JP3765140B2 - Optical bus and signal processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical bus responsible for transmission of an optical signal and a signal processing apparatus that performs signal processing including data transmission and reception using the optical bus.
[0002]
[Prior art]
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 circuit function 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 making them parallel, the operation speed of parallel buses has been improved. However, the system processing speed has been increased in parallel due to signal delays due to the capacitance between connection lines and connection line 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.
[0003]
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. The outline of the optical interconnection technology is described in “Koji Uchida, 9th Circuit Implementation Conference 15C01, pp. 201-202 "and" H. Tomimura et al. "Packaging Technology for Optical Interconnects", IEEE Tokyo No. 33 pp. 81-86, 1994 ”,“ Osamu Wada, April 1993 Electronics, pp 52-55 ”, various forms have been proposed depending on the contents of the system configuration.
[0004]
[Problems to be solved by the invention]
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. Serial optical data buses have been proposed for loop transmission between circuit boards. 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 optical / electrical 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 circuit boards uses optical coupling with a free space by light receiving / light emitting devices arranged on each circuit board, so it is arranged on both sides of the adjacent circuit boards. The light emitting / receiving device is optically aligned and all circuit boards must be optically coupled. Furthermore, since they are coupled through free space, interference (crosstalk) between adjacent optical data transmission paths occurs, and data transmission failure is expected. It is also expected that data transmission failure will occur due to scattering of signal light by the environment in the system frame, such as dust. Furthermore, since the circuit boards are arranged in series, if any of the boards is removed, the connection is interrupted there, and an extra circuit board is required to make up for it. That is, there is a problem that the circuit board cannot be freely inserted and removed, and the number of fixed boards is fixed.
[0005]
A data transmission technique between circuit boards using a two-dimensional array device is disclosed in Japanese Patent Laid-Open No. 61-196210. The technology disclosed herein includes a plate facing a light source having two parallel surfaces, and optically connects between circuit boards via a diffraction grating disposed on the plate surface and an optical path constituted by a reflective element. It is a method of combining. In this method, light emitted from one point can be connected to only 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 misalignment of optical elements, and data transmission failure is expected. The Since the connection information between the circuit boards is determined by the diffraction grating and the reflection element arranged on the plate surface, there are various problems such that the circuit board cannot be freely inserted and removed and the expandability is low.
[0006]
Another technique for data transmission between circuit boards using a two-dimensional array device is disclosed in Japanese Patent Laid-Open No. 4-134415. In this publication, a lens array composed of a plurality of lenses having a negative curvature and a light emitted from a light source are incident on a substrate made of a transparent material having a refractive index higher than that of air from the side surface of the lens array. A data transmission system provided with an optical system is disclosed. This publication also discloses a system in which a low refractive index region or a hologram is formed in the base instead of a plurality of lenses having negative curvature. In these systems, light incident from the side surface of the substrate is distributed and emitted to the upper surface of the substrate from the plurality of lenses having the negative curvature described above, an area having a low refractive index instead of this, or a portion where a hologram is formed. It is comprised so that. Therefore, it is conceivable that the intensity of the emitted signal varies depending on the positional relationship between the incident position of the light and the exit position on the substrate surface on which the plurality of lenses, an alternative low refractive index region, or a hologram is formed. In addition, it is considered that the rate at which light incident from the side surface of the substrate escapes from the side surface facing the incident surface is high, and the efficiency of light used for signal propagation is low. Furthermore, since it is necessary to arrange the optical input element of the circuit board at the position of a plurality of lenses having a negative curvature formed on the surface of the base, a low refractive index area instead of this, or a hologram, the arrangement of the circuit board There are various problems that the degree of freedom is low and the expandability of the system is low.
[0007]
As a means for solving these problems, it is conceivable to employ an optical bus that propagates incident light. Such an optical bus includes light diffusing means for diffusing incident light so that incident light is reliably emitted from any of a plurality of emission points. However, when the light incident on such an optical bus is observed at one output point, in addition to the light traveling straight toward the output point, the light that has been reflected once or many times and reaches the output point is variously reflected. It exists, spreads in time, and when pulsed light is incident, the pulse is observed as a greatly broken waveform, which hinders speeding up of optical signal transmission.
