JP2003207696A - Optical coupling part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the structure of an optical coupling part which can easily adjust the light outputted from an optical fiber. <P>SOLUTION: A metal cap 104 having a window for guiding a light output out is fixed to a metal stem 103 where a semiconductor laser 101 and a monitor diode 102 for monitoring the rear light output of the semiconductor laser are fixed and a semiconductor laser package in which an optical element is sealed against external environment. A spacer 106 of arbitrary thickness, and a glass field lens 105 fixed to a metal frame for coupling the light output of the semiconductor laser with an optical fiber are provided in this order; and the distance between the semiconductor laser 101 and lens 105 is adjusted by varying the thickness of a spacer 106, and the optical coupling magnification between the semiconductor laser and optical fiber is varied to control the quantity of light coupled with the optical fiber to a desired value. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a structure of an optical coupling part,
Especially, the optical coupling between the semiconductor laser and the optical fiber sealed in the metal stem and the metal cap with the window is controlled to any desired value by changing the thickness of the spacer inserted between the semiconductor laser and the lens, and The present invention relates to the structure of an optical coupling section that makes it possible to adjust the optical output from a fiber.

[0002]

2. Description of the Related Art The structure of a conventional optical coupling section is shown in FIG. A semiconductor laser diode (semiconductor LD) 601, a monitor diode 602, and a metal stem 6 for fixing them.
03 and a metal cap 604 with a lens. As shown in FIG. 6B, the light emitted from the semiconductor LD 601 is condensed by the lens and forms an image at the focal position 605.

At this time, with respect to the distance L1 from the semiconductor LD to the lens and the distance L2 from the lens to the optical fiber side, L2 / L1 is the image magnification M, and the spot size φ of the light beam at the semiconductor LD position is multiplied by M. It becomes the spot size of the light beam condensed on the fiber side and is coupled to the optical fiber.

The spot size of the semiconductor LD is 0.84 μ
Since the spot size of the optical fiber is about 5 m, the L1 and L2 are usually determined so as to achieve an image magnification of about 6 times, aiming at the optimum coupling magnification.

Further, the DF affected by the reflected return light
In the case of B laser, an isolator is inserted in the optical path.

FIG. 7 shows the structure of an optical module including an isolator. It is composed of a package 701 including a cap with a lens that seals a semiconductor laser and a metal stem, a ferrule 702 that fixes an optical fiber, and metal parts 703 and 704 that fix them. The isolator 705 is fixed to the tip of the ferrule 702 in the optical path, and the isolator 705 is also aligned and fixed at the same time when the optical fiber is aligned with the focal position of the semiconductor laser.

[0007]

By the way, the transmission speed and the optical output are specified for the characteristics of the optical module. When the semiconductor laser is directly modulated by turning the current on and off, the higher the transmission speed, the faster the rising of the optical output, so that a larger modulation current is required. The larger the modulation current, the larger the light output at the same time, but it often exceeds the upper limit of the light output required by the module characteristics.

In order to reduce the light output, a method of adding an attenuator to the connector portion of the optical fiber output is used to clear the light.

However, this method causes an increase in the number of parts and causes a cost increase, and it is necessary to prepare several kinds of attenuators in order to cope with optical outputs of various standards.

Further, when it is necessary to suppress reflected return light such as a DFB laser, a component in which an isolator chip is fixed to the tip of an optical fiber in advance is centered and fixed to the laser. It is necessary to fix the isolator chip with directivity to the direction of the laser chip,
Normally, the optical fiber with an isolator chip is rotated to align the direction, and then the alignment is fixed.

However, when the isolator is rotated, the optical fiber generates a force in the direction opposite to the rotation direction due to its torsional rigidity, which makes it difficult to properly align the directions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and to provide an optical coupling between a semiconductor laser sealed with a metal stem and a metal cap with a window and an optical fiber by a spacer inserted between the semiconductor laser and a lens. Another object of the present invention is to provide a structure of an optical coupling part in which the desired output can be controlled by changing the thickness and the optical output from the optical fiber can be easily adjusted.

A second object of the present invention is to provide a structure for facilitating alignment of the isolator with respect to the semiconductor laser by fixing an isolator for suppressing reflected return light to the semiconductor laser having a fixed lens. It is in.

