Abstract:
In a device of the present invention for allowing signal light to enter a light guide body using an optical fiber, a light guide body, which is constituted by dispersing particles for scattering the signal light in an optical medium, is selected as a light guide path which requires an area where a light diffusing function is performed just after incidence of the signal light. An optical connecting material intervenes between one end of the optical fiber from which the signal light is output and opposed one end surface of a particle dispersing light guide body and a desired diffusing function is obtained.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority under 35 USC 119 from Japanese Patent Application No. 2003-13074, the disclosure of which is incorporated by reference herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a light signal transmitting device for transmitting a light signal between a plurality of circuit boards and between a plurality of devices, and a signal processing device composed of the light signal transmitting device.  
         [0004]     2. Description of the Related Art  
         [0005]     Conventionally, signals are generally received and transmitted between a plurality of circuit boards and between a plurality of devices via electrical connection. It is, however, hard for the electrical connection to cope with speed-increase of signal transmission due to skew between channels, crosstalk, increase in fan-out and the like.  
         [0006]     Japanese Patent Application Laid-Open (JP-A) No. 2-41042 suggests a light data bus in which a light emitting/light receiving device is provided on both surfaces of each circuit board, and the light emitting/light receiving devices on the adjacent circuit boards are spatially connected by light.  
         [0007]     Because this technique, however, requires optical-electrical conversion at every communication between the adjacent circuit boards, cost and latency increase, and because free space propagation is used, locating is difficult and the technique has a weakness for crosstalk, dust and the like.  
         [0008]     Further, JP-A No. 61-196210 suggests a technique in which circuit boards are optically coupled with each other via an optical path composed of a diffraction grating and a reflecting element arranged on a surface of a plate.  
         [0009]     In this technique, however, because light emitted from one point can be connected only with one fixed point, multiple connections cannot be carried out.  
         [0010]     In view of such circumstances, JP-A No. 10-123350 suggests a signal processing device in which light scatterers having refractive index different from that of a light transmitting layer are dispersed in the light transmitting layer.  
         [0011]     In this signal processing device, incident signal light is diffused by the light scatterers dispersed in the light transmitting layer, and the signal can be received and transmitted between arbitrary circuit boards optically connected with the light transmitting layer.  
         [0012]     JP-A NO. 2000-241655 discloses an optical coupler having a configuration where a transmission diffusing layer is formed on one end of an incident portion of the light transmitting layer and a plurality of optical fibers are brought into contact with the transmission diffusing layer.  
         [0013]     A mode where a diffusing layer is used so as to diffuse incident light includes two typical modes. They are a mode in which a transmission diffusing layer is provided on an incident side of a light guide body, and a mode in which a reflection diffusing layer is provided on the other end of the light guide body. In the mode using the reflection diffusing layer, because the incident portion for the signal light is normally made of a flat light transmitting material, one ends of the optical fibers can be coupled with the light guide body by adhesive or the like. For example, when it is demanded that a length of the light guide body is shortened by performing a diffusing function just after incidence, an area for causing diffusion is required on the incident side for the signal light.  
         [0014]     In the light signal transmitting device in which the transmission diffusing layer is provided on the incident portion disclosed in JP-A No. 2000-241655, because the incident light is refracted and diffused by fine irregularities formed on a surface of the transmission diffusing layer, it is necessary to lay an air layer in gaps between the optical fibers and the irregularities on the diffusing layer. That is to say, in principle, an adhesive material having refractive index smaller than that of the optical fibers or the diffusing layer can be provided to the gaps of the irregularities, but actually the adhesive material, which has refractive index small enough to an extent of maintaining diffusing properties, is expensive. Because option is limited, the air layer is laid and the optical fibers are physically fixed by using a holding member or the like. In this bumping structure, however, when a resin material such as adhesive for holding the optical fibers intrudes into the air layer portion corresponding to the gaps at the time of production, the diffusing function is deteriorated outstandingly.  
         [0015]     In the light guide body in which diffusing particles are dispersed in the entire light guide body disclosed in JP-A No. 10-123350, particles representing the light diffusing function are present just after incidence. A light signal is emitted from one ends of the optical fibers, and the incident sides of the optical fibers are connected with the light guide body. As such a connecting method, however, an advantageous method is not disclosed.  