[0008]
In view of the above circumstances, an object of the present invention is to provide an optical bus in which an optical signal transmission is speeded up, and a signal processing device employing the optical bus.
[0009]
[Means for Solving the Problems]
The optical bus of the present invention that achieves the above object is as follows.
The signal light incident on the signal light input / output unit, which has a plurality of signal light input / output units that are at least one of signal light incident or signal light emission on the end surface, is formed in a sheet shape. An optical bus that diffuses and propagates and exits from the signal light input / output unit, and extends from the inside of the optical bus toward the optical bus end surface along a portion of the optical bus excluding the signal light input / output unit. An antireflection layer for preventing reflection of signal light toward the inside of the optical bus is provided.
[0010]
The signal light incident from the signal light input / output unit responsible for the signal light is scattered in the optical bus and travels to each signal light input / output unit responsible for the emission of the signal light. Of the signal light that travels, the signal light that passes through the path that is reflected by the end face of the optical bus along the way will go through a path that is largely detoured compared to the signal light that travels directly to the signal light input / output section. There is a large delay until it reaches.
[0011]
Accordingly, when an antireflection layer is provided on the end face or in the vicinity thereof as in the present invention, the signal light taking a greatly detoured path that is reflected by the end face is attenuated, and therefore the time of the signal light incident on the optical bus is reduced. The spread is narrowed, and the transmission speed of the optical signal via the optical bus is improved.
Moreover, the signal processing device of the present invention that achieves the above-described object is
(1) Substrate (2) A signal light emitting part for emitting signal light, an electronic circuit for generating a signal to be carried on the signal light emitted from the signal light emitting part, a signal light incident part for receiving signal light, and this A plurality of circuit boards (3) on which at least one of an electronic circuit that performs signal processing based on a signal carried by signal light incident from a signal light incident portion is mounted and formed into a sheet shape, and signal light is incident on an end surface. Or an optical bus having a plurality of signal light input / output units that bear at least one of the output of the signal light, diffusing and propagating the signal light incident from the signal light input / output unit, and emitting from the signal light input / output unit In addition, reflection of signal light from the inside of the optical bus toward the end face of the optical bus to the inside of the optical bus is prevented at a portion along the end face of the optical bus excluding the signal light input / output unit. With antireflection layer Optical bus (4) The circuit board is fixed on the substrate so that the signal light emitting part or signal light incident part mounted on the circuit board is coupled to the optical bus at the signal light input / output part. A plurality of substrate fixing portions are provided.
[0012]
Since the signal processing apparatus of the present invention employs the optical bus of the present invention, high-speed communication using optical signals can be realized.
In the signal processing apparatus of the present invention, the number of circuit boards optically coupled to the optical bus in the signal light input / output unit of the optical bus can be freely increased or decreased within the maximum number of signal light input / output units. It is possible to construct a system that is resistant to environmental changes and rich in expandability. Further, at the same time that the circuit board is fixed to the base fixing part, the signal light emitting part or the signal light incident part mounted on the circuit board is optically coupled to the optical bus, and fine alignment is not necessary.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a signal processing of the present invention having a sheet-like optical data bus which is an embodiment of the optical bus of the present invention and a plurality of circuit boards optically connected to each other by the sheet-like optical data bus. FIG. 2 is a schematic configuration diagram of an embodiment of the apparatus, and FIG.
[0014]
A sheet-like optical data bus 30 according to an embodiment of the present invention is fixed on a support substrate 20 which is an example of a substrate according to the present invention and constitutes the signal processing apparatus 10 shown in FIG.
The sheet-like optical data bus 30 has a structure in which optical transmission layers 31 and cladding layers 32 are alternately stacked. The optical transmission layer 31 is a layer responsible for transmission of signal light, and this optical transmission layer 31 has a plurality of signal light input / output sections 33 responsible for incidence or emission of signal light on the end face as shown in FIG. In addition, light scatterers 34 for diffusing the signal light incident from the signal light input / output unit 33 throughout the light transmission layer 31 are scattered inside the light transmission layer 31. In addition, a light absorbing layer 35 that absorbs signal light from the inside of the light transmitting layer 31 toward the end face of the light transmitting layer 31 is formed inside the light transmitting layer 31, and this light absorbing layer 35 is shown in FIG. In this way, it is formed along the portion of the end face of the optical transmission layer 31 excluding the signal light input / output unit 33.
