JP4037850B2 - Optical data bus laminate - Google Patents

Description

  The present invention relates to an optical data bus responsible for propagation of signal light.

    With the development of very large scale integrated circuits (VLSI), the circuit functions of circuit boards (daughter boards) used in data processing systems have increased significantly. As the number of circuit functions increases, the number of signal connections to each circuit board increases. Therefore, a data bus board (motherboard) that connects each circuit board (daughter board) with a bus structure requires a large number of connection connectors and connection lines. A parallel architecture has been adopted. Although parallel buses have been improved by increasing the number of connection lines and paralleling them, parallel bus operation speeds have been improved. However, the system processing speed has been increased in parallel due to signal delays due to inter-connection wiring capacitance and connection wiring resistance. It may be limited by the operating speed of the bus. In addition, the problem of electromagnetic noise (EMI) due to the high density of parallel bus connection wirings is also a major limitation for improving the processing speed of the system.

In order to solve such a problem and improve the operation speed of the parallel bus, it has been studied to use an in-system optical connection technique called optical interconnection. As described in Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, the outline of the optical interconnection technology has been proposed in various forms depending on the configuration contents of the system.
Junji Uchida, 9th Circuit Implementation Conference 15C01, pp. 201-202 H. Tomimura et al. "Packaging Technology for Optical Interconnects", IEEE Tokyo No. 33 pp. 81-86, 1994 Osamu Wada, Electronics, April 1993, pp. 52-55

  Among various types of conventionally proposed optical interconnection technologies, Japanese Patent Application Laid-Open No. 2-41042 discloses an example in which an optical data transmission method using a high-speed, high-sensitivity light emitting / receiving device is applied to a data bus. The light emitting / receiving devices are arranged on both the front and back surfaces of each circuit board, and the light emitting / receiving devices on the adjacent circuit boards incorporated in the system frame are spatially coupled by light. A serial optical data bus for loop transmission between circuit boards has been proposed. In this method, the signal light sent from a certain circuit board is optical / electrically converted by the adjacent circuit board, and further converted by the circuit board again, and then the signal light is transmitted to the adjacent circuit board. Each circuit board is sequentially arranged in series and transmitted between all circuit boards incorporated in the system frame while repeating photoelectric conversion and electrical / optical conversion on each circuit board. For this reason, the signal transmission speed depends on the light / electric conversion speed and the electric / light conversion speed of the light receiving / light emitting device arranged on each circuit board, and at the same time, is restricted. In addition, data transmission between each circuit board uses optical coupling with a free space by light receiving / light emitting devices arranged on each circuit board. The light emitting / receiving device is optically aligned and all circuit boards must be optically coupled. Furthermore, since each circuit board is coupled via a free space, interference (crosstalk) between adjacent optical data transmission paths occurs, and data transmission failure is expected. In addition, it is expected that the signal light is scattered by the environment in the system frame, for example, dust and the like, resulting in a data transmission failure. Furthermore, since each circuit board is arranged in series, if any board is removed, the connection is interrupted there, and an extra circuit board is required to compensate for that. That is, there is a problem that the circuit boards cannot be freely inserted and removed, and the number of circuit boards is fixed.

  In addition to these, as a data transmission technique between circuit boards using free space, Japanese Patent Application Laid-Open No. 61-196210 includes a plate having two parallel surfaces and facing a light source. Discloses a method of optically coupling circuit boards through an optical path composed of a diffraction grating and a reflective element. In this system, light emitted from one point can be transmitted only to one fixed point, and all circuit boards cannot be connected comprehensively like an electric bus. In addition, since a complicated optical system is required and alignment is difficult, interference (crosstalk) between adjacent optical data transmission paths occurs due to the displacement of the optical element, and data transmission failure is expected. . Since the connection information between the circuit boards is determined by the diffraction grating and the reflecting element arranged on the plate surface, there are various problems that the circuit boards cannot be freely inserted and removed and the expandability is low.

