JP2004191607A - Optical module and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module which realizes low cost manufacturing by a conventional manufacturing device, and increases the mountability of an optical fiber without losing the high speed performance of an electric signal. <P>SOLUTION: This optical module is provided with an LD element 1 held by a stem 4, a ferrule 3 held by a fiber holder 6 for supporting an optical fiber 2 and a mirror 9 for reflecting lights. The mirror 9 is arranged so as to be adjusted and fixed independently of the optical fiber 2 to the direction of the optical axis of the LD element 1, and the ferrule 3 is arranged so that the supporting direction of the optical fiber 2 can be made almost vertical to the optical axis of the LD element 1, and the LD element 1 and the optical fiber 2 are optically connected through the mirror 9. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical module for optically coupling an optical element, such as a laser diode (LD) or a photo diode (PD), used for optical communication and measurement with an optical fiber, and a technique for modularizing the optical element with the optical fiber. It is.
[0002]
[Prior art]
FIG. 4 shows an example of a structural diagram of a conventional optical module using a laser diode element (see Non-Patent Document 1).
[0003]
The conventional optical module has a laser diode (hereinafter abbreviated as LD) element 41 and a ferrule 43 supporting an optical fiber 42, and a ferrule 43 together with a stem 44 and an optical fiber 42 to which the LD element 41 is attached. The optical module for transmission is configured by joining the fiber holder 46 holding the optical fiber through a cylindrical package 45. Incidentally, by using a photodiode (hereinafter abbreviated as PD) element instead of the LD element 41, an optical module for reception can be obtained.
[0004]
A plurality of electrode pins 47 are provided on the stem 44, and an electric signal is supplied to the LD element 41 by using the electrode pins 47. The electrode pins 47 enable mounting on a printed circuit board or the like. An aspherical glass lens 48 for condensing light is provided on the optical axis of the LD element 41 inside the package 45, so that light emitted from the LD element 41 is condensed and guided to the optical fiber 42. . That is, the LD element 41, the aspherical glass lens 48, and the optical fiber 42 are arranged so as to be on the same straight optical axis. In addition, a sealing cap 49 is provided on the stem 44 so as to cover the periphery of the LD element 41 for sealing the LD element 41, and the sealing cap 49 is transmitted through the hermetic sealing glass window 50 to be removed from the LD element 41. Light is being emitted.
[0005]
In the optical module having the above-described structure, the optical axis of the LD element 41 is adjusted by moving the stem 44 in the XY directions, and the ferrule 43 is moved in the Z direction by moving the stem 44 through the aspherical glass lens 48. By adjusting the optical path length to the optical fiber 42, the light from the LD element 41 is optically coupled to the optical fiber 42 in an optimal state.
[0006]
The cylindrical optical module called a coaxial optical module is widely used as a communication optical module for transmitting and receiving optical signals by using an LD element, a PD element, and the like. The coaxial optical module is easy to manufacture because the members such as the package 45 have a cylindrical shape, and the alignment work involved in the manufacturing is simple as described above. And can be manufactured at low cost.
[0007]
[Non-patent document 1]
Proc. Of the IEICE Spring National Convention, 1990, p. 4-319
[0008]
[Problems to be solved by the invention]
In the coaxial optical module, electric signals are basically exchanged using the electrode pins. Therefore, when the optical module is mounted on a printed board, it is often mounted horizontally by bending the electrode pins. In such a mounting method, the length of the electrode pins is affected by signal delay, and the electric signal band is limited to about 1 GHz, which is not suitable for transmission of an ultra-high-speed signal exceeding several GHz.
[0009]
In order to improve the band of the electric signal, the optical module may be set upright on the substrate so as to make the electrode pins as short as possible. In this mounting method, the optical fiber itself attached to the optical module is also attached vertically to the substrate. However, the optical fiber itself has a minimum bending radius specified to prevent breakage, and cannot be bent with a very small bending radius R. As a result, the mountability of the optical fiber is extremely poor, and high density cannot be achieved. .
