JP2010191231A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module, in which each optical element can obtain high optical coupling efficiency while achieving a smaller size by reducing the number of part items. <P>SOLUTION: The optical module includes an optical element-mounting substrate on which at least two optical elements different in wavelength to be used are mounted; a wavelength multiplexer/demultiplexer having a parallel flat plate-like substrate fixed within a package while being inclined by an angle θ in a two-dimensional cross section relative to the optical element-mounting substrate; and a lens disposed in a position facing the optical element-mounting substrate across the parallel flat plate-like substrate. The wavelength multiplexer/demultiplexer includes a wavelength selecting filter on a first surface of the parallel flat plate-like substrate, and a mirror on a second surface opposed to the first surface. The distance along an advancing direction of light between the first optical element and the wavelength multiplexer/demultiplexer is smaller than the distance along the advancing direction of light between the second optical element and the wavelength multiplexer/demultiplexer, and a first light entering into or emitting from the first optical element is higher in the frequency of reflection within the wavelength multiplexer/demultiplexer than a second light entering into or emitting from the second optical element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical module, and in particular, a multi-wavelength optical transmission module that multiplexes and transmits light of a plurality of wavelengths, an optical reception module that demultiplexes and receives light having a plurality of wavelengths combined, and The present invention relates to a structure of a bidirectional optical transmission / reception module that performs transmission / reception with one module.

In recent years, in the information and communication field, communication traffic for exchanging large amounts of data at high speed using light has been rapidly developed. In particular, broadband access lines are accelerating due to the explosive spread of the Internet, and a remarkable market launch of FTTH (Fiber To The Home) service is seen.
Among the optical transmission systems of FTTH, the demand for the PON (passive optical network) system in which a single fiber is shared by a plurality of subscribers is increased from the accommodation station. By splitting the data transmitted over the fiber of 16 to 32 with a splitter and distributing it to each subscriber's house, the fiber installation cost can be greatly reduced.
Further, an ONU (Optical Network Unit) is laid as a terminal device on each subscriber side, and a downstream signal (wavelength 1.5 μm) from the accommodation station to the subscriber side and an upstream signal (from the subscriber side to the accommodation station ( Wavelength multiplexing (WDM) of wavelength 1.3 μm) allows uplink and downlink signals to be transmitted using the same fiber. Further, a two-wavelength bidirectional optical module is mounted in the ONU, and a light emitting element (LD: Laser Diode) for transmitting an upstream signal, a light receiving element (PD: Photo Detector) for receiving a downstream signal, It is basically composed of a WDM filter that separates downstream signals.

A conventional optical module system is shown in FIG. FIG. 22 shows a basic configuration of a single core bidirectional (BI-Directional) module in which optical components such as a light emitting element 375, a light receiving element 372, and a wavelength selection filter 377 are spatially arranged in a package 378.
In this method, since each optical component can be manufactured independently, it is easy to secure the manufacturing yield. Further, optical connection is possible by so-called active alignment in which the optical axis is aligned with the fiber 370 while operating the optical elements (375, 372) mounted on the CAN packages (373, 376) each integrating the lenses (371, 374). Therefore, there is an advantage that stable optical coupling efficiency can be obtained. On the other hand, the number of parts and the number of processing steps are large, and it is a disadvantage that it is disadvantageous for miniaturization and cost reduction.
FIG. 23 shows a basic configuration of the second system of the single-core bidirectional module disclosed in Non-Patent Document 1 below.
In this example, a light emitting element 382, a light receiving element 386, and a wavelength selection filter 383 on a transparent substrate 384 are mounted in one package 387. The transparent substrate 384 is mounted at a predetermined angle by a support member 385. The light emitting element 382 and the light receiving element 386 are optically connected to the single mode fiber 380 through the lens 381.
The feature of this example is that all the optical components are mounted in one package to reduce the size of the module. However, the light emitting element 382, the light receiving element 386, and the wavelength selection filter 383 need to be arranged three-dimensionally as in the optical module of FIG. There is also a problem that it is complicated.
Further, considering expandability, for example, in the case of a three-wavelength bidirectional optical module, it is necessary to at least double the number of optical components and the mounting area, and it becomes increasingly difficult to reduce the size and cost.

In order to achieve both wavelength expandability and miniaturization / cost reduction, it is necessary to perform the wavelength multiplexer / demultiplexer in a compact space. As a compact wavelength multiplexer / demultiplexer, there is a method of mounting a plurality of filter units on a common parallelogram prism or other optical block.
For example, in the multiplexing device disclosed in Patent Document 1 below, as shown in FIG. 24, each of the wavelength selection filters (397, 398, 399) and the mirrors (395, 396) has a wavelength of light passing through the substrate. Are attached to each other at predetermined positions on a transparent substrate. The fiber 392 through which the outgoing light beam 390 and the incident light beam 391 propagate is optically connected via a rod lens 393 to a wavelength multiplexer / demultiplexer 394 including a transparent substrate.
In the wavelength multiplexer / demultiplexer, light of a specific wavelength is sequentially transmitted by each optical filter, light of another specific wavelength is reflected, and the light forms a zigzag optical path. Each filter removes or adds light of a specific wavelength.
As prior art documents related to the invention of the present application, there are the following.

