JPH10104474A - Optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent coupling characteristics by providing at least >=2 kinds of lens having different optical characteristics on the surface of a resin molding body facing an optical fiber. SOLUTION: The 1st lens L1 and 2nd lens L2 which have the different optical characteristics are provided on the surface of a photoconduction device which faces the optical fiber. The lens L1 is a convex lens which has a lens diameter 11 of approximately 150 to 300μm. The lens L2, on the other hand, is an annular convex lens which has a lens diameter 12 of approximately 1.1 to 1.2. A light emitting diode 3 is put hermetically in the resin molding body which is transparent to light emission wavelength. The light which is emitted by the light emitting diode 3 and passed through the lens L1 is made incident on an end surface of the core part 51 of a quartz fiber 5 at, for example, a 20 to 30 deg. angle of incidence through the light converging effect of the lens L1 to become light which contribute to the transmission of the optical fiber. Light which exits through the lens L2, on the other hand, is made incident on an end surface of the core part 61 of a plastic optical fiber 6 at, for example, a 20 to 30 deg. angle of incidence to become light which contributes to the transmission of the optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device for transmitting light via an optical fiber, and more particularly to an optical transmission device having a light emitting element or a light receiving element which can be coupled to various kinds of optical fibers.

[0002]

2. Description of the Related Art FIG. 5A is a cross-sectional view showing the structure of a joint between a general optical fiber cable and an optical transmission device.
As shown in the figure, an optical connector plug 104 is attached to an end of an optical fiber cable 106, and a ferrule 10 is attached to the center of the optical connector plug 104.
5 are protrudingly provided. The ferrule 105 supports and fixes an optical fiber cable 106.

[0003] The optical transmission module 107 comprises a module main body 103 and an optical transmission device 101 provided therein. A ferrule fitting portion corresponding to the shape of the ferrule 105 is formed at the center of the module main body 103. The optical transmission device 101 is installed at the bottom of the fitting portion. In the optical transmission device 101, an optical element 102 which is a light emitting element or a light receiving element is sealed in a transparent resin molded body.

FIG. 5B is a cross-sectional view showing a state where the optical connector plug 104 and the optical transmission module 107 are connected. Optical connector plug 104 and optical transmission module 10
7 is fitted and fixed, and the end face of the optical fiber cable 106 faces the optical element 102 in the optical transmission device 101 via a transparent sealing resin.

[0005] Generally, the number of optical fibers coupled to one optical transmission module is not one. By replacing the optical connector plug 104 or the fiber with a ferrule to be coupled to the optical transmission module 107, the optical fiber to be coupled can be selected according to the application.

The optical fiber to be coupled may be, for example, a quartz fiber, a plastic fiber, or a fiber having a different diameter in each case, or an SI in which the refractive index distribution in the fiber changes stepwise between the core portion and the cladding portion.
Type (step index type) fiber and GI type (graded index type) fiber in which the refractive index of the core portion changes gradually.

FIGS. 6A and 6B show an area A surrounded by a broken line in FIG.
FIG. 2 is an enlarged cross-sectional view of a coupling portion between the optical transmission device 101 and the optical transmission device 101. For convenience, only a part of the optical fiber and the optical transmission device is shown.
Note that a case where a light emitting diode which is a light emitting element is used as the optical element 102 is shown. FIG. 6A shows a case where the quartz fiber 106G is selected as the optical fiber to be coupled, and FIG. 6B shows a case where the plastic fiber 106P is selected as the optical fiber to be coupled.

[0008] Each fiber of the coupling portion and the surface S of the optical transmission device
1 is not completely in contact, as shown in the figure,
They face each other at a certain interval. Quartz fiber 10
The surface S1 of the optical transmission device corresponding to the end face of 6G has a flat surface with high smoothness formed by grinding in order to avoid reflection loss of light due to unevenness.

The silica fiber 106G generally has a core 106GI of 50 μm to 200 μm, while the plastic fiber 106P has a core 106PI of 500 μm.
The diameters are large, from about μm to about 1000 μm, and their outer diameters are significantly different.