       SUMMARY OF THE INVENTION  
       [0016]     It is, therefore, one objective of the present invention to improve performance and reliability in connection between an optical fiber, for allowing a light signal to enter a light guide body, and the light guide body for branching the incident light to many emitting portions utilizing diffusion.  
         [0017]     In order to achieve the objective, a first aspect of the invention is a light signal transmitting device for allowing signal light entering from one end of at least one optical fiber on an incident side to enter a light guide body, and emitting the signal light towards a plurality of output nodes. The light guide body is constituted so that particles for scattering the signal light are dispersed in an optical medium, and includes a light transmitting connecting material for optically connecting the optical fiber with one end surface of the light guide body.  
         [0018]     According to the invention, in a configuration using a light guide path which allows the signal light to enter the light guide body using the optical fiber and requires an area where a light diffusing function is performed just after incidence of the signal light, the light guide body, which is constituted so that the particles for scattering the signal light are dispersed in the optical medium, is selected as the light guide path. As a result, even when an optical connecting material is laid between one end of the optical fiber from which the signal light is output and opposed one end surface of the light guide body, the desired diffusing function can be obtained.  
         [0019]     As a result, even in the light signal transmitting device in which a diffusing area is provided on the incident side for the signal light, reliability of connection with the optical fiber is improved.  
         [0020]     The optical fiber, the light guide body, the light receiving element and the like may be fixed to the nodes on the output side for the signal light by light transmitting resin, or they may be bumped against the nodes, or they may be arranged on the nodes via a minute gap.  
         [0021]     The connecting material can be arranged in a gap between one end of the optical fiber and one end surface of the light guide body. From a viewpoint of stability of the connection between the optical fiber and the light guide body, the connecting material is sometimes formed so as to seal at least a partial side surface of the optical fiber and the entire light guide body.  
         [0022]     Further, an average particle diameter of the particles to be dispersed in the optical medium is set to be not less than a wavelength of the signal light. When the average particle diameter is set to be not less than the wavelength of the signal light, Mie scattering is dominant as diffusion of the incident signal by means of the particles. In the Mie scattering, forward scattering is dominant as scattering of light, and incident light can be transmitted to the other end of the light guide body while it is being diffused efficiently. Meanwhile, when the particle diameter is not more than the wavelength of the signal light, Rayleigh scattering, in which isotropic scattering is dominant, is dominant in diffusion, and thereby increasing transmission loss of the signal light to the other end of the light guide body. For this reason, in the invention, actually the average particle diameter of the dispersing particles is sometimes set to be not less than the wavelength of the signal light.  
         [0023]     As the optical fiber to be connected, a plastic optical fiber is frequently used in view of connecting alignment tolerance with respect to the light guide body.  
         [0024]     Further, a second aspect of the invention is a signal processing device including: the light signal transmitting device; a light emitting element for emitting a light signal according to an electric signal to the other end of the optical fiber or a light receiving element for converting the light signal received from the other end of the optical fiber into an electric signal; and an electric circuit for processing the electric signal.  
         [0025]     With this configuration, in the signal processing device using the light signal transmitting device where the diffusing area is provided on the incident side for the signal light, diffusing performance and connecting reliability become high. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIG. 1  is a schematic constitution diagram of a transmission type optical star coupler according to a first embodiment of the present invention.  
         [0027]      FIG. 2  is a schematic constitution diagram of a reflection type optical star coupler according to a second embodiment of the invention.  
         [0028]      FIG. 3  is a perspective view of a signal processing device according to a third embodiment of the invention.  
         [0029]      FIG. 4  is a perspective view of an optical wiring board laminator according to the third embodiment of the invention.  
         [0030]      FIG. 5  is a perspective view of the optical wiring board according to the third embodiment of the invention.  
         [0031]      FIG. 6  is a sectional view of the signal processing device according to a fourth embodiment of the invention.  
         [0032]      FIG. 7  is a perspective view of the optical wiring board laminator according to the fourth embodiment of the invention.  
         [0033]      FIG. 8  is a sectional view of a connecting portion (optical connector) between the optical wiring board and the circuit board according to the fourth embodiment of the invention.  
         [0034]      FIG. 9  is a perspective view of the optical wiring board laminator according to a fifth embodiment of the invention.  
         [0035]      FIG. 10  is a perspective view of a ferrule connecting portion of the optical wiring board laminator according to the fifth embodiment of the invention.  
         [0036]      FIG. 11  is a perspective view illustrating a modified example of the optical wiring board laminator according to the fifth embodiment of the invention.  
