JP2000111738A - Optical data bus and its manufacture and signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical data bus that the sue efficiency of an incident light can be increased, and signal light transmission can be quickened by constituting this optical data bus by laminating plural sheets which are respectively made of some materials among plural materials. SOLUTION: An optical data bus is provided with 5 light transmission layers 21 constituted so as to laminated with light shade layers interposed. Each light transmission layer 21 is composed of 9 refractivity distribution layers 211-215 while the refractivity distribution layers 212-215 are successively laminated in a veridical direction with the refractivity distribution layer 211 as a center. The refractivity of each of those 9 refractivity distribution layers 211-215 is continuously changed related to the thickness direction. That is, the refractivity of each of those 9 refractivity distribution layers 211-215 is continuously decreased according as it goes from the refractivity distribution layer 211 positioned at the center of the laminated direction of those 9 refractivity distribution layers 211-215 toward the refractivity distribution layers 215 positioned at the both edges of the laminated direction of those 9 refractivity distribution layers 211-215.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical data bus for transmitting an optical signal, a method of manufacturing the optical data bus, and a signal processing device using the optical data bus.

[0002]

2. Description of the Related Art With the development of very large scale integrated circuits (VLSI), circuit functions of circuit boards (daughter boards) used in data processing systems have been greatly increased. As the number of signal connections to each circuit board increases as circuit functions increase, the data bus board (motherboard) that connects each circuit board (daughter board) with a bus structure requires a large number of connectors and connection lines. A parallel architecture is adopted. The operation speed of the parallel bus has been improved by increasing the parallelism by increasing the number of connection lines and miniaturization, but the processing speed of the system has been reduced due to the signal delay caused by the capacitance between the connection lines and the resistance of the connection lines. It may be limited by the operating speed of the bus. In addition, electromagnetic noise (EMI: E
Electromagnetic Interferen
The problem of ce) is also a great constraint on improving the processing speed of the system.

In order to solve such a problem and improve the operation speed of the parallel bus, use of an in-system optical connection technique called optical interconnection has been studied. The outline of the optical interconnection technology is described in “Sadaji Uchida, Academic Lecture Meeting on Circuit Packaging, 15C01, pp. 146-64”. 201
-202] and "Hisami Tomomi, et al.," Current Situation and Trend of Optical Interconnection Technology ", IEEE Tokyo Sec.
tion DenshiTokyo No. 33 p
p. 81-86, 1994], various modes are proposed depending on the configuration of the system.

Among various types of optical interconnection technologies proposed in the past, Japanese Patent Application Laid-Open No. 2-41042 discloses an optical data transmission system using a high-speed, high-sensitivity light emitting / receiving device applied to a data bus. An example is disclosed in which light emitting / receiving devices are arranged on both front and back surfaces of each circuit board, and light emitting / receiving devices on adjacent circuit boards incorporated in the system frame are spatially optically coupled. A serial optical data bus for loop transmission between circuit boards has been proposed. In this method, a signal light sent from a certain circuit board is subjected to optical / electrical conversion on an adjacent circuit board, and further subjected to electrical / optical conversion on the circuit board again, and then transmitted to the next adjacent circuit board. Each of the circuit boards is sequentially arranged in series, and is transmitted between all the 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 optical / electrical conversion / electrical / optical conversion speed of the light receiving / light emitting device arranged on each circuit board and is also restricted by the speed. In addition, since data transmission between each circuit board uses optical coupling via a free space by a light receiving / light emitting device arranged on each circuit board, it is arranged on both front and back surfaces of an adjacent circuit board. It is necessary that the light emitting / receiving devices are optically aligned and all the circuit boards are optically coupled. Furthermore, since the optical data transmission lines are connected via free space, interference between adjacent optical data transmission lines (crosstalk) occurs.
Occurs and data transmission failure is expected. In addition, it is expected that data transmission failure occurs due to scattering of signal light due to an environment in the system frame, for example, dust or the like. Furthermore, since the circuit boards are arranged in series, if any one of the boards is removed, the connection is interrupted there, and an extra circuit board is required to compensate for the disconnection. That is, there is a problem that the circuit board cannot be freely inserted and removed, and the number of circuit boards is fixed.

