JPH0232583A - Semiconductor element module for optical communication - Google Patents

Abstract

PURPOSE:To simplify the adjustment and assembly process of a module by causing a cylindrical lens holder to act as a supporting host material; besides, set an optical semiconductor element and an optical fiber so that the image magnification of a lens is limited to about 1. CONSTITUTION:A ferrule 4 is fixed in advance to a ferrule holder 5. Outgoing rays emitted by a laser diode LD 3 which is loaded to a stem 7 is converted into converging rays by a spherical lens 2' for coupling fibers and after that, the rays reach a light receiving face of an optical fiber 1 in the ferrule 4. A lens holder 6' has a prescribed length and this element makes end faces 5a of the holder 5 and end faces 6'a of the holder 6' come closely into contact and further, makes the reference surface 7a of the stem 7 and the end faces 6'b of the holder 6' come closely into contact. In such a case, directions of an optical axis are disposed so that a distance from the outgoing ray end face of the LD 3 to a main surface of the lens 2' becomes almost equal to a distance from the main surface to a light receiving face of the optical fiber 1 without being adjusted. Such a configuration mentioned above does not have an effect very much on a coupling efficiency even though setting errors of the lens 2' take place up to a usual error range which is set easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor element module for optical communication that is small and has a simple structure.

[Prior Art] An example of a conventional configuration of this type of semiconductor element module is shown in FIG. In Fig. 4, 1 is an optical fiber, 2 is a lens optically coupled to the optical fiber 1, and 3 is a laser diode (
4 is a ferrule that supports the optical fiber 1; 5 is a ferrule holder that fixes the ferrule 4; 6 is a lens holder that supports the lens 2; 7 is a stem that supports the LD 3; 8 is the LD 3 and the lens 2. 9 is a cap supporting the glass window g; 1 is a glass window disposed between the
0 and 10' represent the ferrule 4 and ferrule holder 5, and the ferrule holder 5 and lens holder 6, respectively.
11 is a fixing member for fixing the stem 7 to the lens holder 6, and 12 is a pin for external connection of the LD 3 fixed to the stem 7.

The emitted light from the LD 3 mounted on the stem 7 passes through the glass window 8 of the cap 9 whose interior is hermetically sealed, is converted into convergent light by the fiber coupling lens 2, and then is connected to the optical fiber in the ferrule 4. reaches the light-receiving surface of l. The lens 2 is intended to increase the coupling efficiency of the light emitted from the LD 3 to the optical fiber 1, and is a distributed refraction lens with a spherical surface processed at the tip as shown in Fig. 4 as a lens with little wavefront aberration. Or, a ball lens with a high refractive index is used, and the spot size (approximately 1 μm) of the output light of the LD 3 is adjusted so that it matches the spot size (approximately 5 μm) of the optical fiber on the receiving surface of the optical fiber after passing through the lens 2, i.e. The L port 3 and the optical fiber 1 are arranged so that the magnification of the lens 2 is approximately 5.

In this configuration, the coupling efficiency of the output light from the LD 3 to the optical fiber 1 is as high as 50 or more. However, on the other hand, when allowing 1 dB deterioration of the coupling efficiency, The allowable displacement of the LD 3 in the Y direction is on the order of submicrons, and the allowable displacement in the optical axis direction (Z direction) is several microns or less. On the other hand, the mounting accuracy of the LD 3 with respect to the reference position of the stem 7 is usually about ±20 to 30 μm, and the setting accuracy of the lens 2 with respect to the reference position of the lens holder 6 is also about 50 μm. Therefore, conventional semiconductor element modules for optical communication have been assembled by the method described below.

First, insert the ferrule 4 to which the optical fiber 1 is fixed in advance into the ferrule holder 5, and make initial settings by bringing it into close contact with the lens holder 6.Next, insert the stem 7 on which the LD 3 is mounted onto the optical fiber 1 of the lens holder 6. Insert it on the opposite side. In this state, adjust the stem 7 in each direction of x, y, and z, and move the ferrule holder 5 in the
By moving the ferrule 4 in the direction and moving the ferrule 4 in the Z direction, the optical fiber 1 is also adjusted in three axes. When the stem 7 reaches the optimum position, the LD 3 is extinguished and the stem 7 is fixed to the lens holder 6. It is fixed with member 11. As this fixing member 11, solder is normally used. In that case, due to the thermal expansion and contraction of the component parts, the tension of the solder, etc. during heating and cooling during solder melting and fixation, after solder fixation,
The stem 7 causes a positional deviation on the order of microns from the optimum position, causing a more than permissible deterioration in coupling efficiency. Therefore, in order to correct this, an optical fiber with a relatively large tolerance for positional deviation is used for the LD3. After re-adjusting the optical fiber 1 in three axes by moving the ferrule holder 5 in the X and Y directions and the ferrule 4 in two directions, the optical fiber 1 and the ferrule 4 are fixed at the fixing point 10. Then, the ferrule 4 and lens holder 6 are fixed at a location 10.
' was fixed.

