Connecting device, connecting system, optical waveguide and connecting method

There is provided a connecting system including a connecting apparatus that includes (i) a signal transfer path that transfers one of an electrical signal and an optical signal and (ii) a connecting device that connects the signal transfer path to a connection target component in such a manner that a signal is capable of being transferred therebetween, and a connected apparatus that includes the connection target component to be connected to the signal transfer path. Here, the connecting device includes a moving portion that has therein a sealed space. The moving portion moves an end portion of the signal transfer path closer to the connection target component so that the end portion of the signal transfer path is connected to the connection target component in response to an increase in a pressure within the moving portion, and moves the end portion away from the connection target component in response to a decrease in the pressure within the moving portion.

BACKGROUND

1. Technical Field

The present invention relates to a connecting device, a connecting system, an optical waveguide and a connecting method. More particularly, the present invention relates to a connecting device, a connecting system, an optical waveguide and a connecting method for connecting electrical circuit substrates to each other in such a manner that signal transfer is possible between the electrical circuit substrates.

2. Related Art

A technique has been proposed to signal-connect together two electrical circuit substrates which are parallel to each other based on optical space transmission. For example, refer to Japanese Patent Application Publication No. 09-44272 and T. Szymanski and H. S. Hintor, “Architecture of a Terabit Free-space photonic backplane”, The international conference on optical computing technical digest, October 1994. According to the proposed optical space transmission technique, the signal is transferred without going through any backplanes. Therefore, the two electrical circuit substrates can be efficiently connected to each other.

However, the above-mentioned technique has problems. In order that optical transmission is realized between the two substrates, the substrates need to be highly accurately positioned to prevent misalignment between a light emitting section and a light receiving section. Furthermore, when a large number of optical transfer paths are created, light leakage may cause interference, which may degrade the communication quality. Additionally, when optical transmission is realized between the two substrates, the light emitting section and the light receiving section remain externally exposed. Therefore, dirt and dust may attach to the light emitting section and the light receiving section, and the communication quality may accordingly deteriorate.

SUMMARY

Therefore, it is an object of an aspect of the innovations herein to provide a connecting device, a connecting system, an optical waveguide, and a connecting method which are capable of overcoming the above drawbacks accompanying the related art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the innovations herein.

According to the first aspect related to the innovations herein, one exemplary connecting device may include a connecting device for connecting a signal transfer path to a connection target component in such a manner that a signal is capable of being transferred therebetween. The connecting device includes the signal transfer path that is to be connected to the connection target component, and a moving portion that has therein a sealed space. Here, the moving portion moves an end portion of the signal transfer path closer to the connection target component so that the end portion is connected to the connection target component with signal transfer being possible therebetween in response to an increase in a pressure in the moving portion, and moves the end portion away from the connection target component in response to a decrease in the pressure in the moving portion.

The moving portion may hold, within the sealed space, a portion of the signal transfer path which has a predetermined length and contains the end portion of the signal transfer path. The moving portion may move the end portion of the signal transfer path in a direction towards the connection target component, by expanding or contracting in response to the pressure within the moving portion. The moving portion may be hollow and shaped like an accordion.

The signal transfer path may be an optical waveguide, and the moving portion may move the end portion of the optical waveguide closer to the connection target component in response to the increase in the pressure within the moving portion, so that the end portion of the optical waveguide and the connection target component are optically connected to each other without a contact therebetween. The signal transfer path may be an optical waveguide, and the moving portion may move the end portion of the optical waveguide closer to the connection target component in response to the increase in the pressure within the moving portion, so that the end portion of the optical waveguide and the connection target component are optically connected to each other by using a connector.

The connecting device may include a multicore cable that is formed by clustering together a plurality of optical waveguides by using a stretchable material. Here, the moving portion may move one or more of a plurality of end portions of the plurality of optical waveguides in the multicore cable in a direction towards the connection target component. The optical waveguide may be formed by using a stretchable material, and the moving portion may move the end portion of the optical waveguide closer to the connection target component by expanding the optical waveguide, in order that the end portion is connected to the connection target component.