[0015]
The optical transmission layer 31 preferably has a high light transmittance because signal light propagates through the optical transmission layer 31. In this embodiment, polymethyl methacrylate (PMMA) having a thickness of 0.5 mm per layer is used. As the light scatterer 34 scattered inside the light transmission layer 31, polystyrene (PS) having a light refractive index different from that of PMMA is used. In addition, a material made of a carbon black inorganic pigment is used as the light absorption layer 35 formed inside the light transmission layer 31.
[0016]
The cladding layer 32 is a layer that acts to prevent light in the light transmission layer 31 from leaking in the thickness direction of the layer, and a material having a light refractive index lower than the light refractive index of the light transmission layer 31 is used. Selected. Here, since PMMA is employed for the optical transmission layer 31, a fluorine-containing polymer is preferably employed for the cladding layer 32. The thickness of the cladding layer 32 is 0.5 mm, the same as the thickness of the optical transmission layer 31. A sheet-like optical data bus 30 having a laminated structure shown in FIG. 1 is formed by preparing and stacking these sheet materials and then pressing them.
[0017]
As shown in FIG. 1, board connectors 21,..., 21 are fixed on the support board 20 to which the sheet-like data bus 30 is fixed, and each board connector 21,. Are mounted in a detachable manner.
On the support substrate 20, power supply lines and electrical wirings 22 for transmitting electrical signals are provided. The electrical wirings 22 are connected to the board connector 21 via board connectors 21,. ,..., 21 are electrically connected to an electronic circuit 41 mounted on the circuit boards 40,.
[0018]
Further, as shown in FIG. 2, each circuit board 40,..., 40 is provided with light projecting / receiving elements 42,..., 42 formed of a pair of a laser diode 42a and a photodiode 42b. The laser diode 42a emits red visible light having a wavelength of 650 nm, and the photodiode 42b has sensitivity to the red visible light having a wavelength of 650 nm. When the circuit board 40 is attached to the board connector 21, the light receiving and receiving elements 42,..., 42 are optically coupled to the sheet-like optical data bus 30 so that the signal light input to the sheet-like optical data bus 30 is received. It is arranged at a position facing the output unit 33.
[0019]
FIG. 3 is an explanatory diagram showing a state in which the circuit board is mounted on the board connector in the signal processing apparatus shown in FIGS. 1 and 2, and is an enlarged view corresponding to a part of the signal processing apparatus shown in FIGS. FIG. However, in FIG. 3, the number of layers of the sheet-like optical data bus is generalized.
A plurality of light projecting / receiving elements 42 arranged at the same pitch as the pitch of the light transmission layers 31 in the thickness direction of the sheet-like optical data bus 30 as shown in FIG. An electric signal input / output terminal 43 is arranged at the lower end of the circuit board 40.
[0020]
The electric signal input / output terminal 43 of the circuit board 40 is connected to the board connector 21 on the support board 20 so that the two directions y and z shown in the figure are defined, and the light emitting / receiving element 42 on the circuit board 40 is further defined. Is abutted against the sheet-like optical data bus 30 so that the x direction shown in the figure is defined, and at the same time, the light projecting / receiving element 42 and the optical data bus 30 are optically coupled.
[0021]
In this embodiment, as described above, the electrical connection with the electrical wiring 22 on the support substrate 20 and the optical connection with the sheet-like optical data bus 30 can be achieved simply by correctly mounting the circuit board 40 to the board connector 21. Binding is complete.
Hereinafter, a state until light emitted from the laser diode 42a is received by the photodiode 42b via the sheet-like optical data bus 30 will be described with reference to FIG.