[0014]

In order to achieve the above object, the optical coupling portion of the present invention is constructed as follows.

The optical coupling portion according to the invention of claim 1 is a metal cap having a window for taking out the optical output to a metal stem to which a semiconductor laser and a monitor diode for monitoring the backward optical output of the semiconductor laser are fixed. A semiconductor laser package in which the optical element is sealed against the external environment, a spacer having an arbitrary thickness, and a glass mold lens fixed to a metal frame for coupling the optical output of the semiconductor laser to an optical fiber. And sequentially adjusting the distance between the semiconductor laser and the lens by changing the thickness of the spacer, and changing the optical coupling ratio between the semiconductor laser and the optical fiber to control the amount of light coupled to the optical fiber to a desired value. Is characterized by.

The optical coupling section according to the invention of claim 2 is
A metal cap having a window for taking out the light output to the outside is fixed to a metal stem to which a semiconductor laser and a monitor diode for monitoring the rear light output of the semiconductor laser are fixed, and the optical element is sealed to the external environment. A semiconductor laser package, a spacer with a round hole having an arbitrary thickness, and a ball lens for coupling the optical output of the semiconductor laser to an optical fiber are sequentially provided, and the distance between the semiconductor laser and the lens is set to the spacer thickness. It is characterized in that the amount of light coupled to the optical fiber is controlled to a desired value by adjusting by changing the optical coupling ratio between the semiconductor laser and the optical fiber.

The invention according to claim 3 is characterized in that an isolator for suppressing reflected return light of laser light is fixed to the light output side of the semiconductor laser package to which the lens according to claim 1 or 2 is fixed. To do.

<Operation> According to the present invention, the optical coupling between the semiconductor laser sealed with the metal stem and the metal cap with the window and the optical fiber is changed by changing the thickness of the spacer inserted between the semiconductor laser and the lens. Thus, it becomes possible to control the light output from the optical fiber to any desired value. Therefore, as compared with the case where several kinds of attenuators are prepared, the magnitude of the light output can be reduced more easily, and the light output can be suppressed within the upper limit range required for the module characteristics.

Further, by fixing the isolator to the semiconductor laser package having the lens fixed, it is possible to easily align and fix the isolator. That is, in the conventional structure, when the isolator chip is previously fixed to the tip of the optical fiber and the component is centered and fixed with respect to the laser, when the isolator is rotated, the force of the optical fiber in the direction opposite to the rotation direction is caused by its torsional rigidity. Therefore, it is difficult to properly align the orientation, but there is no such problem.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention. The optical coupling part shown in FIG. 1 has a metal stem 103 having a semiconductor laser 101 and a monitor diode 102 fixed thereto, and a metal cap 104 having a window for taking out a light output to the outside. It has a semiconductor laser package sealed to it. In addition, a spacer 106 that determines the distance between the semiconductor laser and the lens and a glass mold lens 105 with a metal frame that collects light from the semiconductor laser are sequentially provided for this semiconductor laser package. The metal cap 104 is fixed to the metal stem 103 by resistance welding or the like to seal the semiconductor laser 101 from the external environment.

FIG. 2 shows the change in image magnification when the distance between the semiconductor laser and the lens is changed. The focal length of the lens at this time is 1.3 mm. When the distance between the semiconductor laser and the lens is changed from 1.5 mm to 2 mm, the magnification can be greatly changed from 6 times to 2 times.

FIG. 3 shows the rate of deterioration of the coupling efficiency to the optical fiber when the magnification is changed. The coupling loss at the position where the spot size is approximately 6 times that of the optical fiber is 0d.
It can be seen that, assuming B, the binding efficiency can be adjusted by about 4 dB by changing from 6 times to 2 times. As a result, the light output coupled from the semiconductor laser to the optical fiber can be adjusted to about 0 to 4 dB by changing the thickness of the spacer, and the increase in the light output when the semiconductor laser is directly modulated at high speed can be suppressed. Is possible.

