WO2001090791A1

WO2001090791A1 - Optical module

Info

Publication number: WO2001090791A1
Application number: PCT/JP2001/000854
Authority: WO
Inventors: Kazumi Kawamoto; Naoki Matsushima
Original assignee: Hitachi, Ltd.
Priority date: 2000-05-26
Filing date: 2001-02-07
Publication date: 2001-11-29
Also published as: JP3752965B2; JP2001337252A

Abstract

An optical module provided with an optical guide having a totally novel lens function. An optical module comprising an optical guide that has a core part through which light is propagated along the z-axis of a coordinate system in which the z-axis is the optical axis along which the light is propagated, the x-axis is the vertical axis in the cross section perpendicular to the z-axis, and the y-axis is the horizontal axis in the cross section and a clad layer covering the core part. The core part is composed of cores, and the y-z cross section of at least one of the cores has a generally circular shape, a generally elliptic shape, or a shape similar to those.

Description

Specification '

Optical module

Technical field

The present invention relates to an optical transmission module mainly used in an optical transmission system or an optical switching system, and relates to a light emitting element or a light receiving element and an optical fiber, a light emitting element or a light receiving element and an optical circuit, an optical circuit and an optical circuit in the optical transmission module. The present invention relates to optical coupling technology for optical fibers, optical switches, and beam splitters. Background art

Optical transmission of information transmission lines is progressing, and information transmission using optical fibers is planned not only for office buildings in various industries but also for collective houses and individual houses. One of the important issues here is, of course, the cost reduction of the optical transmission system. In particular, there is an urgent need to reduce the price of the optical transmission module connected to the general end-user.

In recent years, semiconductor lasers with an optical beam spot diameter expander have been put into practical use in order to significantly reduce the cost of this optical transmission module. This can be interpreted as adding a lens function to the semiconductor laser in order to remove the lens as a component.

In manufacturing the laser with the light beam spot diameter expander, a selective crystal growth technique is used to make the thickness of the emission end side of the core portion tapered. However, the integration of the beam spot diameter enlargement section affects the optimal design of the laser itself, causing new problems such as not optimizing the laser or making the effect of fabrication errors on the laser characteristics more sensitive. ing. As a result, the manufacturing yield is reduced compared to conventional lasers, and the price of the laser itself is increased. Therefore, the price of the optical transmission module has not been significantly reduced.

In addition, even when using a laser with an optical beam spot diameter expander, the same positioning accuracy as that of the conventional laser and the optical waveguide and optical fiber is required, and it is not possible to achieve a significant improvement in assembly productivity and yield. This is a major issue in reducing the price of optical transmission modules.

Furthermore, for array-type semiconductor lasers, lasers with optical beam spot diameter enlargers are used.

—The practical application of The has not yet been achieved. For this reason, it is necessary to introduce a lens such as a microlens array in an optical parallel transmission module using an array-type semiconductor laser, which requires not only the alignment accuracy of the laser with the optical waveguide and optical fiber, but also the alignment accuracy of the lens. As a result, it has not been possible to achieve significant improvements in assembly productivity and yield, making it difficult to reduce the cost of optical transmission modules. '.

In addition, in a module with an optical circuit realized by an optical waveguide between a semiconductor laser and an optical fiber, the semiconductor laser, the optical circuit, and the optical circuit are used as long as the divergence angle of the far-field image of the semiconductor laser is not approximately equal to that of the optical fiber. The problem is that the optical coupling between the circuit and the optical fiber cannot be optimized at the same time, and the optical circuit must be designed under conditions where each optimization is sacrificed. Or, conversely, there is a problem in that, in order to prioritize the optical coupling efficiency, the problem of miniaturizing an optical circuit is sacrificed.

An object of the present invention is to solve the above-described problems, and an object of the present invention is to provide a completely new optical module including an optical waveguide capable of changing a light beam spot diameter. Disclosure of the invention

Optical transmission modules transmit information over optical fibers, and it is important to increase the efficiency of optical coupling to the fiber. Increasing the optical coupling efficiency is to efficiently excite the eigenmode of the optical fiber. Optical fiber

Two In the case where an optical circuit composed of an optical waveguide is provided in the preceding stage, it is fundamental to efficiently excite the eigenmodes of the optical waveguide and the optical fiber. This is the same between an optical switch and an optical fiber, an optical multiplexer / demultiplexer and an optical fiber, and a beam splitter and an optical fiber.