[0022]
When pulsed light carrying a signal is emitted from the laser diode 42 a on the circuit board 40, this light enters the light transmission layer 31 of the sheet-like optical data bus 30. Of the incident light, light that travels straight toward the end surface of the light transmission layer 31 and light that is scattered by the light scatterers 34 scattered inside the light transmission layer 31 and travels toward the end surface of the light transmission layer 31 is absorbed. Absorbed by layer 35. Accordingly, among the incident light, light that travels straight toward the signal light input / output unit 33 and light that travels toward the signal light input / output unit 33 after being scattered by the light scatterers 34 scattered inside the light transmission layer 31 are included. , Emitted from the signal light input / output unit 33 and detected by the photodiode 42b disposed at the lateral end of the circuit board 40,. In this way, the light emitted from the laser diode 42 a provided on one circuit board 40 is transmitted to the photodiode 42 b provided on each circuit board 40.
[0023]
Here, signal light representing an address and signal light representing data are emitted from the laser diode 42 a and are incident on the same optical transmission layer 31 in time series. The data receiving side is designated by the first address signal light, and only the designated circuit board 40 receives the data signal light. Such transmission / reception of signal light is performed in parallel in the stacked optical transmission layers 31. Here, the transmission / reception timing of the signal light through each optical transmission layer 31 is synchronized with the clock signal light given to one layer of the plurality of stacked optical transmission layers 31, so that each optical transmission layer The signal light transmitted and received via 31 is uniformly defined as a parallel signal. In the present embodiment, the data bus width is, for example, 32 bits, and each layer of the stacked optical transmission layers 31 corresponds to 1 bit. Therefore, address presentation and data transmission / reception are performed via the 32 optical transmission layers 31. Further, in the case of a configuration in which the bus width is further increased, for example, a 64-bit data bus width, the optical transmission layer 31 may be 64 layers. However, it is also possible to adopt a configuration in which two or more bits correspond to one layer of the laminated optical transmission layers 31, or a configuration in which two or more layers of the laminated optical transmission layers 31 correspond to one bit. It is.
[0024]
As described above, in the signal processing device 10, the sheet-like optical data bus 30 including the light absorption layer 35 is employed. Therefore, among the light emitted from the laser diode 42 a and incident on the sheet-like optical data bus 30, Light propagating toward the end face of the transmission layer 31 is prevented from being reflected from the end face of the light transmission layer 31 and emitted from the sheet-like optical data bus 30. Therefore, the time spread of the light emitted from the sheet-like optical data bus 30 with respect to the light incident on the sheet-like optical data bus 30 is narrowed, and high-speed communication using an optical signal can be realized.
[0025]
In the above embodiment, the light absorption layer is formed inside the light transmission layer, but may be formed on the end face of the light transmission layer 31.
In the above embodiment, the light absorption layer is used as the antireflection layer. However, the light transmission layer is used instead of the light absorption layer, and the signal light directed from the inside of the optical bus toward the optical bus end surface is emitted from the end surface. Thus, reflection toward the inside of the optical bus may be prevented.
[0026]
In the above embodiment, polymethyl methacrylate (PMMA) is used as the light transmission layer 31, but instead, a plastic material having similar optical characteristics such as polystyrene (PS) and polycarbonate (PC) is used. Is also possible. Even when polystyrene (PS) or polycarbonate (PC) is used as the optical transmission layer 31, a fluorine-containing polymer can be used for the cladding layer 32. The material of the light scatterer 34 scattered inside the light transmission layer 31 in order to have a light scattering action is a plastic material having a light refractive index different from the light refractive index of the portion responsible for light transmission of the light transmission layer 31. If there is, it is possible to obtain the same action. Further, although the carbon black inorganic pigment is used as the light absorption layer 35, it is also possible to use a black pigment obtained by adding and synthesizing a fine particle organic pigment instead.
[0027]
In the above-described embodiment, the sheet thicknesses of the light transmission layer 31 and the clad layer 32 are both 0.5 mm. However, the thickness may be thicker or thinner as long as the optical characteristics thereof are not impaired. There is no problem. By forming each layer thinly, an optical data bus having a very wide bus width is formed in a small space, and therefore the data transmission rate can be dramatically improved.
