This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010-084298, filed on Mar. 31, 2010, the entire contents of which are incorporated herein by reference.
The embodiment discussed herein is related to a method for manufacturing optical waveguides.
Generally, an optical waveguide has a structure in which a core serving as an optical path is surrounded by a cladding having a refractive index different from that of the core. This difference in refractive indices causes light traveling through the core to be reflected at an interface between the core and the cladding. The core and the cladding are both composed of a resinous material, such as polyimide or epoxy, as a main component. The core is given a refractive index different from that of the cladding by adding fluorine, bromine, or the like to this main component.
Communication using such an optical waveguide is not only used between systems, but also between boards in a device having boards equipped with multiple electronic components. In the case of board-to board communication within the device, the communication is achieved by using multiple optical waveguides for the purpose of achieving parallel communication or high-speed communication. With regard to each optical waveguide used for such communication, narrow cores are embedded in a parallel-arranged fashion within a single cladding. Furthermore, the optical waveguide is manufactured by fixing both ends of the multiple arranged cores and then curing a cladding material around the cores.
See Japanese Laid-open Patent Publication No. 2006-67360 for an example.
According to an aspect of the invention, a method for manufacturing an optical waveguide in which multiple cores are embedded in a parallel-arranged fashion within a single cladding, the cores having a refractive index of light different from that of the cladding, the method includes forming the multiple cores in a state where the adjacent cores are connected by a rib, forming the cladding around the multiple cores by curing a cladding material there around, and a cutting to the rib.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
An embodiment will be described below.
As shown in
The boards 12 are each provided with a central processing unit (CPU) 19, a memory circuit 20, a hard disk unit 21, a photoelectric conversion circuit 22, wiring (not shown) such as a bus for transferring data between these units, and a bus driver. The boards 12 are disposed substantially orthogonally to the base plate 17 of the optical transmission circuit device 11 and are parallel to each other. A lower edge 12a of each board 12 is fitted into a corresponding rail on the base plate 17, as shown in
Referring to
In the base plate 17, rails 25 having openings engageable with the boards 12 extend from the front to the rear (X-axis direction in
Referring to
The optical waveguide 29 will now be described with reference to
In this embodiment, the optical waveguide 29 has eight cores 29a that are arranged parallel to each other, and is formed by filling and curing a cladding 29b there around. The cores 29a each have a core diameter D of 50 μm and are arranged at a pitch P of 250 μm. The cores 29a each have a shape such that a first segment 29a1 thereof extends in a Y-Y direction and second segments 29a2 thereof extend upward orthogonally from opposite ends of the first segment 29a1. A free end 29a3 of each second segment 29a2 is exposed from the cladding 29b. This exposed section is to come into contact with the corresponding optical connector 28.
The cladding 29b is formed into a shape of a thin plate with a thickness H of about 1 mm and a length of about 20 cm. Therefore, the second segments 29a2 of each core 29a each have a length L of about 0.5 mm. (If the drawings were to be made by directly scaling down the aforementioned dimensions, the ratio between the length L and the thickness and the ratio between the pitch P and the core diameter D would be too large, making the explanation very difficult. Therefore, in this embodiment, the scales of the components are set to values different from the aforementioned values.)
Furthermore, the cores 29a and the cladding 29b are both composed of a resinous material, such as polyimide or epoxy, as a main component. The cores 29a are given a refractive index different from that of the cladding 29b by adding fluorine, bromine, or the like to this main component so that light traveling through the cores 29a is reflected at an interface between the cores 29a and the cladding 29b.
As mentioned above, in the related art, an optical waveguide is formed by arranging multiple cores parallel to each other, fixing the ends of the cores, and then forming a cladding around the cores by curing a cladding material there around. However, since the cores are normally composed of a resinous material, as mentioned above, the cores tend to deform readily with decreasing width, which is problematic in terms of linear precision. Moreover, this is also problematic in that, as distance increases, there is a high possibility of a core becoming deformed and coming into contact with an adjacent core. Therefore, at a narrow pitch of 250 μm and with a length of several tens of centimeters, it is difficult to prevent the narrow cores with a width in the order of micrometers, as mentioned above, from coming into contact with each other by simply fixing the ends of the cores.
In light of this, in this embodiment, the multiple cores 29a are formed in a state where ribs that connect the adjacent cores 29a are provided, and the cladding 29b is subsequently formed around the cores 29a by curing a cladding material there around. Finally, the ribs are removed.
A process for forming the cores 29a will be described in detail below.
Regarding the cores 29a in this state, the adjacent cores 29a are connected to each other at three sections of the first segment 29a1 by the ribs 29a4, 29a5, and 29a6, respectively. By providing the ribs at predetermined intervals in the first segment 29a1 of the cores 29a in this manner, the distance between the cores 29a can be properly maintained even if the first segment 29a1 were to be increased in length.
The ribs 29a4, 29a5, and 29a6 and the cores 29a may be composed of the same material, and are integrally formed using a mold in this embodiment. In contrast to the cores in the related art that need to be manufactured one by one before being arranged parallel to each other, the ribs 29a4, 29a5, and 29a6 and the cores 29a in this embodiment can be integrally formed so that the cores 29a can be readily manufactured.