         [0037]      FIG. 12  is a sectional view of the signal processing device according to a sixth embodiment of the invention.  
         [0038]      FIG. 13  is a perspective view of the optical wiring board laminator according to the sixth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     Embodiments of the present invention are explained below with reference to the drawings.  
       First Embodiment  
       [0040]      FIG. 1  illustrates an optical star coupler according to a first embodiment. The first embodiment shows an optical star coupler of 4 by 4. As shown in  FIG. 1 , the optical star coupler has an optical fiber array where one ends of four optical fibers  1 A to  1 D and optical fibers  7 A to  7 D are arranged in a line. The optical fiber array is connected with a particle dispersing light guide body  3  of the invention formed into a rectangular plate shape, with the gaps between both end surfaces and the optical fibers included, by applying an optically transparent resin particle  2  to the entire light guide body. Signal light is input by using a surface light emitting laser (not shown) for generating an infrared ray (wavelength: 780 nm) provided on the other ends of the optical fibers.  
         [0041]     As the particle dispersing light guide body  3 , a material, in which spherical silicone resin particles  5  having refraction index of 1.438 and average particle diameter of 7 μm are dispersed in a PMMA (polymethyl methacrylate) base member  4  having refraction index of 1.485, is used, for example.  
         [0042]     As an adhesive material for the optical fibers  1  and  7  and the particle dispersing light guide body  3 , ultraviolet curing acrylic adhesive (AT6001: NTT Advanced Technology Corporation) having refractive index of 1.51 approximate to that of PMMA is used here. Another connecting materials include ultraviolet curing epoxy adhesive (AT7602: NTT Advanced Technology Corporation) and the like.  
         [0043]     According to this embodiment, signal light transmitted from a light emitting element via the optical fiber  1 A enters the particle dispersing light guide body  3 . The incident signal light is scattered forward by resin particles  5  dispersed in the particle dispersing light guide body, and simultaneously is totally reflected from upper and lower surfaces and side surfaces of the particle dispersing light guide body repeatedly. While the forward scattering and total reflection, the signal light is propagated to an end surface opposed to an end surface where the signal light enters with an approximately uniform light intensity distribution so as to be emitted via the optical fibers  7 A to  7 D.  
         [0044]     The optical star coupler includes a rectangular sheet of 4×20×1 (w×1×t) mm, which is produced by using the particle dispersing light guide body (average particle diameter of the silicone resin particles: 7 μm, resin density: 30000 pieces/mm 3 ), and an SI (step index) type POF (plastic optical fiber) having a fiber diameter of φ1 mm and a length (one side) of 300 mm (for example, CK-40 made by Mitsubishi Rayon Co., Ltd.). Uniformity of an emitted light quantity in such an optical star coupler is about 6% which is a satisfactory result. It is defined that uniformity (%) of an emitted light quantity=maximum emitting efficiency−minimum emitting efficiency/maximum emitting efficiency+minimum emitting efficiency.  
         [0045]     As the base member  4  of the particle dispersing light guide body  3 , a material having high transmittance and comparatively high refractive index is mostly used. Besides PMMA, for example, polycarbonate and polyolefin can be used. Further, as the material  5  of the resin particles to be dispersed, a material, in which transparency is high and a difference in refractive index from that of the base material is 0.01 or more, is mostly used. Besides the silicone resin, a resin, which is obtained by polymerizing methyl methacrylate and divinylbenzene and has a crosslinked structure, such as polyester or polyethylene can be used.  
         [0046]     A size of the resin particles to be dispersed is mostly set to a value in a range from a wavelength or more of the signal light to a value 1000 or less times as large as the wavelength. Actually, the size may be set to a value 1 to 30 times as large as the wavelength.  
         [0047]     When the size of the resin particles to be dispersed exceeds a value 1000 times as large as the wavelength, lateral scattering is predominant, and thus transmission loss of the signal increases. Concretely, when an infrared ray having wavelength of 850 nm is used as the signal light, the size may be set to a value in a range of 0.8 μm to 250 μm.  
         [0048]     A number and a type of the optical fibers composing the optical star coupler are not limited to the embodiment. The optical star coupler is composed of an arbitrary number of the optical fibers that comply with a requirement of a system. The type is not limited to POF, and a quartz fiber and HPCF (hard plastic clad fibers) can be used. The periphery of the rectangular sheet is covered with a member, which has a smaller refractive index than that of the base member of the particle dispersing light guide body (for example, fluorine-contained resin) so as to constitute the optical fiber.  