JP-A-61-103110 IEICE technical report, vol. 107, no. 7, R2007-2, pp. 7-10

However, in the configuration disclosed in FIG. 24, the optical element (406, 407, 408) and the substrate of the wavelength multiplexer / demultiplexer 394 are connected via the rod lens (400, 401, 402) and the fiber (403, 404, 405). It is connected and has a large number of parts, making it difficult to reduce the size.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to reduce the number of components and reduce the size of an optical module, and each optical element has high optical coupling efficiency. It is to provide a technique that can be obtained.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) An optical element mounting substrate on which at least two optical elements having different wavelengths to be used are mounted, and a parallel fixed in the package in a state where the optical element mounting substrate is inclined at an angle θ in a two-dimensional section. A wavelength multiplexer / demultiplexer having a flat substrate; and a lens disposed at a position facing the optical element mounting substrate across the parallel flat substrate, wherein the wavelength multiplexer / demultiplexer A wavelength selection filter is provided on the first surface of the flat substrate, and a mirror is provided on the second surface opposite to the first surface, and the light emitted from the lens or the optical element is the wavelength matching filter. Light that is incident on the wavelength selection filter surface of the duplexer at a non-perpendicular angle, and separates and superimposes light having different wavelengths in the process of multiple reflection of light in a zigzag manner between the wavelength selection filter and the mirror. A module, said at least The distance along the traveling direction of the light between the first optical element in one optical element and the wavelength multiplexer / demultiplexer is the distance between the second optical element in the at least two optical elements and the wavelength combination. The first light that is shorter than the distance along the traveling direction of the light with respect to the duplexer and is incident on the first optical element or emitted from the first optical element is the second optical element. The light is reflected more frequently in the wavelength multiplexer / demultiplexer than the second light incident on the element or emitted from the second optical element.

(2) In (1), a submount on which the at least two optical elements are mounted is provided, and the thickness of the submount is changed to change between the first optical element and the wavelength multiplexer / demultiplexer. The distance along the light traveling direction is made shorter than the distance along the light traveling direction between the second optical element and the wavelength multiplexer / demultiplexer.
(3) In (1), a submount on which the at least two optical elements are mounted, a plurality of the submounts are stacked for each of the at least two optical elements, and the first optical element and the wavelength are stacked. The distance along the traveling direction of light between the multiplexer / demultiplexer is made shorter than the distance along the traveling direction of light between the second optical element and the wavelength multiplexer / demultiplexer.
(4) In (1), a submount for mounting the at least two optical elements is provided, a step is provided in a stem for mounting the optical element mounted on the submount, and the first optical element and The distance along the traveling direction of light between the wavelength multiplexer / demultiplexer is made shorter than the distance along the traveling direction of light between the second optical element and the wavelength multiplexer / demultiplexer.
(5) In (1), a light having a heat sink on which the at least two optical elements are mounted, the thickness of the heat sink being changed, and light between the first optical element and the wavelength multiplexer / demultiplexer Is made shorter than the distance along the light traveling direction between the second optical element and the wavelength multiplexer / demultiplexer.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the optical module of the present invention, it is possible to reduce the number of parts and reduce the size, and each optical element can obtain high optical coupling efficiency.

It is sectional drawing which shows schematic structure of the 3 wavelength bi-directional optical transmission / reception module of Example 1 of this invention. It is a figure explaining the effect | action of the optical module of the 1st Example of this invention. It is sectional drawing which shows schematic structure of an example of the optical module which reduced the number of parts and aimed at size reduction. It is the figure explaining the effect | action of the optical module shown in FIG. FIG. 4 is an equivalent diagram showing an optical arrangement of the optical module shown in FIG. 3. 6 is a graph showing an example of the relationship between the coupling efficiency, the condensing point, and the optical path difference ΔD between the element mounting positions in the optical arrangement shown in FIG. 5. It is a graph for demonstrating the effect of Example 1 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 2 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 3 of this invention. It is a schematic diagram which shows the mounting state of the optical module of Example 3 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 4 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 5 of this invention. It is sectional drawing which shows schematic structure of the 2 wavelength bidirectional optical transmission / reception module of Example 6 of this invention. It is sectional drawing at the time of comprising an optical module with a pigtail using this invention which is Example 7 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 8 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 8 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 9 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 10 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 11 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 12 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 13 of this invention. It is sectional drawing which shows schematic structure of the optical module of Example 14 of this invention. It is sectional drawing which shows schematic structure of an example of the conventional optical module. It is sectional drawing which shows schematic structure of the other example of the conventional optical module. It is sectional drawing which shows the basic composition of the wavelength multiplexer / demultiplexer of a prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
[An example of an optical module that has been reduced in size by reducing the number of parts]
The configuration shown in FIG. 3 is assumed as the configuration of the optical module that is reduced in size by reducing the number of parts. In the configuration of FIG. 3, a submount 14 in which a plurality of optical elements (11, 12, 13) (more specifically, a light emitting element 11 and a light receiving element (12, 13)) are mounted on a CAN stem 10. Has been implemented. Further, typically, a wavelength multiplexer / demultiplexer 2 in which a wavelength selection filter and a mirror are mounted on the front and back surfaces of a transparent substrate is mounted in the CAN package 3.
The wavelength multiplexer / demultiplexer 2 is mounted in the CAN package 3 such that the optical element mounting surface and the filter surface are not parallel to one surface of the submount 14 (θ ≠ 180 degrees). Has been.
The inner surface of the CAN package 3 is provided with, for example, irregularities for mounting the wavelength multiplexer / demultiplexer 2 and the optical element mounting substrate 1 in a non-parallel manner. On the CAN stem 10, optical elements having different working wavelengths are mounted at predetermined positions.
The wavelength multiplexer / demultiplexer 2 uses a substrate having a predetermined thickness made of a material transparent to the wavelength of light to be used having a pair of parallel opposing surfaces as a support substrate, and one of the pair of parallel surfaces is At least one type of wavelength selection filter is provided, and a mirror for reflecting light having a wavelength not selected by the wavelength selection filter is provided on the other surface. At this time, these filters and mirrors are provided with windows for light to enter and exit.

