JP2007094211A - Optical transmitting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitting system for stably transmitting data regardless of a relative position of an optical fiber and a light receiving element even when the optical fiber has a fluctuating curved state and a short optical path length. <P>SOLUTION: The optical transmitting system comprises a means for enlarging a distribution angle of light from a light emitting element. The optical transmitting system comprises the light emitting element, and an angle enlarging means enlarging a distribution angle of light incident on an incident end from the light emitting element and emitting the angle-enlarged light from the emission end. The distribution angle is an angle made from a straight line connecting a point of optical intensity of a half of the maximum optical intensity and the light source or the optical element, and the optical axis, in a normal face to the optical axis and a far field pattern (hereafter, referred to as FFP) of light emitted from an optical element. The angle enlarging means emits by enlarging the distribution angle of light from the light emitting element incident on the incident end. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical transmission device that makes light incident on an optical fiber.

  In recent years, as mobile phones that have become widespread, folding type, slide type, and rotary type mobile phones have come to be frequently used for convenience and other reasons during use and carrying. In the case of a foldable, slide-type, or rotary-type mobile phone, modules such as a communication function unit, an amplifier circuit unit, and a display circuit unit are distributed and arranged in a plurality of cases. Wiring connecting the arranged modules is required to be flexible and strong enough to withstand driving.

  In addition, wiring between each module requires high-speed data transmission due to the multi-functionality of mobile phones such as music playback function, video playback function, and photography function, countermeasures against electromagnetic interference with external devices, and demands for long-term use. Therefore, low power consumption is required.

An attempt has been made to use an optical fiber as a wiring that satisfies these requirements (for example, see Patent Document 1).
JP2003-244295A.

  When an optical fiber is used for wiring between modules, the module is equipped with a light emitting element that enters light into the optical fiber and a light receiving element that receives light emitted from the optical fiber, and the light receiving element emits light that propagates through the optical fiber. Data transmission is performed by receiving light from the element. Further, in order to perform stable data transmission, it is necessary to align the optical axes among the light emitting element, the optical fiber, and the light receiving element. In the following description, “arrange the optical axes” is abbreviated as “alignment”.

  Alignment is facilitated by increasing the core diameter of the optical fiber. However, if the core diameter of the optical fiber is large, light is incident from a position different from the central axis of the optical fiber due to an assembly error between the light emitting element and the optical fiber. Sometimes.

  When the optical path length of the optical fiber is long, even if light is incident from a position different from the central axis of the optical fiber, the light is disturbed during propagation through the optical fiber. “Near field pattern” is abbreviated as “NFP”).

  However, in the case of an optical fiber that is as short as several centimeters as between mobile phone modules and has a sharp bend with a curvature radius of about 5 mm, if light enters from a position different from the central axis of the optical fiber, Since the light is not sufficiently disturbed during propagation, the NFP at the other end of the optical fiber is non-uniform.

  On the other hand, the diameter of the light receiving surface of the light receiving element is required to be small in order to perform high-speed data communication. When the diameter of the light receiving surface of the light receiving element is smaller than the diameter of the core of the optical fiber, the light receiving element cannot receive all of the light emitted from the other end of the optical fiber, Only light emitted from a part can be received.

  Therefore, when there is an assembly error between the light emitting element and the optical fiber, and the NFP at the other end of the optical fiber is not uniform, the light receiving element cannot receive a sufficient amount of light depending on the relative position between the optical fiber and the light receiving element. Sometimes.

  Furthermore, since the bending state of the optical fiber varies depending on the operation such as folding and rotation of the mobile phone, the NFP also varies depending on the bending state.

  Therefore, even if the alignment accuracy of the light emitting element, the optical fiber, and the light receiving element is improved and the light receiving element is aligned with the NFP at the other end of the optical fiber, the NFP changes due to the fluctuation of the bent state of the optical fiber. May not receive a sufficient amount of light.

  The present invention has been made to solve the above-described problems, and even with an optical fiber having a short optical path length and a variable bending state, stable data transmission can be performed regardless of the relative position between the optical fiber and the light receiving element. An object is to provide an optical transmitter.

  In order to achieve the above object, an optical transmission apparatus according to the present invention includes means for expanding a distribution angle of light from a light emitting element.

  Specifically, the present invention is an optical transmission device comprising: a light emitting element; and an angle expanding unit that expands a distribution angle of light from the light emitting element incident on the incident end and emits the light from the output end.

  The distribution angle is a maximum light intensity of 2 in a far field pattern of light emitted from the light source or the optical element in a plane perpendicular to the optical axis (hereinafter, “far field pattern” is abbreviated as “FFP”). It is an angle formed by a straight line connecting the point of the light intensity of 1 and the light source or the optical element and the optical axis.

  The angle expanding means expands the distribution angle of light from the light emitting element incident on the incident end and emits the light.

  If the exit end of the angle expanding means of the optical transmission device is connected to one end of an optical fiber, the light from the light emitting element is incident on the optical fiber with an increased distribution angle. The angle of incidence of the light at the interface with is small. By reducing the incident angle, the number of times of total reflection of light propagating in the optical fiber increases, and disturbance of the propagating light is promoted.

  As a result of enlarging the light distribution angle, the optical transmitter can make the NFP uniform at the other end of the optical fiber even if the optical path length of the optical fiber is short. Further, even if the optical fiber is bent, the optical transmission device can alleviate the NFP bias at the other end of the optical fiber.