Therefore, for example, when the eigenmodes of a semiconductor laser, an optical waveguide, and an optical fiber are different from each other, increasing the optical coupling between these optical components (semiconductor laser, optical waveguide, and optical fiber) requires the eigenmode of the optical component in the preceding stage. It is necessary to insert a mode converter that approximately converts the eigenmode into the eigenmode of the subsequent optical component. That is, it is necessary to convert the eigenmode between optical components so that each optical component can be excited in its own eigenmode. Also, in order for the light beam spot converter to function as a mode converter for improving the optical coupling characteristics, it is necessary to control the wavefront so as not to change the beam spot diameter abruptly, and to perform mode conversion smoothly.

Then, in order to achieve the above object, the present invention was configured as in the appended claims.

These can be manufactured without using any special technology other than the process of forming the optical waveguide, and the mode conversion can be performed smoothly by controlling the wavefront. For example, using a plurality of segmented cores, adjusting the spacing between the cores to keep the effective refractive index almost constant, and changing the width of the segmented cores along the z-axis to create a smooth wavefront Control can be performed. Also, for example, the core part near the optical axis (z-axis) along the z-axis is thick and far from the optical axis so that the width of the segmented core becomes a shape whose y-z cross section can be regarded as substantially circular. By reducing the thickness of the core according to, the propagation speed (phase velocity) of light in a region with a high refractive index can be reduced, and the propagation speed of light can be increased as the distance from the optical axis increases. As a result, the incident laser light has a wavefront curved so as to converge on the optical axis in the light traveling direction, so that the eigenmode of the preceding optical component is approximately converted to the eigenmode of the subsequent optical component. thing

Three Becomes possible.

On the other hand, the incident laser light is subjected to a wavefront curve so as to converge toward the optical axis. However, when the refractive index difference between the core and the clad is small, the refractive power is extremely small, and the laser light has a substantially circular shape. If the number of cores is small, the beam diameter of the incident laser light will increase. Therefore, it is important to optimize the shape and number of the cores, thereby making it possible to reduce the beam diameter to the waveguide eigenmode diameter of the optical circuit with a small loss. Proper determination of the beam diameter expansion rate is important to increase both the optical coupling efficiency and the tolerance for axial deviation (tolerance) without sacrificing the other. For example, as will be described later, it is important to optimize the radius and the number of substantially circular cores as parameters.

■ Becomes.

Furthermore, the beam diameter is kept constant in the region of the rectangular core group by forming a connection between the core group having a substantially circular segment shape and the rectangular group having a y-z cross section. Since the beam deviated from the optical axis is returned to the optical axis, the alignment tolerance can be improved.

Thus, when light from a light emitting device such as an LD (semiconductor laser) enters the light beam spot variable optical waveguide, the eigenmode of the single mode optical waveguide is smoothly converted into a mode without a large loss. Can be. In addition, it is possible to realize highly efficient optical coupling with a reduced tolerance for positional deviation (tolerance).

In order to reduce the large beam diameter at the entrance end, it is necessary to realize a wavefront transformation equivalent to a convex lens, so a converter equivalent to this convex lens has a laser with a large beam diameter at the entrance end. The aperture is large enough to receive light. BRIEF DESCRIPTION OF THE FIGURES

Four FIG. 1 is a perspective view schematically showing a light beam spot converter according to the present invention. FIG. 2 is a cross-sectional view and a plan view showing a first embodiment of the light beam spot converter according to the present invention. FIG. 3 is a sectional view and a plan view showing second and third embodiments of the light beam spot converter according to the present invention. FIG. 4 is a light intensity contour diagram showing the operation of the light beam spot converter according to the first embodiment of the present invention. FIG. 5 is a diagram showing an optical coupling characteristic of the light beam spot converter according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view explaining a manufacturing process of the optical beam spot converter of the present invention. FIG. 7 is a perspective view of an optical transmission module with an optical beam spot converter according to a fourth embodiment of the present invention. FIG. 8 is a perspective view of a first parallel optical transmission module with a light beam spot converter according to a fifth embodiment of the present invention. FIG. 9 is a perspective view of a second parallel optical transmission module with an optical beam spot converter according to a sixth embodiment of the present invention. FIG. 10 is a diagram for explaining a seventh embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an optical waveguide having an optical beam spot converter.