The optical element 102 has, for example, a light emitting layer 110 on a conductive base material 120. The conductive base material is directly die-bonded on the lead frame 140 with a conductive adhesive, and the electrodes formed on the surface of the light emitting layer are connected to the lead frame 1 by bonding wires 130.
40.

An arrow shown in FIG. 1 illustrates the traveling direction of the emitted light when the optical element 102 is a light emitting diode. The light-emitting diode has a planar light-emitting portion and the emitted light has no directivity, so the emission angle of the emitted light is extremely wide.

[0012]

FIG. 6A and FIG.
As shown in (b), when the optical transmission device has a light emitting element, it is important for coupling the optical fiber and the optical transmission device that the light emitted from the light emitting element is first transmitted to the optical fiber as efficiently as possible. It is to take in. That is, it is desired that the “light coupling efficiency”, which is a ratio of the amount of light that can contribute to the transmission of the optical fiber to the amount of light emitted from the light emitting element, be set as high as possible.

However, as described above, there are many types of optical fibers to which one optical transmission device is coupled, and it is difficult to realize high optical coupling efficiency for all the fibers.

For example, as shown in FIG. 6B, when a plastic fiber is connected to an optical transmission device, a relatively large amount of light is emitted from the plastic fiber 106P because the fiber diameter is large with respect to the area of the light emitting portion. Core 106PI
And high optical coupling efficiency can be obtained. However, as shown in FIG. 6 (a), when the optical transmission device is coupled to a quartz fiber having a small fiber diameter, as shown in FIG. The coupling efficiency is lower than when coupling to a plastic fiber.

As shown in FIG. 7, an optical transmission device having a condensing lens LG on the exit surface has been considered in order to increase the optical coupling efficiency to the quartz fiber 106G having a small diameter. By condensing the light emitted from the light emitting element 102 into the quartz fiber 106G from the lens LG, the optical coupling efficiency can be increased.

However, when the optical transmission device shown in FIG. 7 is coupled to a plastic fiber, since the lens is formed on the surface of the optical transmission device, the end face of the plastic fiber and the light emitting element are compared with the case where the surface is flat. The optical distance to the plastic fiber is widened, and the optical coupling efficiency with respect to the plastic fiber is reduced as compared with the case where the optical fiber is coupled to the flat-surface optical transmission device shown in FIG.

Conversely, if a lens having a large diameter is formed on the surface of the optical transmission device so as to increase the optical coupling efficiency of the plastic fiber, the optical coupling efficiency with respect to the plastic fiber can be increased. There is almost no effect on the fiber because the curvature of the lens is small.

On the other hand, when the distance of the optical fiber coupled to the optical transmission device is long, or when high-speed communication is performed using the optical fiber, the influence of the coupling state between the optical transmission device and the optical fiber on the “propagation delay”. It becomes a problem.

That is, if the angles of the light entering the optical fiber from the optical transmission device are not uniform, a difference occurs in the propagation distance of the light according to the incident angle of the light. For example, the propagation distance of light that has been almost perpendicularly incident on the end face of the optical fiber is shorter than the propagation distance of light that has entered obliquely. Such a difference in light propagation distance becomes more remarkable as the transmission distance is longer and the transmission speed is faster, and a transmission error is more likely to occur.

In the case of using a GI optical fiber, the above-mentioned propagation delay does not cause much problems because the change in the refractive index of the core suppresses the occurrence of a difference in light propagation speed. It becomes a problem.

Although the above description is directed to the case where a light emitting element is provided in an optical transmission device, even when a light receiving element is provided in an optical transmission device, light transmitted through a fiber can be efficiently received by a light receiving element. Therefore, it is desired to suppress the optical coupling loss at the coupling section as much as possible. But,
As in the case described above, it is difficult to similarly suppress optical coupling loss for various fibers coupled to the optical transmission device.

An object of the present invention is to provide various types of coupling characteristics for various types of optical fibers, which depend on the coupling state between the optical fiber and the optical transmission device, such as optical coupling efficiency, optical propagation delay, and optical coupling loss. To provide an optical transmission device that can improve the optical transmission.