A data transmission technique between circuit boards using a two-dimensional array device is disclosed in Japanese Patent Laid-Open No. 61-196.
No. 210 discloses this. The technology disclosed herein includes a plate having two parallel surfaces and opposed to a light source, and optically connects between circuit boards via an optical path formed by a diffraction grating and a reflective element arranged on the plate surface. It is a method to combine with. In this method, light emitted from one point can be connected to only one fixed point, and it is not possible to connect all circuit boards comprehensively like an electric bus.
Since an integrated complex optical system including a diffraction grating and a reflective element is required, and alignment is difficult, interference (crosstalk) between adjacent optical data transmission lines occurs due to a displacement of the optical element. Data transmission failure is expected, connection information between circuit boards is determined by the diffraction grating and reflection element arranged on the plate surface, so the circuit board can not be freely inserted and removed, and the expandability is low. There are various problems.

Another technique for transmitting data between circuit boards using a two-dimensional array device is disclosed in Japanese Patent Laid-Open No. 4-1344.
No. 15 discloses this. The technology disclosed herein includes a lens array in which a plurality of lenses having a negative curvature are formed on the surface of a transparent substance having a larger refractive index than air, and a light emitted from the light source. Is transmitted from the side surface of the lens array. Also disclosed is a method of performing data transmission by using a configuration having a region having a small refractive index or a hologram instead of a plurality of lenses having a negative curvature. In such a method, light incident from the side is distributed on a surface from a plurality of lenses having the negative curvature, or a region having a small refractive index or a hologram, and is emitted. Data transmission is in progress. Therefore, it is conceivable that the intensity of the outgoing signal becomes non-uniform due to the positional relationship between the incident position and the outgoing position on the surface where a plurality of lenses or regions having a low refractive index or a hologram is formed. Also, it is considered that the ratio of light incident from the side surface to escape from the opposite side surface is high, and there is a problem that the light use efficiency is low. further,
Since it is necessary to arrange the optical input element of the circuit board in the position of a plurality of lenses having a negative curvature and a low refractive index area or a hologram instead of this, it is necessary to arrange the circuit board. There are various problems such as lack of flexibility and low expandability.

As means for solving these problems, there is a sheet-shaped optical data bus disclosed in Japanese Patent Application Laid-Open No. 10-123350. Since the optical data bus diffuses and propagates the signal light that has entered the inside and emits the signal light to the outside, it is possible to transmit the signal light that enters from a certain incident point to a plurality of emission points. Further, the optical data bus can easily perform optical coupling with a plurality of circuit boards having light receiving / emitting portions, and does not require precise optical alignment. Also, the number of circuit boards,
You can freely change the mounting position of those circuit boards,
A highly scalable and highly flexible system can be constructed. Further, since the optical data bus transmits the signal light by propagating inside the optical data bus instead of propagating in the free space, the scattering of light due to dust and the like is prevented, and the data transmission failure is prevented.

[0008]

In the above-mentioned optical data bus, since the incident signal light is diffused in all directions, the light intensity at the light receiving portion becomes weak, and the speed and power consumption are reduced. May cause problems. In order to solve this problem, a method is conceivable in which a light diffusing means is provided at the signal light incident portion of the sheet-shaped optical data bus, and the light diffusing means diffuses the signal light toward the signal light emitting portion. In this system, the light use efficiency can be improved by controlling the light diffusion distribution of the light diffusion means provided in the signal light incident portion, and the speed is higher than that of the optical data bus disclosed in JP-A-10-123350. And lower power consumption,
The sheet-type optical data bus provided with the light diffusing means at the signal light incident portion also has the following problems.

FIG. 7 is a sectional view in the thickness direction of a sheet-shaped optical data bus having a light diffusing means provided at a signal light incident portion.

[0010] The optical data bus 100 includes a diffuser 102 in a signal light incident portion 101. Therefore, the signal light 1
04 enters the signal light incidence unit 101, the signal light 1
Reference numeral 04 denotes the optical data bus 100 by the diffuser 102.
Is diffused not only in the width direction (the direction perpendicular to the plane of FIG. 7) but also in the thickness direction. Here, two diffused lights 105 and 106 are shown as diffused light. Diffuse light 1
05 reaches the signal light emitting portion 103 while being reflected on the front and back surfaces of the optical data bus 100, while the diffused light 106 directly reaches the signal light emitting portion 103 without being reflected on the front and back surfaces of the optical data bus 100. I do. Accordingly, when the diffused lights 105 and 106 arrive at different times from each other and the waveform of the signal light reaching the signal light emitting unit 103 is observed, the waveform is rounded.