[0010]
Also, in order to improve the band of the electric signal and improve the mountability of the optical fiber, a part of the substrate is cut out, and an optical module is mounted in the notch, thereby shortening the electrode pins and soldering. Such a method is also used. However, in this mounting method, soldering of the electrode pins is difficult, and manual work is required, and as a result, workability is reduced.
[0011]
Therefore, a structure in which an optical fiber is attached in a direction perpendicular to the optical axis of the optical element by arranging a mirror in the optical system of the optical module can be considered. However, simply aligning and assembling the optical path using a mirror causes the mounting direction of the optical element and the optical fiber to be orthogonal when aligning and assembling. Of the conventional manufacturing equipment (the resolution in the X and Y directions is fine, the Z direction is coarse, and the welding position is symmetrical with the Z axis). It becomes necessary, resulting in an increase in cost.
[0012]
Therefore, in general, especially for high-speed applications, the optical module is often modularized using a box-shaped package called a butterfly type. However, this method also has a problem that the package shape is complicated, so that the cost is higher than that of the coaxial optical module.
[0013]
The present invention has been made in view of the above problems, and provides an optical module that can be manufactured at low cost using a conventional manufacturing apparatus and that can enhance the mountability of an optical fiber without impairing the high speed of an electric signal. The purpose is to do.
[0014]
[Means for Solving the Problems]
An optical module according to the present invention that solves the above-described problem has an optical element held by a housing and an optical fiber supporting unit that is held by the housing and supports an optical fiber, and is provided in an optical axis direction of the optical element. Light reflecting means for reflecting light is provided so that the light can be adjusted and fixed independently of the optical fiber, and the optical element and the optical fiber are optically coupled by the light reflecting means. The optical module has a lens that is generally used as a means for optical coupling.In order to adjust the optical path length between the optical element and the optical fiber, rather than adjusting the position of the optical fiber, the optical reflection is performed. The optimal optical coupling is obtained by adjusting the position of the means.
[0015]
An optical module according to the present invention for solving the above-mentioned problems is characterized in that the optical fiber supporting means is disposed so that the supporting direction of the optical fiber is substantially perpendicular to the optical axis of the optical element. That is, since the optical fiber is substantially perpendicular to the optical axis of the optical element, the optical fiber is arranged parallel to the substrate on which the optical module is mounted vertically.
[0016]
An optical module according to the present invention for solving the above-mentioned problems is characterized in that the light reflecting means is a mirror or a prism. Further, an optical module having a configuration in which a lens is omitted by using a concave mirror as the light reflecting means may be used.
[0017]
The method for manufacturing an optical module according to the present invention that solves the above-mentioned problems includes the optical module according to any of the above,
Using an optical fiber supporting means for supporting the optical fiber, the optical fiber is fixed to the first housing,
Light reflecting means for adjusting the position of the first housing on the optical fiber side with respect to the second housing holding the optical element and reflecting light provided on the first housing on the optical fiber side After adjusting the position of the optical element in the optical axis direction and determining the position where the optical coupling between the optical fiber and the optical element is optimal,
The light reflecting means is fixed to the first housing on the optical fiber side, and the first housing on the optical fiber side is further fixed to the second housing on the optical element side.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
FIG. 1 is a structural diagram of an optical module showing an example of an embodiment according to the present invention.
[0019]
As shown in FIG. 1, the optical module according to the present invention has an LD (Laser Diode) element 1 as an optical element and a ferrule 3 as optical fiber supporting means for supporting the optical fiber 2. As a first housing for holding the ferrule 3 together with the optical fiber 2, a cylindrical fiber holder 6 is provided. As a second housing for holding the LD element 1, a stem 4 for mounting the LD element 1 and an LD element 1 And a cylindrical package 5 for holding the optical fiber together with the stem 4. The optical module is formed by joining the stem 4, the package 5 and the fiber holder 6 into one housing. The stem 4 is provided with an electrode pin 7, and by using the electrode pin 7, an electric signal can be supplied to the LD element 1 and can be mounted on a substrate or the like. A condensing lens 8 is provided on the optical axis of the LD element 1 inside the package 5 to condense light from the LD element 1 and guide the light to the optical fiber 2.