In the y-z section, a case is shown in which a circular segment-shaped core group and a rectangular segment-shaped core group are connected.

In the figure, when a light beam from a semiconductor laser or the like (not shown) enters, the incident light beam is guided to the optical waveguide 14 via the optical beam spot converter 11. Here, the z-axis is the traveling direction of the light beam.

The light beam spot converter 11 further includes a light beam spot diameter expansion width control unit l aa, a light beam spot diameter holding unit 11 b, and a light beam spot diameter reduction unit 11 c.

Five The light beam spot diameter expansion width control unit 11a has a plurality of substantially cylindrical cores, and controls the expansion width of the light beam spot diameter propagating by the action of the convex lens so that the light beam becomes substantially parallel light. Control so that That is, control is performed so that the light beam to be expanded is converged without being expanded by using a substantially cylindrical core. In the figure, a plurality of circular cores having the same diameter are arranged. However, since the diameter of the propagating light beam is enlarged, a core having a diameter equal to or larger than the diameter of the preceding core may be arranged. From the viewpoint of shortening the length of the light beam spot converter, it is preferable to arrange the core so that the diameter gradually increases.

In order to improve the tolerance, this first stage core has a diameter greater than the beam diameter at the point where the incident light beam approximates a Gaussian beam and the intensity is approximately 1 / e2 of the peak intensity. Is preferred. On the other hand, if the diameter is too large, the refractive power is weakened, and it is necessary to increase the number of cores, which increases the beam spot converter length. Therefore, for example, the divergence angle of the laser is about 6 ° to about 45 ° (with lens function: about 6 ° to about 1 °).

5 °, without lens function: 25 ° ~ 45 °) If the distance from the laser is about 5 ~ 50m, it is preferable to place a core with a diameter of about 3 ~ 250m.

Next, the light beam spot diameter holding unit 11b has a plurality of rectangular cores, and is configured to hold the beam diameter of the light beam from the light beam spot diameter expansion width control unit 11a. Is done. The gap between the cores is configured to be almost constant. Due to the length of the light beam spot diameter holding portion 11b, even if the optical axis of the laser and the optical waveguide is shifted due to, for example, a positional shift, the propagating light beam is transmitted to the optical waveguide 14 by the light. It is controlled to converge on the axis (Z axis).

Next, the light beam spot diameter reducing section 11c includes a plurality of substantially cylindrical cores, and the convex lens function acts on the light beam spot diameter holding section 1c.

6 It is configured such that the light beam from 1 b is reduced to approach the beam spot diameter of the optical waveguide 14. In the figure, a plurality of circular cores having the same diameter are arranged. However, since the beam diameter can be reduced, those having a diameter equal to or less than the diameter of the core in the preceding stage may be arranged.

The cores of the optical beam spot converter 11 and the optical waveguide 14 described above are made of the same material, and the core is covered with a clad 12. The relative refractive index difference between the cores 11 and 14 and the cladding 12 is preferably about 0.2 to 2.0% from the single mode condition. Particularly, it is preferably about 0.3 to 0.6%.

With the above configuration, it is possible to control the wavefront so that the beam spot diameter from the laser is not rapidly changed, and to smoothly convert the beam spot diameter to a suitable beam spot diameter adapted to the optical waveguide. In addition, the provision of the beam spot diameter holding portion can improve the tolerance, thereby improving the productivity during assembly. From the viewpoint of improving the coupling efficiency, a configuration without the beam spot diameter holding portion may be employed.

