perpendicular direction.

Two ferrules2,3are inserted into and held in the single split sleeve8, and therefore, can be arranged on the same axis and be arranged taking an inner diameter portion of the split sleeve8as a reference surface. Thus, positioning of two ferrules2,3is facilitated.

In the case of using a sleeve for the optical connector1, the split sleeve8is more preferable than a cylindrical sleeve because the photo-curing resin10can be poured into the sleeve.

Further, the method for manufacturing the optical connector1will be described with reference toFIGS.10A to10D. First, the ferrules2,13are prepared, and the photo-curing resin10is prepared. As shown inFIG.10A, two ferrules2,13are both inserted into the split sleeve8, and are arranged facing each other in the split sleeve8. Further, a clearance is formed between the ferrule2and the ferrule13. It may only be required that the clearance is set to dimensions necessary for forming the optical waveguides5ato5d, and the clearance is 1 mm as one example.

Next, as shown inFIG.10B, the photo-curing resin10is poured into between the ferrule2and the ferrule13through a slit of the split sleeve8, and is arranged between the ferrule2and the ferrule13.

Next, as shown inFIG.10C, light enters the end portions of the photo-curing resin10from each optical fiber4ato4dincluded in two ferrules2,13, and accordingly, the end portions of the photo-curing resin10are cured with the core gaps2c1to2c3,13c1to13c3. In this manner, the core gaps2c1to2c3,13c1to13c3are transferred onto the photo-curing resin10.

Further, the light enters the end portions of the photo-curing resin10from each optical fiber4ato4d, and in this manner, the n optical waveguides5ato5dare formed at the photo-curing resin10such that the variation in the core gap13c1to13c3on one end side of the optical waveguides5ato5dis smaller than the variation in the core gap2c1to2c3on the other end side. The end surface13bis formed in the planar shape. Thus, the end surfaces of the optical waveguides5ato5dcontacting the end surface13bare also formed in a planar shape, and deformation of the end surface is eliminated. On the other hand, the end surface2bis greatly deformed with the roundness from the planar state. Thus, the end surfaces of the optical waveguides5ato5dcontacting the end surface2bare also deformed.

Next, the dads7are formed by curing of the photo-curing resin10. Thereafter, as shown inFIG.10D, the ferrule13is detached from the optical waveguides5ato5d. Such detachment is performed in such a manner that the ferrule13is pulled out of the split sleeve8in the Z-axis direction.

After detachment of the ferrule13, another ferrule (e.g., the ferrule3) and another photo-curing resin are prepared. Another ferrule is a ferrule including n optical fiber insertion holes and including optical fibers in the optical fiber insertion holes, the optical fibers being inserted therein. Further, the prepared another ferrule has variations in the angle of each hole of the ferrule in the axial direction (the Z-axis direction) and a gap between the cores of adjacent ones of the holes of the ferrule, and at an end surface thereof, has a roundness similar to that of the end surface2b. Further, these various variations are equal to or greater than various variations of the ferrule13.

As inFIG.10A, the ferrule13and another ferrule are arranged facing each other in the split sleeve8(a state in which the ferrule2is replaced with another ferrule inFIG.10A). Further, as inFIG.10B, photo-curing resin is arranged between these two ferrules.

Light enters end portions of the photo-curing resin from each optical fiber of two ferrules to cure the end portions of the photo-curing resin with the above-described core gap between adjacent ones of the optical fibers, and in this manner, each core gap is transferred onto the photo-curing resin and n optical waveguides are formed at the photo-curing resin.

Next, dads are formed by curing of the photo-curing resin. Then, the ferrule13is detached from the formed self-forming optical waveguides. In this manner, another ferrule body is formed, which has a configuration similar to that of the ferrule body14ofFIG.10Dand includes another ferrule and other self-forming optical waveguides.

The end portions, which were connected to the ferrule13, of the ferrule body14and another ferrule body are formed with the same core gap13c1to13c3. The ferrule13is, in advance, rotated and adjusted using a not-shown connector housing, and in this manner, the position of each optical fiber4ato4dis determined in such a manner that the ferrule2and the ferrule forming another ferrule body are connected to each other through a connector without rotation adjustment, these ferrules being assembled in the connector housing. Thus, as shown inFIG.9, the optical waveguides5ato5dof these ferrule bodies can be connected to each other with a low loss at the same core gap13c1to13c3.

Further, the end surface13bis formed in the planar shape with no roundness in the direction perpendicular to the Z-axis direction. Thus, when the ferrule2and the ferrule3as another ferrule are connected to each other by connection of the end portions, which were connected to the ferrule13, of these ferrules, a connection state with no spatial clearance as inFIG.9can be formed. Thus, on this point, the ferrule2and the ferrule3can be connected to each other with a low loss.