FIG. 8 is a diagram showing a waveform of signal light having a rounded waveform.

As shown in FIG. 8, when the waveform is rounded, there is an adverse effect on the speed of signal light transmission. This waveform rounding is observed in an optical data bus of a step index (SI) type having a uniform refractive index. Therefore, the optical data bus is provided with a graded index (G) in which the refractive index gradually decreases from the center in the thickness direction toward the front and back surfaces.
By changing to type I), improvement in waveform rounding is expected.

FIG. 9 is a sectional view in the thickness direction of a GI optical data bus.

The refractive index of the optical data bus 200 has the largest refractive index at the center in the thickness direction, and continuously decreases toward the front and back surfaces.

When the signal light 204 enters the signal light incident portion 201, the signal light 204 is diffused by the diffuser 202 toward the inside of the optical data bus 200. Here, two diffused lights 205 and 206 are shown. Diffuse light 205
Is a light propagating toward the signal light emitting portion 203 while drawing a parabola, while the diffused light 206 travels only through the central portion of the optical data bus 200 in the thickness direction at the shortest distance. The light propagates toward 203. As described above, the refractive index of the optical data bus 200 has the largest refractive index at the center in the thickness direction, and continuously decreases toward the front and back surfaces.
The speed increases as the distance from the front and back of the optical data bus 200 increases, and decreases as the distance approaches the center in the thickness direction. On the other hand, the diffused light 206 is
Since the light travels only through the central portion having the largest refractive index in the thickness direction of 00, the propagation speed is lower than that of the diffused light 205. Accordingly, although the optical path lengths of the diffused lights 205 and 206 are different from each other, the diffused lights 205 and 206 are adjusted by adjusting the refractive index of the optical data bus 200 in the thickness direction to an appropriate value.
Each of them can reach the signal light emitting section 203 almost simultaneously, and the rounding of the waveform can be improved.

FIG. 10 is a diagram showing the waveform of the signal light emitted from the GI optical data bus.

A comparison between FIG. 8 and FIG. 10 shows that the use of the GI-type optical data bus improves waveform rounding. However, in the conventional GI-type optical data bus, the difference in the refractive index distribution in the thickness direction of the optical data bus cannot be made sufficiently large, and as compared with the optical data bus shown in FIG. There is a problem that utilization efficiency is deteriorated.

In view of the above circumstances, the present invention employs an optical data bus with high utilization efficiency of incident light and high speed signal light transmission, a method of manufacturing the optical data bus, and the optical data bus. It is an object of the present invention to provide a signal processing device having the above configuration.

[0019]

An optical data bus according to the present invention is formed in a sheet shape, receives signal light, propagates the signal light, and emits the signal light from the central portion in the thickness direction toward the front and back surfaces. Therefore, an optical data bus with a reduced refractive index,
The optical data bus is characterized in that a plurality of sheets each of which is made of any one of at least two kinds of materials are laminated.

A first method of manufacturing an optical data bus according to the present invention has a structure in which a plurality of sheets are stacked, and receives a signal light, propagates the signal light, and emits the signal light. A method of manufacturing an optical data bus in which the refractive index decreases as going from the portion to the front and back surfaces, wherein the plurality of sheets are stacked as the plurality of sheets to form a stacking direction of the plurality of sheets. The refractive index changes continuously in the thickness direction so that the refractive index decreases continuously from the sheet located at the center of the sheet to the sheets located at both ends in the stacking direction of the plurality of sheets. A plurality of such sheets are prepared, and the plurality of sheets are stacked.

A second method of manufacturing an optical data bus according to the present invention has a structure in which a plurality of sheets are stacked, and receives a signal light, propagates the signal light, and emits the signal light. A method of manufacturing an optical data bus in which the refractive index decreases as going from a portion to the front and back surfaces, wherein the plurality of sheets each have a constant refractive index in a thickness direction, and the plurality of sheets. Are stacked, the refractive index decreases stepwise from the sheet located at the center in the stacking direction of the plurality of sheets toward the sheets located at both ends in the stacking direction of the plurality of sheets. It is characterized in that a plurality of sheets having different rates are prepared, and a plurality of these sheets are laminated.