[0023]

A first feature of the optical transmission device of the present invention is that in an optical transmission device coupled to a plurality of types of optical fibers, an optical element and a transmission wavelength for the optical fiber. And a resin molded body for sealing the optical element, and at least two or more lenses having different optical characteristics are provided on the surface of the resin molded body facing the optical fiber.

According to the first feature, by providing two or more types of lenses having different optical characteristics such as a focal length and a lens diameter, the optical transmission device can favorably couple a plurality of types of optical fibers to be coupled. It is possible to provide binding properties.

According to a second feature of the optical transmission device of the present invention, in the optical transmission device having the first feature, each of two or more types of lenses is coupled to the optical transmission device and the optical transmission device. That is, it is optically designed to improve the coupling characteristics with any one of the optical fibers.

According to the second feature, it is possible to provide an optical transmission device capable of obtaining good coupling characteristics with at least two or more types of optical fibers by providing a lens.

A third feature of the optical transmission device according to the present invention is that, in the optical transmission device having the first or second feature, the two or more kinds of lenses are integrally formed with the resin molded body. .

According to the third feature, since the lens can be molded at the same time when the resin molded body for encapsulating the optical element is molded, the optical transmission device can be easily manufactured without any special process load. be able to.

A fourth feature of the optical transmission device according to the present invention is that, in the optical transmission device having the above-mentioned first feature, the two or more lenses improve the coupling characteristics of optical fibers having different fiber diameters. It was designed optically.

According to the fourth feature, when the optical fiber to be coupled to the optical transmission device is replaced, good coupling characteristics can be obtained even if the diameter of the optical fiber changes. A fifth feature of the optical transmission device according to the present invention is that, in the optical transmission device having the above-mentioned first feature, at least one of the two or more kinds of lenses has an optical characteristic such that a coupling characteristic of a quartz fiber is improved. And at least one other lens is optically designed to improve the coupling characteristics of the plastic fiber.

According to the fifth feature, good coupling characteristics can be obtained for any of a quartz fiber and a plastic fiber having greatly different fiber diameters.

A sixth feature of the optical transmission device of the present invention is that in any one of the above-described second to fifth features, the optical element is a light emitting element, and the transmission wavelength of the optical fiber is the same as that of the first embodiment. This is the light emission wavelength of the light emitting element.

According to the sixth feature, in an optical transmission device having a light emitting element, the coupling characteristics can be improved. Since the coupling between the optical transmission device having the light emitting element and the optical fiber is particularly large compared to the coupling between the optical transmission device having the light receiving element and the optical fiber, the condition at the coupling portion greatly affects the coupling characteristics. The effect of the feature 6 becomes effective.

A seventh feature of the optical transmission device of the present invention is that, in the optical transmission device having the sixth feature, the light emitting element is a light emitting diode.

According to the seventh feature, since a light emitting diode which is a surface light emitter and has a wide light emission angle is used as a light emitting element, the effect of providing a lens for improving the coupling characteristics as described above in an optical transmission device is obtained. Becomes effective.

An eighth feature of the optical transmission device of the present invention is that, in the optical transmission device having the sixth or seventh feature, the coupling characteristic includes at least optical coupling efficiency.

According to the eighth feature, it is possible to provide an optical transmission device with improved optical coupling efficiency, which is a problem particularly in the coupling characteristics.

A ninth feature of the optical transmission device of the present invention is that, in the optical transmission device having the sixth or seventh feature, the coupling characteristic includes at least a transmission delay characteristic in an optical fiber.

According to the ninth feature, an optical signal effective when the propagation delay is particularly problematic, such as when the optical transmission distance extends over a long distance or when high-speed transmission is particularly required. A transmission device can be provided.

According to a tenth feature of the optical transmission device of the present invention, in the optical transmission device having the above-described first to ninth features, of the two or more lenses, the lens having the smallest lens diameter is used as the light emitting element. It is arranged on the center, and another lens is annularly arranged around the center.

According to the tenth feature, the lens can be efficiently arranged on the surface of the optical transmission device. With the lens having the smallest lens diameter, the optical coupling efficiency with respect to an optical fiber having a small diameter can be increased, and good optical coupling efficiency can be provided even with an optical fiber having a large diameter.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical transmission device according to the present invention will be described with reference to FIGS.