By the way, the main loss of the light beam spot converter 11 in the present embodiment is the reflection loss at the interface between the cladding layer and the core layer, and the leakage from the core layer to the cladding layer such as diffraction loss when the periodicity is strong. Radiation loss. Since the reflection loss is almost negligible when the refractive index difference between the clad and the core is small, reducing the diffraction loss is one of the design points. The diffraction loss can be reduced by limiting the number of cores of the same shape or by gently changing the core shape to weaken the periodicity. The optical waveguide shown in FIG. 3 has a configuration in which diffraction loss is considered, and this will be described later.

On the other hand, if the refractive index difference between the cladding and the core is configured to be small, the circular core in the y-z

The refractive power of 1a and 11c becomes weak, and it becomes difficult to convert to the expected beam spot diameter. Therefore, in the optical waveguide shown in Fig. 1, etc.

7 The core is used to obtain a necessary convex lens function.

In FIG. 1, the light beam spot diameter enlargement width control unit 11a and the beam spot diameter reduction unit 11c are configured using a substantially circular core, but a lens having a desired convex lens action can be obtained. The shape does not matter. Any surface may be used as long as it has a curve or a curve approximation on the surface where the light beam enters or exits. Therefore, it may be substantially elliptical.

Fig. 2 shows a light beam spot converter designed based on the results of a simulation based on the above basic concept. FIG. 2 (a) is a sectional view, and FIG. 2 (b) is a y-z plan view at x = 0. In the case of (b), the example is long and cannot be illustrated continuously on the z-axis, so the middle is cut off and divided into two rows.

In this embodiment, a segment-shaped core having a substantially circular shape obtained by approximating the above-mentioned cylindrical shape with a broken line is used. When a mask for forming a segmented core is designed using a general CAD technique, the mask becomes a substantially circular shape approximated by a broken line as shown in FIG. The same applies to the case of forming an elliptical shape. Also, it is connected to a continuous-core optical waveguide while its cross-sectional shape is gently changed. In this embodiment, the refractive index of the core 11 is N 0 = 1.46 4 16, and the refractive indices of the claddings 12 and 13 are both N l = N 2 = 1.45 76. .

This does not include the beam spot diameter holding unit shown in FIG. That is, after the light beam is controlled to be parallel light, the light beam is reduced so as to have a desired beam spot diameter and propagated to the optical waveguide. In this case, the tolerance is not improved as compared with FIG. 1, but the coupling efficiency can be improved.

In the beam spot diameter reduction part, the shape of the core is changed so that the width of light incidence is reduced, but this is to guide the light beam to the optical waveguide while weakening the lens action on the propagating light beam. belongs to. this

8 Will be described in detail later with reference to FIG.

3 (a) is a y-z plan view at x = 0 showing a second embodiment of a small optical beam spot converter according to the present invention, and (b) is a third embodiment according to the present invention. It is a yz top view in X0 which shows an Example. Both the second and third embodiments are configured by connecting a group of segmented cores having a circular y-z cross section and a group of rectangular cores. Both of them have a beam spot diameter holding section and a beam spot diameter reducing section. Is different from that shown in FIG.

In (a) of the second embodiment, a circular segmented core is connected to an optical waveguide of a continuous core while gently changing the cross-sectional shape. That is, the incident light beam is composed of four cylindrical segments of approximately the same diameter, a core group (beam spot diameter expansion control unit), seven approximately rectangular segments, and gradually the Y direction of the core. The core group (beam spot diameter holding part), consisting of five segments, which has a shorter width, a longer length in the Z direction, and a narrower gap between the cores, has four cylindrical members having almost the same diameter. It is configured to be guided to the optical waveguide through a segment and a core group (beam spot diameter reduction part) consisting of five segments in which the width of the core in the Y direction is gradually reduced and the length in the Z direction is increased. Have been.

When a plurality of rectangular cores are arranged in the beam spot diameter holding portion to form a periodic structure, loss due to Bragg diffraction occurs. Considering better tolerance, you want to increase the number of cores, but that will result in losses. Therefore, as shown in the figure, by gradually decreasing the width of the core in the Y direction, increasing the length in the Z direction, and arranging five segments with a narrow gap between the cores, The loss was suppressed by gradually changing the value and weakening the periodicity.

