The present application claims priority under 35 U.S.C. §119 of Japanese Patent Application No. 2011-153621 filed on Jul. 12, 2011, the disclosure of which is expressly incorporated by reference herein in its entity.
1. Technical Field
The present invention relates to optical connectors for coupling optical fibers each including an external optical path and an internal optical path. The invention also provides optical fiber coupling structures.
2. Background Art
In the field of robotics, robots capable of a variety of movements have been actively developed in recent years. Such a robot is typically expected to instantaneously perform a series of operations, such as scanning an internal/external world through a sensor at an end of the robot, processing data using a built-in computer, and operating a driving unit provided at the end.
As a medium for transmitting optical signals in such an application or other use, optical fibers with separate incoming and outgoing paths have been developed. An optical fiber of this type includes an internal structure having an external optical path and an internal optical path.
An example of a conventional optical connector used for such optical fibers is illustrated in
The optical connector 200 includes a connector main body 210 attached to an end of one of the optical fibers 100 and a sleeve 220 attached to an end of the other optical fiber 100. Upon attachment of the sleeve 220 to the connector main body 210, end faces of the internal optical paths 101 of the optical fibers 100 come face to face with each other and end faces of the external optical paths 102 come face to face with each other, thereby connecting the optical fibers 100. Solid arrows in
Unfortunately, the above conventional example may experience crosstalk. Particularly, the optical connector 200 may couple the two optical fibers 100 with very small gaps left between the end faces of the internal optical paths 101 and between the external optical paths 102, so that the gaps allow optical signals from the internal optical paths to find their way into the external optical paths, or vice versa, as indicated with dashed arrows in
It is not impossible to improve the optical connector to eliminate the gap, but such improvement would likely to cause increased number of components and complicated structure. Accordingly, the cost for the optical connector should increase.
The present invention has been contrived in view of the above circumstances, and an object thereof is to provide an optical connector having a simple structure and capable of preventing occurrence of crosstalk, as well as a structure of such connection between optical fibers.
The invention provides an optical connector for coupling a first optical fiber and a second optical fiber. Each of the optical fibers includes an external optical path and an internal optical path. The optical connector includes a holder and a light guide. The holder is configured to securely receive a distal end of the first optical fiber from a first direction and a distal end of the second optical fiber from a second direction that is opposite to the first direction. The light guide has translucency and is configured to be interposed at least one of (i) between end faces of the internal optical paths of the first and the second optical fibers and (ii) between end faces of the external optical paths of the first and the second optical fibers, such that the end faces of the internal optical paths of the first and the second fibers are displaced in a light axis direction from the end faces of the external optical paths of the first and the second optical fibers.
In the optical connector according to this aspect of the invention, the end faces of the internal optical paths of the first and the second optical fiber are displaced in the light axis direction from the end faces of the external optical paths of the first and the second optical fiber. As such, if the first and the second optical fibers are coupled with a gap present at the end faces of the internal optical paths and/or at the end faces of the external optical paths, optical signals carried in one path will not be likely to enter into the other path even. Therefore, the invention can prevent the occurrence of crosstalk between the internal optical paths and the external optical paths of the first and the second optical fiber. In addition, the first and the second optical fibers optically coupled with the translucent light guide interposed between the end faces of the internal optical paths and/or between the end faces of the external optical paths. Such a connector can be manufactured in a simple structure with a smaller number of components, contributing to reduced cost.
The light guide may include a tapered surface in an outer surface thereof. The tapered surface may be located near a leakable portion of the light guide from which light may leak. The tapered surface may reflect the light substantially toward a light traveling direction.
In the optical connector according to this aspect, the tapered surface of the outer surface of the light guide reflects light to reduce leakage of light, minimizing optical transmission loss.
The light guide may include an end face of lens-shape.
In the optical connector according to this aspect, the lens shape formed in the end face of the light guide can provide light collection or other functions as needed, minimizing optical transmission loss.
The holder may include a holder main body and a sleeve. The holder may be generally in a tubular shape with open ends to securely receive the distal end of the first optical fiber from the first direction. The sleeve may be generally in a tubular shape to securely receive the distal end of the second optical fiber from the second direction, the sleeve being attachable into the holder main body from the second direction.
The sleeve may include a housing attachable into the holder main body, the light guide of tubular shape, and a coupling portion interposed between the light guide and the housing to support the light guide within the housing. The light guide may include a first opening to receive the distal end of the internal optical path of the first optical fiber from the first direction, a second opening to receive the distal end of the internal optical path of the second optical fiber from the second direction, an edge of the first opening, against which the end face of the external optical path of the first optical fiber may abut from the first direction, and an edge of the second opening, against which the end face of the external optical path of the second optical fiber may abut from the second direction. The housing, the light guide, and the coupling portion may be formed as a unitary transparent body.