  As a means for solving these problems, a light diffusing unit for diffusing the incident signal light is provided in the optical transmission unit of the sheet-like optical data bus, and the signal light diffused by the light diffusing unit is transmitted in all directions in the optical transmission unit. An optical data bus system that can be propagated to the network is conceivable. In this optical data bus, it is possible to reliably optically couple a plurality of circuit boards having light receiving and emitting portions by a simple mounting method without requiring precise optical alignment. In this method, the number of circuit boards to be attached to the optical data bus and the attachment positions can be freely changed, so that a highly flexible system with high expandability can be constructed. In addition, unlike the method of transmitting light through space, the method of transmitting light through an optical transmission unit is less likely to cause environmental problems due to dust in the air. Furthermore, since it does not require optical alignment when the circuit board is attached to the optical data bus, it has an advantage of being resistant to temperature changes.

  However, in the above method, since the light diffusing unit provided in the optical transmission unit diffuses the signal light in all directions, there is much signal light that escapes outside the optical transmission unit, and the signal light that reaches the light receiving unit However, there is a problem that light utilization efficiency is low.

  In view of the above circumstances, the present invention is an optical data bus that is easy to align with a circuit board at the time of system construction or modification, and has high light utilization efficiency, and data transmission / reception using the optical data bus. An object of the present invention is to provide a signal processing apparatus that performs signal processing including

An optical data bus according to the present invention that achieves the above object is an optical data bus that carries signal light propagation, and includes an optical transmission section having a relatively high refractive index and a cladding section having a relatively low refractive index. And
On the surface of the optical data bus, there is provided a signal light incident part on which signal light is incident,
A light diffuser that diffuses the signal light incident from the signal light incident portion toward the optical transmission portion at a position in contact with the surface of the optical transmission portion on the path of the signal light incident from the signal light incident portion. And the light transmission unit is configured to propagate the signal light diffused by the light diffuser and reflected by the surface of the light transmission unit as internally scattered light.

  As described above, according to the optical data bus of the present invention, the optical data bus has the signal light incident part on which the signal light is incident on the surface of the optical data bus, and on the path of the signal light incident from the signal light incident part. By using a light diffuser that diffuses the signal light incident from the signal light incident portion toward the inside of the light transmission portion at a position in contact with the front surface or the back surface of the light transmission portion, the light utilization efficiency can be improved.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a perspective view (FIG. 1 (a)) showing a first embodiment of an optical data bus of the present invention and a cross-sectional view (FIG. 1 (b)) viewed in the A-A 'direction.

  As shown in FIGS. 1A and 1B, the optical data bus 1 is a sheet-like optical data bus including an optical transmission unit 11 and a clad unit 12 sandwiching the optical transmission unit 11. The optical transmission unit 11 is a layer responsible for propagation of signal light. In this embodiment, PMMA (polymethyl methacrylate) having a high light transmittance and a thickness of 0.5 mm per layer is used. The clad portion 12 is for preventing signal light in the optical transmission unit 11 from leaking out of the optical transmission unit 11, and is formed of a material having a refractive index lower than that of the optical transmission unit 11. In this embodiment, since PMMA is used for the optical transmission unit 11, a fluorine-containing polymer is used for the cladding unit 12.

  On the front surface of the optical data bus 1, there is a signal light incident part 5 for incident the signal light 3, and on the path of the signal light 3 incident from the signal light incident part 5, at a position in contact with the back surface 11 b of the optical transmission part 11. A light diffuser 2 that diffuses the signal light 3 incident from the signal light incident portion 5 toward the inside of the light transmission portion 11 is provided. In this embodiment, the light diffuser 2 is provided at a position in contact with the back surface 11b of the light transmission unit 11 on the path of the signal light 3 incident from the signal light incident unit 5. The position is not limited to the position in contact with the back surface 11 b of the light transmission unit 11, and may be provided at a position in contact with the front surface 11 a of the light transmission unit 11. In this case, the light diffuser is formed to diffuse signal light and transmit incident signal light.

