JPH04100012A - Optical module - Google Patents

Abstract

PURPOSE:To obtain the optical module which has desired coupling efficiency and is stable against disturbance such as temperature variation by rotating polarized light by a polarizer. CONSTITUTION:The light which is emitted by a polarized light source 1 and polarized, for example, as shown by an arrow P1 in a figure is made incident on a polarizer 2 whose axis P0 of polarization is at an angle theta to a polarizing direction P1. Then the light which is transmitted through the polarizer 2 is polarized light P2 in the same direction with the axis P0 of polarization of the polarizer 2 and the intensity of the light is a component in a direction matching the axis P0 of polarization of the polarizer 2 in the incident light. Consequently, the intensity of projection light is adjustable by rotating the polarizer 2 on the optical axis (by varying theta) and the desired coupling efficiency and a desired focusing state are obtained independently of each other, thereby obtaining the optical module which is stable against disturbance such as temperature variation, etc.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an optical module that can supply a desired level of optical output to an optical communication medium in the field of optical communication, etc., and that can achieve a desired coupling efficiency and resist disturbances such as temperature changes. The aim is to provide a light-emitting element module that is stable against the optical axis. and a rotatable polarizer, and is configured to rotate the polarized light by the polarizer to provide a light output adjusted to a desired level.

[Industrial Field of Application] The present invention relates to a light emitting element module, and more particularly to a light emitting element module that can supply a desired level of light output to an optical communication medium in the field of optical communication.

In recent years, in the field of optical communications, high-output light sources are required as light sources for high-speed, large-capacity digital optical communications, and as light sources for analog optical communications used in CATV and the like.

As such light sources, improvements are being made in semiconductor laser chips and the like that serve as light emitters, and at the same time progress is being made in improving coupling optical systems for coupling light emitted from the laser chips to optical fibers.

[Prior Art] FIGS. 4(A) and 4(B) show the structure of a light emitting element module according to a conventional technique. To explain with reference to FIG. 4(A), multi-mode light emitted from a laser 51, which is a light source, becomes a single-mode parallel light beam by a lens 52.
The light is focused by another lens 53 and irradiated onto the light receiving surface of the ferrule 54 provided at the end of the optical fiber 55.

Incidentally, due to the requirements of optical communication systems, the level of the light intensity entering from the ferrule 54 is often determined. This adjustment of the light intensity is performed by moving the ferrule 54 in the direction of the arrow shown in the figure to reduce the incident intensity.

FIG. 4(B) is a cross-sectional view schematically showing the focused state of light incident on the fiber. The incident intensity is adjusted by adjusting the ferrule 54 in the vertical direction in the figure, and when the optimum incident intensity is achieved, the state is as shown in FIG. 4(B). That is, the fiber has a core 56 and a flannel 57 provided around the core, or the optical spot 59 of the incident light with the light intensity adjusted is placed away from the center of the core 56. In this way, since the light spot 59 is coupled to the fiber even from the best focusing position, the reflected light may return to the incident side at the end face of the fiber, or the incident light may enter the Clara I57. For example, this cladding mode leaks to the outside when materials with different refractive indexes come into contact around the cladding 57 at an intermediate position of the optical fiber, causing a change in light intensity. In such light emitting devices, the structural parts are made of metal, or the metal expands and contracts thermally when the outside temperature changes.

At this time, since the expansion and contraction do not occur uniformly, changes occur in the state of collection of light spots and throats on the ferrule. When the focus state is adjusted in the state shown in Figure 4 (B),
A slight displacement can result in a large change in light intensity. Compared to the case where the light spot is focused on the center of the core, when the light spot is adjusted to be shifted from the center of the core, the subsequent allowable amount of deviation becomes smaller, for example, about 172 degrees.

[Problems to be Solved by the Invention] In this way, the focus adjustment of the conventional light emitting element module is
The stability of the bonded system against temperature changes is poor, and it is easily affected by other disturbances.

An object of the present invention is to provide a light emitting element module that achieves a desired coupling efficiency and is stable against disturbances such as temperature changes.

[Means for Solving the Problems] FIGS. 1A, 1B, and 1C are diagrams explaining the principle of the present invention.

FIG. 1(A) shows the configuration. In the figure, polarized light source 1
provides light polarized on the optical axis. A polarizer 2 whose deflection axis is rotatable around the optical axis is disposed on this axis.

Note that a focusing means 3 is arranged for the light transmitted through the polarizer 2, and supplies focused light onto the surface of the photoreceptor 4. The focusing means 3 is, for example, a lens, and the photoreceptor 4 is, for example, a ferrule provided at the end of an optical fiber.

[Effect] The instability of the optical coupling system due to disturbance due to the conventional technology is as follows.
This may be due to the fact that the focusing state is adjusted from the best point in order to obtain the desired coupling efficiency. In the present invention, coupling efficiency is achieved by adjusting the polarizer.

FIG. 1(B) schematically shows the polarization and focusing state of light in light emitting element module No. 2 of FIG. 1(A). The light emitted from the polarized light source 1 is polarized, for example, as shown by arrow P1 in the figure. A polarizer 2 is arranged for this polarized light, and the polarization axis P of the polarizer 2. has an angle of θ with respect to the polarization direction P1 of the incident light. Then, the light transmitted through the polarizer 2 has a polarization axis P of the polarizer 2. becomes polarized light P2 in the same direction. The intensity of this light is equal to the polarization axis P of the polarizer 2 among the incident light. The component in the direction coincides with .