The signal processing device of the present invention comprises: (1) a base; (2) a signal light emitting body for emitting signal light and a circuit for generating a signal to be carried by the signal light emitted from the signal light emitting body. A plurality of circuits on which at least one of both a signal light incident body for receiving signal light and a circuit for performing signal processing based on a signal carried by the signal light incident from the signal light incident body are mounted. Substrate (3) A signal light incident portion for receiving the signal light and a signal light emitting portion for emitting the signal light, the signal light is incident from the signal light incident portion, and the signal light propagates to propagate the signal light. And a plurality of sheets, each of which is made of any one of at least two types of materials, that are stacked so that the refractive index decreases from the center in the thickness direction toward the front and back surfaces. Data bus (4) The signal light emitting member or the signal light incident member mounted on the circuit board is optically coupled to the signal light incident portion or the signal light emitting portion of the optical data bus, respectively. The state is provided with a substrate fixing portion for fixing on the base.

[0023]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing a signal according to an embodiment of the present invention having a plurality of circuit boards optically connected to the optical data bus, which are constituted by using the optical data bus according to the first embodiment of the present invention. It is a schematic structure figure showing a processing unit.

The supporting substrate 1 which is an example of the substrate according to the present invention
An optical data bus 20 having five optical transmission layers 21 is fixed on the optical disk. The refractive index of the light transmission layer 21 changes continuously in the thickness direction. The details of the optical data bus 20 will be described later.

A plurality of board connectors 30 are fixed on the support board 10, and a circuit board 40 is detachably mounted on each board connector 30. This circuit board 40
A light projecting / receiving element 42 for projecting the signal light toward the optical data bus 20 and receiving the signal light emitted from the optical data bus 20, and carrying the signal light projected by the light projecting / receiving element 42 An electronic circuit 41 that generates a signal and performs signal processing based on a signal carried by the signal light received by the light emitting / receiving element 42 is mounted.

A power supply line and an electric wiring 11 for electric signal transmission are provided on the support substrate 10.
As shown in FIG.
When the electronic circuit 41 is mounted on the circuit board 40, the electronic circuit 41 mounted on the circuit board 40 is connected to the electrical wiring 1 via the board connector 30.
1 and is electrically connected. Further, each of these circuit boards 4
By attaching 0 to the board connector 30, each of the five light emitting and receiving elements 42 mounted on each circuit board 40 is optically coupled to each of the five light transmission layers 21.

FIG. 2 is a perspective view of an optical data bus provided in the signal processing device shown in FIG. 1, and FIG. 3 is a perspective view showing an optical transmission layer provided in the optical data bus.

The optical data bus 20, as shown in FIG.
Five light transmission layers 2 stacked with the light shielding layer 24 interposed therebetween
As shown in FIG. 3, each of the optical transmission layers 21 includes a refractive index distribution layer 212, 213, 214, and 215 sequentially stacked vertically around a refractive index distribution layer 211. And nine refractive index distribution layers.
In FIG. 3, the light diffusion layer 50 (see FIG. 2) bonded to the light transmission layer 21 is not shown.

Each of these nine refractive index distribution layers has a refractive index that continuously changes in the thickness direction.
The refractive index increases from the refractive index distribution layer 211 located at the center of the nine refractive index distribution layers in the stacking direction to the refractive index distribution layers 215 positioned at both ends in the stacking direction of the nine refractive index distribution layers. Is continuously decreasing. Here, the refractive index of the refractive index distribution layer 211 is 1.66 at the center of the refractive index
The refractive index continuously decreases toward the front and back surfaces of No. 11, and the refractive index on the front and back surfaces of the refractive index distribution layer 211 is 1.57. Also, the refractive index distribution layers 212 and 21
3, 214, 215 change such that the refractive index decreases continuously from the front surface to the back surface. Here, the refractive index change ranges of the refractive index distribution layers 212, 213, 214, and 215 are 1.57 to 1.49, respectively.
1.49-1.39, 1.39-1.36, 1.36-
1.34. That is, each light transmission layer 21 has a refractive index of 1.66 at the center in the thickness direction, and the refractive index continuously decreases from the center toward the front and back surfaces. The refractive index on the back surface is 1.34.

On each of the two side end faces 22 of each of the optical transmission layers 21 facing the opposite side, three signal light input / output sections 23 for both inputting and outputting signal light are provided. Signal light input / output section 2 on the side end face of each optical transmission layer 21
The light diffusion layer 50 is bonded to the portion where 3 is provided. In FIG. 2, the signal light input / output unit 23 and the light diffusion layer 50 are represented by reference numerals only on one side end surface 22 of the lowermost light transmission layer 21.