  As shown in FIGS. 1A and 1B, signal light 3 is emitted from the light emitting element 13 disposed above the optical data bus 1 and is incident on the signal light incident portion 5 of the optical data bus 1. Then, the signal light 3 passes through the clad part 12 and the light transmission part 11 and enters the light diffuser 2 provided at a position in contact with the back surface 11 b of the light transmission part 11. The signal light 3 is diffused by the light diffuser 2, then reflected by the front surface 11 a and the back surface 11 b of the light transmission unit 11, propagates in the light transmission unit 11 as internal scattered light 4, and is provided at the edge of the light transmission unit 11. It reaches a signal light emitting part (not shown).

  In the optical data bus 1 configured as described above, the behavior of the signal light propagating in the optical data bus 1 varies depending on whether or not the clad portions are formed on the front and back surfaces of the optical transmission unit 11.

  FIG. 2 is a diagram for explaining the behavior of the signal light propagating in the optical data bus 1 shown in FIG.

  As shown in FIG. 2A, in the case of an optical data bus in which no clad is formed on both the front and back surfaces of the optical transmission unit 11, a light diffuser provided on the back surface 11b of the optical transmission unit 11 of the optical data bus. 2, the signal light 2 a satisfying the condition of total reflection at the interface between the light transmission unit 11 and air is totally reflected at the interface and propagates in the light transmission unit 11 as internally scattered light 4. The signal light 2 b that does not satisfy the reflection condition escapes out of the optical transmission unit 11.

  Next, as shown in FIG. 2B, in the case of an optical data bus in which the clad portions 12a and 12b are formed on the front and back surfaces of the optical transmission unit 11 and the light diffuser 2 is formed outside the clad portion 12b. The signal light 2b diffused by the light diffuser 2 and incident on the clad part 12b at an incident angle θ is refracted at the interface between the clad part 12b and the optical transmission part 11 and enters the optical transmission part 11. At the interface between the transmission part 11 and the clad part 12a, the signal light 2b is not reflected in the light transmission part 11 and all escapes to the opposite clad part 12a at the same angle θ. A part of the signal light 2c is totally reflected at the interface between the clad part 12a and the air, but does not contribute to propagation in the optical transmission part 11. If the clad part 12b is formed in this way and the light diffuser 2 is formed on the clad part 12b, the signal light does not propagate in the optical transmission part 11.

  On the other hand, as shown in FIG. 2C, in the case of the optical data bus of this embodiment provided with the light diffuser 2 at a position in contact with the back surface 11b of the optical transmission unit 11, the light diffuser 2 diffuses. Of the received signal light, the signal light 2a that satisfies the total reflection condition at the interface between the optical transmission unit 11 and the cladding unit 12a is totally reflected at the interface between the optical transmission unit 11 and the cladding unit 12a and is internally scattered light 4 in the optical transmission unit 11 Will propagate. In this case, the clad portions 12 a and 12 b formed on the front and back surfaces of the optical transmission unit 11 effectively exhibit the function of confining the signal light within the optical transmission unit 11.

  In the embodiment of FIG. 2 (c), the example in which the light diffuser 2 is provided at a position in contact with the back surface 11 b of the optical transmission unit 11 is shown. However, the optical data bus of the present invention is provided on the front surface 11 b of the optical transmission unit 11. It is good also as a structure provided with the light-diffusion body 2 in the position which touches. In that case, the light diffuser 2 transmits the signal light while diffusing the signal light.

  Further, in the optical data bus 1 shown in FIG. 1, the light diffuser 2 formed at a position in contact with the rear surface 11 b of the optical transmission unit 11 is exposed to the rear surface with respect to the surface on the signal light incident side to the light diffuser 2. The optical data bus 1 may be configured as a reflection layer that reflects the signal light transmitted through the diffuser 2. By doing so, the light utilization efficiency of the optical data bus can be improved. A method for forming the reflective layer will be described later.