FIG. 1A is a cross-sectional view showing a configuration of a coupling portion between an optical transmission device and a quartz fiber according to an embodiment of the present invention. As shown in the figure, the main feature of the optical transmission device of the present embodiment is that a first lens L1 and a second lens L2 having different optical characteristics are provided on the surface of the optical transmission device facing the optical fiber.
2 has.

As shown in the figure, the optical transmission device has a gallium arsenide (G) having an emission wavelength of, for example, 650 nm.
aAs) The light emitting diode 3 is sealed. The light emitting layer is formed of a p-type and an n-type stack, and emits light from the pn junction layer in multiple directions. An electrode is formed on the surface of the light emitting layer, and this electrode is joined to the lead electrode 2a by a bonding wire 4. Further, since the base material 3b on which the light emitting layer is formed has conductivity, it is directly die-bonded on the lead electrode 2b.

The light emitting diode 3 is sealed in a resin molding transparent to the emission wavelength. As shown in the figure, a first lens L1 and a second lens L2 are formed on the emission surface side of the resin in which the light emitting diode 3 is sealed. The optical axis of each lens is a direction passing through the center of the light emitting surface of the light emitting diode and perpendicular to the light emitting surface, and coincides with the optical axis of the optical fiber.

The lens L1 has a lens diameter 11 of about 150 to
It is a 300 μm convex lens. Note that the diameter (l1) of this lens substantially matches the curvature diameter of the lens (lens L2
The same).

As shown by the arrow in FIG. 1A, the light emitted from the light emitting diode and passing through the lens L1 is condensed by the lens L1 so that the core portion 5I of the quartz fiber 5 is condensed.
Light enters the end face at an incident angle of 20 ° to 30 °, and becomes light that contributes to the transmission of the optical fiber.

On the other hand, the lens L2 is a convex lens having a lens diameter l2 of about 1.1 to 1.2 mm. However, since the lens L1 is formed in the central portion, the lens L1 has an annular lens shape.

FIG. 1B is a schematic configuration diagram of a coupling portion when the optical transmission device according to the embodiment of the present invention is coupled to a plastic fiber 6.

As shown by the arrow in FIG. 1B, the light emitted from the light emitting diode and passing through the lens L2 and emitted to the outside is applied to the end face of the core 6I of the plastic fiber 6 by 20 to 30 degrees. Light enters at an incident angle and becomes light contributing to transmission through an optical fiber. The light that passes through the lens L1 that provides effective emission light to the quartz fiber and exits outside is condensed so as to be taken into the quartz fiber smaller than the diameter of the plastic fiber. And provide effective light for transmission.

The optical coupling efficiency obtained in the optical transmission device of the above-described embodiment is smaller than that of the conventional optical transmission device having a flat exit surface shown in FIGS. 6A and 6B. The efficiency can be improved to about twice the value.

FIG. 2 is a graph showing a simulation value of a change in optical coupling efficiency with respect to a coupling fiber when only the diameter of a lens provided on an outgoing light surface is changed in an optical transmission device having a light emitting diode as described above. . The horizontal axis shows the diameter of the lens provided on the outgoing light surface of the optical transmission device, and the vertical axis shows the optical coupling efficiency in percentage. Note that the lens used here has a curvature diameter substantially equal to the lens diameter.
The curve indicated by A is a value obtained when a quartz fiber having a diameter of about 100 μm is used as the coupling fiber, and the curve indicated by B is a value obtained when a plastic fiber having a diameter of about 1 mm is used as the coupling fiber.

As shown in the figure, the optical coupling efficiency for each fiber has a maximum value at a certain lens diameter, and the optical coupling efficiency decreases when the optical coupling efficiency is smaller or larger. The lens diameter at which the optical coupling efficiency is maximized substantially depends on the diameter of the fiber to be coupled. The lens diameter RA is about 150 to 300 μm for quartz fiber, and the lens diameter RB is about 1 for plastic fiber. .1 to 1.2 mm
Can be expected.