Therefore, by rotating the polarizer 2 on the optical axis (
By changing θ), the intensity of the emitted light can be adjusted.

Note that FIG. 1(C) is a graph showing the transmitted light intensity with respect to the change in the angle θ of the polarization axis of the polarizer 2. The intensity of the transmitted light varies in the form of C0820. , therefore polarizer 2
By rotating the , it is possible to provide an arbitrary level of emitted light.

What is important here is to combine the polarized light source 1 with the polarizer 2 to form output light having a desired level of light intensity.

By condensing the light adjusted to the desired light intensity onto the photoreceptor 4 by the focusing means 3, the desired coupling efficiency and desired focusing state can be obtained independently.

[Example] The present invention will be described below with reference to Examples.

FIG. 2 is a schematic cross-sectional view showing a light emitting device module according to an embodiment of the present invention. A laser chip 13 is disposed within the main package 11, and a monitor element 12 for output monitoring is provided behind it. Further, a lens 14 is arranged in front of the laser chip, and a lens 14 is arranged in front of the laser chip.
Converts the light emitted from the rays into parallel rays. In addition, the laser 14
A single mode of light is selected by extracting light traveling in a desired direction in front of it. These laser chip 13, monitor element 12, and lens 14 are arranged on a substrate 19, and this substrate is cooled by a Vertier cooler 18. A sapphire window 20 is provided in front of the main backbone 11, and the emitted light is taken out to the outside through this sapphire window 2o. Polarizer 15 in front of the sapphire window 20
or rotatably mounted. Furthermore, polarizer 15
Another lens 16 is provided in front of the lens 16 to form a so-called two-sphere combination system to focus the incident light on a desired position. This lens 16 is attached to a lens holder 21
is maintained. The light focused by the lens 16 illuminates the end face of the ferrule 22. An optical fiber 23 extends from the ferrule 22, and light incident on the ferrule 22 propagates through the optical fiber 23. Note that the ferrule 22 is held by a core-type holter 17.

With this configuration, the light of other modes emitted from the laser chip 13 is converted into parallel light beams by the lens 14, selected as a single mode, and transmitted through the sapphire window 20 and the polarizer 15. The light intensity is adjusted to a desired intensity by the lens 16, and the light is focused at the optimum position on the surface of the ferrule 22.

Since the incident light is focused on the optimum position on the ferrule 22, this optical coupling system exhibits excellent stability against disturbances caused by thermal changes and the like.

FIG. 3 shows a can type light emitting device module according to another embodiment of the present invention. In this embodiment, a cap 33 is placed over the stem 31 to form a can.

A laser chip 35 is arranged inside this can 33. A monitor tie-out 32 for monitoring is arranged behind the laser chip 35. A polarizer 34 is arranged on the front surface of the can 33, and its rotation angle can be adjusted. Since the light emitted from the laser chip 35 is already polarized, adjusting the angle of the polarizer 34 changes the light intensity of the emitted light. In this way, output light with adjusted light intensity can be provided. In the case of this embodiment, an optical coupling system similar to the embodiment shown in FIG. 2 is constructed by using this can type light emitting element module in combination with an optical system such as a lens and an optical fiber on the light receiving side. .

Although the present invention has been described above with reference to limited examples, the present invention is not limited to these.

For example, instead of a semiconductor laser, a combination of a light emitting diode and a polarizer can be used as the polarized light source.

Optical isolators can also be used. Furthermore, a mirror or the like can be used instead of a lens as a focusing means. The photoreceptor is not limited to optical fibers either. It will be obvious to those skilled in the art that various other changes, improvements, combinations, etc. are possible.

[Effects of the Invention] As explained above, according to the present invention, the desired coupling efficiency can be obtained in the best focusing state, so light emission with excellent stability against disturbances such as temperature changes can be achieved. It is possible to obtain an element module.

[Brief explanation of drawings]

FIGS. 1(A), (B), and (C) are diagrams explaining the principle of the present invention, FIG. 1(A) is a schematic diagram showing the configuration, and FIG.
B) is a conceptual diagram for explaining polarization and focusing, and Fig. 1 (C
) is a graph showing the change in transmitted light intensity with respect to the polarization axis angle of the polarizer, FIG. 2 is a schematic cross-sectional view of a light emitting element module according to an embodiment of the present invention, and FIG. 3 is a graph according to another embodiment of the present invention. 4(A) and 4(B) are schematic cross-sectional views of a can-type light-emitting element module, and are diagrams for explaining the functions of a light-emitting element module according to the conventional technology. FIG. 4(B), which is a schematic diagram for explanation, is a cross-sectional view showing the focused state of light incident on the fiber. In the figure, 13.35 15.34 14.16 Polarized light source Polarizer Focusing means Photoreceptor Laser chip Polarizer Lens ferrule (A) Configuration P convex (B) Polarization and focusing CO52θ ( C) Transmitted light intensity Explanation of the principle of the present invention Fig. 1 Fig. 3 (B) Focusing state on the fiber Conventional technology Fig. 4 59: Optical subometry

Claims (2)

[Claims] (1) A polarized light source (1) capable of generating polarized light polarized along the optical axis; and a polarizer (1) disposed on the optical axis and capable of rotating the polarized light around the optical axis. 2), wherein the polarized light is rotated by the polarizer to provide an optical output adjusted to a desired level. (2) Furthermore, a focusing means (3) capable of focusing the light transmitted through the polarizer (2), and a photoreceptor (4) that receives the light focused by the focusing means (3). The optical module according to claim 1, comprising: