This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-168994, filed on Oct. 6, 2020, the entire contents of which are incorporated herein by reference.
The present disclosure relates to an optical connector cable and a method for manufacturing an optical connector cable.
JP2016-035484A discloses an example of an optical connector cable including optical fibers and a lens module. The lens module is a member optically connecting the optical fibers to optical elements mounted on a circuit board. Fiber grooves for accommodating end portions of the optical fibers are provided in an upper portion of the lens module. An adhesive is injected into clearances between the fiber grooves and the end portions of the optical fibers accommodated in the fiber grooves, and thus the optical fibers are fixed to the lens module. U.S. Pat. No. 9,435,963B2 discloses another example of a lens module.
An optical connector cable of the present disclosure includes a plurality of optical fibers, a lens module, and an adhesive. The plurality of optical fibers each extend in a first direction. The lens module includes a placement portion, a facing surface, and a plurality of lenses. The placement portion is configured to place end portions of the plurality of optical fibers thereon in order in a second direction intersecting the first direction. The facing surface faces distal end surfaces of the plurality of optical fibers. The plurality of lenses are optically coupled to the plurality of optical fibers through the facing surface. The adhesive fixes the plurality of optical fibers to the placement portion. The plurality of respective optical fibers are placed on the placement portion such that the distal end surfaces are separated from the facing surface by predetermined distances, and a part of the adhesive enters spaces between the distal end surfaces and the facing surface.
The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of embodiments of the disclosure with reference to the drawings.
In the lens module described in JP2016-035484A, a distal end surface of each of optical fibers is subjected to positioning such that it comes into contact with an abutment surface of a lens module, and an adhesive is injected into clearances between fiber grooves and end portions of the optical fibers. At this time, ideally, there is no clearance between the distal end surface of each of the optical fibers and the abutment surface. Thus, the adhesive does not enter a space between the distal end surface of each of the optical fibers and the abutment surface. However, actually, a manufacturing error (deviation) to a great or small extent may occur at a position of each of the distal end surfaces of the plurality of optical fibers, the adhesive may enter minute regions between the distal end surfaces of some optical fibers and the abutment surface, and bubbles may be generated inside the adhesive. If such bubbles are positioned inside the adhesive (particularly, on optical axes of the optical fibers), there is concern of occurrence of an optical axis deviation of the optical fibers, a Fresnel loss, or the like. Hence, it is desired to reduce generation of bubbles in an adhesive in an optical connector cable when a plurality of optical fibers are optically coupled.
According to the present disclosure, it is possible to provide an optical connector cable and a method for manufacturing an optical connector cable, in which generation of bubbles in an adhesive can be reduced.
First, details of embodiments of the present disclosure will be enumerated and described. An optical connector cable according to an embodiment includes a plurality of optical fibers, a lens module, and an adhesive. The plurality of optical fibers each extend in a first direction. The lens module has a placement portion, a facing surface, and a plurality of lenses. The placement portion is configured to place end portions of the plurality of optical fibers thereon in order in a second direction intersecting the first direction. The facing surface faces distal end surfaces of the plurality of optical fibers. The plurality of lenses are optically coupled to the plurality of optical fibers through the facing surface. The adhesive fixes the plurality of optical fibers to the placement portion. The plurality of optical fibers are placed on the placement portion such that the distal end surfaces are separated from the facing surface by predetermined distances, and a part of the adhesive enters spaces between the distal end surfaces and the facing surface.
In this optical connector cable, the plurality of optical fibers are placed on the placement portion such that each of the distal end surfaces is separated from the facing surface of the lens module by a predetermined distance. In this optical connector cable, the distal end surface of each of the optical fibers and the facing surface of the lens module are set in advance such that they are separated from each other by a predetermined distance. Thus, bubbles incorporated into the adhesive which has entered a space between the distal end surface of each of the optical fibers and the facing surface of the lens module are easily removed from the adhesive before curing or the like proceeds. According to this optical connector cable, generation of bubbles in an adhesive can be reduced. Therefore, an optical connection loss such as an optical axis deviation of the optical fibers or a Fresnel loss caused by bubbles can be curbed.
As one embodiment, the plurality of optical fibers may include optical fibers differing in separation distances from the distal end surfaces to the facing surface. Focal positions of the plurality of lenses may be positioned between the facing surface and a first distal end surface of a first optical fiber having the shortest separation distance in the plurality of optical fibers. According to this embodiment, since focal points of the lenses are positioned on optical paths between the lenses and the optical fibers which are optically coupled to each other, efficiency of optical coupling between the lenses and the optical fibers can be improved.