In the beam spot diameter reducing section, the beam diameter is reduced to be substantially the same as the beam diameter of the optical waveguide. However, in this embodiment, the width of the core in the Y direction is gradually reduced, and the length in the Z direction is reduced. Place 5 extended segments

9 In this way, it was configured to convert the light into the beam spot diameter of the optical waveguide while gradually weakening the effect of the convex lens. This is because a light beam narrowed down to a short distance by the action of a strong convex lens becomes a beam larger than the NA (numerical aperture) that can be accepted by the optical waveguide of the continuous core, and leaks out of the core within the optical waveguide of the continuous core. This is a loss at the time of propagation. Specifically, a circular shape with a gradually increasing diameter is created, and the circular shape is removed from the optical axis and the width in the Y direction is gradually reduced. . According to this, since the entrance surface and the exit surface of the light beam have a curvature instead of a simple rectangular shape, it is possible to reduce the beam spot diameter while reducing the effect of the convex lens and to realize the mode conversion.

On the other hand, in (b) of the third embodiment, the circular segment-like core group is directly connected to the optical waveguide of the continuous core at the beam spot reducing portion. In other words, the incident light beam gradually becomes a core group consisting of four cylindrical segments of approximately the same diameter (beam spot diameter enlargement control unit), and seven rectangular segments of approximately the same diameter. A core group consisting of five segments (beam spot diameter holding part) with a shorter core width in the Y direction, a longer length in the Z direction, and a narrower gap between cores. It is configured to be guided to the optical waveguide via a core group (beam spot diameter reduction section) consisting of seven segments.

According to this, the same effect as (a) can be obtained, but the optical coupling efficiency is slightly inferior due to the difference in the configuration of the light beam spot diameter reducing portion. The same improvement in tolerance as in (a) can be obtained.

FIG. 4 shows the performance of the light beam spot conversion in the first embodiment, which is shown using the contour line 21 of the light intensity in the yz section. In the figure, the y-axis is enlarged about 5 times, and the length in the z-direction is 300 / im.

In this embodiment, the divergence angle of the far-field image as laser light is

Ten Is assumed, and this is arranged at a distance of 20 j ^ m from the waveguide. FIG. 4 (a) shows the case where the laser is located on the optical axis, and FIG. 4 (b) shows the case where the laser is arranged +2 m away from the y-axis. The laser light enters from the bottom of the figure and travels upward. From Fig. 4 (a), it can be seen that the beam diameter gradually expands with the progress of light and approaches the eigenmode of the optical waveguide after becoming almost constant. That is, it can be seen that mode conversion can be performed smoothly by controlling the wavefront. For this calculation, three-dimensional FD-BPM was used.

FIG. 5 shows the optical coupling characteristics in the first embodiment of the present invention as a relationship between the amount of deviation of the laser in the y direction and the coupling efficiency. Also, the case where laser light is incident on the direct optical waveguide of the conventional method is shown for comparison. As exemplified in this figure, the present invention has achieved an improvement in the allowable amount of axis deviation.

That is, even if there is a displacement in the Y direction, a decrease in the coupling efficiency is suppressed as compared with the conventional example. For example, the position between the light emitting element such as an LD and the optical waveguide with the beam spot diameter converter is reduced. The tolerance of alignment accuracy will be expanded.

This is calculated under specific conditions. For example, when the divergence angle of the laser beam is large, the improvement effect becomes more significant. FIG. 5 merely shows an example of the features of the present invention, and improves the coupling efficiency while keeping the allowable amount of axis deviation at the same level as in the past, that is, the translation curve of the conventional example is moved upward in parallel. Embodiments of the binding characteristics that cause the binding to occur can also be provided. Although not shown, in the second and third embodiments of the present invention, the optical coupling characteristics of the first embodiment shown in FIG. Tolerance has been improved. In the first, second, and third embodiments, an example has been shown in which the maximum coupling efficiency is almost constant and the allowable amount of axis deviation is increased. However, as described above, it is possible to design to increase the maximum coupling efficiency. Become. FIG. 6 shows the manufacturing process of the first, second and third embodiments.