Hereinafter, a method for manufacturing the optical data bus 20 by employing one embodiment of the first method for manufacturing the optical data bus of the present invention will be described.

The refractive index of the refractive index distribution layer 211, which is the central layer of the light transmission layer 21, changes from 1.66 to 1.57. Here, in order to change the refractive index from 1.66 to 1.57, polymerization of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and pyromellitic dianhydride is carried out. And 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, and the content of fluorine in the mixture is reduced to 0 wt%.
To 18 wt%. By changing the content of fluorine from 0 wt% to 18 wt%,
The refractive index can be varied from 1.66 to 1.57. This material is formed into a sheet shape and heated and polymerized, whereby a refractive index distribution layer 211 whose refractive index continuously changes from 1.66 to 1.57 from the center in the thickness direction to the front and back surfaces is formed. It is made.

In producing the refractive index distribution layer 212, 4-N, N-dimethylaminophenyl-N-
A phenyl nitrone-doped polymethyl methacrylate (PMMA) is formed into a sheet to form a PMMA sheet, and the surface of the PMMA sheet is exposed to ultraviolet light (λ = 3).
(65 nm). The irradiation of this ultraviolet light changes the structure of nitron into a three-membered oxaziridine,
The refractive index of the A sheet changes in the thickness direction. The absorbed amount of the irradiated ultraviolet light by the PMMA sheet is the largest on the surface of the PMMA sheet,
It decreases continuously toward the back surface of the MA sheet. Therefore, the refractive index of the PMMA sheet is
It changes so as to decrease continuously from the front surface to the rear surface of the MMA sheet. The refractive index distribution in the thickness direction of the PMMA sheet is determined by the following equation.
It can be determined by the doping amount of N, N-dimethylaminophenyl-N-phenylnitrone and the irradiation time of ultraviolet rays. Here, 4-N, N-dimethylaminophenyl-N-phenyl nitrone was added to the PMMA sheet for 30 minutes.
The doping is carried out by wt%, and ultraviolet rays are irradiated until the refractive index in the thickness direction of the PMMA sheet continuously changes from 1.57 to 1.49. Thus, the refractive index distribution layer 212 is manufactured.

In producing the refractive index distribution layer 213, 2,2,2-trifluoroethyl methacrylate, 1,1,2,2-tetrahydroperfluorodecyl methacrylate, methyl methacrylate, and methacrylic acid Of 2,2,2-trifluoroethyl methacrylate or 1,1,2,2-tetrahydroperfluorodecyl methacrylate to adjust the mixture ratio, followed by hot stretching. Thereby, a refractive index distribution layer 213 whose refractive index continuously changes from 1.49 to 1.39 is produced.

In producing the refractive index distribution layer 214, the mixture ratio of the mixture of perfluorobutenyl vinyl ether and chlorotrifluoroethylene oligomer is adjusted, and the mixture is heated at about 200 ° C. to give the mixture a temperature distribution. , The refractive index in the thickness direction is 1.49 to 1.36.
To produce a preform that changes continuously. By thermally stretching the preform, the refractive index distribution layer 2 is formed.
14 are produced.

For the refractive index distribution layer 215, the mixing ratio of a mixture of perfluorobutenyl vinyl ether, perfluoro 2,2-dimethyl-1,3-dioxole, perfluoro 2-butyltetrahydrofuran, and a chlorotrifluoroethylene oligomer 200 ℃
By heating the mixture to a certain degree and giving the mixture a temperature distribution, a preform whose refractive index changes continuously from 1.36 to 1.34 is produced. The refractive index distribution layer 215 is manufactured by thermally stretching the preform.

The refractive index distribution layer 2 produced as described above
As shown in FIG. 3, the refractive index distribution layers 212, 213, 214, and 215 are sequentially superimposed on the refractive index distribution layer 211 in the vertical direction as shown in FIG. Then, the optical transmission layer 21 is manufactured. Here, the light transmission layer 21
Has a thickness of about 1 mm. Such an optical transmission layer 2
5 are manufactured, and the light transmission layers 21 and the light shielding layers 24 are alternately laminated. An acrylic resin mixed with a silica pigment and having a thickness of about 10 μm is formed on a polyester film to produce a light diffusion layer 50.
The optical data bus 20 having the structure shown in FIG. 2 is manufactured by bonding the light diffusion layers 50 thus manufactured to the optical data bus 20.

