JP7112238B2 - Optical module and optical transmission device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical module and an optical transmission device, and more particularly to technology for enhancing heat conduction in a simple manner.

An optical module having an optical transmission function and/or an optical reception function is used. Such an optical module is generally mounted on an optical transmission device. In view of the work process for mounting, a pluggable module that can be inserted into and removed from an optical transmission device is widely used as such an optical module.

JP 2015-153992 A JP 2009-152428 A

In order to realize an optical transmission function and an optical reception function, an optical module generally includes one or a plurality of optical subassemblies (OSA: Optical SubAssembly). Also, such optical modules further comprise one or more control circuits (eg, ICs), which drive and control the optical subassemblies.

The one or more optical subassemblies and the one or more control circuits generate heat when the optical module is driven. Therefore, it is necessary to dissipate the heat generated from the optical module to the mounted optical transmission device. The optical module includes a housing that houses one or more optical subassemblies and one or more control circuits, and the generated heat is radiated from the housing to the optical transmission device. In order to improve heat dissipation, the housing is made of a material with relatively high thermal conductivity such as metal, and the optical transmission device is provided with a heat sink at the junction with the optical module. In order to further improve heat dissipation, it is conceivable to dispose a heat conductive sheet between the housing of the optical module and the heat sink of the optical transmission device. However, when the optical module is a pluggable module, there is a risk that the heat conductive sheet will come off, and Patent Documents 1 and 2 disclose techniques for suppressing this.

In recent years, high-density mounting has been carried out with the advancement of optical modules. The amount of heat generated by optical modules is also increasing. Accordingly, higher flatness and lower surface roughness (roughness) are required for the outer surface of the housing that is to be joined to the heat sink. The technique disclosed in Patent Document 1 requires a complicated structure on the outer surface of the housing, which impairs flatness and impairs the easiness of insertion and removal (pluggability). Patent Literature 2 discloses a technique in which the heat conductive sheet and the optical module do not come into direct contact when they are inserted and removed, but it is difficult to achieve a low surface roughness. Note that the heat conductive sheets disclosed in Patent Documents 1 and 2 are made of a soft material such as a silicon-based material or an acrylic material containing a filler with high thermal conductivity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical module and an optical transmission device in which thermal conductivity is easily improved.

(1) In order to solve the above problems, an optical module according to the present invention includes one or more optical subassemblies, one or more control circuits for controlling the one or more optical subassemblies, and a first An optical module comprising: a housing including a case and a second case; and a metal plate disposed on an outer surface of the first case, wherein the housing comprises the first case and the second case. The one or more optical subassemblies and the one or more control circuits are housed in the housing by fitting two cases, wherein the metal plate and the It can be plugged into and pulled out of an optical transmission device having a heat sink at the junction.

(2) In the optical module described in (1) above, the surface roughness of the outer surface of the metal plate may be lower than the surface roughness of the outer surface of the first case.

(3) In the optical module described in (1) or (2) above, the flatness of the outer surface of the metal plate may be higher than the flatness of the outer surface of the first case.

(4) In the optical module according to any one of (1) to (3) above, the thermal conductivity of the metal plate may be higher than the thermal conductivity of the first case.

(5) In the optical module according to any one of (1) to (4) above, the metal plate may be sheet metal.

(6) In the optical module according to any one of (1) to (5) above, the height of the outer surface of the metal plate may be higher than the height of the outer surface of the first case. .

(7) The optical module according to any one of (1) to (6) above, wherein an adhesive, an adhesive, or a double-sided tape is provided between the outer surface of the first case and the metal plate. 1 selected from the group may be placed.

(8) The optical module according to any one of (1) to (7) above, wherein a heat conductive sheet is further arranged between the outer surface of the first case and the metal plate. good.

(9) An optical transmission device according to the present invention may be an optical transmission device in which the optical module according to any one of (1) to (8) is mounted.

INDUSTRIAL APPLICABILITY The present invention provides an optical module and an optical transmission device in which thermal conductivity is easily improved.