The connecting device may further include an alignment portion that (i), when the end portion of the signal transfer path is moved closer to the connection target component, comes in contact with a guide member provided on an apparatus including therein the connection target component before the signal transfer path is connected to the connection target component, and (ii), as the end portion of the signal transfer path is further moved closer to the connection target component, is guided by the guide member, thereby reducing misalignment of the end portion of the signal transfer path on a plane perpendicular to a direction in which the end portion of the signal transfer path is moved closer to or away from the connection target component.

The moving portion may be configured so as to connect a plurality of signal transfer paths running in parallel to each other with a plurality of connection target components in a one-to-one correspondence. The connecting device may further include an angle adjusting portion that (i), when end portions of the plurality of signal transfer paths are moved closer to the plurality of connection target components, comes in contact with a guide member that is provided on an apparatus including therein the plurality of connection target components before the plurality of signal transfer paths are connected to the plurality of connection target components in a one-to-one correspondence and (ii), as the end portions of the plurality of signal transfer paths are further moved closer to the plurality of connection target components, is guided by the guide member, thereby reducing angular misalignment of the end portions of the plurality of signal transfer paths on a plane perpendicular to a direction in which the end portions of the plurality of signal transfer paths are moved closer to or away from the plurality of connection target components.

The connecting device may further include a fixing portion that maintains the signal transfer path and the connection target component connected to each other, while the pressure inside the moving portion is reduced after the signal transfer path is connected to the connection target component. The moving portion may include a cleaning portion that cleans a connection portion of the connection target component by expelling a gas inside the moving portion to the connection target component while the pressure inside the moving portion is higher than an outside pressure in order to move the end portion of the signal transfer path closer to the connection target component.

According to the second aspect related to the innovations herein, one exemplary connecting system may include a connecting system including a connecting apparatus that includes (i) a signal transfer path that transfers one of an electrical signal and an optical signal and (ii) a connecting device that connects the signal transfer path to a connection target component in such a manner that a signal is capable of being transferred therebetween, and a connected apparatus that includes the connection target component to be connected to the signal transfer path. Here, the connecting device includes a moving portion that has therein a sealed space. The moving portion moves an end portion of the signal transfer path closer to the connection target component so that the end portion of the signal transfer path is connected to the connection target component in response to an increase in a pressure within the moving portion, and moves the end portion away from the connection target component in response to a decrease in the pressure within the moving portion.

The connecting apparatus and the connected apparatus may be circuit boards having electric circuits formed therein, and the circuit boards may be mounted on the connecting system in parallel to each other. The moving portion may move the end portion of the signal transfer path closer to one of the circuit boards which corresponds to the connected apparatus by moving the end portion of the signal transfer path in a direction perpendicular to the circuit boards in response to the increase in the pressure within the moving portion, so as to connect the end portion of the signal transfer path to the connection target component in such a manner that a signal is capable of being transferred therebetween. The connecting system may further include a backplane that includes a first backplane (BP) connector and a second BP connector, where the first BP connector is to be connected to a board connector provided on a side of one of the circuit boards which corresponds to the connecting apparatus, and the second BP connector is to be connected to a board connector provided on a side of one of the circuit boards which corresponds to the connected apparatus. Here, the backplane may supply a gas supplied thereto from a source outside the connecting system, to the moving portion included in one of the circuit boards which corresponds to the connecting apparatus, via the first BP connector. The connecting system may further include a pressure control section that controls the pressure within the moving portion.

According to the third aspect related to the innovations herein, one exemplary optical waveguide may include an optical waveguide that is formed by using a stretchable material which transmits light therethrough. Here, the optical waveguide is to be used in a state of being expanded in a longitudinal direction thereof.

According to the fourth aspect related to the innovations herein, one exemplary connecting method may include a connecting method for connecting a signal transfer path to a connection target component in such a manner that a signal is capable of being transferred therebetween. The connecting method includes moving an end portion of the signal transfer path closer to the connection target component so that the end portion of the signal transfer path is connected to the connection target component by increasing a pressure within a moving portion that has therein a sealed space, and moving the end portion away from the connection target component by decreasing the pressure within the moving portion.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described. The embodiment does not limit the invention according to the claims, and all the combinations of the features described in the embodiment are not necessarily essential to means provided by aspects of the invention.