Further, the pre-detached ferrule13forms the optical waveguides5ato5din a state in which the variation in the core gap on one end side of the optical waveguides5ato5dis smaller than the variation in the core gap on the other end side. Thus, a loss in connection among the optical waveguides5ato5dand the optical fibers4ato4don one end side can be reduced. Further, use of the ferrule2,3having the variation in the angle of each optical fiber insertion hole2a,3ain the axial direction, the variation in the gap (2c1to2c3,3c1to3c3) between the center points of adjacent ones of the optical fiber insertion holes2a,3a, or the roundness of the end surface2b,3bis acceptable, and on the other hand, the optical connector1can include the optical waveguides5ato5dand the optical fibers4ato4dand the end portions of the optical waveguides5ato5dcan be favorably connected to each other. Further, the connection loss can be easily reduced, and improvement in the yield of the optical connector1and reduction in a manufacturing cost accompanied by such improvement can be achieved.

Detachment of the ferrule13from the optical waveguides5ato5dcan be implemented in such a manner that a mold release agent is applied to the exterior of the ferrule13in advance. With the applied mold release agent, the ferrule13can be smoothly detached from the optical waveguides5ato5dwhile loss of the end portions of the optical waveguides5ato5dupon detachment of the ferrule13is reduced.

The detached ferrule13is, as the master ferrule, repeatedly used for the step of manufacturing another ferrule body. The highly-accurate ferrule13with smaller various variations, the planar end surface13b, and less deformation is detached and repeatedly used, and therefore, the ferrule body of which core gap between the end portions of adjacent ones of the optical waveguides5ato5dis the highly-accurate constant core gap (13c1to13c3) in the ferrule13can be duplicated. On this point, the connection loss of the optical connector can be easily reduced.

In the ferrule2for which it is not necessary to take detachment into consideration, the optical fibers4ato4dmay be inserted and arranged in advance as shown inFIGS.16A and16Bsuch that the end portions of all of the optical fibers4ato4dare retracted from the end surface2b. In this case, the photo-curing resin may be poured into such retracted portions of the end surface2bto optically connect the optical fibers4ato4dand the optical waveguides5ato5dto each other and form the dads7.

Alternatively, as shown inFIGS.14A,14B,15A, and15B, the end surface2bmay be formed with a step such that a step portion12,12′ is recessed from the end surface2b. In this case, the end portions of all of the optical fibers may be formed retracted from the end surface2bas the most-protruding end portion of the ferrule2, and the step portion12,12′ may be filled with the photo-curing resin10. Even if it is not necessary to take detachment of the ferrule3into consideration, the structures shown inFIGS.14A,14B,15A,15B,16A, and16Bare also applicable to the ferrule3.

Further, an axis deviation correction part is formed at each optical waveguide5ato5das indicated by dashed lines inFIGS.7A to7D. A dashed portion sandwiched by chain double-dashed lines at each optical waveguide5ato5dinFIGS.7A to7Dis the axis deviation correction part. These figures show a case where the ferrule2is arranged on the left side. Each optical fiber4ato4dof the ferrules2,3,13has the variations in the angle in the core axial direction and the core gap (2c1to2c3,3c1to3c3,13c1to13c3), and at these optical fibers, the end surfaces2b,3bof the ferrules are formed with the roundness and are deformed. Thus, in the Z-axis direction, the optical fibers4ato4dof the ferrules2,3,13are not arranged on the same axis, and axis deviation is inevitably caused. For this reason, the axis deviation correction part is also inevitably formed upon formation of each optical waveguide5ato5d.

In the optical connector1, the starting location6ato6dof the axis deviation correction part on a ferrule2side varies among the adjacent optical waveguides in the Z-axis direction inFIGS.7A to7D.FIGS.7A to7Dshow that formation of the starting location6aof the optical waveguide5ais started earlier than formation of the starting location6bof the optical waveguide5b. Moreover, it is shown that formation of the starting location6bis started later than formation of the starting location6cof the optical waveguide5c. Further, it is shown that formation of the starting location6cis started earlier than formation of the starting location6dof the optical waveguide5d. Note that focusing on the viewability of the starting locations6ato6dinFIGS.7A to7D, the axis deviation correction part is indicated by the dashed lines and is divided by the chain double-dashed lines. It does not mean that the optical waveguides5ato5dhave such a structure that only the axis deviation correction part is an invisible part.

A difference in the starting location6ato6dis caused due to the variation in the angle of each optical fiber4ato4din the core axial direction and the deformed end surface2b,3bwith the roundness. That is, upon formation of the axis deviation correction parts by incident light from the fibers4ato4dof the ferrules2,3,13, the angle of formation of the axis deviation correction part also varies. Thus, the light simultaneously enters from each optical fiber4ato4dwithout any time difference in entrance of the light from each optical fiber4ato4d, and in this manner, the starting location6ato6dcan be differentiated among the adjacent optical waveguides. Further, since the starting location6ato6dis different among the adjacent optical waveguides, there can be a time difference in the time of end of formation of the axis deviation correction part among the adjacent optical waveguides.

Thus, use of the ferrule2,3,13with the variation in the angle of each hole in the axial direction or the variation in the gap between the center points of adjacent ones of the holes is acceptable, and on the other hand, optical connection among the adjacent optical waveguides5ato5dcan be reduced. Thus, the connection loss of the optical connector1can be easily reduced.