[0020]
Further, the optical module according to the present invention is provided with a mirror 9 serving as light reflecting means for reflecting light, and the mirror 9 is a mirror inserted through an opening at an end of the cylindrical fiber holder 6. By being held by the holder 10, it is fixed to the fiber holder 6 side. The holding surface of the mirror 9 of the mirror holder 10 is formed obliquely so as to have a predetermined angle (45 ° in FIG. 1) with respect to the optical axis of the LD element 1 and the optical fiber 2. With this configuration, the supporting direction of the optical fiber 2, that is, the mounting direction (Y direction) of the ferrule 3 supporting the optical fiber 2 is substantially perpendicular to the optical axis (Z direction) of the LD element 1. Can be provided. In other words, by providing the mirror 9 on the optical axis between the LD element 1 and the optical fiber 2, it becomes possible to optically couple the LD element 1 and the optical fiber 2 arranged in directions substantially orthogonal to each other. .
[0021]
The mirror 9 is provided on the fiber holder 6 together with the mirror holder 10 so that the position thereof can be adjusted (Z direction) in the optical axis direction of the LD element 1 and fixed. By moving independently of the fiber 2, the optical path length, that is, the optical path length from the LD element 1 to the optical fiber 2 can be adjusted to obtain optimal optical coupling. Therefore, it is not necessary to adjust the position of the optical fiber 2 itself, and the optical module can be manufactured by fixing the optical fiber 2 together with the ferrule 3 to the fiber holder 6 from the beginning, and the conventional manufacturing apparatus can be used almost as it is. It becomes possible.
[0022]
Next, a method for manufacturing the optical module according to the present invention having the above structure will be described.
[0023]
First, the lens 8 is fixed to the package 5 by means of brazing, welding, press fitting, or the like, similarly to a conventional optical module. Further, the optical fiber 2 is fixed to the fiber holder 6 together with the ferrule 3.
[0024]
Next, the LD holder 1 is caused to emit light, and while the stem 4 on which the LD holder 1 is mounted is finely adjusted in the XY directions with respect to the package 5 holding the lens 5, the fiber holder 6 is moved in the XY directions. At the same time, the mirror holder 10 is finely adjusted in the Z-axis direction (the optical axis direction of the LD element 1) to search for each position where the light input from the LD element 1 to the optical fiber 2 is maximized. An optimal position for making the optical coupling between the element 1 and the optical fiber 2 optimal is determined.
[0025]
Thereafter, the package 5 and the stem 4 are first joined at a welding point a by YAG laser welding or the like, and then the mirror holder 10 and the fiber holder 6 are joined at a welding point a. 6 and the package 5 are joined at a welding point a, and each member is fixed to complete the optical module. When the optical element is a PD (Photo Diode) element, light is incident from the optical fiber 2 into the optical module, and a point where the light detection signal of the PD element is maximized is fixed.
[0026]
The members used in the optical module according to the present invention are basically cylindrical like those used in the conventional coaxial optical module, and can be manufactured at low cost. The fiber holder 6 itself is different from the related art in that a through hole is provided on the side surface thereof. However, since the above-described optical axis adjustment is performed, not so severe precision is required, and it does not pose a major problem. Rather, by adopting such a structure, the direction of optical axis adjustment is the same as that of the conventional coaxial optical module, and it is possible to divert and assemble the conventional coaxial manufacturing device simply by changing jigs. As a whole, it can be manufactured at low cost.