In the above-described embodiment, as the lens L1 provided at the center of the outgoing light surface of the optical transmission device, a lens having a lens diameter RA for providing an optimum optical coupling efficiency with respect to a quartz fiber is provided. , A lens L2 having a lens diameter RB that provides an optimum optical coupling efficiency to a plastic fiber
As a result, the optical coupling efficiency to both the quartz fiber and the plastic fiber can be improved.

As described above, when the optical transmission device is coupled to a plurality of types of fibers, an optimum lens diameter or the like for obtaining good optical coupling efficiency for each fiber is obtained from the optical design. A plurality of lenses having optical characteristics obtained by the design are formed on the molded resin outer shape of the optical transmission device. At this time, as shown in FIG. 1 (a), the lens having the smallest diameter is disposed at the center, and another concentric annular lens is formed.

A lens having a small diameter has a short optical distance between the lens outer surface having a lens effect and the light emitting element portion.
It is preferable to set the height of the outer surface of the lens low so that a large amount of light can be picked up.

Further, it is preferable that these plural lenses are formed integrally with a transparent resin molded body which seals the light emitting diode, since no extra steps are required. However,
If there is an acute angle portion between the first lens and the second lens or in the outer ring of the second lens when performing the mold processing, mold loss or chipping of the mold is likely to occur during the processing. Therefore, as shown in FIG. 1A, a groove G having a certain width is provided between the lens (L1) formed inside and the lens (L2) formed outside.
When the bottom of the groove G is formed with a curved surface or the outer ring portion of the second lens is formed with a curved surface, molding processing becomes easy. FIG. 3 shows an example in which three types of lenses are formed on the outer surface of the optical transmission device. An optimal lens L3 for providing high optical coupling efficiency to a plastic fiber having a larger diameter than the plastic fiber shown in FIG. 2B is provided on the outer periphery of the lens L2.

When a larger number of lenses are formed on the surface of the optical transmission device, it is preferable to provide a lens having the smallest diameter at the center and arrange annular lenses concentrically around the lens in the same manner as described above.

As a lens formed on the surface of the optical transmission device, a plurality of optical fibers having a high coupling frequency are selected.
For each of these fibers, it is preferable to select a plurality of lenses that are most suitable for improving the coupling characteristics, and obtain a combination lens.

The examples of the above-described embodiment shown in FIGS. 1 and 3 show an example of designing a lens of an optical transmission device so as to particularly increase the optical coupling efficiency of an optical fiber.
Optimal lens design can be performed for other purposes.

For example, when using an SI type fiber and the transmission distance by the optical fiber is long, or when aiming for high-speed communication, design a lens in which light propagation delay is less likely to occur than the optical coupling efficiency. Is more required. In this case, an optimal lens shape is determined by simulation so that the incident angles of the light entering the fibers can be made as uniform as possible with respect to the plurality of fibers to be coupled.

Next, similarly to the lens described in the above-described embodiment, a small-diameter lens corresponding to the quartz fiber is formed on the center of the light emitting surface of the optical transmission device, and a concentric circular lens having a larger diameter is formed on the outer periphery thereof. Form a lens.

FIG. 4 is a perspective view showing the optical transmission device in the above-described embodiment. The optical transmission device is formed of a transparent resin molded body 1 whose outer shape is, for example, a rectangular parallelepiped. An epoxy resin can be used as the resin molded body.

The resin molded body 1 has lead frames 2a and 2b formed by silver plating on two copper plates on a substantially horizontal surface in the center. A light emitting element 3 such as a light emitting diode as described above is die-bonded on a lead frame 2b at the center of the device by a conductive adhesive, and the other lead frame 2a is connected to the light emitting element 3 by a gold bonding wire 4. It is connected to the upper electrode. Lead frame 2a,
Each end of 2b is drawn out of the resin molded body.

A circular groove D having a lens L at the center is formed on the surface of the resin molded body corresponding to the upper part of the light emitting element in accordance with the size of the light emitting element. The shape of the lens L is
As shown in FIG. 1 or 3, it is assumed that a small-diameter lens and a concentric annular lens are arranged in the center.