       Second Embodiment  
       [0049]      FIG. 2  illustrates a reflection type optical star coupler according to a second embodiment. The second embodiment shows a four-branched optical star coupler. As shown in  FIG. 2 , the optical fiber array in which one ends of the four optical fibers  1 A to  1 D are arranged in a line is optically connected with the particle dispersing light guide body of the invention formed into the rectangular plate shape. Further, a reflecting unit  8  is provided on an end of the particle dispersing light guide body of the invention formed into the rectangular plate shape opposite to an end connected with the optical fiber array. The resin  2 , which connects the particle dispersing light guide body  3 , the optical fibers and a gap of the light guide body, is the same as that in the first embodiment, but the resin is applied only to the periphery of the gap.  
         [0050]     According to this embodiment, the signal light which is transmitted from the light emitting element via the optical fiber  1 A enters the particle dispersing light guide body  3 . The incident signal light is scattered forward by the resin  5  dispersed in the particle dispersing light guide path, and simultaneously while the signal light is being totally reflected from the upper and lower surfaces and the side surfaces of the particle dispersing light guide body repeatedly, it is propagated. The signal light is reflected by the reflecting unit  8  on the end of the particle dispersing light guide body opposite to the end connected with the optical fiber array, and it is again totally reflected from the upper and lower surfaces and the side surfaces of the particle dispersing light guide body repeatedly. While the total reflection, the signal light is propagated to the end surface where it enters with an approximately uniform light intensity distribution so as to be emitted via the optical fibers  1 A to  1 D.  
         [0051]     The reflection type optical star coupler is composed of the rectangular particle dispersing light guide body and the SI type POF, and a reflecting surface made of A 1  or the like is formed directly on the end opposite to the end connected with POF by sputtering.  
         [0052]     A number and a type of the optical fibers composing the optical star coupler are not limited to this embodiment or the first embodiment.  
       Third Embodiment  
       [0053]     A third embodiment of the invention is explained with reference to FIGS.  3  to  5 .  FIG. 3  is a schematic constitution perspective view of a signal processing device according to the embodiment. As shown in the drawing, in a signal processing device  1000 , the optical star coupler  10  similar to that explained in the first embodiment is arranged and fixed to an optical wiring board base  800  in a predetermined position of a supporting substrate  100 . The ends of the optical fibers and the light guide body  3  are sealed and fixed by the light transmitting resin (connecting material)  2 . A plurality of electric connectors  200  are annexed on a predetermined position of the supporting substrate  100  with predetermined intervals, and a plurality of circuit boards  500 ,  501 ,  502  and  503  which are optically connected by the optical star coupler  10  are attached to the electric connectors  200 . Further, electronic circuits  400 , a power source line and electric wiring for transmitting an electric signal (not shown) are provided to predetermined positions of the supporting substrate  100 . The electric wiring is electrically connected with electronic circuits (not shown) on the circuit boards  500 ,  501 ,  502  and  503  attached via the electric connectors  200 .  
         [0054]     The circuit boards  501 ,  502  and  503  have an electrical-optical converting circuit  600  as a “light transmitting circuit” for converting an electric signal into a light signal, and an optical-electrical converting circuit  700  as a “light receiving circuit” for converting a light signal into an electric signal. The former electrical-optical converting circuit  600  is composed of, as one example, laser diodes  601  as “light emitting elements” and a laser diode driving circuit  602 . The electrical-optical converting circuit  700  is composed of, as one example, photodiodes  701  as “light receiving elements”, a photodiode driving circuit  702 , and an amplifying circuit  703  for amplifying a light receiving signal in the photodiodes  701  to a level where this signal can be converted as a logical signal.  
         [0055]     An optical bus circuit  1000  shown in  FIG. 3  is such that a number of the circuit boards to be connected is four and a number of channels (a number of bits) is four. In such a case where the bus is composed of a plurality of channels, a plurality of the optical star couplers  10  explained above are used.  
         [0056]     Further, as shown in  FIG. 4 , four optical wiring boards mounted with the optical star coupler  10  are laminated in accordance with that a number of the channels is four.  
