JPS62203108A - Light emitting module - Google Patents

Abstract

PURPOSE:To easily obtain plural outputs, to facilitate the package and adjustment of optical fibers, and to utilize the light output of a light source without any waste by arraying the optical fibers radially in three dimensions within a specific three-dimensional angle. CONSTITUTION:A light emitting element 1, light convergence parts 2-1-2-3, and optical fibers 3-1-3-3 are integrated in one case to form a light emitting module 100. The light emitting part 1A of the light emitting element 1 emits light having the specific three-dimensional angle around an optical-axis direction perpendicular to its surface and the light convergence parts 2-1-2-3 and the optical fibers 3-1-3-3 paired with the light convergence parts 2-1-2-3 are arranged within the three-dimensional angle radially to the light emission source 1A. Light incidence on the optical fiber 2-1 in the optical-axis direction is nearly equal to light incident on the optical fibers 2-2-2-3 in slanting directions. Consequently, none of light components emitted radially from light emission source 1A is wasted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a light emitting module that combines and integrates a light emitting element and an optical fiber, and particularly relates to a light emitting module in which light from a light emitting diode is introduced into a plurality of optical fibers. The invention relates to an integrated light emitting module.

[Prior Art] Conventionally, a light emitting module has one light emitting element and one optical fiber, and the basic configuration is as shown in FIG. Consisting of

Here, the points that must be taken into consideration are (1) high efficiency of optical coupling, and (2) mountability and reliability. In particular, high efficiency is important, and various optical coupling methods have been devised so far (for example, Obtronics (1982)
11, pp18-24). Its optical coupling efficiency (LE
The proportion of light emitted from D that is taken into the optical fiber reaches 60 to 80% for semiconductor lasers, but only a few percent for LEDs. The reason for this will be explained next.

As shown in FIG. 8, the optical fiber consists of two media with different refractive indexes, namely a core 11 (refractive index n+) and a crut 12 (refractive index n2).

>n. Therefore, the light (1) incident on the end face of the core 11 at a certain angle θ propagates inside the core 11 while being reflected at the core-blood interface, but the light (2) incident at a certain critical angle 06 or more cannot propagate within the core and exits to the outside.

In this way, the optical fiber has a critical angle θ at which it can receive light. exists, and this is called the acceptance angle, which is calculated using the following formula.

θ. = 5in-’p Also, N^= sinθ.

is called the numerical aperture of an optical fiber, and is an important quantity that represents the waveguide characteristics of an optical fiber.

In general, the NA of optical fibers used for optical fiber communications
is 0.15 to 0.2, so the acceptance angle is 8 to 11
The optical fiber has a small acceptance angle and a small core diameter (100 μm or less), so the radiation beam spread over a wide angle can be efficiently coupled to the optical fiber. It's very, very difficult.

Generally, there is a lens coupling method as a method for efficiently coupling light to an optical fiber.

Next, the principle of optical coupling is shown in Figures 9 (A) to (C).
This is explained by: Here, the size of the light source 14 is D,
The light imaged on the end face of the optical fiber by the lens 13 -
The size of the image 15 is expressed as D'. Further, the diameter of the core 11 is assumed to be a. Optical power (Pr) coupled to optical fiber
In general, the conditions for maximizing are the size D' of the light source image 15 formed on the end of the optical fiber and the size a of the diameter of the core 11.
This is the case when D'=a, that is, D'=a.

If D'>a in FIG. 9(A), then D' in FIG. 9(B)
'=a, and FIG. 9(C) shows the case where D'<a.

Here, the acceptance angle of the optical fiber is θ. Therefore, when the light source 14 is viewed from the lens 13 side, the solid angle that can be incident on the optical fiber (referred to as the equivalent solid angle of incidence) is the 9th solid angle.
The size decreases in the order of FIG. 9(A), FIG. 9(B), and FIG. 9(C). Therefore, it is clear that the case of FIG. 9(B) and the case of FIG. 9(C) are different from each other in the case of FIG.
), P is larger.

In the case of Fig. 9 (A) and the case of Fig. 9 (B), the case of Fig. 9 (8) is larger in terms of solid angle, but D'> a, and the light source image and the core end face are different. The efficiency decreases by the ratio of the area of . Therefore, although it depends on the radiation intensity distribution, Pf is generally larger in the case of FIG. 9(B).