As one embodiment, a center in the first direction between the first distal end surface and a second distal end surface of a second optical fiber having the longest separation distance from the distal end surfaces to the facing surface may be positioned at an ideal central position when the plurality of optical fibers are placed on the placement portion such that a bubble generation rate in the adhesive is minimized, or may be positioned farther away from the facing surface than the ideal central position. According to this embodiment, the distal end surface provided in each of the optical fibers is positioned in the vicinity of the ideal central position or farther away from the facing surface than the ideal central position. Accordingly, the distal end surface of each of the optical fibers and the facing surface of the lens module are sufficiently separated from each other, and bubbles incorporated into the adhesive are more easily removed. Thus, generation of bubbles in an adhesive can be further reduced.
As one embodiment, the separation distances from the distal end surfaces to the facing surface may be equal to or greater than 25 μm and equal to or less than 50 μm. According to this embodiment, the distal end surface provided in each of the optical fibers is positioned moderately away from the facing surface. Thus, generation of bubbles in an adhesive can be reduced and an optical connection loss can be curbed. More specifically, when the separation distances from the distal end surfaces to the facing surface are shorter than 25 μm, since clearances between the distal end surfaces and the facing surface are extremely small, it takes time to remove bubbles from the adhesive which has entered the clearances or it is difficult to sufficiently remove bubbles. However, bubbles are easily eliminated by causing the separation distances from the distal end surfaces to the facing surface to be equal to or greater than 25 μm. In addition, when the separation distances from the distal end surfaces to the facing surface are greater than 50 μm, although the elimination of bubbles per unit volume is easier, the amount of the adhesive entering the clearances between the distal end surfaces and the facing surface increases and the total amount of bubbles between the distal end surfaces and the facing surface increases. Thus, the total amount of bubbles can be reduced by causing the separation distances from the distal end surfaces to the facing surface to be equal to or less than 50 μm.
As one embodiment, the optical connector cable may further include a circuit board, a plurality of optical elements, and a holding portion. The circuit board may mount the lens module thereon. The plurality of optical elements may be disposed on the circuit board and optically coupled to the plurality of optical fibers through the plurality of lenses, respectively. The holding portion may hold the plurality of optical fibers and have an end surface where end portions of the plurality of optical fibers project. Each of the plurality of optical elements may perform photoelectric conversion of light incident from the corresponding optical fiber or perform photoelectric conversion of light emitted to the corresponding optical fiber. According to this embodiment, the end portion of each of the optical fibers projecting from the holding portion can be easily cut to a suitable length with reference to a reference end surface of the holding portion. In addition, the optical connector cable includes the optical elements performing photoelectric conversion of light. Thus, for example, an electrical signal from a device to which the optical connector cable is connected can be converted into an optical signal and it can be sent out to other devices.
As one embodiment, the adhesive may be a light-transmitting adhesive. According to this embodiment, attenuation of light passing through the inside of the adhesive which has entered a space between the distal end surface of each of the optical fibers and the facing surface of the lens module, can be curbed.
A method for manufacturing the optical connector cable according to the embodiment includes, placing the end portions of the plurality of optical fibers on the placement portion of the lens module, and applying an adhesive to the placement portions to fix the plurality of optical fibers to the lens module. In the placing, the end portions of the plurality of optical fibers are placed such that the center between the first and second distal end surfaces is positioned at the ideal central position or positioned farther away from the facing surface than the ideal central position.
In this method for manufacturing an optical connector cable, the plurality of optical fibers are respectively placed on the placement portion such that the distal end surfaces provided in each thereof is positioned in the vicinity of the ideal central position or farther away from the facing surface than the ideal central position. Accordingly, the distal end surface of each of the optical fibers and the facing surface of the lens module are moderately separated from each other, and bubbles incorporated into the adhesive are more easily removed. Thus, generation of bubbles in an adhesive can be reduced.
Specific examples of an optical connector cable and a method for manufacturing an optical connector cable according to the present disclosure will be described below with reference to the drawings. The present invention is not limited to these examples. The present invention is indicated by the claims, and it is intended to include all changes within meanings and a range equivalent to the claims. In description of the drawings, the same reference signs are applied to the same elements, and duplicate description thereof will be omitted.
With reference to
For example, the optical connector cable 1 is used for transmitting and receiving optical signals between devices, and is an active optical cable (AOC), for example. As illustrated in
The circuit board 10 is a plate-shaped component in which optical elements and electronic elements are mounted or built. As illustrated in
A plurality of optical elements 14 are mounted on the main surface 13 (refer to
The lens module 20 is a plate-shaped component placed on the circuit board 10, and optically couples the optical fibers 31 with the optical elements 14. With reference to
As illustrated in
The lower surface 24 is positioned at a lower portion of the lens module 20 and extends in the direction X and the direction Y. The lower surface 24 is provided closer to the second end surface 22 than to the upper surface 23 in the direction X, and an end portion of the lower surface 24 closer to the second end surface 22 is connected to the second end surface 22. In a state in which the lens module 20 is placed on the circuit board 10, the lower surface 24 comes into contact with the main surface 13 of the circuit board 10.