[0027]
As described above, in the optical module according to the present invention, the optical path length is determined by the position of the fiber 2 in the horizontal direction (Y direction) and the position of the mirror 9 adjusted in the vertical direction (Z direction). . Here, in order to obtain the optimum optical coupling, it is necessary to consider which of the adjustment of the optical path length and the angle shift is more effective for the optical coupling, including the balance thereof. FIG. 2 is a schematic configuration diagram of an optical system in the optical module of FIG. 1 for studying the adjustment of the optical path length and the effectiveness of the angle shift.
[0028]
For example, when the axis shift amount of the optical fiber in which the optical coupling is increased by 0.1 dB by the Gaussian beam approximation is calculated, the position shift in the optical axis direction (Y direction in FIG. 2) is 15 μm, and the angle shift is 15 μm. θ is 0.85 ° (here, values of a spot size: ω = 5 μm and a wavelength: λ = 1.55 μm are used as parameters of a general communication optical fiber). That is, in order to prevent a loss of 0.1 dB or more, ± 15 μm is an allowable value for the positional accuracy in the optical axis direction, and ± 0.85 ° is an allowable value for the angular deviation. .
[0029]
In general component processing accuracy, the figure of ± 15 μm is a very severe value. Also, at the time of assembling, a slight gap or inclination is usually added, so that it is extremely difficult to keep the final positional deviation in the Z direction after assembling within ± 15 μm.
[0030]
On the other hand, in the optical module according to the present invention, in the configuration as shown in FIG. 2, the designed distance between the LD element 1 and the optical fiber 2 is, for example, 8.5 mm, and the angle shift θ = ± 0. When 85 ° is allowed, when the optical path length is estimated, the optical path length changes to 8.38 to 8.64 mm (these values slightly vary depending on the position where the mirror 9 is placed). That is, the position accuracy in the optical axis direction can be adjusted with a large allowable value of approximately ± 120 μm. Therefore, in the optical module according to the present invention, even if a slight angle deviation is allowed, by adjusting the optical path length where the allowable value of the positional accuracy is large, the efficiency of the optical coupling can be optimized, and the component accuracy can be improved. That would make it looser.
[0031]
On the other hand, the mirror holder 10 is fixed to the fiber holder 6 in advance, the fiber holder 6 is floated with respect to the package 5 (movable in the Z direction), and the mirror 9 and the optical fiber 2 are connected. It is considered that modularization is possible even if adjustment is performed in the XYZ directions at the same time. However, a connecting part for fixing the fiber holder 6 to the package 5 is separately required, which increases the cost, and is considered to be disadvantageous in terms of size restrictions and stability in comparison with the optical module having the structure according to the present invention. It is.
[0032]
(Example 2)
FIG. 3 shows another example of the embodiment according to the present invention, in which a multi-port light using a PD-EAM element in which an electro-absorption optical modulator (EAM) and a photodiode (PD) are monolithically integrated. It is a structural diagram of a module. In FIG. 3, the left side from the center line is a cross-sectional view and the right side is an external view so that the internal structure can be easily understood.
[0033]
The multi-port optical module shown in FIG. 3 uses a PD-EAM element 15 as an optical element and controls an optical signal by optical-optical control. The PD-EAM element 15 has a configuration in which an optical signal is input / output in a direction (Y direction) parallel to the element substrate in the EAM portion, and an optical signal is input in a direction (Z direction) perpendicular to the element substrate in the PD portion. is there.
[0034]
The optical module has a submount 14 for holding a PD-EAM element 15 inside a metal box-shaped package 12, and a package 12 via a Peltier cooler 13 for cooling the PD-EAM element 15. It is attached to the bottom. The PD-EAM element 15 has a small element size, and optical coupling must be performed at both ends with high efficiency. Therefore, the sub-mount 14 has an inverted T-shape, and the PD-EAM element 15 is mounted on the protruding end of the central convex portion. A first lens 16 is provided on both sides of the projection in proximity to the PD-EAM element 15, and is fixed to the submount 14 via a lens holder 17.