The operation of the optical module having the configuration shown in FIG. 3 will be described with reference to FIG.
The light having the wavelength of λ1 emitted from the light emitting element 11 reaches the first wavelength selection filter 6. Since the first wavelength selection filter 6 transmits the wavelength of λ1, the light of the wavelength of λ1 passes through the first wavelength selection filter 6 and passes through the package lens 4 to an external optical fiber (not shown). Incident. Here, light having a wavelength of λ1 passes through the first wavelength selection filter 6, is refracted by the transparent substrate, translates the optical path, and enters the external optical fiber (not shown) via the package lens 4. In addition, the light emitting element 11 and the optical fiber are optically connected. At the same time, the optical fiber and the light receiving element (12, 13) are optically connected so that light of wavelengths λ1 and λ2 emitted from the optical fiber is incident on the predetermined light receiving element (12, 13), respectively. Is done.
The light having the combined wavelengths of λ2 and λ3 emitted from the optical fiber enters the transparent substrate 5, undergoes refraction, and reaches the first wavelength selection filter 6. Light having wavelengths of λ2 and λ3 is reflected and reaches the first mirror 8 facing it. The light reflected by the first mirror 8 is incident on a position different from the initial incident position on the surface of the first wavelength selective filter 6. In the simplest design, the light that has been reflected once by the first mirror 8 is incident on the second wavelength selection filter 7, but in this configuration, the reflected light from the first mirror 8 is again in the second state. The light is incident on the first wavelength selection filter 6 and reciprocates between the first wavelength selection filter 6 and the first mirror 8.

The light that has reciprocated twice between the first wavelength selection filter 6 and the first mirror 8 is incident on the second wavelength selection filter 7. Here, the light with the wavelength of λ 2 and the light with the wavelength of λ 3 are separated, and the light with the wavelength of λ 2 passes through the second wavelength selection filter 7, is refracted, and enters the light receiving element 12 perpendicularly. .
On the other hand, light having a wavelength of λ3 is reflected by the second wavelength selection filter 7 and enters the second mirror 9. The light reflected by the second mirror 9 passes through an interface without a filter (with an AR coating) and enters the light receiving element 13.
As described above, since the two planes constituting the wavelength multiplexer / demultiplexer 2 are mounted at an angle that is not perpendicular to the incident light from the fiber and the optical axis of the light emitting element 11, the wavelength selective filter array and the mirror are mounted. Light enters the array obliquely, and light of a specific wavelength is removed or added at the intersection of each filter and the optical axis. That is, the two planes and the optical axis of the light incident on the wavelength multiplexer / demultiplexer 2 have an angle other than 90 degrees, that is, an angle that is not orthogonal to the surface of the submount 14. The wavelength multiplexer / demultiplexer 2 is attached to the CAN stem 10 or the CAN package 3 with the plane inclined by an angle θ1. 3 and 4 are cross-sectional views, and in principle, the value of the angle θ1 does not change in the depth direction of the paper.

FIG. 5 is a diagram schematically showing an optical system equivalent to the optical system of the optical module shown in FIGS. As shown in FIG. 5, the optical element 11, the optical element 12, and the optical element 13 are arranged in series along the optical path from the side closer to the lens. Three elements having different optical distances from the lens are optically coupled to the single mode fiber through a single aspherical lens. As shown in the figure, one of the three elements is located at the condensing point of the lens, and the other element is placed at a position shifted by a certain optical distance (ΔD) from the position where the optimum coupling is obtained. Therefore, the coupling efficiency is reduced accordingly.
The Gaussian beam coupling efficiency η is given by the following equation (1), where ΔL is the deviation in the optical axis direction of the condensing point at the fiber position, w is the radius of the beam waist, and λ is the wavelength.

・・・・・・・・・・・・・・・・・・・ （１）

・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1)

FIG. 6 is a graph plotting the coupling efficiency when w = 5 μm by converting ΔL in the above equation (1) into the optical distance ΔD between the element mounting position and the condensing point.
It shows that the coupling efficiency rapidly deteriorates as ΔD increases. In the module configuration of FIGS. 3 and 4, how to suppress a decrease in coupling efficiency due to the optical path difference of each element from the condensing point is a design issue.
In the optical arrangement shown in FIG. 5, in order to improve the coupling efficiency, the mounting may be performed so that the value of ΔD becomes small as shown in FIG. If specifically described according to the module configuration shown in FIG. 3 and FIG. 4, as shown in FIG. 1 and FIG. 2, the side where the multiple reflection of the incident light within the wavelength multiplexer / demultiplexer is more frequent. By mounting this element close to the wavelength multiplexer / demultiplexer 2, ΔD can be reduced.
In the configuration of FIG. 2, if the distance that the surface of the element is close to the filter is q, the optical distance difference ΔD between the optical element 11 and the optical element 12 is given by the following equation (2).

・・・・・・・・・・・・・・・ （２）

つまり、素子表面をフィルタに近づけた距離分だけ光路差は小さくなる。このとき図６のグラフ中に示すように、結合効率が改善する。
このように、図１、図２の構造により、１本の光ファイバで複数の波長の光を伝送する、波長多重光伝送や１芯双方向光伝送の端末機として用いられる光モジュールに関して、部品点数削減と小型化を実現する光モジュールであって、波長選択フィルタが組み込まれ、光に進行方向に非垂直実装された並行平板透明基板を用いる光モジュールに於いて、部品点数を削減し小型化を図るとともに、各光学素子が高い光結合効率を得ることが可能となる。

(2)

That is, the optical path difference is reduced by the distance that the element surface is close to the filter. At this time, as shown in the graph of FIG. 6, the coupling efficiency is improved.
As described above, with the structure shown in FIGS. 1 and 2, the optical module used as a terminal for wavelength division multiplexing optical transmission or single-core bidirectional optical transmission that transmits light of a plurality of wavelengths through one optical fiber. An optical module that achieves a reduction in the number of points and a reduction in size, with a wavelength selection filter incorporated, and an optical module that uses a parallel-plate transparent substrate that is mounted non-perpendicularly in the direction of travel. In addition, each optical element can obtain high optical coupling efficiency.