  Therefore, since the light receiving element connected to the other end of the optical fiber can receive a sufficient amount of light even if the light receiving surface is small, the present invention is an optical fiber whose optical path length is short and the bending state varies. It is possible to provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element.

  The optical transmission device according to the present invention further includes a multimode optical fiber having one end connected to the emission end of the angle enlarging unit and receiving light from the emission end of the angle enlarging unit as incident light.

  By providing the optical fiber at the exit end of the angle enlarging means, the number of times that the light from the angle enlarging means that has expanded the distribution angle is totally reflected in the optical fiber increases, and the disturbance of the light is promoted. Is done.

  As a result of enlarging the light distribution angle, even if the optical path length of the optical fiber is short, the NFP at the other end of the optical fiber is made uniform. Even if the optical fiber is bent, the NFP bias at the other end of the optical fiber is alleviated.

  Therefore, since the light receiving element connected to the other end of the optical fiber can receive a sufficient amount of light even if the light receiving surface is small, the present invention is an optical fiber whose optical path length is short and the bending state varies. It is possible to provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element.

  The distribution angle of light from the angle expanding means of the optical transmitter according to the present invention is incident on the one end of the optical fiber, and the amount of incident light propagating through the optical fiber by 50 mm is incident on one end of the optical fiber. It is preferable that the angle is 10% or more and 90% or less of the amount of incident light.

  The incident angle of the incident light at the interface between the core and the clad of the optical fiber becomes smaller as the distribution angle expanded by the angle expanding means is closer to 90 °, and the total number of reflections of the incident light in the optical fiber is Since it increases, the effect of this invention becomes large.

  On the other hand, in the optical fiber, light having an incident angle smaller than the critical angle determined by the refractive indexes of the core and the clad is not reflected at the interface between the core and the clad and is transmitted to the clad side. That is, when the distribution angle of the light is large, light having an incident angle smaller than the critical angle among the incident light increases, and transmission loss in the optical fiber increases. As a result of enlarging the light distribution angle, the light intensity is reduced even if the NFP bias at the other end of the optical fiber is mitigated. Therefore, the light receiving element disposed at the other end of the optical fiber receives a sufficient amount of light. become unable.

  In order to stably transmit data in an optical fiber, it is necessary to achieve both relaxation of NFP bias at the other end of the optical fiber and reduction in transmission loss.

  Accordingly, by determining the distribution angle that the angle expanding means expands so that the ratio of the amount of the incident light propagating through the optical fiber by 50 mm is within the range, the present invention can shorten the optical path length and change the bending state. Therefore, it is possible to provide an optical transmission device that can stably transmit data regardless of the relative positions of the optical fiber and the light receiving element.

  The light distribution angle from the angle expanding means of the optical transmission apparatus according to the present invention is preferably larger in the range of 0 ° to 30 ° than the limit angle of the optical fiber.

  The critical angle of the optical fiber is a value obtained by subtracting a critical angle determined by the refractive indexes of the core and the clad from 90 °.

  As described above, it is necessary to achieve both relaxation of NFP bias at the other end of the optical fiber and reduction of transmission loss. Therefore, taking into account that the distribution angle of light from the angle expanding means is changed when entering the optical fiber, it is preferable that the distribution angle expanded by the angle expanding means is within the above range.

  Therefore, the present invention can provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element, even if the optical path length is short and the bending state is changed. .

  The angle expanding means of the optical transmission device according to the present invention refracts light from the light emitting element incident on the incident end, expands a distribution angle of light from the light emitting element, and emits the light from the output end. An optical system having a lens can be obtained.

  The light from the light source is refracted away from the optical axis when transmitted through the concave lens. The angle tilting unit can adjust the distribution angle of light emitted from the exit end by adjusting the size and thickness of the concave lens.

  Therefore, according to the present invention, the distribution angle of light from the light emitting element can be expanded, and even in an optical fiber having a short optical path length and a bent state, the optical fiber and the light receiving element can be stably controlled regardless of relative positions. An optical transmission device capable of data transmission can be provided.

  The angle expanding means of the optical transmission device according to the present invention refracts light from the light emitting element incident on the incident end, expands a distribution angle of light from the light emitting element, and emits the light from the output end. An optical system having a mold lens can be obtained.

  The light from the light source is refracted in the direction of the optical axis when transmitted through the convex lens and concentrated at one point. Thereafter, the light diffuses away from the optical axis. The angle enlarging means can obtain the same operation and effect as the angle tilting means having the concave lens by adjusting the size and thickness of the convex lens.

  Therefore, according to the present invention, the distribution angle of light from the light emitting element can be expanded, and even in an optical fiber having a short optical path length and a bent state, the optical fiber and the light receiving element can be stably controlled regardless of relative positions. An optical transmission device capable of data transmission can be provided.

  The angle enlarging means of the optical transmission device according to the present invention reflects the light from the light emitting element incident on the incident end, expands the distribution angle of the light from the light emitting element, and emits the light from the emission end. An optical system having a reflecting mirror can be obtained.

  The light from the light source is reflected by the concave reflector and concentrated at one point. Thereafter, the light diffuses away from the optical axis. The angle enlarging means can obtain the same operation and effect as the angle tilting means having the concave lens by adjusting the size and thickness of the concave reflecting mirror.

  Therefore, according to the present invention, the distribution angle of light from the light emitting element can be expanded, and even in an optical fiber having a short optical path length and a bent state, the optical fiber and the light receiving element can be stably controlled regardless of relative positions. An optical transmission device capable of data transmission can be provided.