[Problems to be Solved by the Invention] As is clear from the above description, the conventional configuration requires a high-precision positioning process many times and requires a large amount of time for assembly.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor module for optical communication that is appropriately assembled to simplify the complicated adjustment process and thereby reduce manufacturing costs.

[Means for Solving the Problems 1] In order to achieve such an object, the present invention provides a cylinder having first and second end faces substantially perpendicular to the optical axis direction and having a predetermined length. The lens is held inside the shaped structural member.
A ferrule for holding and fixing the optical fiber is fixed to the first end surface, and a surface of the stem on which the optical semiconductor element is mounted, which serves as a reference for the mounting position of the optical semiconductor element, is closely fixed to the first end surface. A surface that serves as a reference for the end face position of the optical fiber with respect to the optical axis direction is closely fixed, and the distance from the light output end face of the optical semiconductor element to the main surface of the lens closest to the optical semiconductor element, and the Features [Function] The present invention is characterized in that the lens is configured and arranged so that the ratio of the distance from the main surface of the lens closest to the optical fiber to the input end surface of the optical fiber is approximately 1. The lens holder, which is a cylindrical structural member having a length of This prevents the optical coupling efficiency of the module from deteriorating due to setting errors in the optical axis direction of the lens to be held and fixed. The surfaces are brought into close contact, and only the stem on which the optical semiconductor element is mounted is adjusted in two axes in a direction perpendicular to the optical axis, and assembly is performed without adjusting the optical axis direction. Although the coupling efficiency is lower than that of the conventional method, the assembly process can be significantly simplified.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, in which 1 is an optical fiber, 2' is a ball lens optically coupled to the optical fiber 1, and 3 is an LD as an example of an optical semiconductor element. ,
4 is a ferrule that supports the optical fiber 1, 5 is a ferrule holder that fixes the ferrule 4, and 6' is a ball lens 2.
a lens holder as a cylindrical structural member having a predetermined length, 7 a stem supporting the LD3, 8 a L
[Glass window placed between 13 and ball lens 2';
9 is a cap supporting the glass window 8, 10' and 1
1' are the fixing points of the ferrule holder 5 and the lens holder 6', and the fixing points of the stem 7 and the lens holder 6', respectively;
2 is a vial for external connection of the LD 3 fixed to the stem 7. 5a is the end face of the ferrule holder 5 which serves as a reference plane in the optical axis direction of the optical fiber 1, and 6'a and 6'b are respectively,
Ferrule holder 5 and stem 7 of lens holder 6'
The end surface 7a for tightly fixing the LD 3 is a reference surface of the stem 7, which serves as a reference surface in the optical axis direction of the LD 3.

The ferrule 4 is mechanically fixed to the ferrule holder 5 in advance. The light emitted from the LD 3 mounted on the stem 7 passes through a glass window 8 attached to a cap 9 whose interior is hermetically sealed, is converted into convergent light by a fiber coupling ball lens 2', and then passes through a ferrule 4. The light within reaches the light-receiving surface of the fiber 1.

The lens holder 6' has a predetermined length, and the end surface 5a of the ferrule holder 5 is the end surface 6' of the lens holder 6'.
The reference surface 7a of the stem 7 is brought into close contact with the end surface 6'b of the lens holder 6'. At this time, without adjusting the optical axis direction, the distance from the output end surface of LD 3 to the main surface (lens center) of ball lens 2' and the distance from this main surface to the light receiving surface of optical fiber 1 are approximately equal. It is arranged like this.

With the above configuration, even if the setting error of the ball lens 2', which conventionally was a factor in deteriorating the coupling efficiency, occurs up to about 100 μm, which is within the normal easy-to-set error range, it will hardly affect the coupling efficiency. do not have.

This will be explained using FIGS. 2 and 3. FIG. 2 shows a state in which the optical fiber 1, the ball lens 2', and the LD3 are arranged at desired ideal positions, and ZLD is the LD.
The distance from the output end surface of No. 3 to the main surface (lens center) of the spherical lens 2', and z7 is the distance from this main surface to the light receiving surface of the optical fiber 1. The ferrule holder end surface 5a is the lens holder end surface 6'a. Since the stem reference surface 7a is in close contact with the lens holder end surface 8'b, (z, , D4
-2r) can be determined by the length of the lens holder 6'. When holding and fixing the ball lens 2' to the lens holder 6' manufactured to have this predetermined length, a setting error actually occurs. In FIG. 2, if the right direction of the optical axis is the positive direction and this setting error is 1 Δ2 mm, then the relative positional variation amount of LD3 with respect to the ideal position ΔZLD”Δz1
, and the relative positional variation amount Δ2 of the optical fiber 1 is Δ2. −Δ
zL, ΔzLo−Δ2. When the setting error of the 0-ball lens is Δz1 in the positive direction, LD3 and optical fiber 1
are each equivalent to a positional change in the negative direction,
The relationship between the respective positional fluctuation amounts is -Δz, . −1Δz2
becomes.