FIG. 1illustrates a board connecting system10in such a state that the circuit boards are not connected to each other.FIG. 2illustrates the board connecting system10in such a state that the circuit boards are connected to each other.

The board connecting system10includes a connecting circuit board11, a connected circuit board12, and a backplane13.

The board connecting system10holds the connecting circuit board11and the connected circuit board12in parallel to each other. Additionally, the board connecting system10signal-connect the connecting circuit board11and the connected circuit board12to each other without using a connector, thereby achieving efficient signal transfer. The board connecting system10is utilized to signal-connect test modules to each other, which are inserted into the test head of a semiconductor test apparatus and kept parallel to each other, for example.

The connecting circuit board11is a circuit board in which an electrical circuit is provided, and is shown as an example of a connecting device relating to the present invention. The connecting circuit board11includes a first circuit substrate21, optical waveguides22and a connecting device23. The first circuit substrate21has a circuit pattern or the like formed therein, and has an electronic component mounted therein. On a predetermined side of the first circuit substrate21, a first board connector24is formed.

Each optical waveguide22is shown as an example of a signal transfer path relating to the present invention, and is an optical fiber or the like which transmits an optical signal. The optical waveguides22may be replaced with transfer paths for an electrical signal. One end of each optical waveguide22is attached to the first circuit substrate21, and optically connected to a light receiving element and/or a light emitting element. The other end of each optical waveguide22is shown as an example of an end portion of the signal transfer path relating to the present invention. The other end of each optical waveguide22is physically released from the first circuit substrate21. The other end of each optical waveguide22is referred to as an open end portion25. Here, the length of each optical waveguide22from its root portion connected to the first circuit substrate21to its open end portion25may be determined in advance.

The connecting device23connects the optical waveguides22to connection target components included in the connected circuit board12in such a manner that signals can be transferred between the connection target components and the optical waveguides22. The connecting device23includes a moving portion26having therein a sealed internal space27, and an air inlet tube28.

The moving portion26is attached to the surface of the first circuit substrate21. The moving portion26is expandable and contractible in a direction substantially perpendicular to the surface of the first circuit substrate21by the pressure of the gas sealed in the internal space27(the air pressure). Specifically speaking, the moving portion26expands in the direction perpendicular to the first circuit substrate21when the air pressure inside the internal space27increases, and contracts in the direction perpendicular to the first circuit substrate21when the air pressure inside the internal space27decreases. In the following description, the direction perpendicular to the surface of the first circuit substrate21is referred to as an X direction.

The moving portion26holds the open end portions25of the optical waveguides22, and houses the optical waveguides22within the internal space27. Hence, when expanded, the moving portion26moves the open end portions25of the optical waveguides22away from the first circuit substrate21. When contracted, the moving portion26moves the open end portions25of the optical waveguides22closer to the first circuit substrate21. Alternatively, the moving portion26may not house the optical waveguides22in the internal space27, and move the open end portions25of the optical waveguides22which are positioned outside the internal space27.

The air inlet tube28is provided on the first circuit substrate21. One end of the air inlet tube28is connected to the internal space27of the moving portion26, and the other end of the air inlet tube28is positioned at substantially the same position as the first board connector24. The air inlet tube28introduces, to the internal space27, compressed air supplied from outside. The provision of the air inlet tube28enables the moving portion26to expand and contract.

The connected circuit board12is a circuit board in which an electrical circuit is disposed, and shown as an example of a connected device relating to the present invention. The connected circuit board12includes a second circuit substrate31, light receiving and emitting elements32, and a guide member33.