In the above-described embodiment, the case where a light emitting diode is used as a light emitting element has been described. However, a similar form can be adopted when a semiconductor laser is used as a light emitting element.

When a photodiode or avalanche photodiode as a light receiving element is used as an optical element, the optical fiber is transmitted to the optical transmission device so as to minimize the coupling loss between the optical fiber and each light receiving element. If a lens that focuses incident light on the light receiving element is designed, the same mode as described above can be obtained. Also in this case, if the diameter of the optical fiber to be coupled is different, the optimum lens diameter also changes accordingly.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0069]

According to the optical transmission device of the present invention, by providing two or more types of lenses having different optical characteristics such as a focal length and a lens diameter, a plurality of types of optical fibers to be coupled by the optical transmission device can be used. , And good bonding characteristics.

Further, if the two or more kinds of lenses are integrally molded with the resin molded body constituting the optical transmission device, the lenses can be molded at the same time as the resin molded body for sealing the optical element is molded. An optical transmission device can be manufactured without a special process load.

Further, by designing each of the two or more kinds of lenses so as to have an optical characteristic for improving the coupling characteristic of the optical fiber to be coupled by the optical transmission device, a plurality of types of optical fibers can be more reliably achieved. In contrast, good bonding characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a coupling portion between an optical transmission device and an optical fiber according to an embodiment of the present invention.

FIG. 2 is a graph showing an optical coupling efficiency with respect to a coupling fiber when only a lens diameter provided on an output light surface is changed in an optical transmission device having a light emitting diode as an optical element.

FIG. 3 is a cross-sectional view illustrating a configuration of a coupling portion between an optical transmission device and a quartz fiber according to another embodiment of the present invention.

FIG. 4 is a perspective view of the optical transmission device according to the embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical transmission module and an optical connector plug, showing a mode of coupling between a conventional optical transmission device and an optical fiber.

FIG. 6 is a cross-sectional view illustrating a configuration of a coupling portion between a conventional optical transmission device and an optical fiber.

FIG. 7 is a cross-sectional view illustrating a configuration of a coupling portion between another conventional optical transmission device and an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sealing resin 2 ... Lead frame 3 ... Light emitting element 4 ... Bonding wire 5 ... Quartz fiber 6 ... Plastic fiber L1 ... 1st lens L2 ... 2nd lens

Claims (10)

[Claims] 1. An optical transmission device coupled to a plurality of types of optical fibers, wherein: an optical element; a resin molded body that is transparent to a wavelength transmitted by the optical fiber and seals the optical element; An optical transmission device having at least two or more types of lenses having different optical characteristics on a surface of the resin molded body facing an optical fiber. 2. The optical system according to claim 1, wherein each of the two or more types of lenses is optically designed to improve a coupling characteristic between the optical transmission device and one of optical fibers coupled to the optical transmission device. An optical transmission device according to claim 1. 3. The optical transmission device according to claim 1, wherein the two or more types of lenses are formed integrally with the resin molded body. 4. The optical transmission device according to claim 1, wherein the two or more kinds of lenses are optically designed so as to improve a coupling characteristic between the optical transmission device and optical fibers having different fiber diameters. 5. The optical transmission device according to claim 1, wherein at least one of the two or more lenses is optically designed so as to improve a coupling characteristic between the optical transmission device and the quartz fiber, and at least one other lens is connected to the optical transmission device. The optical transmission device according to claim 1, wherein the optical transmission device is optically designed so as to improve a coupling characteristic with a plastic fiber. 6. The optical transmission device according to claim 2, wherein the optical element is a light emitting element, and a transmission wavelength of the optical fiber is an emission wavelength of the light emitting element. 7. The optical transmission device according to claim 6, wherein the light emitting element is a light emitting diode. 8. The optical transmission device according to claim 6, wherein the coupling characteristics include at least optical coupling efficiency. 9. The optical transmission device according to claim 6, wherein the coupling characteristic includes at least a transmission delay characteristic in an optical fiber. 10. The lens according to claim 1, wherein a lens having the smallest lens diameter among the two or more kinds of lenses is arranged on the center of the optical element, and another lens is annularly arranged around the lens. The optical transmission device according to claim 1.