1 is a schematic diagram showing the configuration of an optical transmission device and an optical module according to an embodiment of the present invention; FIG. 1 is an external view of an optical module 2 according to an embodiment of the invention; FIG. FIG. 3 is a cross-sectional view showing a junction between the optical transmission device and the optical module according to the embodiment of the present invention; 1 is a perspective view showing the configuration of an optical module according to an embodiment of the invention; FIG. 1 is a cross-sectional view of an optical receiver module according to an embodiment of the present invention; FIG. 1 is a cross-sectional view of an optical receiver module according to an embodiment of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described specifically and in detail based on the drawings. In addition, in all the drawings for describing the embodiments, members having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted. It should be noted that the drawings shown below are only for explaining examples of the embodiments, and the sizes of the drawings and the reduced scales described in this example do not necessarily match.

FIG. 1 is a schematic diagram showing configurations of an optical transmission device 1 and an optical module 2 according to an embodiment of the present invention. The optical transmission device 1 has a printed circuit board 11 and an IC 12 . The optical transmission device 1 is, for example, a large-capacity router or switch. The optical transmission device 1 has, for example, a switching function, and is arranged in a base station or the like. A plurality of optical modules 2 are mounted in the optical transmission device 1, and data for reception (electrical signal for reception) is acquired from the optical modules 2, and what data is transmitted to where using an IC 12 or the like. is determined, data for transmission (electrical signal for transmission) is generated, and the data is transmitted to the corresponding optical module 2 via the printed circuit board 11 .

The optical module 2 is a transceiver with transmitting and receiving functions. The optical module 2 includes a printed circuit board 21, an optical receiving module 23A that converts an optical signal received via the optical fiber 3A into an electrical signal, and an optical transmission module 23A that converts the electrical signal into an optical signal and transmits the optical signal to the optical fiber 3B. and module 23B. The printed circuit board 21, the optical receiver module 23A and the optical transmitter module 23B are connected via flexible boards 22A and 22B (FPC), respectively. An electrical signal is transmitted from the optical receiving module 23A to the printed circuit board 21 via the flexible board 22A, and an electrical signal is transmitted from the printed circuit board 21 to the optical transmitting module 23B via the flexible board 22B. The optical module 2 and the optical transmission device 1 are connected via an electrical connector 5 . The optical receiver module 23A and the optical transmitter module 23B are electrically connected to the printed circuit board 21 and convert optical/electrical signals into electric/optical signals, respectively. The printed circuit board 21 includes a control circuit (eg, IC) for controlling electrical signals transmitted from the optical receiver module 23A and a control circuit (eg, IC) for controlling electrical signals transmitted to the optical transmitter module 23B.

The transmission system according to this embodiment includes two or more optical transmission devices 1, two or more optical modules 2, and one or more optical fibers 3 (not shown: optical fibers 3A and 3B, for example). One or more optical modules 2 are connected to each optical transmission device 1 . An optical fiber 3 connects between the optical modules 2 connected to the two optical transmission devices 1 respectively. Data for transmission generated by one optical transmission device 1 is converted into an optical signal by the connected optical module 2 , and the optical signal is transmitted to the optical fiber 3 . An optical signal transmitted on the optical fiber 3 is received by an optical module 2 connected to the other optical transmission device 1, and the optical module 2 converts the optical signal into an electrical signal, and converts the optical signal into an electrical signal as data for reception. Transmit to the transmission device 1 .

FIG. 2 is an external view of the optical module 2 according to this embodiment. The optical module 2 according to this embodiment is adapted to QSFP-DD (MSA standard), and the transmission rate of the optical module 2 is 400 Gbit/s. As shown in FIG. 2, the optical module 2 has a housing 100 . The housing 100 includes an upper case 101 (first case) and a lower case 102 (second case). The optical module 2 (that is, the housing 100 of the optical module 2 ) further includes a metal plate 103 arranged on the outer (upper) surface of the upper case 101 .

FIG. 3 is a schematic cross-sectional view showing a joint 200 between the optical transmission device 1 and the optical module 2 according to this embodiment. The optical transmission device 1 includes a heat sink 30 at the joint between the optical module 2 and the metal plate 103 . When the optical module 2 is mounted on the optical transmission device 1 , the metal plate 103 and the heat sink 30 are physically in contact with each other at the junction 200 between the optical transmission device 1 and the optical module 2 . The optical module 2 further has a pull-tab 50 at the end connected to the optical fiber, and the user can use the pull-tab 50 when inserting/removing the optical module 2 into/from the optical transmission device 1 . In particular, the pull-tab 50 is useful when pulling out (removing) the optical module 2 .