The second circuit substrate31has a circuit pattern or the like formed therein, and has an electronic component mounted therein. On a predetermined side of the second circuit substrate31, a second board connector34is formed. Each light receiving and emitting element32is shown as an example of the connection target component relating to the present invention, and configured to receive, emit, or receive and emit an optical signal. The light receiving and emitting elements32are provided on the surface of the second circuit substrate31with their light receiving and emitting portions being exposed externally on the surface. The guide member33is attached to the second circuit substrate31. The guide member33guides the moving portion26to a predetermined position, when the moving portion26moves.

The backplane13keeps the connecting circuit board11and the connected circuit board12parallel to each other, and controls the air pressure inside the internal space27of the moving portion26. The backplane13has a base member41, an air supply path42, a first backplane (BP) connector43, a second backplane (BP) connector44and a pressure control section45.

The base member41is a substrate in which the air supply path42, the first BP connector43, the second BP connector44, and the pressure control section45are provided. The air supply path42is an air flow channel formed within the base member41. The air supply path42receives, through its inlet, compressed air which is output from an air compressor100provided outside the board connecting system10. The outlet of the air supply path42for the compressed air is provided at the first BP connector43. When there are a plurality of first BP connectors43, the air flow channel branches into a plurality of sub-channels in the base member41, and the outlets of the sub-channels are respectively provided at the first BP connectors43.

The first and second BP connectors43and44are provided on the surface of the base member41. Into the first BP connector43, the first board connector24, which is formed on the predetermined side of the connecting circuit board11, is inserted. Into the second BP connector44, the second board connector34, which is formed on the predetermined side of the connected circuit board12, is inserted. The first and second BP connectors43and44respectively keep the connecting circuit board11and the connected circuit board12perpendicular to the base member41. Therefore, the connecting circuit board11and the connected circuit board12are mounted on the board connecting system10in such a manner as to be parallel to each other.

When the connecting circuit board11is connected to the first BP connector43, the first BP connector43connects the end portion of the air inlet tube28which is positioned in the vicinity of the first board connector24to the compressed air outlet of the air supply path42. This enables the backplane13to supply the compressed air supplied from the air compressor100to the internal space27in the moving portion26via the air supply path42and the air inlet tube28.

The pressure control section45controls whether to close or open the flow channel or the like which is formed by the air supply path42, so as to control the air pressure within the internal space27of the moving portion26. Specifically speaking, in order to increase the air pressure within the internal space27, the pressure control section45opens the flow channel formed by the air supply path42so as to supply the compressed air supplied from the air compressor100into the internal space27. On the other hand, in order to decrease the air pressure within the internal space27, the pressure control section45closes the flow channel formed by the air supply path42so as to prevent the compressed air supplied from the air compressor100from being supplied into the internal space27.

When the optical waveguides22are expanded in the X direction in the board connecting system10described above, the optical waveguides22included in the connecting circuit board11are positioned so as to oppose the light receiving and emitting elements32included in the connected circuit board12, so that an optical signal can be transferred between the open end portions25of the optical waveguides22and the light receiving and emitting elements32.

When the air pressure in the internal space27of the moving portion26increases, the moving portion26is expanded in the X direction as illustrated inFIG. 2. Accordingly, the open end portions25of the optical waveguides22become closer to the light receiving and emitting sections32. As a result of such movement, the connecting circuit board11and the connected circuit board12are signal-connected to each other. On the other hand, when the air pressure in the internal space27of the moving portion26decreases, the moving portion26is contracted in the X direction as illustrated inFIG. 1. Accordingly, the open end portions25of the optical waveguides22move away from the light receiving and emitting elements32. As a result of such movement, the signal connection between the connecting circuit board11and the connected circuit board12is cut off.

According to the above-described board connecting system10, the open end portions25of the optical waveguides22are moved by the moving portion26which is expandable and contractible in accordance with the air pressure in the internal space27. Therefore, the board connecting system10can connect together, via an optical signal, the connecting circuit board11and the connected circuit board12which are kept parallel to each other, without the optical signal going through the backplane13.