In the optical connector according to this aspect, the holder is provided with the light guide. Such a configuration can reduce the number of components and facilitates assembly of the connector, further contributing to reduction of cost.
The sleeve may further include a chamfer formed around a corner of the edge of the first opening on a side of the light traveling direction.
In the optical connector according to this aspect, the chamfer guides the distal end of the internal optical path of the first optical fiber as entering into the first opening of the sleeve, facilitating the insertion of the optical fiber. In addition, this aspect of invention can minimize optical transmission loss because the chamfer on the side of the light traveling will reflect little light.
An optical fiber coupling structure (optical fiber module) of the invention includes a first optical fiber, a second optical fiber, and a light guide configured in any manner as described above. The first and second optical fibers each include an external optical path, an internal optical path, and an end formed such that a distal end of the internal optical path extends beyond that of the external optical path.
In the optical fiber coupling structure (optical fiber module) of this aspect of the invention, the end faces of the internal optical paths of the first and the second optical fiber are displaced in the light axis direction from the end faces of the external optical paths of the first and the second optical fiber. As such, if the first and the second optical fibers are coupled with a gap present at the end faces of the internal optical path and/or at the end faces of the external optical paths, optical signals carried in one path will not be likely to enter into the other path even. Therefore, the invention can prevent the occurrence of crosstalk between the internal optical paths and the external optical paths of the first and the second optical fiber. In addition, the first and the second optical fibers are optically coupled via the translucent light guide interposed between the end faces of the internal optical paths and/or between the end faces of the external optical paths. Such a structure can be manufactured in a simple structure with a smaller number of components, contributing to reduced cost.
A chamfer may be provided at a corner of the distal end of the internal optical path of at least one of the first and the second optical fibers.
In the optical fiber coupling structure according to this aspect of the invention, the chamfer guides the distal end of the internal optical path of at least one of the first and the second optical fibers as entering into an opening of the light guide, thereby facilitating the insertion of the optical fibers.
An embodiment of the present invention will be described below with reference to
The first and the second optical fibers 100a and 100b have internal structures including internal optical paths 101a, 101b (i.e. outgoing path or on-axis path), external optical paths 102a, 102b (i.e. incoming path or off-axis path) fitted around the internal optical paths 101a, 101b, and coating 103a, 103b coating the external optical path 102a, 102b, respectively. The external optical paths 102a, 102b are hollow multi-core optical fibers with center holes. The internal optical paths 101a, 101b are common single-core optical fibers received in the center holes of the external optical paths 102a, 102b. As shown
As illustrated in
Further, the distal end of the internal optical path 101a (a distal end portion of the internal optical path on a side of a light traveling direction of the internal optical paths) is formed with a chamfer 1011 to serve as a guide, extending entirely around the corner of the distal end of the internal optical path 101a of the first optical fiber 100a.
The optical connector A is provided with a holder 1 to securely receive the distal end of the first optical fiber 100a from the first direction D1 and the distal end of the second optical fiber 100b from the second direction D2.
The holder 1 includes a holder main body 10 and a sleeve 20. The holder 1 is generally molded of resin, but only the sleeve 20 is transparent. The holder main body 10 is generally of tubular shape with open ends such as to securely receive the distal end of the first optical fiber 100a from the first direction D1 (from left side in the drawings). The sleeve 20 is generally of tubular shape such as to securely receive the distal end of the second optical fiber 100b from the second direction D12. The sleeve 20 is attachable into the holder main body 10 from the second direction D2.
The holder main body 10 is formed with a sleeve holding hole 11, opening at the end in the first direction D1 (at the right end in
The sleeve 20 includes the housing 21, a light guide 22, and a coupling portion 23. The housing 21 of tubular shape is attachable into to the sleeve holding hole 11 of the holder main body 10. The light guide 22 is a transparent tube coaxially provided within the housing 21. The coupling portion 23 of annular shape is provided between the light guide 22 and the housing 21 so as to support the light guide 22 within the housing 21 coaxially. The housing 21, the light guide 22, and the coupling portion 23 are unitarily formed. When the first and the second optical fibers 100a, 100b are connected to the optical connector A, the light guide 22 is disposed between the end faces of the external optical paths 102a and 102b of the first and the second optical fibers 100a and 100b, such that the end faces of the internal optical paths 101a, 101b of the first and the second optical fibers 100a, 100b are displaced in a light axis direction from the end face of the external optical paths 102a, 102b of the first and the second optical fibers 100a, 100b.