         [0057]     As shown in  FIG. 5 , the optical star coupler is embedded in the optical wiring boards. As a POF core wire  33 , for example, a POF core wire with a diameter of 1 mm is used. “The optical fiber core wire” is a core material itself in which a coating layer is not formed from an optical fiber. The particle dispersing light guide path  3  is a rectangular sheet of 4×20×1 (w×1×t) mm. As the optical wiring board base  800 , for example, a PMMA board with a thickness of about 2 mm is used. By cutting a surface of the optical wiring board base  800 , a groove having a depth of 1 mm and a width of 1 mm to 4 mm, in which the POF core wire  33  and the rectangular sheet are arranged, is formed.  
         [0058]     Besides PMMA, for example, a plastic material made of PC (polycarbonate) or polyolefin is used as the optical wiring board base  800 , and the optical wiring board base  800  can be produced by injection molding instead of cutting. The material of the optical wiring board base  800  is not limited to the plastic material, and it may be formed by cutting metal such as A 1 .  
       Fourth Embodiment  
       [0059]     A fourth embodiment of the invention is explained with reference to FIGS.  6  to  8 . As shown in  FIGS. 6 and 7 , the signal processing device is composed of an optical wiring board laminator  12  and a plurality of circuit boards  14 . The optical wiring board laminator  12  has a plurality of optical wiring boards (in this embodiment, eight optical wiring boards) formed into a sheet form, and the optical wiring boards  16  are laminated in a direction of a sheet side surface. The circuit boards  14  are optically connected with the optical wiring boards  16 .  
         [0060]     The particle dispersing light guide body, a first groove  38  for housing first optical fibers  36 , and a groove  42  for housing second optical fibers are formed in the optical wiring board base  28  according to their forms and arrangements. The particle dispersing light guide body  3 , the first optical fibers  36  and the second optical fibers  40  are embedded in the optical wiring board base  28 .  
         [0061]     Second locating members  48  are used for holding one ends  36   a  of the first optical fibers  36  and one ends  40   a  of the second optical fibers properly in position to the particle dispersing light guide body  3 . A locating hole  50  is formed on the second locating members  48 . The one ends  36   a  of the first optical fibers  36  and the one ends  40   a  of the second optical fibers are inserted into the locating groove  50  so as to be opposed to the particle dispersing light guide body  3 . After the optical fibers  36  and the light guide body  44  are pre-located in such a manner, the curing resin  2  is applied to between the optical fibers and the light guide body in order to seal and fix them.  
         [0062]     One ends  36   a  of the first optical fibers  36  extend to rear surfaces  26  of the optical wiring boards  16  and are bent so as to extend to upper surfaces  20  of the optical wiring boards  16 . The one ends  40   a  of the second optical fibers  40  extend to front surfaces  24  of the optical wiring boards  16  and are bent so as to extend to the upper surfaces  20  of the optical wiring boards  16 . The other ends  36   b  and  40   b  connected with the one ends  36   a  and  40   a , respectively, face the upper surface  20  of the optical wiring boards  16 , for example. In other words, the other ends  36   b  and  40   b  of the first optical fibers  36  and the second optical fibers  40  are present in vicinities of one surface of the optical wiring boards  16  and may be arranged in a position where they can be optically connected with the circuit boards  14 .  
         [0063]     In order to bump the other ends  36   b  of the first optical fibers  36  and the other ends  40   b  of the second optical fibers  40  properly against the circuit boards  14 , a locating member  30  is provided. Locating holes  52  are formed on the locating member  30 . The other ends  36   b  of the optical fibers  36  and the other ends  40   b  of the second optical fibers  40  are inserted into the locating holes  52 .  
         [0064]     In this embodiment, the eight optical wiring boards  16  are laminated. The other ends  36   b  of the first optical fibers  36  and the other ends  40   b  of the second optical fibers  40  are arranged so as to be regularly in a line to a surface direction and a laminated direction of the optical wiring boards  16 . The circuit boards  14  are connected to a direction directing to the laminated direction of the optical wiring boards  16  and receive/transmit a light signal of 8 bits with the optical wiring board laminator  12 .  