FIG. 3illustrates the cross-section of the connecting device23in such a state that the moving portion26is contracted.FIG. 3also illustrates the cross-sections of the optical waveguides22, the light receiving and emitting elements32, and the guide member33.FIG. 4illustrates the cross-section of the connecting device23in such a state that the moving portion26is expanded.FIG. 4also illustrates the cross-sections of the optical waveguides22, the light receiving and emitting elements32, and the guide member33.

The moving portion26has an accordion-like portion51, a bottom portion52, a support portion53and an alignment portion54.

The accordion-like portion51is a hollow cylinder with an accordion-like cylindrical surface. The accordion-like cylindrical surface enables the according-like portion51to expand and contract in the direction parallel to the axis of the cylinder. The accordion-like portion51is attached at one end thereof to the surface of the first circuit substrate21in such a manner that the optical waveguides22are housed within the accordion-like portion51and that the axis of the cylinder is parallel to the X direction.

The bottom portion52is shaped like a circular board, for example. The bottom portion52is attached to the end portion of the accordion-like portion51which faces away from the first circuit substrate21, so as to tightly seal the accordion-like portion51. The bottom portion52has through holes formed at substantially the center thereof. Here, the optical waveguides22penetrate the bottom portion52through the through holes, so that a portion of each optical waveguide22which contains the open end portion25is positioned outside the accordion-like portion51.

The support portion53is configured so as to fix, to the bottom portion52, the portion of each optical waveguide22which is positioned outside the accordion-like portion51with respect to the bottom portion52. Therefore, as the accordion-like portion51expands/contracts, the open end portions25of the optical waveguides22move in the X direction. The support portion53supports the outer portions of the optical waveguides22in such a manner that the end surfaces of the open end portions25remain perpendicular to the X direction. In this manner, the open end portions25of the optical waveguides22can receive optical signals parallel to the X direction, and emit optical signals in the X direction.

The alignment portion54is guided by the guide member33when the moving portion26expands, so that the open end portions25of the optical waveguides22are positioned so as to be capable of emitting/receiving optical signals to/from the light receiving and emitting sections32.

Specifically speaking, the alignment portion54has a first cylindrical portion61and a first taper portion62. The first cylindrical portion61has a diameter slightly larger than the diameter of the accordion-like portion51. The first taper portion62is shaped like a cylinder whose diameter gradually decreases. Here, the end portion of the first taper portion62which has a larger diameter than the other end portion is connected to the first cylindrical portion61, and the diameter of the first taper portion62decreases as the first taper portion62moves away from the first cylindrical portion61. The alignment portion54is attached to the bottom portion52in such a manner that the end portion of the first taper portion62which has a smaller diameter than the other end portion comes in contact with the bottom portion52and that the central axis of the cylindrical portion coincides with the central axis of the accordion-like portion51. Here, the guide member33is shaped so as to fit in and become engaged with the alignment portion54. To be specific, the guide member33has a second cylindrical portion63and a second taper portion64, similarly to the alignment portion54. As a whole, the guide member33has the same shape as the alignment portion54. The outside dimensions of the guide member33are the same as the inside dimensions of the alignment portion54. The guide member33has the light receiving and emitting elements32arranged at its center. Additionally, the guide member33is attached to the surface of the second circuit substrate31in such a manner that the end portion of the first cylindrical portion61comes in contact with the surface of the second circuit substrate31and that the central axis of the guide member33coincides with the central axis of the alignment portion54.

Referring to the moving portion26described above, the accordion-like portion51, the bottom portion52, and the first circuit substrate21together form the internal space27which is sealed and houses therein the optical waveguides22. The internal space27formed in this manner is supplied with the compressed air transmitted through the air inlet tube28. As the air pressure in the internal space27is decreased, the accordion-like portion51contracts as illustrated inFIG. 3. As a result, the open end portions25of the optical waveguides22move away from the light receiving and emitting elements32, so that the transfer paths of the optical signals are cut off. On the other hand, as the air pressure in the internal space27is increased, the accordion-like portion51expands as illustrated inFIG. 4. As a result, the open end portions25of the optical waveguides22move closer to the light receiving and emitting elements32, so that the transfer paths of the optical signals are established.