[0028]
Furthermore, in the said embodiment, although the plastic material was used for the optical transmission layer 31 and the clad layer 32, it is also possible to use a quartz type glass material instead. In the case of using a quartz-based glass material, a sheet with specific refractive index control is prepared using P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ or the like as a refractive index adjusting material, A large combination is preferable.
[0029]
Further, in the above embodiment, after preparing each single layer sheet such as the light transmission layer 31 and the clad layer 32 in advance, a laminated structure is formed by pressure bonding, but chemical vapor deposition, electron beam evaporation, It is also possible to continuously form a desired laminated structure in a vacuum film forming apparatus such as a plasma polymerization method, and a desired layer structure can be formed by a spin coating method or a roll coating method using a material in which those constituent substances are dissolved in a solvent. It is also possible to form a laminated structure.
[0030]
Further, in the above-described embodiment, polystyrene (PS) is scattered in polymethyl methacrylate (PMMA) in order to give the light transmission layer 31 a scattering action, but the light scatterer 34 is provided inside the light transmission layer 31. Instead of being scattered, the incident part of the laser diode 42a may be provided with a scattering optical element, for example, a light dispersive lens, or the light beam from the laser diode 42a goes straight through the light transmission layer 31. A light diffusing plate that reflects and diffuses light may be disposed at a position where the light beam reaches the opposite side of the light transmission layer 31.
[0031]
【The invention's effect】
As described above, according to the present invention, high-speed communication using an optical signal is realized.
Further, according to the present invention, since the output signal light from a certain circuit board is simultaneously transmitted to all other circuit boards via the optical bus, signal transmission between the circuit boards is optical / electrical conversion, It can be completed with only one electrical / optical conversion. Furthermore, according to the present invention, the circuit board can be freely inserted and removed for system expansion, and at this time, there is no need to use a special short-circuit connector or the like in the empty slot, and a system with high expandability is configured. The
[Brief description of the drawings]
FIG. 1 shows a signal processing of the present invention having a sheet-like optical data bus which is an embodiment of the optical bus of the present invention and a plurality of circuit boards optically connected to each other by the sheet-like optical data bus. It is a schematic block diagram of one Embodiment of an apparatus.
FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG.
FIG. 3 is an enlarged view corresponding to a part of the signal processing apparatus shown in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Signal processing apparatus 20 Support substrate 21 Board connector 22 Electrical wiring 30 Sheet-like optical data bus 31 Optical transmission layer 32 Clad layer 33 Signal light input / output part 34 Light scatterer 35 Light absorption layer 40 Circuit board 41 Electronic circuit 42 Throw Light receiving element 42a Laser diode 42b Photo diode 43 Electric signal input / output terminal

Claims (2)

An optical bus comprising a plurality of signal light input / output portions formed in a sheet shape and responsible for at least one of signal light incidence or signal light emission on an end surface, and an optical transmission layer that propagates the signal light ,
A plurality of light scatterers in the light transmission layer for diffusing the signal light incident from the signal light input / output unit;
An antireflection layer for preventing reflection of the signal light from the inside of the optical bus toward the end face of the optical bus to the inside of the optical bus is provided at a portion along the end face of the optical bus except for the signal light input / output unit. An optical bus characterized by that. Substrate,
A signal light emitting part that emits signal light, an electronic circuit that generates a signal to be carried by the signal light emitted from the signal light emitting part, a signal light incident part that receives the signal light, and an incident light from the signal light incident part A plurality of circuit boards on which at least one of electronic circuits for performing signal processing based on signals carried by signal light is mounted;
An optical bus comprising a plurality of signal light input / output portions formed in a sheet shape and responsible for at least one of signal light incidence or signal light emission on an end surface, and an optical transmission layer that propagates the signal light, And, in the light transmission layer having a plurality of light scatterers for diffusing the signal light incident from the signal light input / output unit, along the end face of the optical bus, except for the signal light input / output unit, An optical bus provided with an antireflection layer for preventing reflection of signal light directed from the inside of the optical bus toward the end face of the optical bus toward the inside of the optical bus, and signal light emission mounted on the circuit board. A signal processing apparatus comprising: a plurality of substrate fixing parts that are fixed on the base body in a state in which the signal light input part is optically coupled to the signal light input / output part of the optical bus; .

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