         [0065]      FIG. 8  illustrates the connected configuration of the circuit boards  14  and the optical wiring boards  16 . The circuit boards  14  have an electric wiring board  54 , and an optical connector  56  provided on one end of the electric wiring board  54 . An optical-electrical converting element  58  and a driving circuit  60  for driving the optical-electrical converting element  58  are provided on a surface of the electric wiring board  54 . The optical-electrical converting element  58  is a light receiving element or a light emitting element. The optical-electrical converting element  58  is arranged on an end of the electric wiring board  54 , and its light receiving or light emitting surface bumps against the other end  36   b  of the first optical fiber  36  and the other end  40   b  of the second optical fiber  40  to connect optically. When optical coupling loss is sufficiently small, a gap may be present between the other end  36   b  of the first optical fiber  36 , the other end  40   b  of the second optical fiber  40  and the optical-electrical converting element  58 .  
         [0066]     In this embodiment, an optical fiber core wire can be used for the first optical fiber  36  and the second optical fiber  40 . As the optical wiring board base  18 , a plastic material such as PMMA, PC or polyolefin is used, and it is produced by cutting or injection molding. The optical wiring board base  18  is not limited to the plastic material, and it can be formed by cutting metal made of A 1 , for example.  
       Fifth Embodiment  
       [0067]     A fifth embodiment of the invention is explained with reference to FIGS.  9  to  11 . The embodiment explains a method of fixing the other end of the first optical fiber and the other end of the second optical fiber in the optical wiring board laminator used in the signal processing device described in the fourth embodiment.  
         [0068]     The first optical fiber  36  is wired along a first optical fiber housing groove  30 , and one end of the first optical fiber  36  is connected with a center on one end surface of the particle dispersing light guide body  3  via the curing resin for connecting. The second optical fibers  40  are wired along second optical fiber housing grooves  32 , and one ends of the second optical fibers  40  are connected with the other end surface of the particle dispersing light guide body  3  on a side opposite to the first optical fiber  36  via the curing resin for connecting. The other ends of the first optical fiber  36  and the second optical fibers  40  protrude from the optical wiring board  18 , and are fixed to ferrules  34 , mentioned later.  
         [0069]     The particle dispersing light guide body  3 , the first optical fiber  36  and the second optical fibers  40  are fixed to the optical wiring board  18  in a following manner in this embodiment. They are embedded in a particle dispersing light guide path housing groove  28 , the first optical fiber housing groove  30  and the second optical fiber housing grooves  32  so as to be sandwiched by the optical wiring boards  18 . The fixing manner is not, however, limited to this. For example, the particle dispersing light guide body  3 , the first optical fiber  36  and the second optical fibers  40  can be fixed to the optical wiring board base by providing fixing members.  
         [0070]     The ferrules  34  are provided along the laminated direction of the optical wiring boards  18 , and optical fiber fixing holes are formed on the ferrules  34 . The other end(s) of the first optical fiber  36  or the second optical fibers  40  is (are) inserted and fixed into the optical fiber fixing hole. A locating hole, through which the other end(s) of the first optical fiber  36  or the second optical fibers  40  is (are) inserted, may be formed on the ferrule  34 , or a V-shaped groove may be provided on the ferrule in order to locate and fix the other end(s) of the first optical fiber  36  or the second optical fibers  40 .  
         [0071]      FIG. 11  illustrates a modified example of the optical wiring board laminator. The other end(s) of the first optical fiber  36  or the second optical fibers  40  is (are) fixed to the ferrules  30 . Because the other ends are connected with the optical connectors  56  on the circuit boards  14  by the ferrules, the optical wiring board base  18  is partially omitted.  
       Sixth Embodiment  
       [0072]     A sixth embodiment of the invention is explained with reference to  FIGS. 12 and 13 . In this embodiment, the optical wiring boards used in the signal processing device are composed of the optical fiber array  40  made of a plurality of optical fibers optically connected with one end surface of the particle dispersing light guide body  3 , and the light reflecting unit  8  provided on the other end surface.  
         [0073]     A particle dispersing light guide body medium housing groove  26  for the particle dispersing light guide body  3 , a reflecting portion housing groove  28  for housing a reflecting portion  22 , and the optical fiber housing groove  30  for housing the optical fibers  40  are formed on one surface of the optical wiring board base  18 . Further, the optical fiber housing groove  30  is formed so as to be connected with a light transmitting medium housing groove  26  on a side opposite to the reflecting portion housing groove  28 . The reflecting portion  8  is allowed to bump against a first end surface  3   a  of the particle dispersing light guide body  3 , and closely fixed to the particle dispersing light guide body  3 . The reflecting portion  8  may be, formed integrally with the particle dispersing light guide body  3  via adhesive or the like.  