The housing 21 has a depression 202 entirely around its outer surface. The depression 202 has a triangular cross-section so as to lock over the projection 13 of the holder main body 10. The housing 21 also has a fiber holding hole 201 at its rear end. The diameter of the fiber holding hole 201 corresponds to the outer diameter of the second optical fiber 100b (substantially equal to or slightly larger than the outer diameter of the second optical fiber 100b). Accordingly, the fiber holding hole 201 can securely receive the distal end of the second optical fiber 100b from the second direction D2.
The light guide 22 has first and the second opening 2211 and 2221 at opposite ends. The respective inner diameters of the first and the second openings 2211, 2221 correspond to the respective outer diameters of the internal optical paths 101a, 101b of the first and the second optical fibers 100a, 100b (substantially equal to or slightly larger than the outer diameters of the internal optical paths 101a, 101b). Accordingly, the first opening 2211 can receive the distal end of the internal optical path 101a of the first optical fiber 100a from the first direction D1, so that the end face of the external optical path 102a of the first optical fiber 100a is abuttable on an edge of the first opening 2211. The second opening 2221 can receive the distal end of the internal optical path 101b of the second optical fiber 100b from the second direction D2, so that the end face of the external optical path 102b of the second optical fiber 100b is abuttable on an edge of the second opening 2221.
The light guide 22 includes a front portion 221 and a rear portion 222. The front portion 221 includes the first opening 2211 and the edge of the first opening 2211, and the rear portion 222 includes the second opening 2221 and the edge of the second opening 2221. The front portion 221 and the rear portion 222 are positioned substantially forward and rearward, respectively, of the coupling portion 23 in the direction of light traveling through the light guide 22. The thickness (outer diameter) of the light guide 22 is not even along the light axis direction (the light traveling direction), and a base end 2213 of the front portion 221 and a base end 2222 of the rear portion 222 are mutually different in thickness. Particularly in this embodiment, the thickness t2 of the base end 2213 is larger than the thickness t1 of the base end 2222 (see
It should be noted that the tapered surface 2214 is positioned near the coupling portion 23 (leakable portion). Light propagating through the light guide 22 is reflected off the tapered surface 2214 to travel substantially in the light traveling direction (see a partially enlarged view on the upper side in
The edge of the first opening 2211 of the front portion 221 of the light guide 22 (distal end portion on a side of the light traveling direction of the external optical path) is formed with a chamfer 2212 to serve as a guide, extending entirely around the corner of the edge of the first opening 2211. Specifically, the chamfer 2212 is formed entirely around the inner corner of the edge of the first opening 2211 such that the inner diameter of the edge gradually increases in the second direction D2. The chamfer 2212 of the light guide 22 and the chamfer 1011 of the first optical fiber 100a facilitate insertion of the distal end of the internal optical path 101a of the first optical fiber 100a into the first opening 2211 of the sleeve 20.
The optical connector A as described above may be connected to the first and second optical cables 100a, 100b in the following steps. First, the distal end of the first optical fiber 100a is securely inserted into the fiber holding hole 12 of the holder main body 10 from the first direction D1. As a result, the distal ends of the external optical path 102a and the internal optical path 101a of the first optical fiber 100a pass through the opening 14 of the holder main body 10 to be received in the sleeve holding hole 11. On the other hand, the distal end of the second optical fiber 100b securely inserted into the fiber holding hole 201 of the sleeve 20 from the second direction D2. As a result, the distal end of the internal optical path 101b of the second optical fiber 100b is received in the second opening 2221 of the light guide 22 of the sleeve 20, and the end face of the external optical path 102b of the second optical fiber 100b abuts the edge of the second opening 2221 of the light guide 22.
Then, the sleeve 20 is inserted into the sleeve holding hole 11 of the holder main body 10 from the second direction D2, so that the projection 13 of the holder main body 10 is lockingly inserted into the depression 202 of the sleeve 20. As a result, the sleeve 20 is attached to the holder main body 10. At this time, the distal end of the internal optical path 101a of the first optical fiber 100a is received in the first opening 2211 of the light guide 22 of the sleeve 20, and the end face of the internal optical path 101a of the first optical fiber 100a is brought into abutment with the end face of the internal optical path 101b of the second optical fiber 100b. On the other hand, the end face of the external optical path 102a of the first optical fiber 100a is brought into abutment with the edge of the first opening 2211 of the light guide 22.
In the assembled state, the first optical fiber 100a and the second optical fiber 100b are arranged such that only the end faces of the internal optical paths 101a and 101b face each other, and that the light guide 22 of the sleeve 20 is interposed between the end faces of the external optical paths 102a and 102b. The light guide 22 is a transparent tubular body of a diameter corresponding to those of the external optical paths 102a and 102b. With such arrangement of the first and the second optical fibers 100a and 100b, the end faces of the internal optical paths 101a, 101b of the first and the second optical fiber 100a, 100b are displaced in the light axis direction from the end faces of the external optical paths 102a, 102b of the first and the second optical fiber 100a, 100b. The above are exemplary steps of coupling the optical fiber 101a and the optical fiber 101b via the optical connector A.