[Example 1]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an optical module according to Embodiment 1 of the present invention. FIG. 1 shows an example in which the present invention is applied to a so-called optical triplexer module of a bidirectional optical transceiver module using three wavelengths.
FIG. 1 shows an example of mounting in a CAN package. An LD submount 14 and a PD submount 15 each mounted with a light emitting element 11 and a light receiving element (12, 13) are mounted on a CAN stem 10, and the wavelength multiplexer / demultiplexer 2 is mounted. Are mounted on a CAN package 3 and constitute a triplexer optical module 1. The thickness of the LD submount 14 was 100 μm, and the thickness of the PD submount 15 was 500 μm.
FIG. 7 is a diagram showing the relationship between the difference in thickness between the LD submount 14 and the PD submount 15 and the coupling efficiency of the LD.
When the LD submount 14 and the PD submount 15 have the same thickness (that is, the difference is 0 μm), the coupling efficiency is −8 dB. On the other hand, as in the structure of this embodiment, the LD submount 14 and the PD submount 15 By setting the thickness to 400 μm, the coupling efficiency can be improved to −3 dB.
The operating wavelengths of the optical elements (11, 12, 13) are (λ1, λ2, λ3), respectively, and the wavelength relationship is λ1 <λ2 <λ3. However, the magnitude relationship between the wavelengths is not limited to this. The optical elements are arranged from the shortest wavelength to the longest wavelength in FIG.

The CAN package 3 is provided with irregularities for enabling the mounting of the wavelength multiplexer / demultiplexer. However, it is sufficient if the wavelength multiplexer / demultiplexer can be fixed inside the CAN package 3. The fixing means is not limited. Therefore, it is not essential to provide unevenness. For example, the package member may be provided with a cut so that the wavelength multiplexer / demultiplexer and the package member can be fitted. Or the package member may be provided with both the unevenness | corrugation and the notch | incision.
The wavelength multiplexer / demultiplexer 2 uses a transparent substrate 5 as a supporting substrate, and a first wavelength selection filter 6 and a second wavelength selection filter 7 are mounted adjacently on one surface, and on an opposite surface parallel to this surface. A first mirror 8 and a second mirror 9 are mounted.
The wavelength multiplexer / demultiplexer 2 was mounted by aligning the outer shape of the CAN cap with the concaves and convexes and adhered with a UV curable resin. The glass substrate was made of BK7 and had a thickness of 1136 μm. The glass substrate is mounted so that the angle with respect to the plane is 20 °, and the projection onto z in FIG. 2, that is, the pitch of the multiple reflection, is 500 μm.

The wavelength selection filter is composed of a dielectric multilayer film made of Ta ₂ O ₅ and SiO ₂ . The first wavelength selection filter 6 has a separation wavelength λth of λ1 <λth <λ2, and transmits light having a wavelength shorter than λth and reflects light having a longer wavelength (so-called short-pass filter). . The second wavelength selection filter 7 was a short-pass filter with a separation wavelength of λ2 <λth <λ3.
The first mirror 8 is the same as the first wavelength selection filter 6, and the second mirror 9 is the same as the second wavelength selection filter 7.
As the light emitting element 11 on the optical element integrated substrate, a vertical emission LD in which microlenses are integrated is used. Although an end emission LD can be used for the light emitting element 11, a vertical emission type is desirable for ease of mounting, and a lens integrated type is desirable from the viewpoint of ease of optical coupling and reduction of the number of components.
For the same reason, it is desirable that the light receiving elements (12, 13) are of the surface incident type. An amplifier and a capacitor are also mounted in the CAN, but they are not shown because they are the same as usual.
The material of the transparent substrate 5 is not particularly limited as long as it is transparent with respect to the wavelength to be used, but is preferably inexpensive and has good processing accuracy. In this example, BK7 is used to satisfy this condition, but other glass materials, dielectrics, and semiconductors may be used.

The operation of this configuration example will be described. The light having the wavelength of λ1 emitted from the light emitting element 11 reaches the first wavelength selection filter 6. Light having a wavelength of λ1 passes through the first wavelength selection filter 6, is refracted by the transparent substrate 5, translates in the optical path, and is optically connected to an external optical fiber via the package lens 4.
On the other hand, the light having the combined wavelengths of λ2 and λ3 emitted from the optical fiber enters the transparent substrate 5, undergoes refraction, and reaches the first wavelength selection filter 6. Light having wavelengths of λ2 and λ3 is reflected and reaches the first mirror 8 facing it. Since the first mirror 8 is the same as the first wavelength selection filter 6, the light having the wavelengths λ2 and λ3 is reflected again. Here, the reason why the same mirror 8 as that of the first wavelength selection filter 6 is used is to improve the stopping power for light having a wavelength of λ1.
The light having the wavelength of λ1 emitted from the light emitting element 11 is slightly reflected on the surface of the lens 4, the end face of the fiber, and other places, and enters again as return light. Even if the return light having the wavelength of λ1 is a small amount, it becomes noise when entering the light receiving element (12, 13). The return light having the wavelength of λ1 passes through the first wavelength selection filter 6, but a small amount is reflected. Therefore, the light is transmitted again by the first mirror 8 and the amount of light is further reduced.
For the reasons as described above, in this embodiment, the first mirror 8 is the same as the first wavelength selection filter 6. However, when the wavelength separation specification is not strict, the normal wavelength dependency is used. Using no mirror is sufficient.

The light reflected by the first mirror 8 enters the filter surface again. In the simplest design, the light that has been reflected once by the first mirror 8 is incident on the second wavelength selection filter 7, but in this configuration, the reflected light from the first mirror 8 is again in the second state. The light is incident on the first wavelength selection filter 6 and reciprocates between the first wavelength selection filter 6 and the first mirror 8.
This is to make the interval between the light emitting element 11 and the light receiving element 12 larger than the projection of the multiple reflection pitch. This is because a light emitting element driven at high speed may become a noise source (referred to as electrical crosstalk) for the light receiving element side. When there is no electrical crosstalk or any other special reason, it is desirable that the number of reflections be minimized by matching the multiple reflection pitch in the glass substrate with the mounting pitch of the elements.
The light that has reciprocated twice between the first wavelength selection filter 6 and the first mirror 8 is incident on the second wavelength selection filter 7. Here, the light with the wavelength λ 2 and the light with the wavelength λ 3 are separated, and the light with the wavelength λ 2 is transmitted through the second wavelength selection filter 7, is refracted, and enters the light receiving element 12 perpendicularly.
On the other hand, light having a wavelength of λ3 is reflected and enters the second mirror 9. For the second mirror 9, the same dielectric multilayer filter as the second wavelength selection filter 7 is used for the same reason as in the case of the first mirror 8. The light reflected by the second mirror 9 passes through an interface without a filter (but with an AR coating) and enters the light receiving element 13.