  In the above-described embodiment, PMMA is used as the optical transmission unit 11. However, instead of PMMA, a plastic material having similar optical characteristics such as polystyrene (PS) and polycarbonate (PC) can be used. is there. Even when polystyrene (PS) or polycarbonate (PC) is used as the light transmission portion, an amorphous fluororesin material dissolved in a perfluoro solvent can be used for the cladding portion. Further, instead of the amorphous fluororesin material, the clad portion may be formed by using amorphous fluororubber or crystalline fluoropolymer in a solution state.

  In the present embodiment, the optical data bus 1 is shown as a single-layer structure. However, an optical data bus used in an actual signal processing device is formed by stacking a plurality of optical data buses 1 as shown in FIG. Used as a bus.

  FIG. 3 is a diagram showing a state in which a plurality of optical data buses shown in FIG. 1 are stacked.

  FIG. 3 shows a state in which a plurality of optical data buses 1 including one optical transmission unit 11 and a clad unit 12 sandwiching the optical transmission unit 11 are stacked via a light absorption layer 15. . The light absorbing layer 15 is for preventing interference of signal light between the plurality of optical data buses 1.

  Next, an embodiment of a signal processing apparatus configured using the optical data bus of the present invention will be described.

  FIG. 4 is a schematic configuration diagram showing an embodiment of the signal processing apparatus of the present invention.

  As shown in FIG. 4, the signal processing device 20 includes a support substrate 21, which is an example of a substrate according to the present invention, an optical transmission unit 22 fixed to the support substrate 21, and a clad unit sandwiching the optical transmission unit 22. 23, a sheet-like optical data bus 24 for transmitting signal light, a plurality of circuit boards 27, and a plurality of board fixing parts 29 for fixing the circuit boards 27 on the support board 21. As the optical data bus 24, a plurality of the optical data buses of the present invention described above with reference to FIG. 1 are used. The plurality of optical data buses 24 are connected to a plurality of circuit boards 27. The signal processing device 20 is configured by being optically and mechanically coupled.

  The plurality of substrate fixing portions 29 provided on the support substrate 21 are arranged so that the signal light input / output end 28 mounted on the circuit substrate 27 is coupled to the optical data bus 24 in the signal light input / output portion 25. 27 is fixed on the support substrate 21. The fixing mechanism of the circuit board 27 by the board fixing part 29 is configured to be detachable. In this embodiment, the signal light incident / exit end 28 on the circuit board 27 side corresponds to one or both of the signal light incident end and the signal light exit end referred to in the present invention, and an optical data bus. The signal light incident / exit section 25 on the 24 side corresponds to one or both of the signal light incident section and the signal light output section referred to in the present invention.

  On the support substrate 21, a power supply line and electrical wiring 21 a for electric signal transmission are provided. The electrical wiring 21 a is connected to each substrate fixing portion 29 via a plurality of substrate fixing portions 29. It is electrically connected to the circuit 26 on the circuit board 27 to be mounted. Each circuit board 27 includes a plurality of signal light incident / exit ends 28 formed of a pair of a light emitting element for emitting signal light and a light receiving element for incident signal light, and signal light emitted from the signal light incident / exit end 28. At least one of a circuit 26 that generates a signal to be carried and a circuit 26 that performs signal processing based on a signal carried by signal light incident from the signal light incident / exit end 28 is mounted.

  When this circuit board 27 is mounted on the board fixing portion 29, each signal light input / output terminal 28 is disposed at a position facing each light transmission portion 22 of the signal light input / output portion 25 of the optical data bus 24, and a certain signal light The signal light emitted from the light emitting element in the input / output terminal 28 enters the optical transmission unit 22 of the optical data bus 24, is scattered in the optical transmission unit 22, and enters the signal light of another circuit board 27. The light is transmitted to the signal light incident / exit section 25 at a position facing the output end 28 and received by the light receiving element in the signal light input / output end 28 optically coupled to the signal light incident / exit section 25.

  As described above, by using the optical data bus of the present invention having the optical diffuser (see FIG. 1) as the optical data bus 24, the optical data bus and the circuit board can be aligned at the time of system construction or modification. An easy signal processing device can be obtained.