Further, the size of the light source 14 greatly influences the optical coupling efficiency with the optical fiber. As shown in FIGS. 1θ (^) and (B), it can be seen that the smaller the light source 14 is, the larger the equivalent solid angle of incidence becomes, and the optical coupling efficiency improves. Therefore, the size of the light source for optical fiber communication is reduced. However, if it is made too small, the optical output of the element itself will also decrease, so there is a limit to practical use.
It is about 40 μm. By the way, even if the size of the light source 14 is as small as 30 μ-, the equivalent solid angle of incidence is only 18
degree (optical fiber core 11 diameter 50 μm, NA 0.
2) and a small LE with a wide-angle radiation intensity distribution.
In D, its optical coupling efficiency is small.

Next, the radiation intensity distribution of the LED will be explained with reference to FIG. 12. A light emitting diode (LED) is generally a surface emitting type, which takes out light in a direction perpendicular to a pn junction surface, and has a flat crystal surface, as shown in FIG. 11, for example. GaA, a constituent material of LEDs
jZ As16th refractive index n! is as high as 3.4, so most of the light generated inside the crystal cannot be taken out to the outside.

= 5in-' (n2/r+1) "Since the F is 17 degrees, light incident on the interface between air 17 and GaAJ2 As1a at an angle of 17 degrees or more is reflected, attenuated and disappears inside the crystal. As a result, only about 1.4% of the actually generated light can be extracted to the outside.The radiation intensity distribution in this case becomes a Lambertian distribution, and the radiation intensity in the direction shifted by an angle θ from the direction perpendicular to the crystal surface is cos
It is proportional to θ. Therefore, the radiation intensity distribution is quite wide.

Furthermore, in order to improve the efficiency of radiation to the outside, a dome-shaped LED has been developed in which the substrate crystal 16' in the light emitting direction is processed into a lens shape, as shown in FIG. In this case, it is possible to extract most of the light generated inside the crystal to the outside. However, even if light can be efficiently extracted to the outside, the absolute value of the radiation intensity of the light that can be coupled to the optical fiber is not much different from that of a flat LED.

The reason for this is that due to the lens effect of the GaAJ2^S crystal layer 16' processed into a dome shape, the actual light emitting surface is enlarged and observed from the top surface of the chip (in the optical axis direction). The size of the apparent emission diameter (effective emission diameter) at that time differs depending on the chip structure, but when the dome diameter is 400μm, even if the actual emission diameter is 30μm, it is 100μI11~2
This is because the optical coupling efficiency is greatly degraded based on the lens coupling principle.

Therefore, with one fiber, most of the light is not utilized, not only in flat type LEDs but especially in dome type LEDs.

In this way, in the conventional light-emitting module that is optically coupled to a single optical fiber, the angle at which the optical fiber receives light is only about 10°, and the core diameter is 100 μm.
Due to the small diameter of the LED, which has a wide beam radiation angle, only a few percent of its light output can enter the optical fiber.

In addition, in order to effectively utilize the light recently extracted outside,
There have been reports of cases where multiple optical fibers are coupled instead of a single optical fiber (1989 IEICE General National Conference 894. 1978).

989). As shown in FIG. 13, the output light from the light emitting element 1 is passed through the optical coupling circuit 2 to the optical fiber 3-1.3-2°3- arranged along the optical axis direction.
3.3-4.3-5.3-6.

In this case, there is a drawback that light that spreads over a wide angle other than in the optical axis direction cannot be effectively introduced into the core portions of the optical fibers 3-1 to 3-6.

In this way, there are examples of optical coupling to multiple optical fibers, but even in this case, optical coupling is performed from the optical axis direction, and in LEDs with a wide radiation beam angle, optical coupling is not possible effectively. Not only is this not possible, but the excess loss is large, and the optical output per fiber is extremely low compared to the optical output after entering a single conventional optical fiber.

Furthermore, conventionally, in order to obtain the desired optical output, the first
As shown in FIG. 4, the light emitting element 1-1. Optical coupling circuit 2-1
．． A light emitting module including the optical fiber 3-1 constitutes one set, and this set includes light emitting elements 1-2 to 1-N.