[Example 2]
FIG. 8 is a cross-sectional view illustrating a schematic configuration of the optical module according to the second embodiment of the present invention.
In this embodiment, submounts are used separately for each optical element, and the thickness of each submount is different.
As shown in FIG. 8, the light emitting element 11 is formed on the LD submount 14 having the thickness t1, the first light receiving element 12 is formed on the PD submount 15 having the thickness t2, and the second light receiving element 13 is formed on the thickness. Each is mounted on the PD submount 16 at t3. At this time, the relationship between the thicknesses of the submounts is t1 <t2 <t3, and the optical path difference is shortened.

[Example 3]
FIG. 9 is a cross-sectional view illustrating a schematic configuration of an optical module according to Embodiment 3 of the present invention. In this embodiment, the common submount 19 common to the light emitting element 11 and the light receiving elements (12, 13), in which the submounts of the three optical elements are shared, is used. The common submount 19 has a step structure as shown in FIG. 9, and has a function of changing the height of the element surface. In this embodiment, a two-step staircase structure is used, but a three-step structure is also possible.
By using the common submount 19 as in the present embodiment, as compared with the case where submounts (16, 17, and 18 in FIG. 8) are individually used for each optical element as in the above-described second embodiment, The manufacturing process becomes easy because the alignment is performed only once.
In order to explain the planar structure of the optical module shown in the sectional view of FIG. 9, a bird's-eye view of the component layout on the CAN stem 10 is shown in FIG. As shown in FIG. 9A, generally, a semiconductor IC chip that functions as an amplifier to which an output signal from the light receiving element 13 is input is mounted in a CAN cap. In this embodiment, the semiconductor chip IC is mounted on a chip submount 19-1 that is separate from the common submount 19. At this time, the thickness of the chip submount 19-1 was set to be approximately the same as the thickness of the region where the light receiving element 13 of the common submount 19 is mounted. By adopting the semiconductor chip submount 19-1 having such a thickness, the length of the bonding wire (BW) connecting the light receiving element 13 and the semiconductor chip IC can be shortened. The electrical interference generated between the wiring of the signal input to the light source, the wiring of the output signal output from the light receiving element 12, and the power supply or ground wiring can be suppressed. In FIG. 9A, since the common submount 19 and the semiconductor chip submount 19-1 are connected by wiring, the heights of both are adjusted. However, for example, when wiring directly to a semiconductor IC chip, the common submount 19 and the semiconductor chip submount 19-1 are common. The thickness of the submount 19-1 is adjusted so that the height of the surface of the submount 19 and that of the semiconductor IC chip are the same, and the length of the BW is shortened. In this component layout, the common submount 19 is divided into two parts between a thin mounting area where the light emitting element 11 is mounted and a thick mounting area where the light receiving elements (12, 13) are mounted. Needless to say, the present invention can be applied to other embodiments.
In FIG. 9A, TLP is a terminal pin. In actuality, the CAN stem 10 has a predetermined thickness, but in FIG.

[Example 4]
FIG. 10 is a cross-sectional view illustrating a schematic configuration of an optical module according to Embodiment 4 of the present invention. In this embodiment, the height is changed by overlapping two stages of PD submounts on which the light receiving elements (12, 13) are mounted. In the element mounting procedure, the light receiving elements (12, 13) are first mounted on the PD sub-mant 15. Next, a submount 20 that is a base is mounted on the stem 10. Next, the PD submount 15 on which the light receiving elements (12, 13) are already mounted is mounted on the base submount 20.

[Example 5]
FIG. 11: is sectional drawing which shows schematic structure of the optical module of Example 5 of this invention. In the present embodiment, the stepped CAN stem 21 is used so that the surface of the light receiving element (12, 13) is closer to the wavelength multiplexer / demultiplexer 2 than the optical element 11.
In the structure shown in FIG. 11, a part of the stem is seated, and the light emitting element 11 is mounted on the part by being fitted with the LD submount 14. The same effect can be obtained in other forms such as the structure.

[Example 6]
FIG. 12 is a cross-sectional view illustrating a schematic configuration of an optical module according to Embodiment 6 of the present invention. In this embodiment, the present invention is applied to a two-wavelength single-core bidirectional (BIDI) module.
As shown in FIG. 12, the BIDI module 40 is the same as the first embodiment in that it includes a CAN stem 30, a wavelength multiplexer / demultiplexer 22, and a CAN package 23. However, since the BIDI module performs transmission and reception at a total of two wavelengths, one upstream wavelength and one downstream wavelength, the optical elements are only the light emitting element 31 and the light receiving element 32. As shown in FIG. 12, the PD submount 34 is thicker than the LD submount 33 to increase the coupling efficiency of the light emitting element 31.

[Example 7]
FIG. 13: is sectional drawing which shows schematic structure of the optical module of Example 7 of this invention. In this embodiment, the present invention is applied to a so-called pigtail type module with a fiber. As shown in FIG. 13, the triplexer optical module 1 according to the first embodiment is mounted on the coaxial module casing 51, and a fiber 52 with a ferrule is further mounted.
In the present embodiment, an example of a pigtail type module has been described, but a re-sectorable module can be configured with the same configuration.