  The angle enlarging means of the optical transmission apparatus according to the present invention reflects a light from the light emitting element incident on the incident end, expands a distribution angle of the light from the light emitting element, and emits the light from the emission end. An optical system having a type reflecting mirror can be obtained.

  The light from the light source is reflected by the convex reflector, and the light diffuses away from the optical axis. The angle enlarging means can obtain the same operation and effect as the angle tilting means having the concave lens by adjusting the size and thickness of the convex reflecting mirror.

  Therefore, according to the present invention, the distribution angle of light from the light emitting element can be expanded, and even in an optical fiber having a short optical path length and a bent state, the optical fiber and the light receiving element can be stably controlled regardless of relative positions. An optical transmission device capable of data transmission can be provided.

  The angle enlarging means of the optical transmitter according to the present invention has an optical waveguide region in which an area of a cross section perpendicular to the light propagation direction monotonously decreases from the incident end to the exit end, and enters the incident end. A tube-type waveguide that propagates light from the light-emitting element and expands the distribution angle of light from the light-emitting element to be emitted from the emission end can be obtained.

  The tubular waveguide guides light from the light emitting element coupled to the incident end with a reflecting surface surrounding a light propagation region to the emitting end by specular reflection or total reflection.

  Further, the shape of the tubular waveguide is a tapered shape in which the cross-sectional area of the optical waveguide region decreases from the incident end to the exit end, and the light incident from the incident end undergoes specular reflection or total reflection. In addition, since the incident angle with respect to the reflecting surface becomes small, the distribution angle of the light emitted from the emitting end becomes large.

  Therefore, the present invention can provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element, even if the optical path length is short and the bending state is changed. .

  The present invention is a multimode type light in which a light emitting element and a surface of one end where light from the light emitting element is incident as incident light have a concave shape that refracts the light from the light emitting element so as to expand a distribution angle. And an optical transmission device including a fiber.

  Since the surface of the one end of the optical fiber is concave, the light incident on the one end is refracted so as to increase the distribution angle. As a result of enlarging the light distribution angle, even if the optical path length of the optical fiber is short, the NFP at the other end of the optical fiber is made uniform. Even if the optical fiber is bent, the NFP bias at the other end of the optical fiber is alleviated.

  Therefore, the present invention can provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element, even if the optical path length is short and the bending state is changed. .

  The present invention is a multimode type light in which a light-emitting element and a surface of one end where light from the light-emitting element is incident as incident light have a convex shape that refracts light from the light-emitting element so as to expand a distribution angle. And an optical transmission device including a fiber.

  Since the surface of the one end of the optical fiber is convex, the light incident on the one end is refracted and converges to one point, and then diffuses so as to increase the light distribution angle. As a result of enlarging the light distribution angle, the optical transmission device can obtain the same effect as an optical transmission device including an optical fiber having a concave surface at the one end.

  Therefore, the present invention can provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element, even if the optical path length is short and the bending state is changed. .

  The optical fiber is described as a step index type optical fiber that propagates by totally reflecting light at the interface between the clad and the core. However, the optical fiber is a gray fiber that propagates by continuously bending the light path. Similar effects can be obtained with a ted index optical fiber.

  The present invention can provide an optical transmitter capable of stably transmitting data regardless of the relative position between the optical fiber and the light receiving element, even if the optical path length is short and the bending state is changed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below.

(Embodiment 1)
One embodiment according to the present invention is an optical transmission device that includes a light emitting element and an angle expanding unit that expands a distribution angle of light from the light emitting element incident on an incident end and emits the light from the emitting end.

  FIG. 1 shows a conceptual diagram of an optical transmission apparatus 901 that is one embodiment according to the present invention. The optical transmitter 901 includes a light emitting element 11 and an angle enlarging means 12. In addition, what can be realized by a normal technique such as a power source, a peripheral circuit, and a substrate necessary for the light emitting element 11 is not illustrated in FIGS. 1 and 2 and subsequent drawings.

  The light emitting element 11 converts an electrical signal into light and emits light A from the surface toward the outside. An LED or a surface emitting LD can be used as the light emitting element 11. A VCSEL can be exemplified as the surface emitting LD.

  The angle enlarging means 12 emits the light B with the distribution angle of the light incident from the incident end 15 expanded from the output end 18. As will be described later, the angle expanding means 12 can set the light B to a desired distribution angle.

  The light distribution angle will be described with reference to FIG. FIG. 2 shows a plane including the light source 21 and the optical axis 22 of the light from the light source 21. The plane 24 is a plane perpendicular to the optical axis 22. The light intensity distribution 25 is a light intensity distribution in the plane 24 of light from the light source 21. In the light intensity distribution 25, 27 is the maximum light intensity, and 28 is a light intensity that is one half of the maximum light intensity 27. An angle γ formed by a straight line 20 connecting the point 29 of the light intensity 28 on the plane 24 and the light source 21 and the optical axis 22 is defined as a distribution angle.

  The angle enlarging means 12 can have the following structure.

  The angle expanding means of the optical transmission device according to the present invention refracts light from the light emitting element incident on the incident end, expands a distribution angle of light from the light emitting element, and emits the light from the output end. An optical system having a lens can be obtained.

  An example of the internal structure of the angle enlarging means 12 is shown in FIG. The angle enlarging means 12 includes a housing 30, an entrance end 15, an exit end 18, and a concave lens 31. In FIG. 3, the same reference numerals as those used in FIG. 1 indicate the same configuration or the same light.