Furthermore, the second segments 29a2 are formed longer than at the time of completion. However, after filling and curing the cladding 29b around the cores 29a, the second segments 29a2 are machined by, for example, cutting and grinding so that the second segments 29a2 do not protrude from the surface of the cladding 29b.
A process for forming the cladding 29b will now be described. When the cores 29a are completely formed, an operator fills and cures a cladding material, such as polyimide or epoxy, around the cores 29a so as to form the cladding 29b.
This process is performed by using a box-shaped mold so that the resultant cladding 29b has a shape of a thin plate.
This process for filling and curing the cladding 29b around the cores 29a is performed without the cores 29a being cut off from the ribs 29a4, 29a5, and 29a6.
Furthermore, in this state, the second segments 29a2 of the cores 29a protrude from the surface of the cladding 29b.
A process for removing the ribs 29a4, 29a5, and 29a6 will now be described. When the cladding 29b is completely formed, a removal process of the ribs 29a4, 29a5, and 29a6 is performed.
This removal process is performed using a tool, such as a drill, from a surface 29b2 of the cladding 29b opposite a surface 29b1 thereof from which the second segments 29a2 protrude.
As mentioned above, since the cores 29a are arranged at a very narrow pitch, the process is performed using, for example, a numerical control (NC) machine tool.
In this case, positioning is performed by estimating the positions of the ribs on the basis of the protruding positions of the second segments 29a2 of the cores 29a.
This process using the NC machine tool will now be described.
The NC machine tool 100 performs various processes on the basis of a command from a computer 200 serving as a higher-level device.
The NC machine tool 100 has a base 110 that can move two-dimensionally on an X-Y plane on the basis of a command from the computer 200. This base 110 is driven by a stepping motor or the like, and because this mechanism itself is commonly known, a detailed description thereof will be omitted here.
The base 110 has sixteen insertion holes 110a. The insertion holes 110a positionally correspond to the second segments 29a2 of the cores 29a in the optical waveguide 29. The second segments 29a2 set in the positions shown in
Reference numeral 120 denotes a drill that can move in a Z-axis direction on the basis of a command from the computer 200. Since this Z-axis moving mechanism is also commonly known, a description thereof will be omitted here.
The computer 200 includes a central processing unit (CPU) 220 and a memory 210.
The memory 210 stores drilling-position information 300 shown in a table in
Referring back to
The drilling process performed by such an NC machine tool 100 will now be described with reference to a flow chart in
When a drilling command is input via the input unit 230, the CPU 220 in the computer 200 refers to the memory 210 so as to acquire one piece of drilling-position information therefrom in step S1001.
Then, in step S1002, the CPU 220 causes the NC machine tool 100 to move the base 110 until the position acquired on the basis of the drilling-position information is aligned with the position of the drill 120 in the X-axis and Y-axis directions.
When this movement is completed, the CPU 220 performs control to move the drill 120 in the Z-axis direction and make the drill 120 perform drilling at that position in step S1003.
When the drilling is completed, the CPU 220 refers to the memory 210 so as to determine whether or not there are any pieces of drilling-position information that have not undergone drilling processing yet. If yes, the process returns to step S1001, whereas if no, the process ends in step S1004.
A process for removing the second segments 29a2 will now be described. After the ribs are completely removed, a removal process of the second segments 29a2 is performed. This removal process is performed by machining the second segments 29a2 by, for example, cutting and grinding so that the second segments 29a2 do not protrude from the surface of the cladding 29b.
Consequently, an optical waveguide 29 having multiple cores 29a within a single cladding 29b can be formed.
Although the holes 29b3, 29b4, and 29b5 are formed by drilling in this embodiment, other cutting techniques, such as laser machining, may alternatively be used so long as similar precision can be obtained.
A second filling and curing process will now be described. The optical waveguide 29 in this state is already satisfactory in terms of function. However, because the ribs 29a4, 29a5, and 29a6 integrally formed with the cores 29a have been removed, there is a possibility that light may somewhat leak since the first segment 29a1 of the cores 29a is partly exposed through the holes. In order to prevent this, the same cladding material used for the cladding 29b is filled and cured again in the holes 29b3, 29b4, and 29b5 so as to eliminate the exposed sections, whereby an optical waveguide 29 with reduced light loss can be formed.
According to this embodiment, the cladding 29b is formed by filling and curing in a state where the ribs 29a4, 29a5, and 29a6 are added between or integrally formed with the adjacent cores 29a, whereby the pitch between the cores 29a can be maintained even when the cores 29a are long or narrow.
Furthermore, in the subsequent removal process, the removing positions of the ribs 29a4, 29a5, and 29a6 are determined by utilizing the sections of the cores 29a that are exposed from the cladding 29b, whereby the ribs 29a4, 29a5, and 29a6 can be readily removed.
Furthermore, since the same cladding material used for the cladding 29b is filled and cured again in the holes formed for removing the ribs 29a4, 29a5, and 29a6, the occurrence of light loss owing to exposed side sections of the cores 29a can be prevented.
All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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2010-084298 | Mar 2010 | JP | national |