Optical coupling circuit 2-2 to 2-N, optical fiber 3-2 to 3-N
There was also an example where N sets were arranged in parallel to obtain N times the optical output.

This not only increases the number of peripheral circuits such as drive circuits in addition to the number of light emitting elements, making the configuration more complex, but also causes electrical interference such as signal-to-noise ratio and frequency characteristics. It had the disadvantage of being extremely uneconomical, such as requiring compensation.

[Problems to be solved by the invention] As mentioned above, in optical fiber communication, (1) How much light output from the light emitting element can be input into the core of the optical fiber (high output)? (2) How much light can be distributed from one light source?
Increasing the number of outputs) is an extremely important issue in extending transmission distance and improving the functionality of optical communication systems.

Therefore, the present inventors performed the following experimental measurements, and considered and studied the results.

That is, the optical coupling characteristics to the fiber were measured for a dome-shaped LED with a relatively uniform far-field radiation intensity distribution as shown in FIG. The results are shown in FIG.

This is a focusing rod lens (N^: 0.46
．． A diameter of 1.8φ) is used, and the coupling direction shown by the optical axis direction of the LED and the direction θ between the rod lens is taken as a parameter, and the light to the graded index optical fiber (Gl-50) is calculated with respect to the pressure between the light source and the lens 1111. This is a measurement of bond strength.

Here, the purpose of using a lens is to selectively image the field pattern near the light source onto the core of the optical fiber, and changing the distance 11!1 corresponds to changing the magnification of the lens. . What can be seen from this measurement result is that when comparing the points where the incident intensity to the optical fiber is maximum, the maximum value is clearly larger in the oblique direction than in the optical axis direction (θ = 0°); The larger θ is, the larger the value is. Further, the larger θ is, the smaller the value is and the maximum value is reached. In other words, it was found that the larger θ is, the more the optical coupling strength is increased by increasing the magnification of the lens. The important feature obtained here is that, as shown in Figure 15, although the radiation pattern has directivity in the optical axis direction, a higher optical coupling strength is obtained in the oblique direction than in the optical axis direction. The point is that

Considering the reason for this, as mentioned above, the optical fiber has an acceptance angle θ. Therefore, not all light incident on the core of the optical fiber can propagate within the optical fiber, but only light within the acceptance angle can propagate. For this reason, the size of the light source becomes an important factor, and the smaller the light source, the better the optical coupling efficiency. Considering the above measurement results, it is thought that this is because the apparent size of the light source becomes smaller as θ becomes larger. This means that the larger θ is, the
This can also be said from the fact that 1 is small when the optical coupling strength is maximum. This is because if the size of the light source is small, the coupling strength is at its maximum, i.e. the size and area of the light source image)
This is because in order for the size and area of the core to match, it is necessary to increase the magnification of the lens, and 2 becomes smaller.

In this way, by utilizing the fact that the optical coupling efficiency improves as θ increases, even if the radiation intensity distribution is generally directional in the optical axis direction, it is possible to obtain high output from the surrounding direction as well as from the optical axis direction. It was found that a high output optical coupling strength above the optical axis can be obtained.

Therefore, they discovered a way to effectively utilize this effect to distribute and couple the light from the light source to multiple optical fibers without wasting any waste.

In view of the above, an object of the present invention is to provide a light emitting module that effectively couples all of the emitted light from a light emitting source element in the direction of its tip axis, as well as the light in oblique directions other than the optical axis, to an optical fiber. It is about providing.

Another object of the present invention is to provide a light emitting module that can distribute the output light from one light source almost uniformly.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a light emitting section with a light emitting section that has a solid angle within which output light from the light emitting section is emitted.
The present invention is characterized in that a plurality of combinations of light condensing means and optical fibers for receiving the light condensed by the condensing means are arranged radially with respect to the light emitting section.

[Function] In the present invention, in order to make effective use of emitted light in directions other than the optical axis direction, which was wasted in the past, optical fibers are arranged radially with respect to the light source and are arranged diagonally. Also from the direction, the light is coupled to the optical fiber via an optical coupling circuit such as a lens.