  Next, a method for manufacturing the above sheet-like optical data bus will be described.

  FIG. 5 is a schematic diagram showing a manufacturing process of the optical data bus shown in FIG.

  First, a mold is prepared in advance, and the mold is heated to the melting temperature of PMMA, and PMMA that is sufficiently heated and in a molten state is poured into the mold, whereby a sheet-like optical transmission unit 31 having a thickness of 0.5 mm (see FIG. 5 (a)) is obtained. Next, for the clad portion, an amorphous fluororesin material dissolved in a perfluoro solvent, which is a lower refractive index material than PMMA, is applied or printed on the front and back surfaces of the sheet-like light transmission portion 31. As a result, a clad portion 32 having a thickness of 10 μm is formed (FIG. 5B). Next, as a preparation for patterning, a mask 33 having a thickness of 2 μm is formed on the entire surface by using a photoresist, and exposure for obtaining a desired pattern is performed, and a 1 mm square is formed at a desired portion of the mask 33 (where a light diffuser is to be formed). An opening 33a having a size of 1 mm is formed (FIG. 5C). Next, in order to remove the clad 32 in the opening 33a, plasma etching is performed using a gas system made of CF4 or the like (FIG. 5D). At this time, if the clad portion 32 in the opening 33a portion is completely removed, the optical transmission portion 31 in the opening 33a portion may be damaged, but this portion will eventually scatter light. Since a diffuser is formed, there is no problem even if slight damage occurs. Next, a diffusion material made of magnesium oxide or the like is deposited on the entire surface on the side where the openings 33a are formed by a vapor deposition method to form a light diffusion layer 34a having a thickness of 5 μm. A 5 μm-thick reflective film 35a made of aluminum or the like is formed (FIG. 5E). Next, the desired light diffuser 34 and the reflective layer 35 can be obtained by peeling off the light diffusion layer 34a, the reflective film 35a, and the mask 33 with a peeling solution and performing lift-off (FIG. 5 (f)).

  In the above description, the size of the opening 33a, that is, the light diffuser 34 is 1 mm square, but it may be circular with a diameter of 1 mm. Further, the thickness of the optical transmission part is 0.5 mm, the thickness of the cladding part is 10 μm, the thickness of the light diffusion layer is 5 μm, and the thickness of the reflective film is 5 μm. It can be thicker or thinner than these dimensions.

  Next, another method for manufacturing the above sheet-like optical data bus will be described.

  FIG. 6 is a schematic diagram showing another manufacturing process of the optical data bus according to the embodiment shown in FIG.

  As shown in FIG. 6A, first, in the same manner as in FIG. 5, a sheet-like optical transmission unit 41 is obtained (FIG. 6A). Next, the light diffuser 44 is formed of a diffusion material made of magnesium oxide or the like by a vapor deposition method on the light transmission portion 41 where the light diffuser is to be formed, and then the reflective layer 45 made of aluminum or the like is formed ( FIG. 6 (b)). In this case, a light diffusing layer 44 is formed only in a portion corresponding to the signal light incident portion in advance using a mask or the like during vapor deposition. Next, the optical data bus 40 is obtained by forming the clad portions 42 on both surfaces of the optical transmission unit 41 by a printing method or the like (FIG. 6C). The thickness of the light diffuser 44 is 5 μm, and the thickness of the reflective layer 45 is also 5 μm. The clad portion 42 is formed by applying or printing an amorphous fluororesin material dissolved in a perfluoro solvent, which is a low refractive material, on both surfaces of the optical transmission portion 41. The thickness of the clad part 42 is 10 μm.

  Next, a simple method for forming the light diffuser and the reflective layer on the optical data bus will be described.

  FIG. 7 is a cross-sectional view of a sticking member for simply forming a light diffuser and a reflective layer on an optical data bus.