[0035]
EAM optical input / output ports 20 are provided on the side surfaces of the package 12, respectively. Two optical input / output ports 20 are provided so as to face each other in the longitudinal direction of the package 12. Further, a glass window 19 for hermetic sealing is provided on the inner surface side of the light input / output port 20 of the package 12 for hermetic sealing of the package 12. The optical input / output port 20 is provided with a second lens 21 for optically coupling the EAM optical fiber 24 with the PD-EAM element 15 inside the package 12. The EAM optical fiber 24 is connected to the ferrule 23 via the ferrule 23. It is fixed to the package 12 by the collar 22.
[0036]
The package 12 is sealed by welding a lid 18 for hermetic sealing from above. The lid 18 is also provided with a light input / output port 25 for PD as a light input / output port. To hermetically seal the package 12, the light input / output port 25 A glass window 19 for hermetic sealing is provided.
[0037]
The optical input / output port 25 has a structure according to the present invention, and a PD lens 26 for optically coupling the PD optical fiber 28 with the PD-EAM element 15 inside the package 12 (corresponding to the second housing). And a mirror 30 (light reflecting means) held by a mirror holder 31. The mirror 30 is disposed so as to be inserted into the cylindrical fiber holder 27 (first housing) from an end thereof. I have. The PD optical fiber 28 is fixed to a side surface of the fiber holder 27 by a ferrule 29 (optical fiber supporting means), and is disposed so as to be substantially perpendicular to an optical axis incident on the PD-EAM element 15. I have. Therefore, the PD optical fiber 28 is provided in the same direction as the EAM optical fiber 24, so that the mountability of the optical fiber can be improved. Even with such an optical fiber arrangement, at the time of light incidence, the optical signal from the PD optical fiber 28 is refracted by the mirror 30 toward the PD-EAM element 15 so that the optical signal is reflected in the light propagation direction of the optical input / output port 20. So that it is incident in a substantially vertical direction.
[0038]
Although not shown, a plurality of electrode pins are provided on the other side surface of the package 12, and these electrode pins enable mounting on a substrate. The electrode pins supply electricity to the PD portion, the EAM portion, the Peltier cooler 13, and the like of the PD-EAM element 15 provided inside the package 12. The PD-EAM element 15 controls the PD element inside the PD-EAM element 15 by supplying an optical signal from the optical input / output port 25, and controls the EAM element inside the PD-EAM element 15 from the PD element. A control signal is supplied to control the optical signal of the PD optical fiber 24.
[0039]
By using the multi-port optical module having the above structure according to the present invention, the optical fiber for PD can be provided in parallel with the optical fiber for EAM, and the mounting density on the substrate can be greatly improved.
[0040]
Next, a method for manufacturing the multi-port optical module having the above structure will be described. The size of the PD-EAM element 15 is as small as several hundred μm square, and it is necessary to perform high-efficiency optical coupling between both end faces and the upper part.
[0041]
In the multi-port optical module, the PD-EAM element 15 is mounted on the protruding end of the central portion of the submount 14, and the first lens 16 for optical coupling is installed and fixed close to both sides. Then, in order to hermetically seal it, it is installed inside the package 12, and the lid 18 is welded and sealed from above. Thereafter, the second lens 21 and the optical fiber 24 are independently optically aligned through the glass window 19 for hermetic sealing on the side surface of the package 12, and optically coupled to the PD-EAM element 15. The reason why two lenses are used for each optical input / output port 20 is to increase the manufacturing yield and to ensure the stability of optical coupling.
[0042]
Thereafter, the PD optical input / output port 25 is joined to the lid 18 using the same procedure as in the first embodiment. That is, the mirror 30 is elongated in the Z direction by using the mirror holder 31, the fiber holder 27 is adjusted in the X and Y directions, the optimum position of the optical coupling is determined, and then the welding is fixed. At this time, while measuring the light receiving current of the PD portion inside the PD-EAM element 15, the positioning is performed by adjusting in the XYZ directions. Since the positional accuracy of the optical axis with respect to the PD portion of the PD-EAM element 15 is relatively low, the present multi-port optical module is optically coupled by a single lens.