By implementing the present invention, optical fibers can be arranged roughly radially around the light emitting element along the optical axis direction, and the emitted light from the light source can be captured without wastage and used effectively.

Furthermore, by coupling to a plurality of optical fibers from an oblique direction, efficient optical coupling can be achieved and high output can be obtained.

Furthermore, since a plurality of optical fibers are coupled to each other, it also functions suitably as an optical distributor.

Moreover, these can realize an extremely excellent light-emitting module that is easy to implement and adjust, and is highly practical.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a light emitting module according to the present invention. In the figure, 1 is a light emitting element, 2-1.2-2.
Reference numeral 2-3 is a light condensing unit, and reference numeral 3-1.3-2.3-'3 is an optical fiber. These parts are integrated into one case to form the light emitting module 100.

Here, in the light emitting portion IA of the light emitting element 1, output light from the light emitting portion IA is emitted at a predetermined solid angle around the optical axis direction perpendicular to the surface thereof.

The above-mentioned light collecting parts 2-1 to 2-3 and these light collecting parts 2-1
The optical fibers 3-1 to 3-3 paired with each of ~2-3 are positioned within such a solid angle, and the light emitting source l^
Arrange radially against.

In FIG. 1, the light that enters the optical fiber 2-1 in the optical axis direction is almost equal to the light that enters the optical fibers 2-2 to 2-3 in the oblique direction. Without wasting the light components emitted to the optical fibers, the light can be effectively collected and taken into each optical fiber, and a high optical output can be obtained as a whole.

In FIGS. 2 and 3, a convex lens is used for the above-mentioned condensing part, and in FIG. 2, the distance between the light emitting part IA and the lens is the same @11, and the lens diameters Dl, D2. This is an example in which the focal length is changed from D3, and Figure 3 shows an example using a lens with the same focal length.
This is an example in which the distance m° C. between the light emitting part and the lens and the lens aperture are changed. Both were constructed so that maximum optical coupling power could be obtained to each optical fiber.

FIG. 4 shows yet another embodiment of the present invention, in which light from a light emitting diode 5 having a dome-shaped light emitting section IA is
The light is focused by two focusing rod lenses 6-1 to 6-7, and the output light is made to enter seven optical fibers 3-1 to 3-7, respectively.

An example of a specific structure of this example is shown in FIG. Here, a light emitting diode 5 is attached to a substrate 9, and a substantially hemispherical hold container 10 is further placed around the light emitting diode 5.
to be placed. This container 10 has holes for inserting the seven rod lenses 6-1 to 6-7 shown in the fourth figure at an angle of 30° with respect to the optical axis direction from the light emitting part IA and the front axis direction.
Provided radially in an inclined direction. Attach the lens holders 7-1-7-7 to these holes, respectively, and then attach the rod lens 6.
-1 to 6-7 are inserted into one ends of these lens holders 7-1 to 7-7. The optical fibers 3-1 to 3-7 are connected to the other ends of the lens holders 7-1 to 7-7, and the optical fiber sleeve 8
-1 to 8-7, respectively.

In this example, the diameter of each rod lens 6-1 to 6-7 is set to 1.
8mm %NA is 0.46, each lens 6-1 to 6-
7 and the light emitting part IA is 3.5 mm, and furthermore, in order to be able to spatially arrange a large number of rod lenses 6.1 to 6-7, these rod lenses 6.1 to 6-
7 about 1+o from each tip of lens holder 7-1 to 7-7.
Make the n stand out.

Here, when a light emitting element with dome-shaped characteristics is used, the optical power from the optical fiber is 86 μW in the optical axis direction.
A high output of about 110 μg in 5 circumferential directions was obtained.

FIG. 6 shows yet another embodiment of the invention. In this example,
Optical fiber 10-1.10-2.10-3.10-4.
Each tip of the fiber 10-5 is melted to form a spherical photosphere fiber, and these fibers are placed directly adjacent to the light emitting portion IA of the light emitting element 5. In this embodiment, the optical fiber and the condensing section are integrated, so the configuration is very simple, and there is also the advantage that the module can be configured in a small size. .