In the present embodiment, the optical waveguide is manufactured on a glass or Si (silicon) substrate by a method similar to a known optical waveguide manufacturing method using a quartz or organic material. For example, in the case of a quartz-based substrate using an Si substrate 55, the formation of a quartz-based film by CVD, EB evaporation, flame deposition, etc. is basically the same as in the production of a quartz-based optical waveguide. . This time, the method using the flame deposition method is shown.

First, the second cladding layer 53 and the core layer 51 are deposited on the Si substrate 55 as glass particles obtained by hydrolyzing the raw material in an oxyhydrogen flame (step (a)). ).

However, the core layer 51 has a high dopant concentration such as titanium oxide or germanium oxide.

Next, the glass particle film is heated to a high temperature in an electric furnace to make it transparent (step (b)). The deposition and transparency of the glass fine particles are usually performed separately for the cladding layer 53 and the core layer 51, but here, the case where they are performed collectively is shown.

Subsequently, the core layer 51 is patterned using photolithography. That is, after applying a resist and transferring a mask pattern, the core 51 is formed by etching with a predetermined depth R IE (reactive ion etching) (step (c)).

After that, the first cladding layer 52 whose refractive index is adjusted according to the dopant amount is deposited as glass fine particles (step (d)), and further heated at a high temperature to make it transparent (step (e)). When a quartz-based material is used, a small amount of an auxiliary dopant is often added to adjust the glass softening temperature and the coefficient of thermal expansion.

Since the core layer is patterned using photolithography in this manner, it is possible to form the core having the shape as in the embodiment including the optical waveguide.

1 2 You. In addition, since photolithography is used, patterning is performed by approximating a curve as shown in FIG. 2 with a straight line. In practice, the corners are rounded. In addition, since a beam spot converter can be formed together with the optical waveguide, the accuracy such as optical axis alignment between them can be easily satisfied.

As described above, since the same photolithography technology as that used to form conventional optical waveguides is used, its manufacture is easy, and additional manufacturing processes solely for manufacturing a beam spot diameter converter increase. There is no disadvantage. Also, since the beam spot diameter converter and the optical waveguide connected to it are formed at the same time, there is no need for adjustment and assembly work such as aligning these optical axes.

FIG. 7 is a conceptual diagram of an optical transmission module using an optical circuit according to a fourth embodiment of the present invention. The optical circuit of this embodiment is an optical circuit having a function of branching and joining by an optical waveguide, and an optical beam spot converter 101 is provided at an end thereof. The figure shows only the area where the light beam spot converter 101 is provided.

The light beam spot converter of the third to third embodiments is formed.

The optical circuit and the optical beam spot converter are fabricated on a Si (silicon) substrate 55 using a quartz or organic material. The fabrication method using quartz is as described above.

A metallization (not shown) for soldering an optical element and an alignment mark (not shown) for alignment are formed on one incident end side of the Si substrate 55. Alignment marks for alignment are also formed on the optical element 102 in advance. The alignment is performed by a so-called passive alignment method based on these marks, and the solder is melted by heating to obtain the optical element 101. Connect. Solder is vapor-deposited on the side of either the substrate or the element by a thickness of several m and patterned to form a solder film pattern. Optical fiber forms V-groove in glass or Si substrate and fills it

13 Then, an optical fiber block 103 covered with a protective plate is prepared. The optical fiber block 103 and the substrate on which the above-described optical element is mounted and on which the optical beam spot converter is formed are aligned by a passive or active alignment method, and adhesively connected using an adhesive 105. I do. The adhesive may be UV-curable or heat-curable, but it is needless to say that an adhesive having small deformation during curing and high reliability is desirable.