[0043]
In this embodiment, the lens 26 is integrated with the fiber holder 27 in order to facilitate manufacture. The basic operation is almost the same as that of the optical module according to the first embodiment, but the variation width (allowable value) of the optical path length is slightly narrowed to about ± 70 μm in the case of the coupling system similar to FIG. . However, there is no problem because the component processing accuracy is within a range that can be mass-produced if it is about ± 50 μm.
[0044]
In the first and second embodiments, a mirror is used as the light reflecting means. However, when a prism capable of obtaining an optically equivalent effect is mounted on the mirror holder instead of the mirror, the same effect as in the first and second embodiments is obtained. The effect of was able to be obtained. It is also conceivable to use a concave mirror as the light reflecting means. In the case of using a concave mirror, a configuration in which a lens is omitted can be adopted.
[0045]
Further, the optical element of the present invention is not limited to an LD element or a PD-EAM element, but is similarly applicable to PDs and LEDs. Also, the purpose is not limited to high-speed use, and the present invention can be widely applied to a case where the mounting direction of the optical fiber is desired to be set at an arbitrary angle (corresponding to the mounting angle of the mirror) due to the arrangement of components. .
[0046]
【The invention's effect】
According to the present invention, since a light reflecting means such as a mirror is provided so as to be adjusted and fixed in the optical axis direction of the optical element, the optical axis can be adjusted with high accuracy, and the final welding position can be set to the conventional value. Similarly, it can be made Z-axis symmetric. As a result, it is possible to utilize the conventional manufacturing equipment, and it is possible to manufacture the semiconductor device with good productivity at low cost. In addition, since the manufacturing equipment does not need to be updated at that time, it is particularly effective for the production of small lots and many kinds of products such as prototypes and custom-made products. Furthermore, the mounting direction of the optical fiber can be improved because the mounting direction of the optical fiber can be arranged in any direction.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical module showing an example of an embodiment according to the present invention.
FIG. 2 is a layout view of an optical system of the optical module shown in FIG.
FIG. 3 is a configuration diagram of an optical module showing another example of the embodiment according to the present invention.
FIG. 4 is a configuration diagram of a conventional optical module using an LD element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 LD element 2 Optical fiber 3 Ferrule 4 Stem 5 Package 6 Fiber holder 7 Electrode pin 8 Lens 9 Mirror 10 Mirror holder a Welding point

Claims (4)

An optical element held by a housing, and an optical module held by the housing and having optical fiber support means for supporting an optical fiber, wherein an optical module for optically coupling the optical element and the optical fiber;
In order to be able to be adjusted and fixed independently of the optical fiber in the optical axis direction of the optical element, light reflecting means for reflecting light is provided,
An optical module, wherein the optical element and the optical fiber are optically coupled by the light reflecting means. The optical module according to claim 1,
An optical module, wherein the optical fiber supporting means is disposed such that a supporting direction of the optical fiber is substantially perpendicular to an optical axis of the optical element. The optical module according to claim 1 or 2,
An optical module, wherein the light reflecting means is a mirror or a prism. Using an optical fiber supporting means for supporting the optical fiber, the optical fiber is fixed to the first housing,
The position of the first housing is adjusted with respect to the second housing holding the optical element, and the position of the light reflecting means for reflecting light provided on the first housing is changed to the position of the light. Adjusted in the optical axis direction of the element, after determining the position where the optical coupling between the optical fiber and the optical element is optimal,
4. The device according to claim 1, wherein the light reflecting unit is fixed to the first housing, and the first housing is fixed to the second housing. 5. Manufacturing method of optical module.

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