When light exits from the n optical fibers4ato4dinto the photo-curing resin10, there is no need to provide a difference in exit time. Thus, reduction in the cost for manufacturing the optical connector1and improvement in the yield of the optical connector1can be achieved.

Note that substantially simultaneous entrance of the light from the optical fibers4ato4dis most preferable because there is no need to perform complicated entrance time control. Note that as long as a time difference in entrance of light from the optical fibers4ato4dis within two to three seconds, such a time difference is within an acceptable range at the manufacturing step.

The starting location of the axis deviation correction part on the ferrule2side has been described above. Instead, shift of a starting location on a ferrule3side (e.g., portions indicated by chain double-dashed lines on the right side inFIGS.7A to7D) may be taken into consideration.

Note that the angle of the ferrule13is rotated and adjusted in advance in the not-shown connector housing, and in this manner, positioning of the ferrule2and the ferrule3can be performed by connection between the ferrule2and the ferrule3through the connector without rotation adjustment.

Next, the optical connector11according to the second embodiment and the method for manufacturing thereof will be described with reference toFIGS.10A to10D,11, and12. Note that the same contents as those in the description above or the first embodiment will be omitted or simply described.

As shown inFIG.12, the optical connector11includes one ferrule and optical elements9, and includes the optical waveguides5ato5damong the optical elements9and the ferrule2. The optical element9is, for example, a vertical cavity surface emitting laser (VCSEL), a light-emitting diode, a laser diode, or a photodiode.

The array of the optical elements9and the ferrule2are held in the single split sleeve8. The array of the optical elements9and the ferrule2are inserted into and held in the single split sleeve8, and therefore, the optical elements9and the optical fibers4ato4dcan be arranged on the same axis and the inner diameter portion of the split sleeve8can be taken as the reference surface. Thus, positioning of the optical elements9and the ferrule2is facilitated.

Further, the method for manufacturing the optical connector11will be described with reference toFIGS.10A to10D,13A, and13B. First, the ferrule body14is produced according to the description ofFIGS.10A to10Dabove. The produced ferrule body14is shown inFIG.13A. As shown inFIG.10D or13A, a ferrule body including at least one ferrule and optical waveguides is also referred to as an optical connector in the present embodiment.

Next, the array of the optical elements9such as VCSELs is prepared, and is also inserted into the split sleeve8. Then, as shown inFIG.13B, the optical waveguides5ato5dand the optical elements9are optically connected to each other. In this manner, the optical connector11is produced. Note that in the description of the method for manufacturing the optical connector11, the length of the split sleeve8is different betweenFIGS.10D and13A, but these sleeves are taken as the same sleeve for the sake of convenience in description. The detached ferrule13is, as the master ferrule, repeatedly used for the step of manufacturing another ferrule body. The optical connector11has advantageous effects similar to those of the optical connector1.

In the above-described embodiment, the structure in which the clearance is provided in the split sleeve and the photo-curing resin is arranged in this clearance has been described with reference toFIGS.10A to10D. On this point, the gap between the ferrules is set to such a gap that the photo-curing resin can be, due to the surface tension thereof, held between the ferrules, and in this manner, the method for manufacturing the optical connector and the configuration of the optical connector without use of the split sleeve8can be also achieved.

Hereinafter, an example according to the present embodiment will be described. Note that the technique of the present disclosure is not limited only to the following example.

Example

An optical connector according to the present example has the structure shown inFIG.9. Optical waveguides5ato5dwere formed according toFIGS.10A to10Cdescribed above. After formation of the optical waveguides5ato5d, the optical waveguides5ato5dwere left for two minutes to promote monomer interdiffusion at a boundary surface between a core and a clad. Thereafter, dads7were formed by UV irradiation.

In this manner, ferrule bodies14were duplicated, and at end portions of the optical waveguides5ato5d, were optically connected to each other. In this manner, the optical connector1having the structure ofFIG.9was manufactured.

After formation of the optical connector1, light with a wavelength of 850 nm propagated from each optical fiber4ato4dto each optical waveguide5ato5d. At this point, an optical connection loss between a ferrule2and a ferrule3was measured.

On the other hand, an optical connector of a comparative example was formed in such a manner that an end surface2bof a ferrule2and an end surface3bof a ferrule3are brought into surface contact with each other with no optical waveguides5ato5dand no clads7in the configuration shown inFIG.9. In the comparative example, light with a wavelength of 850 nm also propagated in each optical fiber4ato4d, and an optical connection loss between the ferrule2and the ferrule3was also measured.

Improvement values of the connection loss in the example as compared to the comparative example are shown in Table 1. Table 1 shows that in two cases, i.e., both of the case of an optical waveguide length of 50 μm and the case of an optical waveguide length of 200 μm, the connection loss has been improved in light propagation paths of all of the optical fibers4ato4d. Note that the optical waveguide length is the length of each optical waveguide5ato5din the Z-axis direction ofFIG.9.