[Example 8]
14 and 15 are sectional views showing a schematic configuration of the optical module according to the eighth embodiment of the present invention. The module of this embodiment is characterized in that only the optical elements are preliminarily assembled in one package, and this and the wavelength multiplexer / demultiplexer are mounted in another package.
As shown in FIG. 14, the configuration of this module includes an optical element mounting CAN package 101, a wavelength multiplexer / demultiplexer 102, a lens 103, and a single mode fiber 104 mounted on a planar package 110.
The configuration of the optical element mounting CAN package 101 is as shown in FIG. 15. The light emitting element 113 is mounted on the LD submount 116 and the light receiving elements (114, 115) are mounted on the PD submount 117 thicker than the LD submount 116. The LD submount 116 and the PD submount 117 are mounted on the CAN stem 118.
In the present embodiment, an example of a planar package is shown, but a module housing other than the planar package, for example, a coaxial package may be used.

[Example 9]
FIG. 16: is sectional drawing which shows schematic structure of the optical module of Example 9 of this invention. This embodiment is an example in which a triplexer module is configured by being mounted on a planar package. As shown in FIG. 16, the triplexer module has the following structure: a planar package 137, an LD submount 129 on which the light emitting element 126 is mounted, a PD submount 130 on which the light receiving elements (127, 128) are mounted, A duplexer 122, a lens 123, and a single mode fiber 124 are mounted.
As shown in FIG. 16, in this embodiment, the LD submount 129 and the PD submount 130 on which the optical elements are surface-mounted are mounted in a form that stands vertically from the bottom surface of the planar package. At that time, the PD submount 130 is mounted so as to be closer to the wavelength multiplexer / demultiplexer 122 than the LD submount 129 as shown in the drawing.
As the planar package, for example, a butterfly package may be used. In the form shown in FIG. 16, three wavelengths are supported, but the feature of this embodiment is that it can be handled relatively easily even if the number of wavelengths is further increased.

[Example 10]
FIG. 17 is a cross-sectional view illustrating a schematic configuration of an optical module that is Embodiment 10 of the present invention. FIG. 17 shows an example in which the present invention is applied to an optical transmission module using light sources of three primary colors of RGB.
FIG. 17 shows an example in which the CAN package 201 is mounted. A heat sink 214 mounted with blue, green, and red light emitting elements (211, 212, 213) is mounted on the CAN stem 210, and the wavelength multiplexer / demultiplexer 202 is mounted on the CAN. It is mounted on the package 203.
As shown in FIG. 17, in order to reduce the optical path difference, the light emitting elements (211, 212, 213) on the heat sink 214 have a longer distance in the wavelength multiplexer / demultiplexer 202 of the emitted light, It is mounted close to the wavelength multiplexer / demultiplexer 202. A lens 215 is mounted immediately above the light emitting element.
The light emission wavelength of each light emitting element (211, 212, 213) corresponds to each color of blue (for example, about 400 nm to 500 nm), green (for example, about 500 nm to 580 nm), and red (for example, about 580 nm to 750 nm). And
For the blue light emitting element 211, a semiconductor laser having InGaN formed on a GaN substrate as an active layer can be used. As the green light emitting element 212, a semiconductor laser using InGaN formed on a GaN substrate as an active layer or a semiconductor laser using ZnCdSe formed on a ZnSe substrate as an active layer can be used. As the red light emitting element 213, a semiconductor laser using an InGaP or InGaAlP quantum well formed on a GaAs substrate as an active layer can be used.

Each of these laser elements is mounted junction-down on the heat sink 214 at a predetermined interval. At this time, blue, green and red were arranged in order from the left in FIG.
The CAN package 203 is provided with unevenness for enabling the wavelength multiplexer / demultiplexer 202 to be mounted. The wavelength multiplexer / demultiplexer 202 has a transparent glass substrate 205 as a supporting substrate, and a first wavelength selection filter 206 and a second wavelength selection filter 207 are mounted adjacent to each other on one surface, and are opposed surfaces parallel to this surface. Is mounted with a mirror 208.
The wavelength multiplexer / demultiplexer was mounted by aligning the outer shape of the CAN cap with the concaves and convexes and adhered with a UV curable resin. The glass substrate was made of BK7 and had a thickness of 1136 μm. The glass substrate is mounted so that the angle with respect to the plane is 20 °, and the projection of the multiple reflection pitch onto the plane is 500 μm.
The wavelength selection filter is composed of a dielectric multilayer film made of Ta ₂ O ₅ and SiO ₂ . The first wavelength selection filter 206 is a filter that transmits blue light and reflects green / red light (so-called short pass filter).
The second wavelength selection filter 207 is a short-pass filter that transmits blue / green light and reflects red light.
As the mirror 208, a Ta ₂ O ₅ / SiO ₂ multilayer film that reflects light of green and red wavelengths is used, but a metal such as aluminum can also be used.

The lens 215 has a structure in which three lenses are formed on a submount glass substrate. Each of the three lenses was designed to have a function of suppressing the spread angle of light emitted from the laser light sources (211, 212, 213).
The material of the transparent substrate 205 and the lens 215 is not limited as long as it is transparent with respect to the wavelength to be used, but is preferably inexpensive and has good processing accuracy. In this example, BK7 is used to satisfy this condition, but other glass materials, dielectrics, and semiconductors may be used.
Specifically, red light emitted from the light emitting element (semiconductor light emitting element) 213 reaches the wavelength multiplexer / demultiplexer 202. Since the wavelength multiplexer / demultiplexer 2 is mounted at a non-perpendicular angle with respect to the optical axis, the light propagates through the wavelength multiplexer / demultiplexer 202 after receiving a certain amount of refraction determined by the difference in refractive index. The light is reflected by 208 and reaches the second wavelength selection filter 207. A light emitting element (semiconductor light emitting element) 212 that emits green light is mounted immediately below the second wavelength selection filter 207. Since the second wavelength selection filter 207 reflects red light and transmits green light, the red light and the green light are combined and passed through the wavelength multiplexer / demultiplexer 202 with the same optical axis. Propagate. When this combined light reaches the first wavelength selection filter 206, blue light is combined by the same mechanism, and finally the light of the three primary colors of red, blue, and green is combined and emitted outside the module. Is done. The emission intensity of each of the red, blue and green light emitting elements can be controlled by a drive circuit connected to each element.