The manner in which signal light emitted from one light emitting / receiving element 42 is received by another light emitting / receiving element 42 will be described below with reference to FIG.

FIG. 4 is a top view showing an optical data bus provided in the signal processing device shown in FIG. 1 and a light emitting / receiving element mounted on a circuit board provided in the signal processing device.

When the signal light emitted from a certain light emitting / receiving element 42 enters the light diffusion layer 50 of the signal light input / output unit 23, the signal light is diffused by the light diffusion layer 50 and the signal light input / output on the opposite side. The light propagates inside the light transmission layer 21 toward the portion 23.
Here, as described above, the refractive index of the light transmission layer 21 at the central part in the thickness direction is 1.66, and the refractive index continuously decreases from the central part toward the front and back surfaces. The refractive index on the back surface is 1.34. By setting the refractive index in this manner, in each of the signal light input / output sections 23, the diffused light propagating toward the signal light input / output section 23 transmits the diffused light in the thickness direction of the optical transmission layer 21. At almost the same time regardless of the propagation angle, the signal light input / output unit 2
3 and is received by another light emitting / receiving element 42. Thus, regardless of the propagation angle of the diffused light in the thickness direction of the optical transmission layer 21, the diffused light reaches the signal light input / output unit 23 almost at the same time. Is suppressed, and the speed of signal light transmission is increased.

In a conventional GI type optical data bus,
The light transmission layer having a different refractive index in the thickness direction is made of a single-layer sheet made of a predetermined material. However, in the thickness direction of the optical transmission layer, the difference between the maximum value and the minimum value of the refractive index cannot be increased, and there is a problem that the utilization efficiency of the signal light incident on the optical transmission layer is low. Is the optical transmission layer 21 included in the optical data bus 20 of the present embodiment.
Is formed by stacking a plurality of refractive index distribution layers, so that the maximum value and the minimum value of the refractive index in the thickness direction of the optical transmission layer 21 are different from those of the conventional GI optical data bus. The difference can be increased, and the utilization efficiency of incident light can be improved. In particular, each optical transmission layer 21 included in the optical data bus of this embodiment has a refractive index difference δ between the central part in the thickness direction and the front and back surfaces, and δ = 1.66-1.34 = 0.32 ≧ 0.32. 0.1. As described above, by setting the refractive index difference δ to 0.1 or more, the utilization efficiency of incident light can be further improved.

Next, an optical data bus according to a second embodiment of the present invention will be described. In describing the optical data bus of the second embodiment, only differences from the optical data bus of the first embodiment (see FIG. 1) will be described with reference to FIG.

FIG. 5 is a perspective view showing an optical transmission layer provided in the optical data bus according to the second embodiment of the present invention.

The difference between the optical data bus of the first embodiment and the optical data bus of the second embodiment is that the refractive index of the optical transmission layer 21 provided in the optical data bus of the first embodiment is thick. Whereas the refractive index of the optical transmission bus 31 included in the optical data bus of the second embodiment is changed in a stepwise manner in the thickness direction, while the optical data bus of the second embodiment is continuously changed in the thickness direction. .

As shown in FIG. 5, each of the optical transmission layers 31 provided in the optical data bus of the second embodiment has
The constant refractive index layers 312, 313, 314, 315, 316, 317, and the vertical direction centering on the constant refractive index layer 311.
318 are composed of fifteen constant refractive index layers sequentially laminated. In FIG. 5, the light diffusion layer adhered to the light transmission layer 31 is not shown.

The refractive index of each of the fifteen constant refractive index layers is constant in the thickness direction within one layer, and the refractive index positioned at the center of the fifteen refractive index distribution layers in the laminating direction. From the constant refractive index layer 311, the constant refractive index layers 3 located at both ends of the fifteen constant refractive index layers in the laminating direction.
The refractive index decreases stepwise toward 18. Here, the constant refractive index layers 311, 312, 313,
The refractive indices of 314, 315, 316, 317 and 318 are
1.66, 1.61, 1.56, 1.51,
1.46, 1.41, 1.36, 1.31. That is, one light transmission layer 31 has a refractive index at the center in the thickness direction of 1.66, and the refractive index decreases in a stepwise manner from the center toward the front and back surfaces, and the refractive index at the front and back surfaces increases. Is 1.31.