Referring to the connecting device23, when the open end portions25move closer to the light receiving and emitting elements32as a result of the expansion of the moving portion26, the internal surface of the first cylindrical portion61comes in contact with the external surface of the second taper portion64, before the optical waveguides22become connected to the light receiving and emitting elements32. As the open end portions25move further closer to the light receiving and emitting elements32, the alignment portion54is guided by the tilted surface of the second taper portion64. Ultimately, the alignment portion54is engaged with the guide member33. With this engagement, the connecting device23reduces the misalignment between the open end portions25and the light receiving and emitting elements32on the plane perpendicular to the X direction, which may be caused when the open end portions25are moved closer to the light receiving and emitting elements32.

Here, the guide member33and the alignment portion54, which are designed to reduce the misalignment between the open end portions25and the light receiving and emitting elements32on the plane perpendicular to the X direction, may be a pin provided so that its longitudinal direction extends in the X direction and a member which guides the pin, for example.

Referring to the connecting device23, the length of each optical waveguide22, the position of each light receiving and emitting element32and other variables are determined in such a manner that, when the open end portions25of the optical waveguides22and the light receiving and emitting elements32are signal-connected to each other as a result of the expansion of the moving portion26, there is a minute space formed between the open end portions25and the light receiving and emitting elements32. Which is to say, the light receiving and emitting elements32and the open end portions25of the optical waveguides22are optically connected to each other without contacting each other. Consider a case where there is slight vertical misalignment between the open end portions25and the light receiving and emitting elements32. In this case, light can not be transferred between the open end portions25and the light receiving and emitting elements32if the open end portions25and the light receiving and emitting elements32physically contact with each other. On the contrary, light can be transferred between the open end portions25and the light receiving and emitting elements32if a slight space is formed between the open end portions25and the light receiving and emitting elements32.

Alternatively, the open end portions25of the optical waveguides22and the light receiving and emitting elements32may be directly connected to each other by using a connecter, without a slight space being formed between the open end portions25and the light receiving and emitting elements32. This configuration prevents the misalignment.

FIG. 5is a perspective view illustrating an angle adjusting portion71provided in the alignment portion54and a guide groove72provided in the guide member33.FIG. 6is a perspective view illustrating the angle adjusting portion71provided in the alignment portion54, which is seen from a different direction than inFIG. 5.

Referring to the board connecting system10, the guide groove72and the angle adjusting portion71may be respectively provided in the guide member33and the alignment portion54, when the optical waveguides22running in parallel are connected to the plurality of light receiving and emitting elements32in a one-to-one correspondence.

The angle adjusting portion71is, for example, a projection formed in the internal wall of the first cylindrical portion61of the alignment portion54. The angle adjusting portion71has a planar shape of a triangle, and a vertex73of the triangle points to the light receiving and emitting elements32, for example.

The guide groove72is, for example, a groove portion formed in the external wall of the second cylindrical portion63of the guide member33. The depth and planar shape of the guide groove72are determined in correspondence with the thickness and planar shape of the angle adjusting portion71, in order that the mechanical interference between the angle adjusting portion71and the guide member33does not obstruct the expansion of the moving portion26. The guide groove72has a first taper side77and a second taper side78. When the moving portion26is completely expanded to such a degree that the alignment portion54is perfectly engaged with the guide member33, the first and second taper sides77and78of the guide groove72come in contact with a first side74and a second side75of the angle adjusting portion71which meet at the vertex73of the triangle.

The board connecting system10is provided with the above-described guide groove72and the angle adjusting portion71. Therefore, as the open end portions25of the optical waveguides22move closer to the light receiving and emitting elements32, the first side74or second side75of the angle adjusting portion71comes in contact with the guide groove72of the guide member33before the optical waveguides22get connected to the light receiving and emitting elements32. As the open end portions25of the optical waveguides22move further closer to the light receiving and emitting elements32, the angle adjusting portion71is guided by the first and second taper sides77and78of the guide member33. In this manner, the rotation angle, on the plane perpendicular to the X direction, between the open end portions25of the optical waveguides22and the light receiving and emitting elements32is arranged at a predetermined position. This reduces angular misalignment, on the plane perpendicular to the X direction, of the open end portions25of the optical waveguides22.