[Example 11]
FIG. 18 is a cross-sectional view illustrating a schematic configuration of the optical module according to the eleventh embodiment of the present invention. The present embodiment is an example in which a multi-wavelength receiving module is configured. The LD submount (224, 225, 226) on which the light receiving elements (221, 222, 223) are mounted is mounted on the CAN stem 210.
The operation of this optical module is as follows. Light in which three wavelengths of λ1, λ2, and λ3 are multiplexed enters through the lens 204. The light beam that has reached the wavelength multiplexer / demultiplexer 202 is propagated through the wavelength multiplexer / demultiplexer 202 after reaching a predetermined refraction determined by the difference in refractive index, and reaches the first wavelength selection filter 206. The first wavelength selection filter 206 has a property of transmitting light having a wavelength of λ1 and reflecting light having wavelengths of λ2 and λ3. Accordingly, light having a wavelength of λ1 passes through the first wavelength selection filter 206 and reaches the light receiving element 221, and the optical signal is converted into an electrical signal.
The light having the wavelengths λ 2 and λ 3 reflected by the first wavelength selection filter 206 is reflected once again by the mirror 208 and reaches the second wavelength selection filter 207. The second wavelength selection filter 207 has a property of transmitting light having a wavelength of λ2 and reflecting light having a wavelength of λ3. Light having a wavelength of λ 2 that has passed through the second wavelength selection filter 207 enters the light receiving element 222. On the other hand, light having a wavelength of λ3 is once again reflected by the mirror 208, and finally enters the light receiving element 223.
As for the thickness of the submount, the LD submount 226 for the light receiving element 223 to which light having the wavelength of λ3 having the highest number of reflections is incident is the thickest, and the LD submount 225 for the light receiving element 222 to which light having the wavelength of λ2 is incident. However, the LD submount 224 for the light receiving element 221 into which light having a wavelength of λ1 that does not reflect is incident is the thinnest.

[Example 12]
19 and 20 are cross-sectional views showing a schematic configuration of an optical module according to Embodiment 12 of the present invention. This module is an optical module that multiplexes and transmits three types of wavelengths. Only the light-emitting elements are assembled in one package in advance, and the wavelength multiplexer / demultiplexer is mounted in another package.
As shown in FIG. 19, this module has a planar package 260 in which an optical element mounting CAN package 251, a wavelength multiplexer / demultiplexer 252, a lens 253, and a single mode fiber 254 are mounted.
The optical element mounting CAN package 251 includes a CAN stem 263 on which elements are mounted and a CAN cap 262 with a lens 261. A heat sink 264 is formed on the CAN stem 263, and light emitting elements 265, 266, and 267 are mounted on the heat sink 264 at different heights.
In the present embodiment, an example of a planar package is shown, but a module housing other than the planar package, for example, a coaxial package may be used.

[Example 13]
FIG. 21 is a cross-sectional view illustrating a schematic configuration of the optical module according to the thirteenth embodiment of the present invention. This module is an optical module that multiplexes and transmits three types of wavelengths. The planar package 317 includes three types of light emitting elements 307, 308, and 309, a first lens 310 corresponding to each light emitting element, A wavelength multiplexer / demultiplexer 302, a lens 303, and a single mode fiber 305 are mounted. The light emitting elements (307, 308, 309) are mounted on the submount 306.
Although the embodiment shown in FIG. 21 is compatible with three wavelengths, the feature of this embodiment is that it can be handled relatively easily even if the number of wavelengths is further increased.
As described above, according to each of the above-described embodiments, an optical transmission module that multiplexes and transmits light of a plurality of wavelengths, or an optical reception module that demultiplexes and receives the combined light for each wavelength. Or, for single-core bidirectional optical transceiver modules, while maintaining low loss optical characteristics and high reliability, optical modules that can significantly reduce the number of optical components and mounting processes and at the same time realize high coupling efficiency of each optical element Can be provided.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

1 Triplexer optical module 2, 22, 102, 122, 202, 252, 302, 394 Wavelength multiplexer / demultiplexer 3, 23, 112, 203, 262, 373, 376 CAN package 4, 24, 103, 111, 123, 204, 215, 253, 261, 268, 303, 310, 371, 374, 381 Lens 5, 25, 105, 205 Transparent substrate (glass substrate)
6, 7, 26, 106, 107, 206, 207, 377, 383, 397, 398, 399 Wavelength selection filter 8, 9, 27, 108, 109, 208, 395, 396 Mirror 10, 30, 118, 210, 263 CAN stem 11, 31, 113, 126, 265, 266, 267, 307, 308, 309, 375, 382 Light-emitting element 12, 13, 32, 114, 115, 127, 128, 221, 222, 223, 372 386 Light-receiving element 14, 15, 16, 17, 18, 33, 34, 116, 117, 129, 130, 224, 225, 226, 306 Submount 19 Common submant 19-1 Submant for semiconductor chip 20 Base submount 21 CAN stem with steps 40 BIDI module 51 Pigtail module Enclosure 52, 104, 124, 254, 305, 370, 380 Single mode fiber 101, 251 Optical element mounted CAN package 110 Package 121 Planar triplexer module 137, 260, 317 Planar package 201 RGB three-wavelength transmission module 211 Blue Light-emitting element 212 Green light-emitting element 213 Red light-emitting element 214, 264 Heat sink 301 Flat type optical transmission module 378, 387 Single-core bidirectional optical module package 384 Transparent substrate 385 Support member 390 Emission light 391 Incident light 392, 403, 404, 405 Fiber 393, 400, 401, 402 Rod lens 406, 407, 408 Semiconductor light emitting element or light receiving element WB Wire IC Semiconductor chip TLP Terminal pin

