JP2000056168A - Optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin optical transmitter with simple and compact constitution and transmitting a beam made incident from a side surface of an optical waveguide to a waveguide direction with high coupling efficiency. SOLUTION: The optical transmitter 100 is provided with an optical waveguide (optical fiber 10), a light emitting device 30 and a diffraction grating 20. The light emitting device 30 is arranged so as to emit the beam toward the side surface of a core 12. The diffraction grating 20 is formed integrally with the core exposed part 16 of the optical fiber 10. The beam emitted from the light emitting device 30 is made incident on the core 12 through the diffraction grating 20 to advance in the waveguide direction. The diffraction angle of the diffraction grating 20 is set in an angle that the beam made incident on the optical fiber 10 is nearly totally reflected by a boundary surface between the core 12 and a clad 14, and the beam is transmitted with the high coupling efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical transmission device used in, for example, an optical fiber communication system.

[0002]

BACKGROUND ART An optical module used in an optical fiber communication system includes:
This is a device in which a light-emitting element, a light-receiving element, an optical waveguide, and the like are optically coupled to each other and housed in a package. As a conventional optical module, for example,
There is an optical module disclosed in 237016.
This optical module includes a component having a guide hole,
A light emitting element is arranged below the guide hole. Then, the light emitting element is connected to the optical fiber by inserting the optical fiber into the guide hole.

However, this optical module requires a component having a guide hole. In order to connect the optical fiber and the light emitting element with low loss, it is necessary to secure the position and dimensional accuracy of the guide hole. It is not easy to make such a part. Further, in this optical module, since the optical fiber is installed in a direction perpendicular to the substrate on which the light emitting element and the like are mounted, it is difficult to reduce the thickness of the optical module.

An object of the present invention is to provide an optical transmission device having a simple and compact structure, capable of transmitting light incident from a side surface of an optical waveguide in a waveguide direction with high coupling efficiency, and capable of reducing the thickness. Is to do.

[0005]

An optical transmission device according to the present invention includes an optical waveguide, a light emitting device, and a diffraction grating, and the light emitting device emits light toward a side surface of a core of the optical waveguide. The diffraction grating is formed integrally with the optical waveguide or the light emitting device, and light emitted from the light emitting device enters the core via the diffraction grating and is guided. It has a configuration that travels in the wave direction.

According to this optical transmission device, the light emitted from the light emitting device is introduced into the core from the side surface of the optical waveguide via the diffraction grating. Therefore, the optical waveguide can be installed in parallel with the substrate on which the light emitting device or the like is mounted, and therefore, the thickness of the optical transmission device can be reduced.

Further, when the diffraction grating is formed on the optical waveguide, the diffraction grating can be formed in an arbitrary size in a region where the diffraction grating is formed, for example, in the exposed portion of the core. On the other hand, when the diffraction grating is formed in the light emitting device,
The area of the optical waveguide facing the light emitting device can be set to any size. Therefore, alignment between the optical waveguide on which the diffraction grating is formed and the light emitting device, or alignment between the light emitting device on which the diffraction grating is formed and the optical waveguide are extremely easy because high accuracy is not required. Accordingly, it is not necessary to perform extremely high-precision optical axis alignment normally required for an optical module, and an optical transmission device can be easily manufactured.

It is preferable that the diffraction angle of the diffraction grating is set to an angle at which light incident on the optical waveguide is almost totally reflected at an interface between a core and a clad. When the diffraction angle of the diffraction grating is set in this manner, light can be introduced into the core at such an angle as to be totally reflected at the interface between the core and the clad of the optical waveguide by the diffraction grating, resulting in high optical coupling efficiency Can be achieved. Such a diffraction grating is preferably a comb-tooth type, which generates diffracted light in only one direction.

Preferably, the diffraction grating is formed on a core of the optical waveguide. In that case, the following aspects can be taken.

(A) An embodiment in which a clad portion outside the formation region of the diffraction grating is removed to form an exposed core portion, and the diffraction grating is formed in the exposed core portion.

(B) An embodiment in which the exposed core portion is formed on the side facing the light emitting device, and the diffraction grating is formed in the exposed core portion.

(C) An embodiment in which the diffraction grating is of a reflection type, and the core exposed portion is formed on the side opposite to the side where the light emitting device is arranged, and the diffraction grating is formed on the core exposed portion.