FIG. 4 shows a second embodiment of the present invention. In the optical coupling part shown in FIG. 4, a metal cap 404 having a window for taking out light output to the outside is fixed to a metal stem 403 to which a semiconductor laser 401 and a monitor diode 402 are fixed, and the optical element is exposed to an external environment. It has a semiconductor laser package sealed to it. In addition, a spacer 406 that determines the distance between the semiconductor laser and the lens and a ball lens 405 that condenses light from the semiconductor laser 401 are sequentially provided for this semiconductor laser package. The metal cap 404 is fixed to the metal stem 403 by resistance welding or the like to seal the semiconductor laser 401 from the external environment.

The ball lens 4 is placed in the hole of the spacer 406.
It is possible to easily align the center of the spacer with the center of the lens by fitting 05 and fixing it with an adhesive or the like. Further, the light output from the semiconductor laser 401 can be controlled by changing the thickness of the spacer 406.

FIG. 5 shows a third embodiment of the present invention. The optical coupling part shown in FIG. 5 includes a semiconductor laser 501 and a monitor diode 50 for monitoring the backward optical output of the semiconductor laser.
2 is fixed to the metal stem 503, and a metal cap 504 having a window for taking out light output to the outside is fixed, and a spacer 505 and glass with a metal frame are attached to a semiconductor laser package in which the optical element is sealed from the external environment. The mold lens 506 is fixed, and the isolator 507 that suppresses the reflected light to the semiconductor laser is fixed thereon. By fixing the isolator 507 directly on the lens 506, it is possible to position and fix more easily than when the structure in which the isolator is previously fixed to the optical fiber is not centered and fixed without being displaced from the center of the optical axis. It is possible to

[0027]

As described above, according to the present invention, the optical coupling between the semiconductor laser and the optical fiber sealed in the metal stem and the metal cap with the window is adjusted by the thickness of the spacer inserted between the semiconductor laser and the lens. Since the structure is controlled to an arbitrary desired value by changing the height, the optical output from the optical fiber can be adjusted.

Further, according to the present invention, since the isolator is fixed to the semiconductor laser package having the lens fixed,
The isolator can be easily aligned and fixed, and reflected return light can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical coupling section according to a first embodiment of the present invention.

2 is a graph showing the relationship between the distance between the semiconductor laser and the lens in the optical coupling part of FIG. 1 and the image magnification.

FIG. 3 is a graph showing the relationship between the image magnification and the coupling loss of the optical coupling part in FIG.

FIG. 4 is a diagram showing a configuration of an optical coupling section according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of an optical coupling section according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration and an image forming relationship of a conventional optical coupling unit.

FIG. 7 is a diagram showing a configuration of another conventional optical coupling unit.

[Explanation of symbols]

101, 401, 501 semiconductor lasers 102, 402, 502 Monitor diode 103, 403, 503 Metal stem 104, 404, 504 Metal cap 105 Glass mold lens with metal frame 106, 406, 505 spacer 405 ball lens 506 Glass mold lens with metal frame 507 Isolator

Claims (3)

[Claims] 1. A metal cap having a window for extracting the light output to the outside is fixed to a metal stem to which a semiconductor laser and a monitor diode for monitoring the backward light output of the semiconductor laser are fixed, and the optical element is connected to the outside. A semiconductor laser package sealed against the environment, a spacer having an arbitrary thickness, and a glass mold lens fixed to a metal frame for coupling the optical output of the semiconductor laser to an optical fiber are sequentially provided, and the semiconductor laser and the lens are provided. An optical coupling part characterized in that the distance between them is adjusted by changing the thickness of the spacer, and the optical coupling ratio between the semiconductor laser and the optical fiber is changed to control the amount of light coupled to the optical fiber to a desired value. 2. A metal cap having a window for extracting the light output to the outside is fixed to a metal stem to which a semiconductor laser and a monitor diode for monitoring the rear light output of the semiconductor laser are fixed, and the optical element is externally connected. A semiconductor laser package sealed against the environment, a spacer with a round hole of an arbitrary thickness, and a ball lens for coupling the optical output of the semiconductor laser to an optical fiber are sequentially provided, and the distance between the semiconductor laser and the lens is provided. Is adjusted by changing the thickness of the spacer, and the optical coupling ratio between the semiconductor laser and the optical fiber is changed to control the amount of light coupled to the optical fiber to a desired value. 3. An optical coupling part, wherein an isolator for suppressing reflected return light of the semiconductor laser light is fixed to the light output side of the semiconductor laser package to which the lens according to claim 1 or 2 is fixed.