FIG. 4 is a perspective view showing the configuration of the optical module 2 according to this embodiment. The main components housed inside are shown with the upper case 101 and the case 102 separated. For the sake of simplicity, only major parts are shown, and other parts are omitted. As shown in FIG. 4, the optical module 2 comprises two optical subassemblies 104, 105 (one or more optical subassemblies). The optical receiver module 23A shown in FIG. 2 generally includes one or more optical subassemblies, but here includes one optical subassembly 104. The optical receiver module 23A shown in FIG. The optical subassembly 104 is a ROSA (Receiver Optical Subassembly) having four 100 Gbit/s class (more specifically, 50 GBaud class by PAM4 signal) receiving elements. That is, the optical subassembly 104 has four or four wave optical inputs and corresponding four channel electrical outputs. The optical transmitter module 23B shown in FIG. 2 generally includes one or more optical subassemblies, but here includes one optical subassembly 105. FIG. The optical subassembly 105 is a TOSA (Transmitter Optical Subassembly) equipped with a 100 Gbit/s class (more specifically, 50 GBaud class by PAM4 signal) light emitting element. That is, the optical subassembly 105 has 4-channel electrical inputs and corresponding 4-channel or 4-wave optical outputs. The housings of the optical subassemblies 104 and 105 are BOX type.

The optical module 2 further comprises control ICs 106 and 107 arranged on the printed circuit board 21 . Here, the control ICs 106 and 107 are one or more control circuits that control one or more optical subassemblies. The printed circuit board 21 also has electrical components not shown. The printed circuit board 21 is housed in the lower case 102 . The optical module 2 further includes heat dissipation sheets 111 , 112 , 113 and 114 . Heat dissipation sheets 111 and 112 are attached to the upper surfaces of control ICs 106 and 107, respectively. Heat radiation sheets 113 and 114 are attached to the upper surfaces of the box-shaped housings of the optical subassemblies 104 and 105, respectively. That is, the heat radiation sheets 113 and 114 are attached to at least part of the upper surfaces of the optical subassemblies 104 and 105, respectively. By fitting the upper case 101 and the lower case 102 to the housing 100, one or a plurality of optical subassemblies (here, optical subassemblies 104 and 105) and one or a plurality of control units are installed inside the housing 100. When the upper case 101 and the lower case 102, which house the circuits (control ICs 106, 107), are fitted together, the heat radiation sheets 111, 112, 113, 114 and the inner (lower) surface of the upper case 101 come into physical contact with the surface of The heat radiation sheets 111, 112, 113, 114 are heat conductive sheets made of silicon-based or acrylic-based materials containing fillers with high thermal conductivity. 107 is a heat radiating portion for conducting heat generated in the upper case 101 . The heat radiation part is not limited to the heat radiation sheet, and may be heat radiation grease.

The metal plate 103 is arranged on the outer (upper) surface of the upper case 101, and an adhesive 120 is arranged between the metal plate 103 and the outer surface of the upper case 101, and the adhesive 120 is applied to the metal plate. 103 is fixed on the outer surface of the upper case 101 . The adhesive 120 is desirably made of a material with high thermal conductivity. Moreover, it is desirable that the adhesive 120 is applied thinly so as not to cause any problem in heat radiation from the upper case 101 to the metal plate 103 . Instead of the adhesive 120, the metal plate 103 may be fixed by brazing. Note that the upper case 101 and the lower case 102 are fixed by mounting screws 125 .

A main feature of the optical module 2 according to this embodiment is that the metal plate 103 is arranged on the outer surface (outer surface) of the upper case 101 . The upper case 101 and the lower case 102 are made of metal such as an aluminum alloy or a zinc alloy. In order to mold the upper case 101 and the lower case 102, working processes such as die casting and cutting are generally used. However, when the upper case 101 is formed by die casting or cutting, the outer surface of the upper case can be made to have a higher flatness (a flatter plane) or a lower surface roughness (a smoother surface roughness). becomes difficult. Here, flatness is the degree of deviation of a planar body from a geometrically correct plane. The surface roughness represents the state (unevenness) of the machined surface of the part, and is the degree of roughness of a periodic shape in which peaks and valleys with different heights, depths, and intervals are continuous. It is also possible to increase the flatness and smoothen the surface roughness by surface polishing after die casting, but this is very disadvantageous in terms of cost. It is conceivable that the standard requires stricter requirements for the flatness and surface roughness of the surface of the housing 100 at the junction 200 between the housing 100 of the optical module 2 and the heat sink 30 of the optical transmission device 1 . On the other hand, in the optical module 2 according to this embodiment, the metal plate 103 is arranged at the joint 200, making it easier to achieve higher flatness and lower surface roughness. Physical contact between the metal plate 103, which has an outer surface with high flatness and low surface roughness, and the heat sink 30 allows contact with a higher degree of adhesion, thereby reducing the contact thermal resistance. , heat dissipation is improved.