(D) The diffraction grating is of a reflection type, and the exposed core portion is formed by removing a part of a core and a clad portion outside the core, and the diffraction grating is formed in the exposed core portion. Aspects.

Further, the diffraction grating may be formed on a light emitting surface of the light emitting device.

It is preferable that the light emitting device is integrally connected to the optical waveguide by a connecting portion. The light emitting device is directly coupled to the optical waveguide by the coupling portion,
It does not require another optical component for optical coupling, and has an extremely simple and compact structure.

The light emitting device is preferably of a hybrid type in which a light emitting element and an integrated circuit element for driving the light emitting element are mounted. The light emitting element of the light emitting device is preferably a surface emitting laser. Further, a plurality of surface emitting lasers that emit light of different wavelengths may be used as the light emitting element. The light emitting device is appropriately selected depending on the use of the optical transmission device of the present invention. Similarly, as the optical waveguide, an optical fiber or a planar optical waveguide can be used depending on the use of the optical transmission device.

[0017]

(First Embodiment) FIG. 1 is a partial sectional view schematically showing an optical transmission device 100 according to the present invention. FIG. 2 is a cross-sectional view of the optical fiber 10 shown in FIG. 1 along the line AA.

The optical transmission device 100 includes an optical fiber 10 and
The light-emitting device 30 includes a light-emitting device 30 and a coupling unit 40 that couples the optical fiber 10 and the light-emitting device 30.

The optical fiber 10 comprises a core 12 and a clad 1
And 4. Then, a part of the clad 14 is removed at the end of the optical fiber 10 to form a core exposed portion 16. The core exposed portion 16 becomes a region where the diffraction grating 20 is formed. The diffraction grating 20 is formed on the surface of the core exposed part 16.

The light emitting device 30 has a surface emitting laser 34 and a semiconductor substrate (integrated circuit element) 32 having an electronic circuit for driving the surface emitting laser 34. Such a light emitting device 30 is not particularly limited, and a known hybrid element can be used. The light emitting device 30 is fixed to the core exposed portion 16 by a coupling portion 40 in which at least a light passage is transparent. The coupling portion 40 is formed of, for example, a transparent resin, and can be formed by injection molding or the like.

The diffraction angle of the light emitted from the surface emitting laser 34 by the diffraction grating 20 is set to an angle at which the light incident on the optical fiber 10 is almost totally reflected at the interface between the core 12 and the clad 14. By setting the diffraction angle in this way, high light coupling efficiency can be obtained. Here, the diffraction angle is
As shown in FIG. 1, the angle θ is the angle between the direction of the light emitted from the surface emitting laser 34 and the diffracted light. Optical fiber 10
In order to efficiently transmit the light incident on the diffraction grating in the waveguide direction, it is preferable that the diffraction grating 20 has a comb-tooth shape that generates diffracted light in only one direction.

The method of forming the diffraction grating 20 is not particularly limited. For example, when a plastic fiber is used as the optical fiber, the core exposed portion 16 is heated and softened. By pressing, a diffraction grating having a predetermined shape can be formed.

As the optical fiber 10, a plastic fiber having a large core diameter is preferable. A plastic fiber having a large core diameter is easier to mold and cut than a glass fiber, so that a part of the clad 14 can be easily removed and the diffraction grating 20 can be easily formed at the exposed core portion 16. In addition, the plastic fiber having a large core diameter allows the light emitting device 30 to be easily mounted.

According to the optical transmission device 100, the light emitted from the surface emitting laser 34 of the light emitting device 30
Is introduced into the core via the diffraction grating 20 formed on the surface of the core. Then, the light is introduced into the core 12 at such an angle as to be totally reflected at the interface between the core 12 and the clad 14 by the diffraction grating 20, so that the light can be efficiently transmitted in the waveguide direction of the optical fiber 10. Further, since the light emitting device 30 is directly coupled to the cut surfaces of the core 12 and the clad 14 by the coupling section 40, another optical component for optical coupling is not required, and the structure is extremely simple and small.

Further, according to the optical transmission device 100, the light emitted from the light emitting device 30 is introduced into the core 12 from the side surface of the optical fiber 10 via the diffraction grating 20.
Therefore, the optical fiber 10 is installed in parallel with a substrate (not shown) on which the light emitting device 30 and the like are mounted, and therefore, the thickness of the optical transmission device 100 can be reduced. This effect can be achieved in all the embodiments described below.