Hereinafter, a method of manufacturing the optical data bus according to the second embodiment using the second embodiment of the optical data bus according to the present invention will be described.

Constant refractive index layers 311 and 312 (refractive index 1.
66, 1.61), respectively,
Polymerization product of 2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and pyromellitic dianhydride, and 2,2'-bis (trifluoromethyl)
It is produced by setting the content of fluorine in the mixture of -4,4'-diaminobiphenyl to 0 wt% and 10 wt%.

In forming the constant refractive index layers 313 and 314, 4-N, N-dimethylaminophenyl-N-phenyl nitrone was 30 wt%,
PMMA doped with 10 wt% is formed into a sheet and
An MMA sheet is formed and irradiated with ultraviolet rays (λ = 365 nm). Thus, constant refractive index layers 313 and 314 having a refractive index of 1.55 and 1.51 are produced.

In manufacturing the constant refractive index layers 315 and 316, 2,2,2-trifluoroethyl methacrylate, 1,1,2,2-tetrahydroperfluorodecyl methacrylate, methyl methacrylate, and methacryl Polymerization is performed by adjusting the mixing ratio of a mixture of an acid with 2,2,2-trifluoroethyl methacrylate or 1,1,2,2-tetrahydroperfluorodecyl methacrylate, and the film is stretched by heating. Thereby, constant refractive index layers 315 and 316 having refractive indexes of 1.46 and 1.41 are manufactured.

Constant refractive index layer 317 (refractive index: 1.36)
Is prepared by adjusting the mixture ratio of a mixture of perfluorobutenyl vinyl ether and chlorotrifluoroethylene oligomer, heating the mixture at about 200 ° C., and giving the mixture a temperature distribution.

Constant refractive index layer 318 (refractive index: 1.31)
Is produced by adjusting the mixing ratio of perfluorobutenyl vinyl ether, perfluoro-2,2-dimethyl-1,3-dioxole, and tetrafluoroethylene, polymerizing the resultant, and hot-stretching.

The constant refractive index layer 3 manufactured as described above
11,312,313,314,315,316,31
7, 318, as shown in FIG.
Constant refractive index layers 312, 313 in the vertical direction with respect to
314, 315, 316, 317, and 318 are sequentially laminated and bonded by a method such as thermocompression bonding, whereby the optical transmission layer 31 is manufactured.

As described above, even if the refractive index of the light transmission layer 31 itself is changed stepwise instead of continuously, waveform rounding is suppressed and the efficiency of use of incident light is improved.

In this case, the refractive index difference between adjacent refractive index distribution layers is 0.05. However, if the optical transmission layer 21 itself has a desired refractive index difference, the refractive index difference between the refractive index distribution layers is obtained. The difference need not be 0.05.

[0057]

Embodiments of the present invention will be described below.

As an example, the optical data bus 20 shown in FIGS. 1 and 2 was used.
The optical data bus shown in FIG. 9 was used. Hereinafter, experimental results of the efficiency of use of incident light of the signal light incident on the optical data bus will be described.

FIG. 6 is a graph showing the results of the experiment.

This graph shows the incident light use efficiency of the example and the comparative examples 1 and 2. Here, the incident light utilization efficiency is a ratio of the signal light incident on the optical data bus received by the light receiving element. From this graph, it can be seen that the optical data bus of the example has higher incident light utilization efficiency than the optical data buses of Comparative Examples 1 and 2.

[0061]

As described above, according to the present invention,
An optical data bus with high utilization efficiency of incident light and high-speed signal light transmission, a method of manufacturing the optical data bus, and a signal processing device employing the optical data bus are obtained.

[Brief description of the drawings]

FIG. 1 illustrates a signal processing apparatus according to an embodiment of the present invention, which includes a plurality of circuit boards optically connected to the optical data bus, which are configured using the optical data bus according to the first embodiment of the present invention. FIG.

FIG. 2 is a perspective view of an optical data bus included in the signal processing device shown in FIG.

FIG. 3 is a perspective view showing an optical transmission layer provided in the optical data bus.

4 is a top view showing an optical data bus provided in the signal processing device shown in FIG. 1 and a light emitting / receiving element mounted on a circuit board provided in the signal processing device.