         [0074]     In this embodiment, although the particle dispersing light guide body and the reflecting portion  8  are provided separately, the reflecting portion  8  may be formed directly on the one end surface of the particle dispersing light guide body. A 1  is used in order to form the reflection portion directly by sputtering or vapor deposition.  
         [0075]     By housing the optical fibers  40  in the optical fiber housing groove  30  of the optical wiring board base  18 , one end of the optical fiber  40  is arranged so as to be opposed to a second end surface  3   b  of the particle dispersing light guide body  3 , and they are optically connected via the light transmitting curing resin  2  with the gap between the one end and the light guide body  3  being included. The optical fibers  40  are fixed in a bundle form to the connected portion by one end fixing member. The optical fibers  40  have bent portions  40   b  which are bent upward so as to have a predetermined radius of curvature, and the other ends  40   c  of the optical fibers  40  which extend from the one ends via the bent portions  40   b  face the upper surfaces of the optical wiring boards as mentioned above. The other ends  40   c  of the optical fibers  40  are inserted and fixed into an other end fixing member  34  provided on the upper surface of the optical wiring board, so as to be connected with optical-electrical converting elements of the circuit boards  14 . One ends of the circuit boards  14  have optical connectors, and the optical-electrical converting elements in the optical connectors bump against the other ends  40   c  of the optical fibers  40 , respectively, in order to connect optically.  
         [0076]     In this embodiment, the eight optical wiring boards are laminated, the other ends  40   c  of the optical fibers  40  are arranged regularly in a line to the sheet direction and the laminated direction of the optical wiring boards. The circuit boards  14  are connected to the direction directing to the laminated direction of the optical wiring boards so as to receive and transmit a light signal of 8 bits to/from the optical wiring board laminator  12 .  
         [0077]     In the above configuration, light output from an arbitrary optical-electrical converting element of the circuit board  14  is input from the other end  40   c  of either optical fiber connected with the optical-electrical converting element into the optical wiring board. The input light is entered into the particle dispersing light guide body  3  via the optical fiber  40 , reflected by the reflecting portion  8 , and again propagated to the particle dispersing light guide body  3  so as to be output to the circuit board  14  via another optical fiber  40 .  
         [0078]     The light signal transmitting device and the signal processing device described in the embodiments can be applied to, for example, an in-circuit emulator (ICE), a radio communication equipment, a server device and the like.  
         [0079]     A signal can be optically transmitted between components such as a CPU, a memory, and an internal LSI of the in-circuit emulator by the light signal transmitting device and the signal processing device in the embodiments. As a result, delay of signal transmission can be suppressed, and the speed of signal transmission can be increased. Further, the signal is optically transmitted between the internal components in order to prevent distortion of a signal waveform due to ringing and a reflected wave, thereby making timing verification by means of emulation accurate.  
         [0080]     Further, many base stations and exchanges stations are connected via a network, and the base stations transmit and receive signals to/from mobile stations (mobile phones) via a radio communication line. In a mobile communication system such as a mobile phone, many wirings are required for connecting a transmitter-receiver and the signal processing device, and a number of pins of a connector for connecting the boards of the transmitter-receiver and the signal processing device with a case increases according to a wiring quantity. In the base station of such a mobile communication system, the optical star coupler, the optical wiring boards and the light signal transmitting device described in the embodiments are used. As a result, a number of wirings between the device for processing a signal and the device for transmitting/receiving a radio signal can be reduced. Further, a pin neck of a connector for fixing the signal processing device and the radio signal transmitting/receiving device to a back panel is omitted. Consequently, the radio communication device with a reduced force required for punching can be obtained.  
         [0081]     In a prior server system constituted by electric transmission, a transmission speed is limited, and thus it is hard to reduce a number of bits (a number of signal lines, a number of control lines and the like). This causes enlargement of the device. The light signal transmitting device and the signal processing device described in the embodiments are used in such a server system, thereby enabling high-speed signal transmission, and a larger scale of the system is structured. For this reason, an optical server system which connects a plurality of cabinets can be provided.  
         [0082]     As explained above, as to the light signal transmitting device of the invention, even in a light signal transmitting device in which a diffusing area is provided on an incident side for signal light, reliability of connection to optical fibers can be improved.  
         [0083]     Further, according to the light signal transmitting device of the invention, an optical bus system, in which resistance to environmental conditions such as temperature change and dust is good, can be constituted.