Further, the diffraction grating 20 can be manufactured at an arbitrary size in the exposed core portion 16. Therefore, the alignment between the diffraction grating 20 and the light emitting device 30 is extremely easy since high accuracy is not required. Accordingly, it is not necessary to perform extremely high-precision optical axis alignment normally required for an optical module, and an optical transmission device can be easily manufactured.

Further, since the coupling portion 40 is formed so as to seal the light emitting device 30, it also has a function of protecting the light emitting device 30. And the coupling part 40 is at least
The refractive index and the like are set in consideration of the fact that the light emitted from the surface emitting laser 34 is efficiently sent to the diffraction grating 20.

(Second Embodiment) FIG. 3 is a partial sectional view schematically showing an optical transmission device 200 according to a second embodiment of the present invention. The optical transmission device 200 is different from the optical transmission device 100 of the first embodiment in the formation position of the diffraction grating 20, and the other configuration is the same. Optical transmission device 100
The same members as those described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the optical transmission device 200, the core exposed portion 16 is formed on the side opposite to the light emitting device 30. That is, the light emitting device 30 is disposed below the optical fiber 10, and the core exposed portion 16 is formed above the optical fiber 10. Unlike the diffraction grating of the first embodiment, the diffraction grating 20 of this example needs to reflect light incident on the optical fiber 10, and is therefore configured by a reflection type diffraction grating.

In the optical transmission device 200 of the present embodiment, the same operation and effect as those of the optical transmission device 100 of the first embodiment can be achieved.

(Third Embodiment) FIG. 4 is a partial sectional view schematically showing an optical transmission device 300 according to a third embodiment of the present invention. The optical transmission device 300 is different from the optical transmission device 100 of the first embodiment in the formation position of the diffraction grating 20, and the other configuration is the same. Optical transmission device 100
The same members as those described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The optical transmission device 300 includes the core exposed portion 1
6 differs from the optical transmission device 200 according to the second embodiment in that the core 6 is formed inside the core 12 instead of the surface. That is, in the optical transmission device 300, the core exposed portion 16 is formed substantially at the center of the core 12, and the exposed surface thereof forms a plane along the optical waveguide direction. And
The diffraction grating 20 is different from the optical transmission device 200 according to the second embodiment.
Similarly, a reflection type diffraction grating is used.

In the optical transmission device 300 of the present embodiment, the same operation and effect as those of the optical transmission device 100 of the first embodiment can be achieved. Further, the optical transmission device 30
0, the core 12 of the first and second embodiments
The core exposed portion 16 can be formed by simultaneously cutting the core 12 and the clad 14 linearly as compared with the case where the clad 14 is removed from the side surface of
Molding becomes easy.

(Fourth Embodiment) FIG. 5 is a partial sectional view schematically showing an optical transmission device 400 according to a fourth embodiment of the present invention. The optical transmission device 400 includes the optical fiber 1
0, the light emitting device 30, the optical fiber 10, and the light emitting device 30
And a coupling part 40 for coupling the two.

The optical fiber 10 comprises a core 12 and a clad 1
And 4. Then, a part of the clad 14 is removed at the end of the optical fiber 10 to form a core exposed portion 16.

The light emitting device 30 has a surface emitting laser 34 and a semiconductor substrate (integrated circuit element) 32 having an electronic circuit for driving the surface emitting laser 34. Such a light emitting device 30 is not particularly limited, and a known hybrid element can be used. Then, the light emitting device 30
The diffraction grating 20 is formed on the light emission surface of the surface emitting laser 34, that is, on the upper surface of the surface emitting laser 34. The light emitting device 30 can be configured such that at least the light passage is transparent, and the core exposing portion 16 is
It is fixed to. The coupling portion 40 is formed of, for example, a transparent resin, and can be formed by injection molding or application and curing of a transparent resin liquid.

The diffraction angle of the diffraction grating 20 is
Is set at an angle at which the light incident on the interface is substantially totally reflected at the interface between the core 12 and the clad 14. By setting the diffraction angle in this way, high light coupling efficiency can be obtained. Here, the diffraction angle is, as shown in FIG.
Is the angle θ between the direction of the light emitted from the substrate (the direction perpendicular to the upper surface of the surface emitting laser 34) and the diffracted light. In order to efficiently transmit the light incident on the optical fiber 10 in the waveguide direction, it is preferable that the diffraction grating 20 has a comb-like shape as in the first embodiment.