Figure 3 shows the deterioration in coupling efficiency (1 dB deterioration) when a lens with a diameter of 2.5 or @ is used as the ball lens 2'.
These positions against! ! It shows the effect of Jl amount ΔZLO and Δzr. Here, the broken line is 1 dll for the optimal coupling efficiency of the conventional configuration example (spherical lens image magnification of about 3, coupling efficiency of 13 zero), and the solid line is the configuration example of the present invention (spherical lens image magnification of about 1, coupling efficiency of 1). It shows iso-efficiency curves during deterioration. On the other hand, the amount of positional variation ΔZLO and Δ2. between the LD and the optical fiber due to lens setting errors. As mentioned above, the relationship is a straight line of Δ21.0-Δz1.As is clear from the diagram, the iso-efficiency curve of the configuration of this example is Δ21.0-Δz1.
Since the characteristics include the straight line of ΔZ, there is extremely little deterioration in coupling efficiency due to lens setting errors.By the way,
Lens setting error when allowing 1dB deterioration in coupling efficiency is ±250
It is about 50 μm, which is the normal error range that is easy to set.
It can be seen that the coupling efficiency can be almost completely ignored.

Furthermore, the iso-efficiency curve at 1 dB deterioration is ΔzLD−Δzr
±50 to 7 in both vertical and horizontal directions with respect to the straight line.
Since there is a margin of about 0 μm, the position setting error of optical fiber 1 and LD 3 (respectively ±
20~30μff1) and the length error of the lens holder 6' (
Even if there is a difference of ±10 μm), the deterioration is within about 1 dB relative to the optimum coupling efficiency, and assembly is possible without adjusting the optical axis direction.

In the direction perpendicular to the optical axis, on the side of optical fiber l,
Fixed ferrule 4 of optical fiber 1 and ball lens 2'
into the lens holder 6', and insert the ferrule holder end face 5
a and the lens holder end surface 6'a (fixed point lO
′) is fixed. On the LD3 side, the stem reference plane 7a
The lens holder is adjusted in two axes in a state where it is brought into close contact with the end surface 6'b of the lens holder. When maximum bonding is obtained in this state, the close contact portion (fixed location 11') is fixed. Further, in the above configuration, the allowable displacement amount of the LD 3 in the direction perpendicular to the optical axis when 1 dll deterioration of the coupling efficiency is allowed, and the positional displacement that occurs when fixed is tolerable.

Here, as a fixing method, conventional fixing by soldering is possible. Alternatively, since the fixed portion is in close contact, laser welding, resistance welding, etc. can be used, and a highly reliable semiconductor element module for optical communication can be provided.

In the embodiment shown in Fig. 1, we have described the case where a spherical lens is used, but instead of using a distributed refractive index lens or an aspherical lens, the above-mentioned result can be achieved by using a similar arrangement. Effects can be obtained.

Furthermore, on the upper side, although the optical fiber light receiving surface is set perpendicular to the optical axis, the return light from the end face of the tip fiber is
In order to reduce the influence on the optical fiber 1 and the ferrule 4, it is effective to incline the end surfaces of the optical fiber 1 and the ferrule 4 by about 5 degrees with respect to the optical axis. In addition, although the above example shows the case of an LD as an optical semiconductor element, the optical semiconductor element used in the module of the present invention is not limited to an LD, and various optical semiconductor elements can be used regardless of whether it is a light emitting element or a light receiving element. Of course you can.

[Effects of the Invention] As explained above, according to the present invention, 1) the length of the lens holder is used as a reference, and the lens image magnification is set to 1.
By doing so, deterioration in coupling efficiency due to lens setting errors can be almost ignored.

2) According to the above item 1), the adjustment and assembly process of the module can be simplified, and therefore the module can be obtained at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of the state in which the optical fiber 1, the ball lens 2' and the LD 3 are arranged at desired ideal positions, and FIG. 3 is the ball Deterioration in coupling efficiency (ldB deterioration) when a lens with a diameter of 2.5++m is used as lens 2'
The position degree wJ amount Δ21.0 and Δ2. FIG. 4 is a sectional view showing an example of a conventional configuration. 1... Optical fiber, the following effects can be obtained. 2... Lens, 2'... Ball lens, 3... Laser diode, 4... Ferrule, 5... Ferrule holder, 6.6'... Lens holder, 6 a, 6 b. ...End face for close fixation, 7...Stem, 7a...Reference surface, 8...Glass window, 9...Cap, 10, 10', 11'...Fixing location, 11...
Fixing member, 12... External connection bin.

Claims (1)

[Claims] 1) A lens is held and fixed inside a cylindrical structural member having a predetermined length and first and second end surfaces substantially perpendicular to the optical axis direction, and the first end surface has a , an end face of the optical fiber with respect to the optical axis direction of a ferrule that holds and fixes the optical fiber on the second end face, which is closely fixed to a reference surface of the optical semiconductor element mounting position of the stem on which the optical semiconductor element is mounted; A surface serving as a reference position is tightly fixed, and the distance from the light emitting end face of the optical semiconductor element to the main surface of the lens closest to the optical semiconductor element, and the distance of the lens closest to the optical fiber. 1. A semiconductor element module for optical communication, characterized in that the semiconductor element module is configured and arranged so that the ratio of the distance from the main surface to the input end surface of the optical fiber is approximately 1.