The metal plate 103 is desirably made of sheet metal. Sheet metal is formed by compressing a metal material through rollers, and it is easy to process the surface of a metal plate made of sheet metal to have a lower surface roughness. By arranging the metal plate 103 on the outer surface of the upper case 101, the surface of the housing 100 having a lower surface roughness can be realized by a simple method. It is desirable that the surface roughness of the outer surface of the metal plate 103 is lower than the surface roughness of the outer surface of the upper case 101, that is, smoother (closer to a mirror surface). It is desirable that the flatness of the outer surface of the metal plate 103 is higher than the flatness of the outer surface of the upper case 101 . Since sheet metal can be realized with various types of metals (including alloys), the metal plate 103 can be formed using a metal material having high thermal conductivity (for example, copper). It is desirable that the thermal conductivity of (the metal that constitutes) the metal plate 103 is higher than the thermal conductivity of (the metal that constitutes) the upper case 101 from the viewpoint of improving heat dissipation.

By arranging the metal plate 103 on the outer surface of the upper case 101 , unlike the case where a heat dissipation sheet is arranged at the connection point 200 with the heat sink 30 , there is a problem that the metal plate 103 is peeled off when the optical module 2 is inserted or removed. will not be.

5A and 5B are cross-sectional views of the optical module 2. FIG. 5A is an enlarged view of the optical module 2 portion of the circle A shown in FIG. 3, and FIG. 5B is an enlarged view of the optical module 2 portion of the circle B shown in FIG. The portion shown in FIG. 5A is a portion including the outer end of the metal plate 103 (the end connected to the optical fiber 3). The portion shown in FIG. 5B is a portion including the inner end of the metal plate 103 (the end connected to the optical transmission device 1). The outer surface of the upper case 101 is flat, and the metal plate 103 may be arranged as it is on part of the flat portion. However, it is desirable that the outer surface of the upper case 101 according to this embodiment is formed with grooves corresponding to the thickness of the metal plate 103 so that the metal plate 103 can be accommodated therein. The groove preferably has substantially the same shape as the metal plate 103 in a plan view, and more precisely, has a shape that spreads outward from the outer edge of the metal plate 103 by a predetermined width. The predetermined width is desirably a small value that is possible in consideration of manufacturing accuracy and the like. When the metal plate 103 is fixed by the adhesive 120, the height of the outer surface of the metal plate 103 is higher than the height of the outer surface of the upper case 101, which is convenient when inserting and removing the optical module 2. This is preferable from the viewpoint of the friction of the metal plate 103 and the degree of adhesion to the heat sink 30 during mounting. Here, the height of the outer surface of the upper case 101 means the height of the flat surface extending outward from the outer edge of the metal plate 103 . It should be noted that the term “higher” as used herein refers to being positioned further outside of the interior of the housing 100 .

Here, the metal plate 103 is fixed to the outer surface of the upper case 101 using an adhesive 120, but is not limited to this, and may be a heat conductive double-sided tape, a double-sided tape, or an adhesive. Alternatively, the metal plate 103 may be fixed to the outer surface of the upper case 101 by using. Furthermore, a flexible thermally conductive sheet (radiating sheet) may be arranged between the outer surface of upper case 101 and metal plate 103 . A heat conductive sheet with double-sided tape attached to each side of the heat conductive sheet is used, and between the outer surface of the upper case 101 and the heat conductive sheet, and between the heat conductive sheet and the metal plate 103, It may be fixed by any one selected from the group consisting of an adhesive, a (thermally conductive) double-sided tape, and an adhesive. When the optical module 2 is mounted on the optical transmission device 1, it is pressed by the heat sink 30 in contact with the metal plate 103. Due to the flexibility of the heat conductive sheet, the adhesion between the metal plate 103 and the heat sink 30 is further improved. effect. Considering that the metal plate 103 is pressed by the heat sink 30 and comes closer to the upper case 101 when mounted, the height of the upper surface of the metal plate 103 is higher than the height of the outer surface of the upper case 101 when mounted. 2 is not mounted on the optical transmission device 1, the height of the upper surface of the metal plate 103 is higher than the outer surface of the upper case 101 (compared to the case where the metal plate 103 is fixed only by the adhesive 120). ) is even higher.