  As shown in FIG. 7, this member is a seal-like sticking member comprising a transparent adhesive layer 51, a light diffuser 52, a base material 53, and a reflective layer 54, and is stuck to a desired location on the optical data bus. Thus, the light diffuser and the reflective layer can be easily formed on the optical data bus. The transparent adhesive layer 51 is a 20 μm layer made of a two-component curable acrylic pressure-sensitive adhesive for adhering the sticking member to the optical data bus, and the light diffuser 52 is obtained by mixing silica pigment into acrylic resin. It is a 10 μm layer made of a diffusing material, the base material 53 is a 50 μm layer made of a polyester film, and the reflective layer 54 is a reflective film formed by vapor deposition of aluminum or the like. After pasting such a pasting member on a desired location on the optical data bus, an amorphous fluororesin material dissolved in a perfluoro solvent is printed on the pasting member by a printing method or the like to form a clad portion. Thus, the optical data bus of the present invention can be easily formed. The refractive index of the transparent adhesive layer 51 is set to about 1.46, which is smaller than the refractive index 1.49 of PMMA used for the optical transmission unit. This is larger than the refractive index of 1.34 of the amorphous fluororesin material dissolved in the perfluoro solvent formed as the clad portion. Since the refractive index of the transparent adhesive layer 51 is close to the refractive index of the light transmission part, most of the signal light diffused by the light diffuser 52 is incident on the light transmission part. Further, since the thickness of the transparent adhesive layer 51 is sufficiently thin as 20 μm, the light reflected at the interface between the transparent adhesive layer 51 and the light transmission part is scattered again by the light diffuser 52. There is no loss of signal light in this part.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a first embodiment of an optical data bus of the present invention and a cross-sectional view seen in the A-A ′ direction. It is a figure explaining the behavior of the signal light which propagates the inside of the optical data bus | bath 1 shown in FIG. FIG. 2 is a diagram illustrating a state in which a plurality of optical data buses illustrated in FIG. 1 are stacked. It is a schematic block diagram which shows one Embodiment of the signal processing apparatus of this invention. FIG. 3 is a schematic diagram showing a manufacturing process of the optical data bus shown in FIG. 1. It is a schematic diagram which shows the other manufacturing process of the optical data bus | bath of embodiment shown in FIG. It is sectional drawing of the sticking member for forming a light diffusing body and a reflective layer easily on an optical data bus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical data bus 2 Optical diffuser 2a, 2b, 2c Signal light 3 Signal light 4 Internal scattered light 5 Signal light incident part 11 Optical transmission part 11a Front surface 11b Back surface 12, 12a, 12b Clad part 13 Light emitting element 14 Light receiving element 15 Light Absorption layer 20 Signal processing device 21 Support substrate 21a Electrical wiring 22 Optical transmission unit 23 Clad unit 24 Optical data bus 25 Signal light input / output unit 26 Circuit 27 Circuit board 28 Signal light input / output end 29 Substrate fixing unit 31 Optical transmission unit 32 Cladding part 33 Mask 33a Opening 34 Light diffuser 34a Light diffusion layer 35 Reflective layer 35a Reflective film 40 Optical data bus 41 Optical transmission part 42 Cladding part 44 Light diffuser 45 Reflective layer 51 Transparent adhesive layer 52 Light diffuser 53 Base material 54 Reflective layer

Claims (1)

Responsible for propagation of signal light , comprising: an optical transmission unit having a relatively high refractive index; and a clad unit sandwiching the optical transmission unit and having a relatively small refractive index formed so as to sandwich the optical transmission unit the optical data bus laminate comprising a sheet-shaped optical data bus laminating a plurality,
Said optical data bus each surface, and the signal light input unit where the signal light is incident,
The signal incident from the signal light incident part at a position in contact with the surface of the optical transmission part on the path of the signal light incident from the signal light incident part, formed only in the part corresponding to the signal light incident part A light diffuser for diffusing light into the light transmission section;
The optical data bus laminate, wherein the optical transmission unit propagates the signal light diffused by the light diffuser .

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