  The incident end 15, the concave lens 31, and the emission end 18 are arranged in the housing 30 so that the light from the incidence end 15 can irradiate the concave lens 31 and the light from the concave lens 31 can be emitted from the emission end 18. The light transmitted through the concave lens 31 is refracted and the distribution angle is expanded. The distribution angle of the light from the concave lens 31 can be adjusted by adjusting the size of the concave lens 31 and the curved state of the lens surface.

  Accordingly, the angle enlarging means 12 emits the light B, in which the distribution angle of the light A incident on the incident end 15 is expanded, from the emission end 18.

  The angle expanding means of the optical transmission device according to the present invention refracts light from the light emitting element incident on the incident end, expands a distribution angle of light from the light emitting element, and emits the light from the output end. An optical system having a mold lens can be obtained.

  Another example of the internal structure of the angle enlarging means 12 is shown in FIG. The angle enlarging means 12 includes a housing 30, an entrance end 15, an exit end 18, and a convex lens 41. In FIG. 4, the same reference numerals as those used in FIG. 1 indicate the same configuration or the same light.

  The incident end 15, the convex lens 41, and the exit end 18 are arranged in the housing 30 so that the light from the entrance end 15 irradiates the convex lens 41 and the light from the convex lens 41 can exit from the exit end 18. Is done. The light transmitted through the convex lens 41 is refracted and converged and then diffused. The distribution angle of light from the convex lens 41 can be adjusted by adjusting the size of the convex lens 41 and the position of the focal point.

  Accordingly, the angle enlarging means 12 emits the light B, in which the distribution angle of the light A incident on the incident end 15 is expanded, from the emission end 18.

  The angle enlarging means of the optical transmission device according to the present invention reflects the light from the light emitting element incident on the incident end, expands the distribution angle of the light from the light emitting element, and emits the light from the emission end. An optical system having a reflecting mirror can be obtained.

  Another example of the internal structure of the angle enlarging means 12 is shown in FIG. The angle enlarging means 12 includes a housing 30, an entrance end 15, an exit end 18 reflecting mirror 55, and a concave reflecting mirror 51. In FIG. 5, the same reference numerals as those used in FIG. 1 indicate the same configuration or the same light.

  The reflecting mirror 55 is a mirror that specularly reflects incident light.

  The light from the incident end 15 is reflected by the reflecting mirror 55 to irradiate the concave reflecting mirror 51, and the light from the concave reflecting mirror 51 can be emitted from the emitting end 18, so that the incident end 15, the reflecting mirror 55, and the concave reflecting mirror can be emitted. 51 and the emitting end 18 are disposed in the housing 30. The light reflected by the concave reflecting mirror 51 is diffused after being converged. By adjusting the size of the concave reflecting mirror 51 and the position of the focal point, the distribution angle of light from the concave reflecting mirror 51 can be adjusted.

  Accordingly, the angle enlarging means 12 emits the light B, in which the distribution angle of the light A incident on the incident end 15 is expanded, from the emission end 18.

  The angle enlarging means of the optical transmission apparatus according to the present invention reflects a light from the light emitting element incident on the incident end, expands a distribution angle of the light from the light emitting element, and emits the light from the emission end. An optical system having a type reflecting mirror can be obtained.

  Another example of the internal structure of the angle enlarging means 12 is shown in FIG. The angle enlarging means 12 includes a housing 30, an incident end 15, an exit end 18 reflecting mirror 55, and a convex reflecting mirror 61. In FIG. 6, the same reference numerals as those used in FIGS. 1 and 5 indicate the same configuration or the same light.

  The light from the incident end 15 is reflected by the reflecting mirror 55 to irradiate the convex reflecting mirror 61, and the light from the convex reflecting mirror 61 can be emitted from the emitting end 18. The mold reflecting mirror 61 and the emitting end 18 are disposed in the housing 30. The light reflected by the convex reflector 61 is diffused so that the distribution angle is enlarged. The distribution angle of light from the convex reflector 61 can be adjusted by adjusting the size of the convex reflector 61 and the curved state of the reflecting surface.

  Accordingly, the angle enlarging means 12 emits the light B, in which the distribution angle of the light A incident on the incident end 15 is expanded, from the emission end 18.

  The angle enlarging means of the optical transmitter according to the present invention has an optical waveguide region in which an area of a cross section perpendicular to the light propagation direction monotonously decreases from the incident end to the exit end, and enters the incident end. A tube-type waveguide that propagates light from the light-emitting element and expands the distribution angle of light from the light-emitting element to be emitted from the emission end can be obtained.

  Another example of the internal structure of the angle enlarging means 12 is shown in FIG. The angle enlarging means 12 includes a housing 30, an incident end 15, an exit end 18, and a tubular waveguide 71. In FIG. 7, the same reference numerals as those used in FIGS. 1 and 3 indicate the same configuration or the same light.

  The tube-type waveguide 71 is a hollow tube that propagates light from the incident end 15 and exits from the exit end 18. A reflection surface 73 that reflects light is disposed on the inner wall of the tubular waveguide 71. The reflection surface 73 can be a reflection mirror that specularly reflects light.

  The tubular waveguide 71 may have a structure in which a medium having a high refractive index is covered with a medium having a low refractive index. The light is totally reflected at the interface between the medium having a high refractive index and the medium having a low refractive index. Therefore, the interface can be the reflective surface 73.