The plurality of fiber grooves 25 are a placement portion in which distal end parts 33 (end portions) of a plurality of optical fibers 31 are placed. Each of the fiber grooves 25 is a V groove extending in the direction X (a groove having a V-shape in a YZ plane). Each of the fiber grooves 25 regulates the position of one of the optical fibers 31 with respect to the lens module 20 and prevents misalignment of each of the optical fibers 31 in the direction Y. As illustrated in
As illustrated in
As illustrated in
As illustrated in
The plurality of lenses 28 are optically coupled to the optical elements 14, respectively. As illustrated in
Returning to
Each of the optical fibers 31 may be formed by covering a glass fiber constituted of a core and a cladding surrounding the core with a resin, for example. Each of the optical fibers 31 may be a single mode optical fiber (SMF) or a multi-mode optical fiber (MMF). In the present embodiment, the optical fiber cable 30 has four optical fibers 31, but the number of optical fibers 31 is not limited.
The holding portion 40 is a member collectively holding the plurality of optical fibers 31. With reference to
The pair of protruding portions 43 are members protruding from the outer surface of the main body portion 42 toward the distal end side in the direction X. As illustrated in
The reference end surface 44 is provided between the pair of protruding portions 43 and extends in the direction Y and the direction Z. The plurality of optical fibers 31 project from the reference end surface 44 toward the distal end. The extending direction of each of the optical fibers 31 projecting from the reference end surface 44 and the extending direction of the reference end surface 44 may form a right angle, for example. Each of the optical fibers 31 may be cut to have a desired length on the basis of the length from the reference end surface 44 to the distal end surface of each of the optical fibers 31, for example. The foregoing members constituting the holding portion 40, which are the cylinder portion 41, the main body portion 42, and the pair of protruding portions 43, may be integrally formed by performing injection molding of a resin (e.g. a polyamide resin).
Next, with reference to
The plurality of optical fibers 31 include an optical fiber 31a, an optical fiber 31b, an optical fiber 31c, and an optical fiber 31d, and are placed side by side in the direction Y. The optical fiber 31a has a distal end surface S1, the optical fiber 31b has a distal end surface S2, the optical fiber 31c has a distal end surface S3, and the optical fiber 31d has a distal end surface S4. In the following description, the distal end surface S1 to the distal end surface S4 will be generically referred to as “distal end surfaces S”.
The distal end surfaces S of the optical fibers 31 are positioned such that they are separated from the facing surface 27 by predetermined distances. Although illustration is omitted in
Here, a position of the distal end surface S (first distal end surface) having the shortest separation distance to the facing surface 27 in the direction X will be referred to as a first position P1. In the present embodiment, the position of the distal end surface S2 becomes the first position P1. A position of the distal end surface S (second distal end surface) having the longest separation distance to the facing surface 27 in the direction X will be referred to as a second position P2. In the present embodiment, the position of the distal end surface S4 becomes the second position P2. A position where a distance D1 from the first position P1 and a distance D2 from the second position P2 become equivalent to each other in the direction X will be referred to as a central position P3. The distal end surface S1 and the distal end surface S3 respectively provided in the optical fiber 31a and the optical fiber 31c are positioned between the first position P1 and the second position P2 in the direction X. In the present embodiment, the distal end surface S1 and the distal end surface S3 are present substantially at the same position in the direction X. The plurality of lenses 28 provided in the lens module 20 (refer to
As described above with reference to
As illustrated in
As illustrated in
Next, the distal end parts 33 of the plurality of optical fibers 31 are individually placed in the plurality of fiber grooves 25 provided in the lens module 20 (Step S11). At this time, as illustrated in
Next, the adhesive 29 is applied to the lens module 20, and the distal end part 33 of each of the optical fibers 31 is fixed to the lens module 20 (Step S12). Specifically, as illustrated in
Hereinabove, in the optical connector cable 1 according to the present embodiment, the plurality of optical fibers 31 are placed in the fiber grooves 25 (the placement portion) such that the distal end surfaces S are separated from the facing surface 27 of the lens module 20 by predetermined distances. In other words, it is constituted such that all the optical fibers 31 of the optical fiber cable 30 are separated from the facing surface 27. In this manner, in the optical connector cable 1, the distal end surface S of each of the optical fibers 31 and the facing surface 27 of the lens module 20 are set in advance such that they are separated from each other by a predetermined distance, and thus bubbles incorporated into the adhesive 29 which has entered a space between the distal end surface S of each of the optical fibers 31 and the facing surface 27 of the lens module 20 are easily removed from the adhesive 29 before curing or the like. According to this optical connector cable 1, the generation rate of bubbles in the adhesive 29 can be reduced. For this reason, occurrence of defects caused by bubbles, such as an optical axis deviation of the optical fibers 31 or a Fresnel loss can be curbed.