The optical module, the optical transmission device, and the optical transmission system according to the embodiments of the present invention have been described above. The present invention is not limited to the above embodiments, and various modifications are possible, and the present invention can be widely applied. The configurations described in the above embodiments can be replaced with configurations that are substantially the same, configurations that produce the same effects, or configurations that can achieve the same purpose.

In the above embodiment, the optical module 2 is compatible with QSFP-DD, but it is not limited to this and may be compatible with other standards. The present invention has a particular effect in standards that require a lower surface roughness value (or a higher flatness value) on the surface of the housing at the joint.

In the above embodiment, the metal plate 103 is made of sheet metal, but is not limited to this, and other processes may be used as long as a surface with a desired surface roughness (or flatness) can be achieved. It may be formed by a method. In the above embodiment, the control circuit is a driving IC, but the control circuit is not limited to this and may have another configuration.

In the above embodiment, the optical module 2 includes four-channel optical subassemblies 104 and 105, but is not limited to this and may include one or a plurality of optical subassemblies. In the above embodiments, the housings of the optical subassemblies 104 and 105 are of the BOX type, but are not limited to this. The housing of the optical subassembly may be cylindrical. Also, the optical module 2 may be limited to either the optical transmission function or the optical reception function. That is, the optical module 2 may comprise either an optical transmission subassembly or an optical reception subassembly only.

1 optical transmission device 2 optical module 3, 3A, 3B optical fiber 11, 21 printed circuit board 12 IC, 22A, 22B flexible substrate 23A, 100 optical receiving module 23B, optical transmitting module 30 heat sink 50 pull tab 100 housing 101 upper case 102 lower case 103 metal plate 104, 105 optical subassembly 106, 107 control IC 111, 112, 113, 114 heat dissipation sheet 120 adhesive 125 mounting screw 200 joints.

Claims (10)

one or more optical subassemblies;
one or more control circuits for controlling the one or more optical subassemblies;
a housing including a first case and a second case;
a metal plate disposed on the outer surface of the first case;
An optical module comprising
The outer surface of the first case is made of metal,
The housing stores the one or more optical subassemblies and the one or more control circuits inside the housing by fitting the first case and the second case. death,
the surface roughness of the outer surface of the metal plate is lower than the surface roughness of the outer surface of the first case;
An optical module capable of being inserted/extracted from an optical transmission device having a heat sink at a contact point with the metal plate . The optical module according to claim 1 ,
The flatness of the outer surface of the metal plate is higher than the flatness of the outer surface of the first case,
An optical module characterized by: one or more optical subassemblies;
one or more control circuits for controlling the one or more optical subassemblies;
a housing including a first case and a second case;
a metal plate disposed on the outer surface of the first case;
An optical module comprising
The outer surface of the first case is made of metal,
The housing stores the one or more optical subassemblies and the one or more control circuits inside the housing by fitting the first case and the second case. death,
The flatness of the outer surface of the metal plate is higher than the flatness of the outer surface of the first case,
An optical module capable of being inserted/extracted from an optical transmission device having a heat sink at a contact point with the metal plate . The optical module according to any one of claims 1 to 3,
the thermal conductivity of the metal plate is higher than the thermal conductivity of the first case;
An optical module characterized by: The optical module according to any one of claims 1 to 4,
wherein the metal plate is sheet metal;
An optical module characterized by: The optical module according to any one of claims 1 to 5,
The height of the outer surface of the metal plate is higher than the height of the outer surface of the first case,
An optical module characterized by: The optical module according to any one of claims 1 to 6,
Between the outer surface of the first case and the metal plate, 1 selected from the group consisting of an adhesive, an adhesive, and a double-sided tape is arranged.
An optical module characterized by: The optical module according to any one of claims 1 to 7,
A thermally conductive sheet is further disposed between the outer surface of the first case and the metal plate;
An optical module characterized by: The optical module according to any one of claims 1 to 8,
The outer surface of the first case is formed with a groove having substantially the same shape as the metal plate in plan view,
An optical module characterized by: An optical transmission device mounted with the optical module according to any one of claims 1 to 9.

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