  In the incident end 15, the emission end 18, and the tube-shaped waveguide 71, light from the incident end 15 is incident on the optical waveguide region of the tube-shaped waveguide 51, and light from the tube-shaped waveguide 71 is emitted from the emission end 18. The position is determined so that it can be arranged in the housing 30.

  Since the optical waveguide region of the tubular waveguide 71 has a tapered shape, the light distribution angle is expanded by the reflection of light from the incident end 15 by the reflection surface 73.

  Accordingly, the angle enlarging means 12 emits the light B, in which the distribution angle of the light A incident on the incident end 15 is expanded, from the emission end 18.

  If one end of the optical fiber is connected to the output end 18 of the optical transmitter 901 and the light B whose distribution angle is expanded is incident, the number of times that the light B is totally reflected during the propagation of the optical fiber increases, and the disturbance of the light is promoted. Is done. As a result, the optical transmitter 901 can alleviate the NFP bias at the other end even if the optical fiber is short and bent.

  Therefore, since the optical transmission device 901 can irradiate the light receiving element disposed at the other end of the optical fiber with a light amount sufficient for reception, even if the optical fiber has a short optical path length and a bent state, Stable data transmission is possible regardless of the relative position between the fiber and the light receiving element.

(Embodiment 2)
This embodiment preferably further includes a multi-mode optical fiber having one end connected to the exit end of the angle enlarging unit and entering light from the exit end of the angle enlarging unit as incident light.

  FIG. 8 shows a conceptual diagram of an optical transmitter 908 according to another embodiment of the present invention. The optical transmission device 908 includes the light emitting element 11, the angle expanding means 12, and the optical fiber 85. In FIG. 8, the same reference numerals as those used in FIG. 1 indicate the same configuration or the same light.

  The optical fiber 85 is a multimode type optical fiber. The optical fiber 85 may be a glass fiber, a plastic fiber (POF), or an optical fiber having a glass core and a plastic cladding. The length of the optical fiber can be exemplified by 5 mm or more and 300 mm or less, and preferably 5 mm or more and 50 mm or less.

  The optical transmission device 908 connects the emission end 18 of the optical transmission device 901 and one end 86 of the optical fiber 85. As described with reference to FIG. 1, the optical transmission device 901 emits the light B whose distribution angle is enlarged from the emission end 18. The light B enters the one end 86 of the optical fiber 85 as incident light, propagates through the core of the optical fiber 85, and exits from the other end 87.

  The light B that has entered the optical fiber 85 as incident light propagates through the optical fiber 85 in the same manner as the optical fiber described with reference to the optical transmission device 901 in FIG. 1, and therefore the optical transmission device 908 has a short optical fiber 85 and is bent. Also, the NFP bias at the other end 87 can be alleviated.

  Therefore, the optical transmission device 908 can obtain the same effect as that of the optical transmission device 901 of FIG. 1, and even if the optical fiber has a short optical path length and a bent state, the relative relationship between the optical fiber and the light receiving element can be obtained. Stable data transmission regardless of position.

  In addition, it is preferable that the light distribution angle from the angle enlarging means is larger than the limit angle of the optical fiber in the range of 0 ° to 30 °.

  In order to promote disturbance of the light B, the distribution angle of the light B from the angle expanding means 12 is set to 0 ° or more, more preferably D2 ° or more.

光ファイバ内を伝搬する光のうち、前記界面に入射する角度θ_１が限界角度θ_ｃより大きい光はクラッド８５ｂ側へ透過するため伝送損失を発生させる。 FIG. 9 is a diagram for explaining conditions under which light is totally reflected at the interface between the core 85a and the clad 85b of the optical fiber 85. As shown in FIG. In FIG. 9, the same reference numerals as those used in FIGS. 1 and 8 indicate the same configuration or the same light. Reference numeral 91 denotes an optical path of arbitrary light propagating through the optical fiber 85. If the refractive index of the core 85a is n ₁ and the refractive index of the clad 85b is n ₂ , an angle smaller than the limit angle θ _c defined by Equation 1 in order for light to be totally reflected at the interface of the optical fiber 85. It is necessary to enter the interface at θ ₁ .

Of the light propagating in the optical fiber, light having an angle θ ₁ incident on the interface larger than the limit angle θ _c is transmitted to the clad 85 _b side, causing transmission loss.

  Therefore, in order to reduce the transmission loss of light in the optical fiber 85, it is preferable that the distribution angle of the light B from the angle expanding means 12 is 30 ° or less.

Furthermore, in order to further reduce the transmission loss of light in the optical fiber 85, the angle theta ₁ of all light to smaller than a limit angle theta _c in the optical fiber 85, light B from the angle enlarging means 12 distribution angle Is more preferably E2 ° or less.

  When the amount of incident light A is large and allows a constant transmission loss, the distribution angle of light from the angle expanding means is incident on the one end of the optical fiber and propagates through the optical fiber by 50 mm. You may determine in the range of the angle from which the light quantity of incident light becomes 10% or more and 90% or less of the light quantity of the said incident light which injects into the end of the said optical fiber.

  That is, the distribution angle of the light B from the angle expanding means 12 is such that the light quantity of light emitted from the other end 87 of the optical fiber 85 is the optical fiber 85 in the optical fiber 85 having a length from one end 86 to the other end 87 of 50 mm. It is preferable that it be determined to be 10% or more and 90% or less of the light amount of the light B incident on one end 86, and it is more preferable that it be determined to be α2% or more and β2% or less.