The optical connector A and the optical fiber coupling structure (optical fiber module) as described above have may advantageous features. First, as illustrated in
The optical connector A is also advantageous in effective transmission of optical signals. Particularly, light propagating along the external optical path 102b of the second optical fiber 100b into the light guide 22 of the sleeve 20 may diffuse near the coupling portion 23. However, as the light guide 22 has the tapered surface 2214 around its outer surface near the coupling portion 23, a major part of the propagating light returns back toward the light guide 22 as described above, minimizing deviation of light toward the housing 21. Moreover, the sleeve 20 has the chamfer 2212 for guiding around the distal end portion, on the side of the light traveling direction of the external optical path, of the front portion 221. Having a diameter gradually increasing in the light traveling direction, the chamfer 2212 is able to reflect light toward the light traveling direction (see a partially enlarged view on the lower side in
The connector A described as an exemplary embodiment above may be modified within the scope of claims.
In the optical connector A according to the embodiment described above and illustrated in
This is in contrast with the first variant of the optical connector A as illustrated in
In the reverse light direction type described above, an alternative sleeve 20 as illustrated in
The second, the third, and the fourth variants can achieve similar effects to those of the optical connector A according to the above embodiment. Particularly, as the sleeve 20 of each variant has the tapered surfaces 2223, 2233′, 2214′, and 2223″, respectively that can reflect light, which could have leaked from the light guide 22 into the housing 21 through the coupling portion 23, substantially toward the light traveling direction. Accordingly, each of the variants can minimize optical transmission loss of the light propagating through the light guide.
Further, the sleeve 20 according to the fifth variant illustrated in
Moreover, the optical connector A according to the embodiment described above is configured such that the sleeve 20 of the holder 1 includes the light guide 22. However, the optical connector of the invention may be modified as in the optical connector of a sixth variant illustrated in
A seventh variant as illustrated in
The optical connector of the seventh variant includes the light guide 2 and the light guide 3 as separate components. In an eighth variant as illustrated in
The light guide 4 according to the eighth variant includes a tuboid light guide 41 interposed between the end faces of the external optical paths 102a and 102b of the first optical fiber 100a and the second optical fiber 100b, a cylindrical light guide 42 interposed between the end faces of the internal optical paths 101a and 101b of the first optical fiber 100a and the second optical fiber 100b, and a coupling portion 43 interposed between the light guide 42 and the light guide 41 to support the light guide 42 within the light guide 41. The light guide 4 is provided as a transparent body in which the light guide 41, the light guide 42, and the coupling portion 43 are integrated.
The light guide 41 and the light guide 42 of the light guide 4 is provided with tapered surfaces 411 and 421, respectively, to provide the same functions as described above (see a partially enlarged view in
Another advantageous feature of the eighth variant is that the light guide 4 is provided with a lens-shape 422, similarly to the fifth variant illustrated in
It should be noted that the optical connector and the optical fiber coupling structure (optical fiber module) of the invention is not limited to the embodiment and its variants described above. Firstly, the optical fibers may be modified in accordance with its applications. For example, the optical fibers may be configured such that the internal optical paths (on-axis path) and the external optical paths (off-axis path) may not be concentric to each other. The external optical paths of the optical fibers may be of single core. Secondly, the holder may be of any shape that can securely receive the distal ends of the first and second optical fibers. Thirdly, the light guide may be of any configuration such as to have translucency and be interposed at least one of (i) between end faces of the internal optical paths of the first and the second optical fibers and (ii) between end faces of the external optical paths of the first and the second optical fibers, such that the end faces of the internal optical paths of the first and the second fibers are displaced from the end faces of the external optical paths of the first and the second optical fibers in a light axis direction. The light guides 2 and 3 and the sleeve 20 may be integrally formed. The light guide 4 and the sleeve 20 may be integrally formed. The light guide 22 of the optical connector A of the above embodiment and the light guide of the first to the fifth variants may be separately provided from the sleeve 20. The light guide may or may not be provided with a lens-shaped end face. If provided, the lens-shaped end face may be of any configuration such that it faces one of the end faces of the internal optical paths and the external optical paths of the first and the second optical fibers. The lens shape of the light guide may be modified in any manner such as to collect or diffuse light from an internal or external optical path and guide the light into the light guide. In the optical connector A of the above embodiment and the variants except the third to the fifth, the light guide may be modified such that its front portion can be inserted into the opening of the holder main body.
Number | Date | Country | Kind |
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2011-153621 | Jul 2011 | JP | national |