Claims (11)

An optical element mounting substrate on which at least two optical elements having different working wavelengths are mounted;
A wavelength multiplexer / demultiplexer having a parallel plate-like substrate fixed in a package in a state inclined by an angle θ in a two-dimensional section with respect to the optical element mounting substrate;
A lens disposed at a position facing the optical element mounting substrate across the parallel flat substrate,
The wavelength multiplexer / demultiplexer includes a wavelength selection filter on a first surface on the parallel plate substrate and a mirror on a second surface facing the first surface, and the lens or the optical element. The light emitted from the wavelength multiplexer / demultiplexer is incident on the wavelength selection filter surface of the wavelength multiplexer / demultiplexer at a non-perpendicular angle, and the light is multiply reflected zigzag between the wavelength selection filter and the mirror. An optical module that separates and superimposes light of different wavelengths,
The distance along the traveling direction of light between the first optical element in the at least two optical elements and the wavelength multiplexer / demultiplexer is the second optical element in the at least two optical elements. Shorter than the distance along the traveling direction of light between the wavelength multiplexer / demultiplexer,
The first light incident on the first optical element or emitted from the first optical element is incident on the second optical element or emitted from the second optical element. An optical module, characterized in that the light is reflected more frequently in the wavelength multiplexer / demultiplexer. A submount on which the at least two optical elements are mounted;
By changing the thickness of the submount, the distance along the light traveling direction between the first optical element and the wavelength multiplexer / demultiplexer is changed to the second optical element and the wavelength multiplexer / demultiplexer. The optical module according to claim 1, wherein the distance is shorter than a distance along a traveling direction of light between the optical module and the optical unit. A submount on which the at least two optical elements are mounted;
A plurality of the submounts are stacked for each of the at least two optical elements, and the distance along the light traveling direction between the first optical element and the wavelength multiplexer / demultiplexer is set as the second optical element. 2. The optical module according to claim 1, wherein the distance is shorter than a distance along a traveling direction of light between the element and the wavelength multiplexer / demultiplexer. A submount on which the at least two optical elements are mounted;
A step is provided in a stem on which the optical element mounted on the submount is mounted, and a distance along a traveling direction of light between the first optical element and the wavelength multiplexer / demultiplexer is set to the second optical element. 2. The optical module according to claim 1, wherein the distance between the optical element and the wavelength multiplexer / demultiplexer is shorter than a distance along a traveling direction of light. A heat sink carrying the at least two optical elements;
By changing the thickness of the heat sink, the distance along the traveling direction of light between the first optical element and the wavelength multiplexer / demultiplexer is set as the distance between the second optical element and the wavelength multiplexer / demultiplexer. The optical module according to claim 1, wherein the distance is shorter than the distance along the traveling direction of the light between the optical module and the optical module. An optical element mounting substrate on which the first to third optical elements having different working wavelengths are mounted;
A wavelength multiplexer / demultiplexer having a parallel plate-like substrate fixed in a package in a state inclined by an angle θ in a two-dimensional section with respect to the optical element mounting substrate;
A lens disposed at a position facing the optical element mounting substrate across the parallel flat substrate,
The wavelength multiplexer / demultiplexer includes a first wavelength selection filter, a second wavelength selection filter on a first surface on the parallel plate-shaped substrate, and a part of a second surface facing the first surface. And the light emitted from the lens or the optical element is incident on the wavelength selection filter surface of the wavelength multiplexer / demultiplexer at a non-perpendicular angle, and the wavelength An optical module that separates and superimposes light having different wavelengths in the process of multiple reflections of light in a zigzag manner between a selection filter and the mirror,
The distance along the traveling direction of light between the first optical element and the wavelength multiplexer / demultiplexer is along the traveling direction of light between the second optical element and the wavelength multiplexer / demultiplexer. Shorter than the distance
The first light incident on the first optical element or emitted from the first optical element is incident on the second optical element or emitted from the second optical element. An optical module, characterized in that the light is reflected more frequently in the wavelength multiplexer / demultiplexer. The first optical element is a light emitting element that emits the first light,
The second optical element is a light receiving element on which the second light is incident,
The first light emitted from the first optical element is incident on the first wavelength selection filter surface of the wavelength multiplexer / demultiplexer at a non-perpendicular angle and is transmitted through the first wavelength selection filter. Is incident on the lens,
The second light incident from the lens is incident on the second surface of the wavelength multiplexer / demultiplexer at a non-perpendicular angle, and is multiple times by the first wavelength selection filter and the first mirror. The optical module according to claim 6, wherein the optical module is incident on the second wavelength selection filter after being reflected, is transmitted through the second wavelength selection filter, and is incident on the second optical element. A distance between the third optical element and the wavelength multiplexer / demultiplexer is shorter than a distance between the second optical element and the wavelength multiplexer / demultiplexer;
The second light is reflected in the wavelength multiplexer / demultiplexer more frequently than the third light incident on the third optical element or emitted from the third optical element. The optical module according to claim 6, wherein the optical module is light. The third optical element is a light receiving element on which the third light is incident,
The third light incident from the lens is incident on the second surface of the wavelength multiplexer / demultiplexer at a non-perpendicular angle, and the third light is applied a plurality of times by the first wavelength selection filter and the first mirror. After being reflected and incident on the second wavelength selective filter, the light is reflected by the second wavelength selective filter and the second mirror and then incident on the third optical element. Item 9. The optical module according to Item 8. A submount on which the first to third optical elements are mounted;
The distance between the first to third optical elements and the wavelength multiplexer / demultiplexer along the traveling direction of light is varied by changing the thickness of the submount. 9. The optical module according to 9. The first mirror is composed of the first wavelength selection filter,
The optical module according to claim 6, wherein the second mirror includes the second wavelength selection filter.

Images