(Embodiment 3)
In another embodiment of the present invention, a light emitting element and a surface of one end where light from the light emitting element is incident as incident light have a concave shape that refracts light from the light emitting element so as to expand a distribution angle. An optical transmission device comprising a multimode type optical fiber.

  FIG. 10 shows a conceptual diagram of an optical transmission apparatus 910 that is another embodiment according to the present invention. FIG. 10 is a diagram of a cut surface at a plane including the central axis 85 c of the optical fiber 85. The optical transmission device 910 includes a light emitting element 11 and an optical fiber 85. 10, the same reference numerals as those used in FIGS. 1 and 8 indicate the same configuration and the same light.

  The configuration of the optical transmission device 910 is the same as the configuration of the optical transmission device 901 in FIG. 1, but the surface of the one end 86 of the optical fiber 85 is processed into a concave shape. When the light A from the light emitting element 11 enters the core 85a from the one end 86, the distribution angle is enlarged. Since the light A having an increased distribution angle propagates through the optical fiber 85 as incident light, the optical transmission device 910 can obtain the same effects as those described in the optical transmission device 901 of FIG.

  Therefore, the optical transmission device 910 can stably transmit data regardless of the relative position between the optical fiber and the light receiving element, even if the optical fiber has a short optical path length and a bent state.

(Embodiment 4)
In another embodiment according to the present invention, a light emitting element and a surface of one end where the light from the light emitting element is incident as incident light have a convex shape that refracts the light from the light emitting element so as to expand a distribution angle. An optical transmission device comprising a multimode type optical fiber.

  FIG. 11 shows a conceptual diagram of an optical transmission apparatus 911 which is another embodiment according to the present invention. FIG. 11 is a cross-sectional view of the optical fiber 85 taken along the plane including the central axis 85c. The optical transmission device 911 includes a light emitting element 11 and an optical fiber 85. 10, the same reference numerals as those used in FIGS. 1, 8, and 10 indicate the same configuration and the same light.

  The configuration of the optical transmission device 911 is the same as the configuration of the optical transmission device 901 in FIG. 1, but the surface of the one end 86 of the optical fiber 85 is processed into a convex shape. The light A from the light emitting element 11 is incident on the core 85a from one end 86, and then converges to one point and diffuses so that the distribution angle is expanded. Since the light A having an increased distribution angle propagates through the optical fiber 85 as incident light, the optical transmission device 911 can obtain the same effects as those described in the optical transmission device 901 of FIG.

  Therefore, even if the optical transmission device 911 is an optical fiber having a short optical path length and a bent state, the optical transmission device 911 can stably transmit data regardless of the relative position between the optical fiber and the light receiving element.

(Simulation result 1)
The dependence of the incident position and distribution angle of the light A at the one end 86 of the optical fiber 85 on the NFP at the other end 87 of the optical fiber 85 will be described in more detail with reference to simulation results.

  The optical transmitter that performs the simulation is the optical transmitter 908 in FIG. FIG. 12 shows a diagram in which the light receiving element 160 is connected to the other end 87 of the optical fiber 85 of the optical transmitter 908. In FIG. 12, the same reference numerals as those used in FIGS. 1 and 8 indicate the same configuration and the same light.

  The simulation conditions are as follows. The optical fiber 85 has a core diameter of 0.24 cm, a diameter to the surface of the cladding covering the core of 0.25 cm, and an optical path length from one end 86 to the other end 87 is 1 cm. In order to give the optical fiber 85 a bent state, the optical fiber 85 is bent uniformly from one end 86 to the other end 87 along a circle having a radius of 5 mm.

  The central axis direction of the optical fiber 85 is defined as the Z direction, and the direction in which light propagates from the one end 86 to the other end 87 is defined as the positive Z direction. Further, in the cross section perpendicular to the Z direction of the optical fiber 85 (hereinafter, “the cross section perpendicular to the Z direction of the optical fiber” is abbreviated as “optical fiber cross section”), the radial direction of the circle having the radius of 5 mm is the X direction. And the center direction of the circle is the positive direction of X. Further, in the cross section of the optical fiber, a direction perpendicular to the X direction and the Z direction is defined as a Y direction, and a front direction from the back side in FIG. 12 is defined as a positive direction of Y.

  FIG. 13 shows the position of the optical axis of the light B incident on the one end 86 where the simulation is performed. In FIG. 13, the same reference numerals as those used in FIGS. 1, 8, and 12 have the same configuration and the same function. In FIG. 13, the Z direction is positive from the front side of the drawing to the back side.

  B-0, B-1, B-2, B-3, and B-4 are optical axis positions of the light B incident on one end 86, respectively. If the intersection of the central axis of the optical fiber 85 and the surface of the one end 86 is the origin (0, 0), the optical axis position B-0 is the coordinate (0, 0), and the optical axis position B-1 is the coordinate (0. 1, 0), the optical axis position B-2 is coordinates (0, 0.1), the optical axis position B-3 is coordinates (-0.1, 0), and the optical axis position B-4 is coordinates (0,-). 0.1). The unit of coordinates is mm.

Table 1 shows a list of simulation conditions for performing a simulation with the optical transmitter 908. Condition No. The simulation conditions marked with * in the column indicate comparative examples.

  For example, condition no. 8 is a simulation condition in which the light B obtained by enlarging the distribution angle of the light A by 1.7 times by the angle enlarging means 12 is incident on the optical fiber 85 from the position of the coordinates (0, −0.1) of the surface of the one end 86. It means that there is.