FIG. 8 is a conceptual diagram of a parallel optical transmission module using an array-type optical element according to a fifth embodiment of the present invention. A light beam spot converter 201 is formed on the Si substrate 55, and then a metallization (not shown) for soldering an optical element to one of the incident ends and an alignment mark for alignment are formed. (Not shown) is formed. Alignment marks for alignment are also formed on the optical element 202 in advance, the alignment is performed by a so-called passive alignment method based on these marks, and the solder is melted by heating to obtain the optical element 2. 0 Connect 1 Solder is vapor-deposited on the side of either the substrate or the element by a thickness of several m and patterned to form a solder film pattern. The optical fiber bundle 203 is formed with a V-groove formed in the Si substrate, embedded in the groove, and a block 204 of the optical fiber bundle 203 covered with a protective plate (not shown) is produced. Keep it. The optical fiber bundle block 204 and the substrate on which the optical element is mounted and on which the optical beam spot converter is formed are aligned by a passive or active alignment method, and adhesively bonded using an adhesive 105 I do. In active alignment, alignment is basically performed using the channels at both ends, but alignment may be performed using the center channel, and is not limited to a specific method.

FIG. 9 is a conceptual diagram showing a second parallel optical transmission module using an array type optical element according to a sixth embodiment of the present invention. The difference from the fifth embodiment is that an optical beam spot converter is manufactured on a substrate 55 in which a V-groove is formed, and an optical element 201 is mounted. Since a substrate with a V-groove is used, light

14 Beam spot converters are easy to make using organic materials. If an organic material for an optical waveguide is used, a film can be formed by spin coating and baking. However, it is difficult to produce a flat film due to the presence of the V-groove. In this embodiment, a thick resist is applied, and this is removed to the surface of the substrate by etching. Was. An alignment mark is formed in the vicinity of the V-groove, a light beam spot converter is manufactured based on this alignment mark, and if a device mounting pattern is formed, mutual alignment accuracy is determined by the mask alignment accuracy. Patterning is possible, and extremely efficient optical coupling can be realized. The optical elements are aligned by passive alignment and connected by solder. Then insert the optical fiber into the V-groove, apply adhesive, cover with a protective plate and

Cures and adheres by UV irradiation or heating. The module further requires electrical connection and sealing of the element, etc., but a known method may be applied, or the module is not directly related to the present invention, and therefore description thereof is omitted.

FIG. 10 is a conceptual diagram showing a signal connection of an exchange or a computer using a parallel optical transmission module according to a seventh embodiment of the present invention. It is used for the purpose of high-speed signal transmission between processors of large computers, between processors and storage devices, reduction in the weight and thickness of high-density signal wiring, and improvement in noise resistance. The devices 301 and 302 include signal connection boards 25 3 a, 25 3 b, 25 3 c, and 25 3 d, etc., and are mounted on each signal connection board. Has a plurality of parallel optical transmission modules 251a and the like and LSI parts 252 and the like. In the parallel optical transmission module 255a, information is converted from an electrical signal to an optical signal and transmitted to the optical fiber array 255a via the multi-core optical connector 255a. Signals are transmitted between the devices via an optical fiber array bundle 256 that includes similar optical fiber arrays. The parallel optical transmission module 25 1 b on the signal connection board 25 3 b of the other device connected to the optical fiber array 255 a converts the optical signal into an electric signal,

1 5 Signal transmission by light between devices becomes possible.

Although not shown, the beam spot diameter conversion described above is applied to the portion of the optical switch that connects to the optical fiber, the tip of the optical waveguide before branching of the beam splitter, and the tip of each optical waveguide after branching. An optical waveguide with a function can also be formed. This can also improve the tolerance and the optical coupling efficiency.

According to the embodiments described above, the beam expansion rate can be varied by designing the core shape. For example, in an optical module including an optical element, an optical fiber, and an optical circuit including an optical waveguide, an optical circuit Optimal beam spot converters can be formed at both ends of the optical element and optical fiber individually, which has a great effect on improving the light use efficiency of the optical module and facilitating manufacturing. In addition, since the manufacturing is easy, it is effective in reducing the price of the optical module. In addition, since the optical beam spot converters of the embodiments described above can be manufactured on a substrate on which an optical circuit and an optical element are mounted, the configuration of the optical module is simple, mounting is easy, and the optical module is low. From this point, the effect on price is also great.