FIG. 7illustrates a multicore cable80and the connecting device23connecting the multicore cable80, relating to a first modification example of the present embodiment. Except for the multicore cable80, the board connecting system10relating to the first modification example is substantially the same as the board connecting system10illustrated inFIG. 1. Therefore, the other constituents are not explained here.

The board connecting system10may include therein the multicore cable80that is formed by clustering one or more optical waveguides22with the use of a stretchable material. In this case, the moving portion26of the connecting device23houses the multicore cable80in the internal space27, and moves the end portion of the multicore cable80in the X direction. When the board connecting system10uses the multicore cable80, the plurality of optical waveguides22are prevented from contacting each other.

FIGS. 8A and 8Billustrate the optical waveguides22and the connecting device23, relating to a second modification example of the present embodiment. Except for the optical waveguides22and the connecting device23, the board connecting system10relating to the second modification example is substantially the same as the board connecting system10illustrated inFIG. 1. Therefore, the other constituents are not explained here.

The optical waveguides22may be, for example, formed by stretchable optical waveguides made of a material such as an optically-transparent resin. Such stretchable optical waveguides are made of a polymer material which is similar to rubber or the like and is transparent so as to transmit therethrough the wavelength of an optical signal to be transferred. In each stretchable optical waveguide, the refractive index is different between the core region in which the optical signal is trapped and the clad region surrounding the core region. With such a configuration, each stretchable optical waveguide transfers the optical signal based on the repetitive light reflection at the interface between the core region and the clad region. The stretchable optical waveguides can be realized by using a stretchable substance whose base material is a generally-used fluorine resin or PMMA plastic material by following a conventional optical waveguide manufacturing process or a conventional fiber manufacturing process.

Since the optical waveguides22are formed by using a stretchable material, the length of each optical waveguide22decreases and the diameter of each optical waveguide22increases, when the moving portion26of the connecting device23is contracted, as illustrated inFIG. 6A. On the other hand, when the moving portion26of the connecting device23is expanded, the length of each optical waveguide22becomes larger than when the moving portion26is contracted and the diameter of each optical waveguide22becomes smaller than when the moving portion26is contracted, as illustrated inFIG. 6B. The optical waveguides22are used for transferring light therethrough in the state of being expanded in the longitudinal direction thereof.

Being made of a stretchable material, the optical waveguides22do not bend but keep their straight shape even when the moving portion26is contracted. Therefore, the size of the internal space27can be reduced, resulting in reducing the size of the connecting device23. Here, the multicore cable80relating to the first modification example may be formed by using the above-mentioned stretchable optical waveguides.

FIG. 9Ais a cross-sectional view illustrating the guide member33having therein guide dents81relating to a third modification example of the present embodiment.FIG. 9Bis a cross-sectional view illustrating the alignment portion54having therein guide projections82relating to the third modification example.FIG. 10Ais a plan view illustrating the guide member33having therein the guide dents81relating to the third modification example.FIG. 10Bis a plan view illustrating the alignment portion54having therein the guide projections82relating to the third modification example. Except for the guide member33and the alignment portion54, the board connecting system10relating to the third modification example is substantially the same as the board connecting system10illustrated inFIG. 1. Therefore, the other constituents are not explained here.

Referring to the board connecting system10, the guide dents81are provided in the guide member33and the guide projections82are provided in the alignment portion54, when the plurality of optical waveguides22running in parallel are connected to the plurality of light receiving and emitting elements32in a one-to-one correspondence.

The guide projections82are formed on a circular flange portion83. Here, the flange portion83is formed by bending, at right angles, the edge portion of the first cylindrical portion61of the alignment portion54. The guide projections82are hemispherical elevations of the main surface of the flange portion83towards the light receiving and emitting elements32.