[Effects of the Invention] As is clear from the above, according to the present invention, (1) whereas conventionally optical fibers are arranged two-dimensionally on a plane, in the present invention optical fibers are arranged three-dimensionally in a predetermined three-dimensional manner; By arranging them radially within a corner, multiple outputs can be easily achieved, and implementation and adjustment are also easy. Furthermore, the light output from the light source can be used without wasting it.

↓ (2) Since the optical coupling efficiency is higher when coupled in an oblique direction,
Even if the radiation intensity distribution is directional in the optical axis direction, high-power optical coupling output can be obtained from directions other than the optical axis direction, and long-distance distribution is possible.

(3) Since it is output through multiple optical fibers,
This light emitting module can function as a light distributor.

(4) Functionally, the conventional method shown in Figure 14 uses multiple light emitting modules, but this increases the number of peripheral circuits such as drive circuits in addition to the number of light emitting elements, making the configuration complex. In contrast, the light-emitting module of the present invention is extremely uneconomical, as it not only causes electrical interference such as signal-to-noise ratio and frequency characteristics, but also requires compensation for variations between elements. It is extremely economical in terms of construction, and the structure can be simplified.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of a light emitting module according to the present invention, Fig. 2 is a block diagram of an embodiment in which optical coupling lenses according to the present invention are arranged on the same circumference, and Fig. 3 is a block diagram of an embodiment of the light emitting module according to the present invention. Fig. 4 is a perspective view of an embodiment of the light emitting module according to the present invention, and Fig. 5 is a sectional view of an embodiment of the light emitting module according to the present invention. , FIG. 6 is another implementation component of the light emitting module according to the present invention, FIG. 8 is an explanatory diagram of the light receiving principle of the optical fiber, and FIG. 9 (A)
~(C) is an explanatory diagram of the optical coupling principle of optical fibers, Figures 10 (A) and (B) are explanatory diagrams of the optical coupling principle depending on the size of the light emitting source, and Figure 11 is an explanation of the principle of surface emitting diode. Fig. 12 is an explanatory diagram of a dome-shaped diode, Fig. 14 is a configuration diagram of a conventional multiplex light emitting module, Fig. 15 is a radiation intensity distribution characteristic diagram of a dome-shaped light emitting diode, and Fig. 16 is a dome-shaped light emitting diode. FIG. 1.1-1.1-2.1-3. ..., 1-N...
- Light emitting element, 2.2-1.2-2.2-3-... Optical coupling circuit, 3.3-1.3-2.3-3.3-4.3-5.
3-6.3-7.3-N - Optical fiber, 5... Dome-shaped light emitting diode (LED), 6-1.
6-2.6-3.8-4.6-5.6-6.6-7...
・Focusing rod lens, 7-1.7-2.7-3-...Lens holder, 8-1
．． 8-2.8-3...Fiber sleeve, 9...Light emitting element substrate, io...Hold container, 10-1.10-2.10-3.10-4.10-5.
... Spherical fiber, 11... Core, 12... Clad, 13.13-1.13-2.13-3... Lens, 1
4... Light source, 15... Light source image, 16--- GaAj2As crystal, 16'... Lens-shaped GaAj2Asf substrate crystal, 1
7...Air. ** Mobigu bow fire 1φ, - mouth, 0 lever 〉〉〉Fig. 4 Urushi climbing bow ゛゛゛゛゛゛゛゛゛゛゛〇〇〇〇〇〇〉〉〉〉〉〉〉〉〉〉〉〉〉〉〉〉71z尤纤/) Recharge point 哩 / 7-bit diagram Fig. 8 A≦P2-PJ A-phii<'7T 尤 (4-pin, reason 1 ←) Reference figure 9 Fig. 1 O-be Theory of type 4 buoyode e no bow diagram Figure 12 Figure 13
Figure 15

Claims (1)

[Scope of Claims] 1) A light condensing means and a light that receives the light condensed by the light condensing means within a solid angle from which output light from the light emitting section is emitted with respect to the light emitting section. A light emitting module characterized in that a plurality of fiber combinations are arranged radially with respect to the light emitting section. 2) In the light emitting module according to claim 1, the combinations are arranged radially with respect to the light emitting section so that the optical outputs of the optical fibers in each of the plurality of combinations have substantially equal intensities. A light emitting module characterized by being arranged in.