FIG. 5 is a perspective view showing an optical transmission layer provided in an optical data bus according to a second embodiment of the present invention.

FIG. 6 is a graph showing experimental results.

FIG. 7 is a cross-sectional view in the thickness direction of a sheet-shaped optical data bus provided with a light diffusing means at a signal light incident portion.

FIG. 8 is a diagram illustrating a waveform of signal light having a rounded waveform.

FIG. 9 is a cross-sectional view in the thickness direction of a GI optical data bus.

FIG. 10 is a diagram illustrating a waveform of signal light emitted from a conventional GI optical data bus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Support board 11 Electric wiring 20 Optical data bus 21 Optical transmission layer 22 Side end surface 23 Signal light input / output part 24 Light shielding layer 30 Board connector 40 Circuit board 41 Electronic circuit 42 Light emitting / receiving element 50 Light diffusion layer 211, 212, 213 , 214, 215 Refractive index distribution layers 312, 313, 314, 315, 316, 317, 3
18 Constant refractive index layer

Claims (7)

[Claims] An optical data bus which is formed in a sheet shape, receives a signal light, propagates the signal light, and emits the signal light, the refractive index decreasing from a central portion in a thickness direction to a front and back surface. An optical data bus, wherein the optical data bus is formed by laminating a plurality of sheets each made of any one of at least two kinds of materials. 2. The plurality of sheets each have a refractive index that continuously changes in a thickness direction, and the plurality of sheets as a whole are located at the center in the stacking direction of the plurality of sheets. 2. The light according to claim 1, wherein the plurality of sheets are stacked such that the refractive index decreases continuously toward the sheets located at both ends in the stacking direction of the plurality of sheets. Data bus. 3. The plurality of sheets each have a constant refractive index in the thickness direction within one sheet, and the plurality of sheets as a whole have a center in the stacking direction of the plurality of sheets. 2. The sheet is stacked such that the refractive index decreases stepwise from the sheet located at the end of the plurality of sheets toward the sheets located at both ends in the stacking direction of the plurality of sheets. Optical data bus. 4. The optical data bus according to claim 1, wherein a difference in refractive index between a central portion in a thickness direction of the optical data bus and front and back surfaces of the optical data bus is 0.1 or more. 5. A structure in which a plurality of sheets are laminated, a signal light is incident, the signal light is propagated and emitted, and the refractive index decreases from the center in the thickness direction toward the front and back surfaces. The optical data bus manufacturing method, wherein, as the plurality of sheets, by stacking the plurality of sheets, from the sheet located in the center of the stacking direction of the plurality of sheets, the plurality of sheets Prepare a plurality of sheets, each having a refractive index continuously changed in the thickness direction, so that the refractive index continuously decreases toward the sheets located at both ends in the stacking direction of the sheets. A method for manufacturing an optical data bus, comprising laminating the sheets. 6. A structure in which a plurality of sheets are stacked, a signal light is incident, the signal light is propagated and emitted, and the refractive index decreases from the center in the thickness direction toward the front and back surfaces. A method for manufacturing an optical data bus, wherein the plurality of sheets each have a constant refractive index in the thickness direction, and the plurality of sheets are stacked to form the plurality of sheets. A sheet having a refractive index whose refractive index decreases stepwise from the sheet located at the center in the stacking direction of the sheets toward the sheets located at both ends in the stacking direction of these sheets is prepared. And a method of manufacturing an optical data bus. 7. A base, a signal light emitting body for emitting signal light, and a circuit for generating a signal to be carried by the signal light emitted from the signal light emitting body; a signal light incident body for receiving the signal light; A plurality of circuit boards on each of which at least one of a circuit for performing signal processing based on a signal carried by the signal light incident from the signal light incident body is mounted, a signal light incident portion for receiving the signal light, and a signal A signal light emitting portion for emitting light; a signal light incident portion from which the signal light is incident, the signal light propagates, and the signal light is emitted from the signal light emitting portion. An optical data bus in which a plurality of sheets made of such a material are stacked so that the refractive index decreases from the center in the thickness direction toward the front and back surfaces, and the circuit board is mounted on the circuit board. Signal light output And a substrate fixing portion for fixing the body or the signal light incident body on the base in a state of being optically coupled to the signal light incident portion or the signal light emitting portion of the optical data bus, respectively. Signal processing device.