In the foregoing embodiment, the plurality of optical fibers 31 include optical fibers (the optical fiber 31a to the optical fiber 31d) differing in separation distances from the distal end surfaces S to the facing surface 27. The focal positions Pf of the plurality of lenses 28 are positioned between the facing surface 27 and the first position P1 of the distal end surface S2 provided in the optical fiber 31b having the shortest separation distance in the direction X. Accordingly, since the focal points of the lenses 28 are positioned on the optical paths between the lenses 28 and the optical fibers 31 which are optically coupled to each other, efficiency of optical coupling between the lenses 28 and the optical fibers 31 can be improved.
In the foregoing embodiment, the central position P3 between the first position P1 of the distal end surfaces S provided in the plurality of optical fibers 31 and the second position P2 of the distal end surface S4 provided in the optical fiber 31d having the longest separation distance from the distal end surfaces S to the facing surface 27 in the direction X, is positioned at the ideal central position P4 or is positioned farther away from the facing surface 27 than the ideal central position P4. Accordingly, each of the distal end surfaces S provided in each of the optical fibers 31 is positioned in the vicinity of the ideal central position P4 or farther away from the facing surface 27 than the ideal central position P4. For this reason, the distal end surface S of each of the optical fibers 31 and the facing surface 27 of the lens module 20 are sufficiently separated from each other, and bubbles incorporated into the adhesive 29 are more easily removed. Thus, the generation rate of bubbles can be further reduced.
In the foregoing embodiment, the separation distances from the distal end surfaces S to the facing surface 27 may be equal to or greater than 25 μm and equal to or less than 50 μm. Accordingly, the distal end surfaces S provided in the optical fibers 31 are positioned moderately away from the facing surface 27. Thus, the generation rate of bubbles in the adhesive 29 can be reduced.
In the foregoing embodiment, the optical connector cable 1 includes the circuit board 10, the plurality of optical elements 14, and the holding portion 40. The circuit board 10 mounts the lens module 20 thereon. The plurality of optical elements 14 are disposed on the circuit board 10 and optically coupled to the plurality of optical fibers 31 through the plurality of lenses 28 therebetween. The holding portion 40 has the reference end surface 44 having end portions of the plurality of optical fibers 31 projecting thereon and collectively holds the plurality of optical fibers 31. Each of the plurality of optical elements 14 performs photoelectric conversion of light incident from the corresponding optical fiber 31 or performs photoelectric conversion of light emitted to the corresponding optical fiber 31. Accordingly, the distal end part 33 of each of the optical fibers 31 projecting from the holding portion 40 can be easily cut to a suitable length with reference to the reference end surface 44 of the holding portion 40. In addition, the optical connector cable 1 includes the optical elements 14 each performing photoelectric conversion of light. Accordingly, for example, an electrical signal from a device to which the optical connector cable 1 is connected can be converted into an optical signal and it can be sent out to other devices. That is, a communication speed between devices connected to each other by the optical connector cable 1 can be improved.
In the foregoing embodiment, the adhesive 29 is a light-transmitting adhesive. Accordingly, attenuation of light passing through the inside of the adhesive 29 which has entered a space between the distal end surface S of each of the optical fibers 31 and the facing surface 27 of the lens module 20 can be curbed.
In the method for manufacturing the optical connector cable 1 according to the present embodiment, each of the optical fibers 31 is placed in each of the fiber grooves 25 (the placement portion) such that the central position P3 for the distal end surfaces S provided in the optical fibers 31 is positioned at the ideal central position P4 or is positioned farther away from the facing surface 27 than the ideal central position P4. Accordingly, each of the distal end surfaces S provided in each of the optical fibers 31 is positioned in the vicinity of the ideal central position P4 or farther away from the facing surface 27 than the ideal central position P4. For this reason, the distal end surface S of each of the optical fibers 31 and the facing surface 27 of the lens module 20 are sufficiently separated from each other, and bubbles incorporated into the adhesive 29 are more easily removed. Thus, the generation rate of bubbles in the adhesive 29 can be further reduced.
Hereinabove, the embodiments according to the present disclosure have been described in detail, but the present disclosure is not limited to the foregoing embodiments and can be applied to various embodiments. For example, the optical connector cable 1 according to the foregoing embodiments have a constitution in which the light L emitted from the optical fibers 31 is incident on the optical elements 14. However, when the optical elements 14 are light emitting elements such as VCSELs, the optical connector cable 1 may have a constitution in which the light L emitted from the optical elements 14 is incident on the optical fibers 31. At this time, the light L emitted from the optical elements 14 may be converted into collimate light (parallel light) by the lenses 28 and may be incident on the optical fibers 31 after being reflected by the mirror 23a.
Number | Date | Country | Kind |
---|---|---|---|
2020-168994 | Oct 2020 | JP | national |