Furthermore, an optical beam spot converter capable of performing beam spot conversion with an extremely simple process can be realized, and the cost of the optical beam spot converter itself can be reduced compared to those requiring a method such as selective crystal growth. It is possible. Furthermore, since it is composed of a segmented core, it is also effective in downsizing the optical beam spot converter (reducing the element length). Industrial applicability

According to the present invention, it is possible to realize a completely new optical module including an optical waveguide capable of changing the light beam spot diameter.

Claims

The scope of the claims

1. The optical axis, which is the direction of light propagation, is the z-axis, the vertical axis is the X-axis, and the horizontal axis is the y-axis in a cross section perpendicular to the z-axis. The origin of the X-axis and the y-axis is approximately An optical module including an optical waveguide having a core portion formed so as to propagate light in the z-axis direction as a center, and a cladding layer surrounding the core portion,

An optical module, wherein a core portion of the optical waveguide is formed by a plurality of cores, and at least one of the cores has a substantially circular or substantially elliptical cross section, or an approximate shape thereof. .

2. An enlarging part for enlarging the spot diameter of the light beam and a reducing part for reducing the spot diameter of the light beam using a core whose cross section y-z can be regarded as a circle, an ellipse, a substantially circle or a substantially ellipse. The optical module according to claim 1, wherein the optical module is formed.

3. In addition to a plurality of cores whose y-z cross section can be regarded as a circle, an ellipse, a substantially circle or a substantially ellipse, a plurality of cores having a y-z cross section of a rectangular shape are used as the expanded portion and the core. 3. The light module according to claim 2, wherein the light module is formed between the reduced portion.

4. The optical module according to claim 3, wherein the plurality of cores each having a rectangular shape in the yz section have different lengths in the y-axis direction of the cores.

5. The optical module according to claim 2, wherein a length of the plurality of cores arranged in the reduced portion in the y-axis direction is different.

6. The optical axis, which is the direction of light propagation, is the z axis, the vertical axis is the X axis, and the horizontal axis is the y axis in a cross section perpendicular to the z axis. The origin of the X axis and the y axis is defined on the substrate. An optical module comprising an optical waveguide having a core portion formed so as to propagate light substantially in the z-axis direction in the z-axis direction, and a cladding layer surrounding the core portion,

1 7 An optical module, wherein a core portion of the optical waveguide is formed of a plurality of cores, and at least a surface of one of the cores on which a light beam enters or exits has a shape having a curvature. .

7. An enlarged portion for enlarging the spot diameter of the light beam and a reduced portion for reducing the spot diameter of the light beam using the core.

Optical module according to 6.

8. The optical module according to claim 7, wherein a plurality of cores each having a rectangular shape in the yz section are formed between the enlarged portion and the reduced portion.

9. The optical module according to claim 8, wherein the plurality of cores each having a rectangular shape in the yz section have different lengths in the y-axis direction of the cores.

10. The optical module according to claim 8, wherein the plurality of cores arranged in the reduced portion have different lengths in the y-axis direction of the cores.

11. An optical module comprising an optical waveguide having a core portion formed so as to propagate light and a cladding layer surrounding the core portion, wherein the optical waveguide is a beam having an incident light beam. An optical module comprising: a first region that propagates by increasing a spot diameter; and a second region that propagates by reducing a beam spot diameter of a light beam from the first region.

12. A third region is provided between the first region and the second region, the third region acting to maintain a beam spot diameter of the light beam from the first region. The optical module according to claim 11.

13. A core portion located in the first region or the second region is formed of a plurality of cores, and a surface of at least one of the cores at which a light beam enters or exits has a curvature. 13. The optical module according to claim 12, wherein:

14. The light according to claim 12, wherein the core portion located in the third region is formed by a plurality of cores, and the core has a rectangular shape.

1 8 module.

15. The optical module according to claim 14, wherein a width of a core on which the light beam is incident is gradually reduced in a core portion located in the third region.

16. The optical module according to any one of claims 13 to 15, wherein a width of a core on which the light beam is incident is gradually reduced in a core portion located in the second region.

17. The optical module according to claim 1, wherein the optical module is an optical switch, an optical multiplexer / demultiplexer, or a beam splitter.

18. An optical transmission system comprising the optical module according to any one of claims 1 to 17.