The method of forming the diffraction grating 20 is not particularly limited, and a known method can be used. For example, the diffraction grating 20 can be formed by using polyimide or silicon oxide and performing photolithography or etching as needed.

As the optical fiber 10, it is preferable to use a plastic fiber as in the first embodiment. Such a plastic fiber is easier to mold and cut than a glass fiber.
It is easy to form a core exposed part 16 by removing a part of the core. Also, such plastic fiber is
Since the core diameter is large, mounting of the light emitting device 30 is easy.

According to the optical transmission device 400, the light emitted from the surface emitting laser 34 of the light emitting device 30 passes through the diffraction grating 20 formed on the surface of the surface emitting laser 34,
It is introduced into the core 12 of the optical fiber 10. Then, the light is introduced into the core 12 by the diffraction grating 20 at an angle such that the light is totally reflected at the interface between the core 12 and the clad 14, so that the light is efficiently transmitted in the waveguide direction of the optical fiber 10.
Further, since the light emitting device 30 is directly coupled to the core 12 by the coupling section 40, another optical component for optical coupling is not required, and the structure is extremely simple and small.

The diffraction grating 20 has a surface emitting laser 34.
On the other hand, the core exposed portion 16 facing the surface emitting laser 34 can be formed in an arbitrary size. Therefore, alignment between the diffraction grating 20 and the core exposed portion 16 is extremely easy since high accuracy is not required. Accordingly, it is not necessary to perform extremely high-precision optical axis alignment normally required for an optical module, and an optical transmission device can be easily manufactured.

Further, since the coupling portion 40 is formed in a state where the surface emitting laser 34 of the light emitting device 30 is sealed, it also has a function of protecting the light emitting device 30. And the joining part 4
The refractive index of 0 is preferably substantially equal to the refractive index of the core 12 so that light emitted from the surface emitting laser 34 and diffracted by the diffraction grating 20 is guided to the optical fiber 10 with high efficiency. In this example, the coupling portion 40 is formed around the surface emitting laser 34, but, of course, the coupling portion 40 may be formed so as to seal the entire light emitting device 30.

(Fifth Embodiment) FIG. 6 is a partial sectional view schematically showing an optical transmission device 500 according to a fifth embodiment of the present invention. FIG. 7 shows the optical transmission device 50 shown in FIG.
It is sectional drawing along the BB line of 0.

The optical transmission device 500 has a planar optical waveguide 50, a light emitting device 30, and a coupling section 40 for coupling the planar optical waveguide 50 and the light emitting device 30.

The planar optical waveguide 50 has a core 52 and a clad 54. Then, a part of the surface of the core 52 is a region where the diffraction grating 20 is formed.

The light emitting device 30 has a surface emitting laser 34 and a semiconductor substrate (integrated circuit element) 32 having an electronic circuit for driving the surface emitting laser 34. Such a light emitting device 30 is not particularly limited, and a known hybrid element can be used. The light-emitting device 30 is configured such that at least
2 is fixed to the surface portion. The coupling portion 40 is formed of, for example, a transparent resin, and can be formed by injection molding or the like.

The diffraction angle of the diffraction grating 20 is set to an angle at which light incident on the planar optical waveguide 50 is almost totally reflected at the interface between the core 52 and the clad 54. By setting the diffraction angle in this way, high light coupling efficiency can be obtained. Here, the diffraction angle refers to the angle between the direction of the light emitted from the surface emitting laser 34 and the diffracted light. In order to efficiently transmit the light incident on the planar optical waveguide 50 in the waveguide direction, it is preferable that the diffraction grating 20 has a comb-like shape as in the first embodiment.

The method of forming the diffraction grating 20 is not particularly limited. For example, when a plastic optical waveguide 50 is used, the surface of the core 52 is heated and softened. By pressing the mold against the surface of the surface 52, a diffraction grating having a predetermined shape can be formed.

According to the optical transmission device 500, the light emitted from the surface emitting laser 34 of the light emitting device 30
Is introduced into the core via the diffraction grating 20 formed on the surface of the core. Then, the light is introduced into the core 52 by the diffraction grating 20 at an angle such that the light is totally reflected at the interface between the core 52 and the clad 54, so that the planar optical waveguide 50
Can be efficiently transmitted in the waveguide direction. Further, since the light emitting device 30 is directly coupled to the core 52 by the coupling section 40, another optical component for optical coupling is not required, and the structure is extremely simple and small.