The guide dents81are formed in a circular plate84whose diameter is larger than the diameter of the second cylindrical portion63of the guide member33. Here, the circular plate84is provided at the bottom portion52of the second cylindrical portion63. The guide dents81are hemispherical depressions of the main surface of the edge portion of the circular plate84which is more outside than the second cylindrical portion63.

The guide dents81are formed at such positions that the guide projections82fit in the guide dents81when the moving portion26is completely expanded so that the alignment portion54is perfectly engaged with the guide member33.

In a case where the above-described guide dents81and guide projections82are provided in the board connecting system10, as the open end portions25of the optical waveguides22are moved closer to the light receiving and emitting elements32, the guide projections82of the alignment portion54come in contact with the internal walls of the hemispherical guide dents81of the guide member33before the optical waveguides22are connected to the light receiving and emitting elements32. As the open end portions25of the optical waveguides22are further moved closer to the light receiving and emitting elements32, the alignment portion54is guided by the guide dents81. Therefore, the rotational angle between the open end portions25of the optical waveguides22and the light receiving and emitting elements32is positioned at a predetermined position on the plane perpendicular to the X direction. This reduces the angular misalignment of the open end portions25of the optical waveguides22on the plane perpendicular to the X direction.

FIG. 11illustrates the board connecting system10provided with a fixing portion92relating to a fourth modification example of the present embodiment. Except for the fixing portion92, the board connecting system10relating to the fourth modification example is substantially the same as the board connecting system10shown inFIG. 1. Therefore, the other constituents are not explained here.

The board connecting system10may have the fixing portion92that maintains the optical waveguides22and the light receiving and emitting elements32connected to each other, while the air pressure in the internal space27of the moving portion26is reduced after the optical waveguides22are connected to the light receiving and emitting elements32.

For example, the fixing portion92is realized by a mobile pin provided in the connected circuit board12, as illustrated inFIG. 11. When realized by a pin, the fixing portion92is inserted through an insertion opening94formed at a given position in the guide member33and an insertion opening94formed at a corresponding position in the alignment portion54, while the guide member33is engaged with the alignment portion54with signal connection being established therebetween. Here, the vertical movement of the fixing portion92, that is to say, inserting and extracting the fixing portion92into/from the insertion openings94, is controlled by a driving mechanism. When inserted into the insertion openings94, the fixing portion92can maintain the optical waveguides22and the light receiving and emitting elements32connected to each other.

According to the above-described board connecting system10, the fixing portion92can prevent vibration or the like from cutting off the connection between the optical waveguides22and the light receiving and emitting elements32.

FIG. 12illustrates the connecting device23provided with a cleaning portion96relating to a fifth modification example of the present embodiment. Except for the cleaning portion96, the board connecting system10relating to the fifth modification example is substantially the same as the board connecting system10illustrated inFIG. 1. Therefore, the other constituents are not explained here.

The moving portion26of the connecting device23may include the cleaning portion96that cleans the connection portions of the light emitting and receiving elements32and the open end portions25, by expelling the gas in the internal space27to the light emitting and receiving elements32, while the air pressure inside the internal space27is higher than the outside pressure in order to move the open end portions25of the optical waveguides22closer to the light receiving and emitting elements32.

For example, the cleaning portion96is realized by a nozzle provided at the bottom portion52, as illustrated inFIG. 12. When the cleaning portion96is realized by a nozzle, one end portion is connected to the internal space27and the opening of the other end portion is directed towards the connection portions of the light receiving and emitting elements32and the open end portions25. Here, the diameter of the cleaning portion96is sufficiently smaller than the diameter of the air inlet tube28. With such a configuration, the cleaning portion96expels the air in the internal space27out as the air pressure inside the internal space27increases. Which is to say, when the open end portions25of the optical waveguides22are moved closer to the light receiving and emitting elements32, the cleaning portion96can expel the air to the connection portions of the light receiving and emitting elements32and the open end portions25to clean the connecting portions.

While the embodiment of the present invention has been described, the technical scope of the invention is not limited to the above described embodiment. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiment. It is also apparent from the scope of the claims that the embodiment added with such alternations or improvements can be included in the technical scope of the invention.