  The results of NFP at the other end 87 of the optical fiber 85 simulated under the simulation conditions shown in Table 1 are shown in FIGS. 14 to FIG. 21, the light intensity of NFP is displayed in hue, indicating that the light intensity increases from brown to white.

  FIG. 1 is a result of simulation. Due to the bending of the optical fiber 85, the light B is biased in the negative X direction, and the NFP at the other end 87 has a strong light intensity in the negative X direction.

  FIG. 2 is a result of simulation. The light B propagating due to the bending of the optical fiber 85 diffuses in the negative X direction, and the NFP bias at the other end 87 is alleviated.

  FIG. 3 is a result of simulation. The light B propagating due to the bending of the optical fiber 85 is further biased in the negative X direction, and the NFP at the other end 87 is largely biased in the negative X direction.

  FIG. 4 is a result of simulation. Similarly to the reason described with reference to FIG. 15, the NFP at the other end 87 has a strong light intensity in the negative direction of X. Since the light B is incident from the negative Y position, the NFP at the other end 87 also has a strong light intensity in the negative Y direction.

  18 to 21 show the condition No. 1 in which the distribution angle of the light B is enlarged. No. 5 to Condition No. 8 shows the result of simulation. 14 and 18, FIG. 15, FIG. 19, FIG. 16 and FIG. 20, and FIG. 17 and FIG. 21, where the incident position of the light B is equal, Since the number of total reflections increases in the core 85a, light is distributed near the center of the other end 87 and in the positive X direction, and the NFP bias is alleviated.

(Simulation result 2)
Next, the simulation result about the light quantity which a light receiving element can receive on the simulation conditions shown in Table 1 is shown.

  The light receiving element 160 is simulated as a photodiode (PD) having a circular light receiving surface 161 having a diameter of 0.1 cm. Similar to the relationship between the light emitting element 11 and the optical fiber 85, even if the light receiving element 11 and the optical fiber 85 are aligned, the central axis of the optical fiber 85 and the center position of the light receiving surface 161 of the light receiving element 160 may be different. .

  FIGS. 22 and 23 show the relative positions of the output end 87 of the optical fiber 85 and the light receiving surface 161 of the light receiving element 160 for performing the simulation. FIG. 22 is a diagram when there is no assembly error between the optical fiber 85 and the light receiving element 160, and the center of the light receiving surface 161 of the light receiving element 160 is at the origin of the surface of the other end 87. FIG. 23 is a view in the case where there is an assembly error between the optical fiber 85 and the light receiving element 160, and the center of the light receiving surface 161 of the light receiving element 160 is at the coordinates (0.05, 0) of the surface of the other end 87. The coordinate unit is mm.

In the case of FIG. 1 to condition no. Table 2 shows the result of the simulation of No. 8. In Table 2, the amount of incident light A incident on the optical fiber 85 and the amount and ratio of light received by the light receiving element 160 are shown as attenuation amounts, and the unit is dB.

  Condition No. 1 to condition no. From the simulation result of No. 4, when the distribution angle of the light B is equal to the distribution angle of the light A, the amount of attenuation differs greatly depending on the optical axis position of the light B. When the light B is incident from the optical axis position B-3, the attenuation amount is the largest and becomes −43.14 dB. That is, the attenuation amount is greatly affected by the bending of the optical fiber 85 as described with reference to FIGS.

  Next, condition no. 1 and condition no. 5, Condition No. 2 and condition no. 6 and condition no. 4 and condition no. 8, in the case where the relative position between the optical fiber 85 and the light receiving element 160 is as shown in FIG. 22, the attenuation amount under the condition that the distribution angle of the light B is enlarged is that the distribution angle of the light B is the same as the distribution angle of the light A. This is equivalent to the attenuation amount under the same condition, and even if the distribution angle of the light B is enlarged, the influence on the light received by the light receiving element 160 is small.

  On the other hand, Condition No. 7 is the same as the condition No. 7. 3, and the distribution angle of the light B is expanded, so that the light receiving element 160 can increase the amount of received light and perform stable optical communication.

In the case of FIG. 23, the condition No. 1 to condition no. Table 3 shows the result of the simulation of No. 8. Similar to the case of FIG. 22, the evaluation is made by the attenuation.

  Condition No. in Table 2 and Table 3 1 to condition no. If the simulation results of 4 are compared, the attenuation amount of the light B from any optical axis position is large. In particular, the attenuation amount when the light B is incident from the optical axis position B-3 is as large as −131.92 dB.

  As a result, when the distribution angle of the light B is equal to the distribution angle of the light A, the attenuation amount is greatly affected by the assembly error of the light emitting element 11, the optical fiber 85, and the light receiving element 160 and the bending of the optical fiber 85, The light receiving element 160 indicates that the amount of light that can be received decreases. That is, it becomes impossible to transmit data stably between modules.

  Next, Condition No. 1 and condition no. 5, Condition No. 2 and condition no. 6, Condition No. 3 and condition no. 7 and condition no. 4 and condition no. 8, in the case where the relative position between the optical fiber 85 and the light receiving element 160 is FIG. 23, the attenuation amount under the condition that the distribution angle of the light B is enlarged is that the distribution angle of the light B is the same as the distribution angle of the light A. This is an improvement over the attenuation under equal conditions. In particular, condition no. 7 is the same as the condition No. 7. This is significantly improved from the above-mentioned attenuation amount of 3.