Further, the diffraction grating 20 can be manufactured at an arbitrary size on the surface of the core 52. Therefore, the alignment between the diffraction grating 20 and the light emitting device 30 is extremely easy since high accuracy is not required. Accordingly, it is not necessary to perform extremely high-precision optical axis alignment normally required for an optical module, and an optical transmission device can be easily manufactured.

Further, since the coupling portion 40 is formed in a state where the light emitting device 30 is sealed, it also has a function of protecting the light emitting device 30. And the coupling part 40 is at least
The refractive index and the like are set in consideration of the fact that the light emitted from the surface emitting laser 34 is efficiently sent to the diffraction grating 20.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can take various forms within the scope of the invention. For example, a mode similar to the second embodiment can be applied to a planar optical waveguide.

In the above-described embodiment, an example has been described in which the light emitting device is integrated with the optical waveguide by the coupling portion. However, it is also possible to connect the light emitting device and the optical waveguide by other connecting means, for example, a connector housing, instead of the connecting portion.

[0054]

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view schematically illustrating an optical transmission device according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a cross section of the optical fiber shown in FIG. 1 along line AA.

FIG. 3 is a partial cross-sectional view schematically illustrating an optical transmission device according to a second embodiment of the present invention.

FIG. 4 is a partial cross-sectional view schematically showing an optical transmission device according to a third embodiment of the present invention.

FIG. 5 is a partial sectional view schematically showing an optical transmission device according to a fourth embodiment of the present invention.

FIG. 6 is a partial sectional view schematically showing an optical transmission device according to a fifth embodiment of the present invention.

7 is a diagram schematically showing a cross section of the optical transmission device shown in FIG. 6 along the line BB.

DESCRIPTION OF SYMBOLS 10 Optical fiber 12 Core 14 Cladding 16 Core exposed part 20 Diffraction grating 30 Light emitting device 32 Integrated circuit element 34 Surface emitting laser 40 Coupling part 50 Planar type optical waveguide 52 Core 54 Cladding 100, 200, 300, 400, 500 Optical transmission device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shojiro Kitamura 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Inventor Tsugio Ide 3-3-5, Yamato Suwa City, Nagano Prefecture Seiko Epson F term (reference) 2H037 BA02 CA06 CA36 CA37 DA03 DA04 DA06

Claims (13)

[Claims] 1. An optical waveguide, comprising: a light emitting device; and a diffraction grating, wherein the light emitting device is arranged to emit light toward a side surface of a core of the optical waveguide; An optical transmission device wherein light formed integrally with a wave path or the light emitting device and emitted from the light emitting device enters the core via the diffraction grating and travels in a waveguide direction. 2. The optical transmission device according to claim 1, wherein a diffraction angle of the diffraction grating is set to an angle at which light incident on the optical waveguide is substantially totally reflected at an interface between a core and a clad. 3. The optical transmission device according to claim 1, wherein the diffraction grating has a comb shape and generates diffracted light in only one direction. 4. The optical transmission device according to claim 1, wherein the diffraction grating is formed in a core of the optical waveguide. 5. The optical transmission device according to claim 4, wherein a clad portion outside a region where the diffraction grating is formed is removed to form a core exposed portion, and the diffraction grating is formed in the core exposed portion. 6. The optical transmission device according to claim 5, wherein the exposed core portion is formed on a side facing the light emitting device, and the diffraction grating is formed on the exposed core portion. 7. The diffraction grating according to claim 5, wherein the diffraction grating is a reflection type, and the core exposed portion is formed on a side opposite to a side where the light emitting device is arranged, and the diffraction grating is formed on the core exposed portion. Optical transmission equipment. 8. The diffraction grating according to claim 4, wherein the diffraction grating is of a reflection type, and the core exposed portion is formed by removing a part of a core and a clad portion outside the core. An optical transmission device in which is formed. 9. The optical transmission device according to claim 1, wherein the diffraction grating is formed on a light emitting surface of the light emitting device. 10. The light-emitting device according to claim 1, wherein the light-emitting device is integrally coupled to the optical waveguide.
Optical transmission device. 11. The optical transmission device according to claim 1, wherein the light emitting device includes a light emitting element and an integrated circuit element for driving the light emitting element. 12. The optical transmission device according to claim 1, wherein the light emitting device is a surface emitting laser. 13. The optical transmission device according to claim 12, wherein the light emitting device includes, as the light emitting element, a plurality of surface emitting lasers that emit light of different wavelengths.