  Therefore, by expanding the distribution angle of the light B and entering the optical fiber, the influence of the assembly error of the light emitting element 11, the optical fiber 85, and the light receiving element 160 can be reduced, and the influence of the bent state of the optical fiber can also be reduced. Therefore, even if the optical transmission device 908 is an optical fiber having a short optical path length and a bent state, the optical transmission device 908 can stably transmit data regardless of the relative position between the optical fiber and the light receiving element.

  The optical transmitter of the present invention can be used as a lighting device or a laser marking device.

It is a conceptual diagram of the optical transmitter 901 which is one Embodiment which concerns on this invention. It is an explanatory view about the distribution angle of light. 2 is an example of an internal structure of an angle enlarging means 12. It is another example of the internal structure of the angle expansion means 12. It is another example of the internal structure of the angle expansion means 12. It is another example of the internal structure of the angle expansion means 12. It is another example of the internal structure of the angle expansion means 12. It is a conceptual diagram of the optical transmitter 908 which is other embodiment which concerns on this invention. It is a figure explaining the conditions which light totally reflects in the interface of the core 85a and the clad | crud 85b of the optical fiber 85. FIG. It is a conceptual diagram of the optical transmitter 910 which is other embodiment which concerns on this invention. It is a conceptual diagram of the optical transmitter 911 which is other embodiment which concerns on this invention. FIG. 6 is a diagram in which a light receiving element 160 is connected to the other end 87 of the optical fiber 85 of the optical transmitter 908. This is the position of the optical axis of the light B incident on one end 86 of the optical fiber 85. Simulation condition No. 1 is a result of simulation. Simulation condition No. 2 is a result of simulation. Simulation condition No. 3 is a result of simulation. Simulation condition No. 4 is a result of simulation. Simulation condition No. 5 is a result of simulation. Simulation condition No. 6 is a result of simulation. Simulation condition No. 7 is a result of simulation. Simulation condition No. 8 shows the result of simulation. 4 is a diagram showing a relative position between an output end 87 of an optical fiber 85 and a light receiving surface 161 of a light receiving element 160. FIG. 4 is a diagram showing a relative position between an output end 87 of an optical fiber 85 and a light receiving surface 161 of a light receiving element 160. FIG.

Explanation of symbols

901, 908, 910, 911 Optical transmitter 11 Light emitting element 12 Angle expanding means 15 Incident end 18 Ejecting end 20 Straight line 21 Light source 22 Optical axis 24 Plane 25 Light intensity distribution 27 Maximum light intensity point 28 Light intensity point 29 Point 30 on the plane 24 of the light intensity point 28 Case 31 Concave lens 41 Convex lens 51 Concave reflector 55 Reflective mirror 61 Convex reflector 71 Tubular waveguide 73 Reflecting surface 85 Optical fiber 85a Core 85b Cladding 85c Center axis 86 One end 87 Other end 160 Light receiving element 161 Light receiving surface γ Angle A, B Light θ ₁ Incident angle

Claims (11)

A light emitting element;
An angle enlarging means for enlarging a distribution angle of light from the light emitting element incident on the incident end and emitting from the exit end;
An optical transmission device comprising:   The multi-mode type optical fiber which has one end connected to the emission end of the angle enlarging means and which receives light from the emission end of the angle enlarging means as incident light. Optical transmitter.   The light distribution angle from the angle expanding means is 10% of the amount of incident light incident on the one end of the optical fiber, and the amount of incident light propagating through the optical fiber by 50 mm is incident on one end of the optical fiber. The optical transmitter according to claim 2, wherein the angle is an angle that is not less than 90% and not more than 90%.   4. The optical transmission device according to claim 2, wherein a distribution angle of light from the angle expanding means is larger in a range of 0 ° to 30 ° than a limit angle of the optical fiber. 5.   The angle expanding means is an optical system having a concave lens that refracts light from the light emitting element incident on the incident end and expands a distribution angle of light from the light emitting element and emits the light from the output end. The optical transmission device according to claim 1, wherein:   The angle expanding means is an optical system having a convex lens that refracts light from the light emitting element incident on the incident end and expands a distribution angle of light from the light emitting element and emits the light from the output end. The optical transmission device according to claim 1, wherein the optical transmission device is an optical transmission device.   The angle expanding means is an optical system having a concave reflecting mirror that reflects light from the light emitting element incident on the incident end and expands a distribution angle of light from the light emitting element and emits the light from the output end. The optical transmission device according to claim 1, wherein the optical transmission device is an optical transmission device.   The angle expanding means is an optical system having a convex reflecting mirror that reflects light from the light emitting element incident on the incident end, expands a distribution angle of light from the light emitting element, and emits the light from the output end. The optical transmission device according to claim 1, wherein the optical transmission device is provided.   The angle expanding means has an optical waveguide region in which the area of a cross section perpendicular to the light propagation direction monotonously decreases from the incident end to the exit end, and propagates light from the light emitting element incident on the incident end. 5. The optical transmission device according to claim 1, wherein the optical transmission device is a tube-type waveguide that expands a distribution angle of light from the light-emitting element and emits the light from the emission end. A light emitting element;
A multi-mode optical fiber having a concave surface that refracts light from the light emitting element so that a surface of one end that receives light from the light emitting element as incident light is enlarged;
An optical transmission device comprising: A light emitting element;
A multi-mode optical fiber having a convex surface that refracts light from the light emitting element so that a surface of one end that receives light from the light emitting element as incident light expands a distribution angle;
An optical transmission device comprising:

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